Speaker 1: Get technology with tech Stuff from dot Com. Hey there,
Speaker 1: and welcome to tech Stuff. I am your host, Jonathan Strickland.
Speaker 1: I'm a senior writer win how Stuff Works dot Com,
Speaker 1: and sometimes my voice cracks for no reason. Today we're
Speaker 1: going to continue our journey into the scary world of
Speaker 1: weather forecasting. Uh. I say scary because weather is a
Speaker 1: powerful thing. It can bring with it some pretty intense
Speaker 1: uh storms and and win things like that. I mean,
Speaker 1: obviously you can have nice weather too, but who wants
Speaker 1: to talk about that? I mean, you're not gonna have
Speaker 1: an emergency weather broadcast burst into your favorite viewing time
Speaker 1: of watching ALF and say warning, things are gonna be
Speaker 1: really nice this afternoon. So we're gonna talk about today
Speaker 1: about some of the tools that meteorologists use in order
Speaker 1: to get information about what's going on at this very
Speaker 1: moment as far as the weather is concerned. In our
Speaker 1: last episode, we covered the basics of how weather works,
Speaker 1: so that man, it was more of a science based show,
Speaker 1: less technology, but it was important so that we can
Speaker 1: build the foundation to understand why meteorology is so incredibly
Speaker 1: complicated and so process or heavy. Like when you talk
Speaker 1: about supercomputers. One of the main uses for supercomputers these
Speaker 1: days is to run weather models. And that's because you're
Speaker 1: talking about an enormous amount of data that has to
Speaker 1: be processed running you know, various types of calculations on
Speaker 1: it in order to create the outputs that we use
Speaker 1: for weather forecasts. And as our weather models become more
Speaker 1: and more high resolution, more precise, using more more readings
Speaker 1: per hour, that demand of processing power increases quite a bit.
Speaker 1: So let's talk about just the stuff that meteorologists used
Speaker 1: to gather that data. This isn't even about the weather models.
Speaker 1: In our next episode, we will cover how weather models work,
Speaker 1: because it's fascinating all in its own. Today we're gonna
Speaker 1: focus on the stuff that meteorologists used to get the
Speaker 1: data that feeds into those weather models. Uh So, meteorologists
Speaker 1: do a few different things. They do make observations of
Speaker 1: current weather conditions, so they're telling you what's happening right now,
Speaker 1: and that's what I'm focusing on for this episode and
Speaker 1: the next one will look more at the forecasting side.
Speaker 1: How do they actually predict what will happen next. Observations
Speaker 1: let you know the current conditions. They include data like
Speaker 1: wind speed, wind direction, air pressure, temperature, humidity, u V,
Speaker 1: radiation numbers, smog fog, all of these things and more.
Speaker 1: Are you need observation stations throughout any given region, the
Speaker 1: region that you are responsible for, let's say, and you
Speaker 1: need to have a lot of them in order for
Speaker 1: you to get a more complete picture of what is
Speaker 1: really actually happening. If you have only a few observation points,
Speaker 1: then you would have what we would call low resolution.
Speaker 1: You would not have a very accurate accurate view of
Speaker 1: what was going on within the region, unless your region
Speaker 1: is particularly small. Let's say that you are responsible for
Speaker 1: gathering the information across an entire county. Well, a county
Speaker 1: could be lots of square mileage, and depending upon where
Speaker 1: your observation stations are, you might have information that's very
Speaker 1: relevant for a specific part of that county, but it
Speaker 1: might not be so relevant for other parts of the county.
Speaker 1: And yet you have to create weather forecasts based on
Speaker 1: your observations. It means the further out you go from
Speaker 1: those observation stations, the less reliable that data is going
Speaker 1: to be because it may not reflect what the actual
Speaker 1: conditions are further away from those observation stations. So having
Speaker 1: a high density of observation stations is critical for having
Speaker 1: very precise, whether a picture of what's going on with
Speaker 1: the weather and thus making more accurate weather forecasts. So
Speaker 1: it could cause a problem, right Like, you could end
Speaker 1: up giving a weather forecast that ends up being useless
Speaker 1: for a significant percentage of the people who are relying
Speaker 1: upon your weather forecasts if they happen to live far
Speaker 1: away from where your observation stations are. So let's think
Speaker 1: of this in more concrete terms and you'll really understand
Speaker 1: how this can become a problem. Let's say that you
Speaker 1: have a region that includes some different areas within with
Speaker 1: different levels of elevation. So let's say that you're at
Speaker 1: the foothills of a mountain range. Well, we'll say this
Speaker 1: the appal Achians. So, uh, I live in Atlanta, Georgia,
Speaker 1: where on what is called the Piedmont it is h
Speaker 1: hilly but not mountainous area. If I were further northeast
Speaker 1: of here, or even just further north of here, I
Speaker 1: would start getting into the foothills of the Appalachian Mountains.
Speaker 1: So let's say that I'm on Just like that, I'm
Speaker 1: looking at a region where it's covering the end of
Speaker 1: the Piedmont into the foothills. That's several different areas of
Speaker 1: different elevation. That means that those different areas are going
Speaker 1: to experience different weather patterns because weather is all about
Speaker 1: atmospheric movement and things that are going on within the atmosphere.
Speaker 1: Atmosphere is going to move over the topographical features of
Speaker 1: any given region, the geography, and with hills and mountains,
Speaker 1: that means the weather is going to do different things
Speaker 1: in those different areas. So you're going to have folks
Speaker 1: checking the weather report and wondering why it says there's
Speaker 1: no chance brain while they're being rained on, and it
Speaker 1: may be because they live on the opposite side of
Speaker 1: a mountain from where you are with your observation stations,
Speaker 1: and at the observation stations everything's bone dry because that's
Speaker 1: what you know, that's what you've based your forecast on,
Speaker 1: because that was where the data was coming from. But
Speaker 1: on the other side of the mountain, because you've had
Speaker 1: warm air masses pushed up to higher elevations as they
Speaker 1: moved over a mountain, They've then cooled down, water has condensed,
Speaker 1: and precipitation has begun to fall. People on the other
Speaker 1: side of the mountain they get rained on, and yet
Speaker 1: they're living in that same region that's being covered by you,
Speaker 1: because that's the county they are in, or the zip code.
Speaker 1: This is why it gets really problematic when you start
Speaker 1: making weather forecasts, because they depend so heavily upon the
Speaker 1: geography of the respective regions and the geography and and
Speaker 1: observation stations within that geography. Now, if you have observation
Speaker 1: stations throughout your area, you can give much more precise
Speaker 1: weather forecasts. And say, in this part of the county,
Speaker 1: you would expect conditions to be dry, but up here
Speaker 1: over in the mountains, you're gonna start seeing some rain.
Speaker 1: So you start seeing where the complexity comes into play.
Speaker 1: And this is a very small scale example of this problem.
Speaker 1: Once you start looking at it from say a statewide
Speaker 1: or nationwide or global perspective, you begin to realize this
Speaker 1: is really complicated stuff, and this is a big challenge
Speaker 1: for meteorologists. You might notice that many weather apps allow
Speaker 1: you to search for weather forecasts by zip codes, but again,
Speaker 1: zip codes do not necessarily conform to geography, and you
Speaker 1: could have lots of different geographic regions within a single
Speaker 1: zip code, and that means that the weather forecast for
Speaker 1: one of those parts of the zip code may not
Speaker 1: be accurate for all the other parts. So if I
Speaker 1: check my app and it says hey, it's gonna rain,
Speaker 1: and I step outside and it's sunny, I might think, well,
Speaker 1: what the heck is wrong with this weather forecast app? Again,
Speaker 1: they have to try and give you a forecast that's
Speaker 1: going to be relevant for the entire zip code, even
Speaker 1: if different parts of that zip code are in different
Speaker 1: geographical regions, like different geographical features mountains or streams or
Speaker 1: lakes or ocean or whatever it may be. So you
Speaker 1: can't really take all that into account if your criteria
Speaker 1: for generating a forecast is based solely upon zip codes.
Speaker 1: That's why a lot of different weather apps and services
Speaker 1: are now using geolocation data to give you a more
Speaker 1: precise weather forecast for your your requests. So, if you're
Speaker 1: carrying a mobile device and you have a weather app
Speaker 1: on it and it's asking hey, can I have access
Speaker 1: to your GPS or location data? If you say yes,
Speaker 1: then the weather app can look for your location and
Speaker 1: try and base the forecast for you closer to observation
Speaker 1: stations that are relevant to your your actual location So
Speaker 1: if I happen to be in a part of the
Speaker 1: county that is not the main population center and thus
Speaker 1: not the place that the forecast is really gonna cater to,
Speaker 1: I might get something more personalized saying, hey, well, based
Speaker 1: upon where you are, you're gonna be Charlie Brown and
Speaker 1: have a little cloud follow you all day raining just
Speaker 1: on you, which has never quite happened to me, but
Speaker 1: some days it feels that way. It's sidesteps that zip
Speaker 1: code problem, so that the weather forecasting system can consult
Speaker 1: the observation stations really closest to you at that time
Speaker 1: and to project weather based upon that. But even then
Speaker 1: you can still run into issues. So, for example, if
Speaker 1: you happen to be closest to an airport observation station,
Speaker 1: I mean most really all airports have some form of
Speaker 1: meteorological meteor logical boy man, that's gonna be a lot
Speaker 1: of fun today. Meteorological observation stations. Almost all air airports
Speaker 1: have at least some element of that, because clearly the
Speaker 1: weather conditions are very important when it comes to air travel.
Speaker 1: One problem with that is that airports have very big
Speaker 1: runways and uh tarmax things that absorb a lot of
Speaker 1: heat and give off a lot of heat, more so
Speaker 1: than the surrounding area. And as we learned in our
Speaker 1: last episode, heat is a big important factor when it
Speaker 1: comes to impacting weather systems. So if you happen to
Speaker 1: be close to an airport, that might end up throwing
Speaker 1: off some of the readings that you would get because
Speaker 1: it has this island effect right at the airport, But
Speaker 1: that might not extend very far outside of the airport's borders.
Speaker 1: So while you're getting observation data that's close to you,
Speaker 1: it may still not be relevant to you. A lot
Speaker 1: of this sounds like I'm apologizing for weather forecasts that
Speaker 1: aren't entirely accurate, and I guess you could argue that
Speaker 1: I kind of am. But mostly what I want to
Speaker 1: stress is just, um, what a tough job this is.
Speaker 1: It's an interesting and fascinating thing, and we've learned so
Speaker 1: much about atmospheric fluid dynamics and just how weather works
Speaker 1: in general as a result of lots and lots of
Speaker 1: men and women putting their heads together and and making
Speaker 1: observations and sussing all this out. But it's still really
Speaker 1: really hard to do, which is why it's one of
Speaker 1: the reasons why we don't do it perfectly now. Besides resolution,
Speaker 1: as in how many observation stations you have within a
Speaker 1: given region, you have to take those observations frequently. This
Speaker 1: helps with precision. If you take one observation in the day,
Speaker 1: early in the day, and that's it, then you can't
Speaker 1: take into account any changes that happen afterward, which means
Speaker 1: that you can never really update your forecast. And that
Speaker 1: means that the further away you get in time from
Speaker 1: that initial observation, the less precise and accurate your forecast
Speaker 1: is going to be. If you continuously or at least
Speaker 1: regularly take observations, you can then update your forecast as
Speaker 1: a result when conditions change, and that way you can
Speaker 1: keep your at least your immediate forecast more accurate. You
Speaker 1: may notice that the further out you go from the
Speaker 1: point of forecast from the current time, the less accurate
Speaker 1: these forecasts tend to tend to be. So if you're
Speaker 1: looking at a date that's ten days out, it might
Speaker 1: be more or less right on the money, or maybe
Speaker 1: way off base. Because weather is again very complicated and
Speaker 1: constantly changing. Uh So you want to make sure that
Speaker 1: the information you're relying on doesn't age so much as
Speaker 1: to be irrelevant. So you need lots of observation stations.
Speaker 1: You need to take a lot of observations per given
Speaker 1: unit of time, and the combination of those two requirements
Speaker 1: means that you are generating an enormous amount of data
Speaker 1: that then has to go someplace and then be processed
Speaker 1: for you to get forecasts. This is why you need
Speaker 1: those hefty computers like supercomputers to process meteorological data. And
Speaker 1: more on that in the next episode. But first let's
Speaker 1: talk about some of the basic instruments these meteorologists are
Speaker 1: using to gather actual weather data. Then in our next
Speaker 1: episode will move on to how they use that to
Speaker 1: create models for weather. And also why are there different models.
Speaker 1: You've probably heard of various weather models. Why do we
Speaker 1: not just have one? Why are there multiples? And why
Speaker 1: are some quote unquote better than others in very specific scenarios.
Speaker 1: We're going to cover that in the next episode. Now,
Speaker 1: generally speaking, meteorological instruments fall into two broadcat gregories. You
Speaker 1: have direct sensors also called institute sensors. They're inside the
Speaker 1: situation like a thermometer that is left out to measure
Speaker 1: the temperature of the air. It's institute. It is a
Speaker 1: direct sensor. It's directly measuring the temperature of the air outside.
Speaker 1: Then you have remote sensors that are measuring something that's
Speaker 1: much further away. The name pretty much gives you the
Speaker 1: indication of what it does. Now, we're going to talk
Speaker 1: about both types in this episode. Direct sensors include lots
Speaker 1: of stuff that you're familiar with, and we're gonna start
Speaker 1: off with a good old, easy one to to talk
Speaker 1: about thermometers, the noble thermometer telling us such information like dude,
Speaker 1: it's wicked cold out that today, but on your coat,
Speaker 1: or seriously, buddy, it's boiling out there. Let's play some
Speaker 1: player unknowns battlegrounds in the air conditioned house. But how
Speaker 1: do thermommeters actually work? So let's start with your basic
Speaker 1: mercury thermometer. It's something that is still being used around
Speaker 1: the world. It's your basic bulb thermometer. It depends upon
Speaker 1: a simple physical principle, which is that a liquids volume
Speaker 1: changes relative to the temperature of the liquid. So when
Speaker 1: you heat a liquid up, it's molecules decide to do
Speaker 1: the equivalent of the guy I'm always seated next to
Speaker 1: on a long distance plane ride. In other words, it
Speaker 1: spreads out well beyond its normal parameters. You know who
Speaker 1: I'm talking about. Give me my arm rest back. But
Speaker 1: that's what happens with liquids. You heat them up, the
Speaker 1: molecules get more energy, they get excited, they move around more,
Speaker 1: and they spread apart. So as a result, the liquid expands,
Speaker 1: and if, of course you do this long enough, the
Speaker 1: liquid will end up turning into a gas, which is
Speaker 1: even more free form than liquid. Obvious asleep. When liquids
Speaker 1: get cold, those molecules end up huddling together, not so
Speaker 1: much for warmth, but because they have less energy they
Speaker 1: don't move around so much, so the liquid actually takes
Speaker 1: up less space than it normally would. So your basic
Speaker 1: bulb thermometer consists of a small bulb at the base
Speaker 1: and a narrow, long, closed tube leading up from that
Speaker 1: bulb base. These physical proportions accentuate the change in volume
Speaker 1: of the liquid, So you want the bulb to be
Speaker 1: small because you want any changes in temperature in whatever
Speaker 1: environment you are measuring to rapidly be reflected within the
Speaker 1: thermometer itself. So, for example, if you're talking about outside.
Speaker 1: Any drastic change in the outside temperature, you want that
Speaker 1: to be reflected in an outside thermometer pretty quickly. Typically
Speaker 1: those temperatures don't increase or drop that fast. But let's
Speaker 1: say you want to go from room temperature thermometer and
Speaker 1: you're testing someone's temperature. You want to find out they
Speaker 1: have a fever or not. You don't want to have
Speaker 1: to wait a very long time for that change in
Speaker 1: temperature to UH to happen within the mercury inside that thermometer.
Speaker 1: So that's why that bulb is small. It's just a
Speaker 1: small amount of liquid. Doesn't change take very long for
Speaker 1: that change in temperature to move through the liquid, and
Speaker 1: thus the volume increases inside the the thermometer. UH. With weather,
Speaker 1: it means you you'd want something that will remain liquid
Speaker 1: at temperatures found across most of the planet, which is
Speaker 1: why we use mercury. Mercury is a metal. It is
Speaker 1: a metal that is liquid at room temperature and a
Speaker 1: lot of temperatures that you will find on Earth. Very
Speaker 1: useful in that sense, it's not going to boil away
Speaker 1: rapidly at high a temperatures, nor does it freeze at
Speaker 1: your typical low temperatures. When you get two very low,
Speaker 1: which does happen on Earth, mercury will free So it's
Speaker 1: not perfect, but it's reliable and it's easy to read
Speaker 1: the differences. It's um it shows up well in a
Speaker 1: glass thermometer, and as it turns out, uh, mercury liquid
Speaker 1: mercury is is pretty reliable. It remains liquid at temperatures
Speaker 1: that range from six D seventy four degrees fahrenheit, which
Speaker 1: is three D fifty six point seventy three degrees celsius,
Speaker 1: all the way down to its freezing point of minus
Speaker 1: thirty eight fahrenheit or minus thirty eight point eight three celsius.
Speaker 1: But hey, here's a fun fact. The most extreme cold
Speaker 1: temperatures on Earth get way below minus thirty eight celsius.
Speaker 1: In fact, in NASA released satellite data that measured the
Speaker 1: lowest recorded temperature at minus ninety four point seven celsius,
Speaker 1: which is minus one thirty five point eight fahrenheit. At
Speaker 1: that temperature, mercury itself would freeze. So for very low
Speaker 1: temperatures you cannot use a mercury thermometer. You just you're
Speaker 1: not gonna it's gonna be as cold as it gets.
Speaker 1: It's already frozen. It's a solid, so you actually have
Speaker 1: to use a different kind of liquid. If you want
Speaker 1: to use a liquid thermometer, alcohol works. Uh. They call
Speaker 1: them spirit thermometers in the old days because you're talking
Speaker 1: about spirits alcohol. Alcohol is a very low freezing point,
Speaker 1: and it's boiling point, however, is much lower than mercury,
Speaker 1: so you can't use it for very high temperature things,
Speaker 1: you know, but it works great for low temperature applications.
Speaker 1: And uh, this actually leads me to an interesting question
Speaker 1: that I think is fun to tackle, even though it's
Speaker 1: not not quite as technical. How did we come up
Speaker 1: with the fahrenheit and celsius scales? Well, it all has
Speaker 1: to do with the freezing and boiling points of water,
Speaker 1: which makes sense. Water is very prevalent here on Earth.
Speaker 1: Most of our surface of our planet is covered in water.
Speaker 1: We depend upon water for our survival, so the temperatures
Speaker 1: at which water will freeze or boil are obviously important
Speaker 1: to us. So fahrenheit will start with that because that
Speaker 1: scale was proposed first. That came from Daniel Danny Boy
Speaker 1: fahrenheit in fourteen and as far as I know, no
Speaker 1: one else called him Danny Boy, but I'm waiting for
Speaker 1: it to catch On fourteen, he decided to use a
Speaker 1: scale designed actually by a predecessor of his. It was
Speaker 1: not it was not completely invented by Fahrenheit. He took
Speaker 1: a scale that was made by a man named Olaus Rummer.
Speaker 1: Rummer's thermometer listed zero as the lowest point. That was
Speaker 1: not the freezing point, but it was as low as
Speaker 1: the thermometer could register. Was zero and at seven point
Speaker 1: five on Rumors scale, that's where I would melt into water,
Speaker 1: or if you prefer where water would freeze into ice.
Speaker 1: It is the freezing point or melting point, depending upon
Speaker 1: your perspective. That was seven and a half on or
Speaker 1: scale at twenty two and a half that was considered
Speaker 1: body temperature, and sixty was the temperature for boiling water.
Speaker 1: So it went from zero to sixty with boiling water
Speaker 1: being at the top and freezing being at about seven
Speaker 1: and a half fahrenheit to create a mercury thermometer, and
Speaker 1: it was capable of making more precise measurements than the
Speaker 1: the spirit thermometer that Rumor had been using. And because
Speaker 1: of that precision, since you could measure smaller changes in temperature,
Speaker 1: fair Kneit felt that there needed to be a scale
Speaker 1: that would be broader than than Rumor's scale so that
Speaker 1: you could easily talk about tiny changes in temperature. Right,
Speaker 1: it's just getting an extra level of precision in there,
Speaker 1: and it means that you don't have to subdivide those
Speaker 1: units into further and further decimal points in order to
Speaker 1: describe the differences of temperature changes. So Fahrenheit ended up
Speaker 1: first taking rumor scale and he multiplied it by four. Uh.
Speaker 1: He then adjusted the scale. He started doing some research
Speaker 1: and realized that just multiplying it by four it meant
Speaker 1: that it wasn't as accurate as it needed to be.
Speaker 1: He had more levels of precision, but the accuracy was off.
Speaker 1: Multiplying it by four it multiplied not just the scale
Speaker 1: but also the imprecision of that original scale. So he
Speaker 1: started to try and refine it. Fahrenheit ended up after
Speaker 1: he passed away, people took his scale and began to
Speaker 1: refine it more, and they began to establish the freezing
Speaker 1: point and boiling point of water, and decided to set
Speaker 1: the freezing point and boiling point apart by one eighty degrees,
Speaker 1: which is important in math, but not so great for
Speaker 1: just casual conversation, So some people would say it was
Speaker 1: kind of an arbitrary decision to make it a one
Speaker 1: degree difference between freezing and boiling. The temperature of freezing
Speaker 1: water was eventually established as thirty two degrees, which means
Speaker 1: boiling water would be two hundred twelve degrees. One benefit
Speaker 1: of the scale was that the units would allow for
Speaker 1: subtle descriptions of temperature changes without the need for decimals.
Speaker 1: So if you were to describe the temperature as rising
Speaker 1: from eighty six to eighty seven in fahrenheit, that's easy.
Speaker 1: But if you wanted to say the same thing in celsius,
Speaker 1: to take those same two temperatures and talk about that increase,
Speaker 1: you'd say it went from thirty degrees celsius to thirty
Speaker 1: point six degrees celsius, or so if you said thirty
Speaker 1: one celsius, you're not being as precise because that's a
Speaker 1: greater change in temperature than what you're actually referring to.
Speaker 1: Now that being at having the temperature for freezing water
Speaker 1: set at thirty two degrees is a bit frustrating, but
Speaker 1: I think I have an explanation for this. This is
Speaker 1: Jonathan's supposition corner. I kind of wish I could get
Speaker 1: Dylan to make a musical sting for this. That just
Speaker 1: sounds confusing. All right, here's here's my pitch. Why is
Speaker 1: water freezing at thirty two degrees? Why is it thirty
Speaker 1: two degrees? Why is it not zero? Why would you
Speaker 1: not start at zero for the freezing point of water?
Speaker 1: If water is the really important part on your scale,
Speaker 1: it's because it can get colder than freezing here on Earth.
Speaker 1: And so you've got fahrenheit saying, well, I want a
Speaker 1: scale that I can measure the temperature even when it's
Speaker 1: colder than freezing, because some days it is colder than freezing,
Speaker 1: so I need my scale to be able to reflect that.
Speaker 1: But how do I measure that? If I've set freezing
Speaker 1: as zero? Where do I go from there? I mean,
Speaker 1: I can't have the mercury go further down. I've got it.
Speaker 1: I'll set freezing higher up on the scale, And that
Speaker 1: way you can still describe stuff that's colder than freezing water,
Speaker 1: but not colder than what I can measure. So, uh,
Speaker 1: you set the bottom of your scale lower than the
Speaker 1: temperature for freezing. In that way, every measurement you take
Speaker 1: is a positive unit, you don't have to create negative units,
Speaker 1: So you just set your scales based at the temperature
Speaker 1: lower than what it tends to get down to. Right.
Speaker 1: So Fair Knight, say as well, doesn't often get colder
Speaker 1: than today, So today is gonna be zero, and everything
Speaker 1: above that will be fine, because how could it get
Speaker 1: colder than today? That's Jonathan's supposition, corner, y'all? All right,
Speaker 1: but what about Celsius. Celsius was the brainchild of Andres
Speaker 1: Celsius in seventy two, so a few decades after Fair
Speaker 1: and Height, he had the clever idea of creating a
Speaker 1: temperature scale where the freezing and boiling points of water
Speaker 1: would be separated by one hundred degrees, making it much
Speaker 1: easier to talk about, especially for mathematic uh purposes. So
Speaker 1: zero to one, taking that simple decimal scale, it makes sense, uh,
Speaker 1: Although originally he intended to make one hundred the freezing
Speaker 1: point of water and zero the boiling point of water,
Speaker 1: so in other words, the scale was inverted. The higher
Speaker 1: the unit number, the lower the temperature would be. So
Speaker 1: really he was creating a scale to measure cold, not heat.
Speaker 1: So a one hundred degrees Celsius in the original implementation
Speaker 1: would be freezing temperatures, whereas a zero degrees celsius in
Speaker 1: the original implementation would be boiling water. Guests arguing that
Speaker 1: why would you ever get hotter than boiling water? Maybe Uh,
Speaker 1: this did not stick obviously. His contemporaries ended up deciding
Speaker 1: that that was not logical and perhaps a bit whacka noodle,
Speaker 1: and so they flipped it so that zero is freezing
Speaker 1: on is boiling. Uh. Celsius did not live to see
Speaker 1: his his his standard became a standard. It was not
Speaker 1: a standard during his lifetime. He actually passed away only
Speaker 1: a couple of years after proposing it, so he did
Speaker 1: not get to see how it was adopted by almost
Speaker 1: the entire world, with the exception of some notable places
Speaker 1: such as the United States of America, where we still
Speaker 1: use fahrenheit and not celsius. Although I still like fahrenheit
Speaker 1: because it is easier to talk about more subtle changes
Speaker 1: in temperature than it is with celsius. Also, I just
Speaker 1: grew up with it, so at this point it's hard
Speaker 1: for me to sit there and think, like, if someone
Speaker 1: tells me it's twenty five degrees celsius, I have no real,
Speaker 1: no real correlation of that in my brain. Like I
Speaker 1: couldn't tell you how warm or cold twenty five degrees
Speaker 1: celsius is um but if you tell me that it's
Speaker 1: eighty nine degrees fahrenheit, I know how hot you're talking.
Speaker 1: So you know fun times. But what if you wanted
Speaker 1: to convert fare kneit to celsius and you don't have
Speaker 1: access to Google, which makes it really easy to do
Speaker 1: and how I did it whenever I needed to make conversions.
Speaker 1: Let's say that you want to do a conversion of
Speaker 1: fahrenheit to celsius, but you don't have access to a
Speaker 1: temperature calculator. Well, you just follow this handy dandy guide.
Speaker 1: You take your fahreneit temperature, you subtract thirty two from
Speaker 1: that temperature. Then you multiply your new number by the
Speaker 1: number five. Then you divide that new number by the
Speaker 1: number nine. Now you know what temperature it was half
Speaker 1: an hour ago before you had to deal with all
Speaker 1: that math. It's a joke. I'm a liberal arts major,
Speaker 1: so make a lot of jokes about being bad at math.
Speaker 1: They're mostly jokes, there's some truth to them. Honestly, I
Speaker 1: don't think anyone really knows how math works. That's also
Speaker 1: a joke. These days, more thermometers are actually electronic. They're
Speaker 1: not based upon some liquid moving up or down a tube.
Speaker 1: Based on changes in temperature, they end up using thermo resistors,
Speaker 1: or sometimes they're just called thermistors. That's also not a joke.
Speaker 1: They really are called that. These are materials they experience
Speaker 1: a change in electrical resistance due to temperature fluctuation. So remember,
Speaker 1: electrical resistance is the tendency of a material to resist
Speaker 1: or impede the flow of electrons through that material. If
Speaker 1: you have a material that has a very low resistance
Speaker 1: like copper, those are good conductors. Metals that have our
Speaker 1: materials rather that have a very high resistance like rubber
Speaker 1: are really good insulators. And temperature turns out can affect
Speaker 1: some materials with their electrical resistance, which means that at
Speaker 1: certain temperatures electricity may pass more easily through that material
Speaker 1: than at other temperatures. So that is the basis for
Speaker 1: electronic thermometers. The most common thermistors have a resistance that
Speaker 1: decreases as temperatures increase. In other words, they become more
Speaker 1: conductive the warmer it gets. This is called a negative
Speaker 1: temperature coefficient or NTC thermistor because it's this uh see
Speaker 1: saw kind of relationship, right, the temperature increases, resistance decreases.
Speaker 1: There are also some that have a resistance that increases
Speaker 1: with temperature. These are called positive temperature coefficient or PTC
Speaker 1: therm mists. So with these, as the temperature goes up
Speaker 1: in the material, so does its electrical resistance. But most
Speaker 1: electronic thermometers use NTC therm mists. The relationship between temperature
Speaker 1: change and variation resistance is not a constant, so you
Speaker 1: cannot say that resistance changes by the same amount of ohms.
Speaker 1: Those are the units we use to measure electrical resistance.
Speaker 1: But you can't say that it's gonna change by the
Speaker 1: same number of ohm's per degree of celsius. So if
Speaker 1: you go from twenty three to twenty four degrees celsius
Speaker 1: and then twenty four to twenty five degrees celsius and
Speaker 1: twenty five to twenty six degrees celsius, the difference in
Speaker 1: resistance by ohms is not going to be linear in
Speaker 1: relation to those changes in temperature. Typically, thermistor resistance varies
Speaker 1: in a nonlinear way, but in a way that you
Speaker 1: can still factor by using a formula, So you have
Speaker 1: to design a formula that takes all of this into
Speaker 1: account in order for you to relay a change in
Speaker 1: resistance as being a change in temperature. So an electronic
Speaker 1: thermometers microprocessor detects and measures these changes in resistance, takes
Speaker 1: that formula into account, converts those measurements into temperature units.
Speaker 1: Their mists are also used in other applications as well,
Speaker 1: so you might use one to protect a circuit from
Speaker 1: electrical overload. You've got electricity running through a circuit. A
Speaker 1: current is running through the circuit. Let's say that the
Speaker 1: current increases uh to a point where it's going to
Speaker 1: cause issues with the circuit if it continues on this path.
Speaker 1: If you have a thermistor positive a PTC thermistor in
Speaker 1: that circuit, then as it warms up, its resistance will increase.
Speaker 1: So current runs through the thermistor that makes it generate
Speaker 1: heat that ends up changing its electrical resistance, and eventually
Speaker 1: it ends up becoming a barrier to current, so that
Speaker 1: the current cannot continue to flow through the circuit, and
Speaker 1: thus the thermistor will end up protecting the rest of
Speaker 1: the circuit from electrical overload. So that's one potential application
Speaker 1: of a thermistor outside of electronic thermometers. I thought it
Speaker 1: was pretty nifty. Well, I've got more nifty things to say,
Speaker 1: and we're going to move away from temperature. But before
Speaker 1: I do that, let's take a quick break to thank
Speaker 1: our sponsor. All Right, so we've covered temperature. Now let's
Speaker 1: tackle our next sensor, the barometer. Barometers measure air pressure,
Speaker 1: and as I mentioned in that last episode about whether
Speaker 1: air pressure plays an enormous role in how weather behaves.
Speaker 1: So knowing the current air pressure conditions helps meteorologists understand
Speaker 1: what might happen next. So, for example, if your area
Speaker 1: happens to be under high air pressure, that's an indicator
Speaker 1: that you're not likely to see very much rain that day.
Speaker 1: High air pressure systems tend to keep rain systems out. Typically,
Speaker 1: if the pressure is starting to drop, so you're seeing
Speaker 1: a change in air pressure, that could indicate that it's
Speaker 1: going to get windy. It might possibly indicate that there's
Speaker 1: some wet weather on the way because a low pressure
Speaker 1: system is moving into what was a high pressure system.
Speaker 1: But you have to have something to measure that air
Speaker 1: pressure changes. An air pressure at any given altitude are
Speaker 1: typically too subtle for humans to really pick up on. Right, Like,
Speaker 1: if I'm at sea level, I'm not likely to detect
Speaker 1: very subtle changes in air pressure, but I would notice
Speaker 1: the difference if I were to go from say, Death
Speaker 1: Valley to Mount Everest. Those changes in altitude are so
Speaker 1: dramatic that the differences an air pressure would be noticeable
Speaker 1: and actually a fatal problem. On Mount Everest, I wouldn't
Speaker 1: be able to adjust to that remarkable drop an air pressure,
Speaker 1: not to mention temperature, uh that rapidly. I would need
Speaker 1: to acclimate to it to avoid getting sick and potentially
Speaker 1: having a really fatal problems. So, yes, you can detect
Speaker 1: differences an air pressure, but typically if you're at a
Speaker 1: single altitude, you're not moving up or down. You're just
Speaker 1: experiencing changes in air pressure due to pressure systems. You
Speaker 1: probably aren't going to be conscious of that change in
Speaker 1: air pressure because it's it tends to be fairly subtle,
Speaker 1: even though it can mean some major changes in weather.
Speaker 1: Barometers measure air pressure. They detect how much air is
Speaker 1: pressing down on them, so in a way, it's kind
Speaker 1: of like a set of scales for the atmosphere. So
Speaker 1: how do you do that? How do you make something
Speaker 1: that can actually detect how much air is pushing down
Speaker 1: on them? Well, the simplest type really is called a
Speaker 1: Tori Chilian barometer, and it's named after its inventor, Evangelista Barometer. No,
Speaker 1: I'm sorry, wait, Evangelista Toricelli. He was an Italian physicist
Speaker 1: and a mathematician of the seventeen century. Torchelli is one
Speaker 1: of the mathematicians who laid the groundwork for integral calculus,
Speaker 1: but I'm not going to hold that against him. Toward
Speaker 1: Chelli worked with Galileo who gave tor Chelly the idea
Speaker 1: that he should experiment with glass tubes and mercury to
Speaker 1: study things like vacuums as well as other physical properties.
Speaker 1: And this was in sixteen three. So tore Chelly took
Speaker 1: a tube that was four ft long or about one
Speaker 1: point two meters. It was sealed at one end, so
Speaker 1: think of like a test tube. He filled it with
Speaker 1: liquid mercury, and then he overtook, turned the tube and
Speaker 1: put the end of it in a dish that had
Speaker 1: raised sides. So at first mercury started to come out
Speaker 1: of the tube and into the dish, but eventually the
Speaker 1: mercury settled and it was at a level above the dish.
Speaker 1: It was, you know, like several inches above where the
Speaker 1: base of the dish was above the level of the
Speaker 1: rest of the mercury. And he thought, uh, that's kind
Speaker 1: of interesting. The mercury did not sink all the way
Speaker 1: down to the level of the dish. It actually remained
Speaker 1: up quite a bit. And the area behind the mercury
Speaker 1: at the top of the tube, so near the sealed end,
Speaker 1: that was a vacuum. He had created a vacuum in
Speaker 1: this way. There was nothing, no air in that part
Speaker 1: of the tube. Then he noted that the mercury's level
Speaker 1: would change day to day, and some days the mercury
Speaker 1: would actually end up being higher in the tube than
Speaker 1: it was the day before. So this meant the mercury
Speaker 1: wasn't just leaking out. Right. If you kept coming out
Speaker 1: day after day and the mercury level is getting gradually
Speaker 1: lower every single day, your conclusion might be this mercury
Speaker 1: is very gradually leaking out of the tube into the dish.
Speaker 1: But if you come back one day and the mercury
Speaker 1: is actually higher up in the tube than it was
Speaker 1: the day before, something else has to be happening. It
Speaker 1: can't just be leaking out. So towards Shelly figured that
Speaker 1: atmospheric pressure was the reason for the changes in the
Speaker 1: height of the mercury in the tube. On high pressure days,
Speaker 1: when the air is pressing down harder because there's essentially
Speaker 1: more dense air above you, then it ends up pressing
Speaker 1: down on the mercury in the dish, which forces mercury
Speaker 1: up the tube. Because again, the mercury that's in the
Speaker 1: tube with the vacuum in it, it's not being affected
Speaker 1: by the changes in air pressure. It's only the mercury
Speaker 1: that's in the dish that gets that effect. On low
Speaker 1: pressure days, there's not as much air pressing down against
Speaker 1: the mercury in the dish, and so more of it
Speaker 1: starts to come out of the tube into the dish itself.
Speaker 1: So he never actually published his findings on this. Despite
Speaker 1: the fact that this was a really remarkable discovery, he
Speaker 1: wasn't really concerned with it. He didn't think of it
Speaker 1: as being particularly important, particularly in regards with his interest
Speaker 1: in advancing mathematics toward Chilian barometers tend to use mercury
Speaker 1: instead of other liquids, but it's not because of temperature.
Speaker 1: Way thermometers are you don't necessarily worry about your barometer
Speaker 1: overheating or freezing. It's because mercury is more dense than
Speaker 1: water is, so you could create a barometer using water.
Speaker 1: In fact, there were barometers that used water that predate
Speaker 1: the tour Chilian barometers. But the problem is that water's
Speaker 1: density is so much less that you need a much
Speaker 1: longer tube to be able to see that the changes.
Speaker 1: Otherwise you're gonna max out very early on because water
Speaker 1: is less dense, right, it doesn't take as much pressure
Speaker 1: to force water up a tube, so you have to
Speaker 1: have much longer tube in order to be able to
Speaker 1: to see these changes. Uh and it means that it
Speaker 1: would be very difficult to take measurements, so mercury being
Speaker 1: more dense made more sense. Also, it was very easy
Speaker 1: to read it inside the barometer because again you're using
Speaker 1: clear glass. Mercury is a silvery liquid, so it was
Speaker 1: very easy to read the changes in the levels in
Speaker 1: uh torre Chelian barometer. Now, at at sea level under
Speaker 1: normal circumstances, under one atmosphere of pressure, mercury would rise
Speaker 1: up to about the seventy six centimeter or thirty mark
Speaker 1: in a torrey Chellian barometer, and while changes in air
Speaker 1: pressure will be measurable with such a barometer, you wouldn't
Speaker 1: see dramatic differences in the height of the mercury unless
Speaker 1: you were to take the whole thing to a mountaintop
Speaker 1: or something. So in other words, you could watch the
Speaker 1: mercury in the barometer and it could very accurately and
Speaker 1: with great precision, show you the changes in barometric pressure.
Speaker 1: But those changes wouldn't necessarily be really dramatic because you're
Speaker 1: talking about again the same altitude. Were you to take
Speaker 1: a mercury barometer at Death Valley and then magically transport
Speaker 1: yourself to Mount Everest, you would see a very dramatic
Speaker 1: change in the height of the mercury in that barometer. Now,
Speaker 1: maybe you've seen barometers that haven't entical dial that either
Speaker 1: turns left or right along a semicircular scale that tells
Speaker 1: you what the barometric pressure is. So how did those work? Well,
Speaker 1: these are called aneroid barometers, and they're pretty clever. Inside
Speaker 1: of these, there's a sealed, air tight metal box, and
Speaker 1: attached to that metal box is a spring. Now, when
Speaker 1: the air pressure is high, it compresses this metal box,
Speaker 1: and that ends up pulling on the string on the
Speaker 1: spring rather, which then creates the force necessary to move
Speaker 1: the dial, so it indicates a high pressure system is
Speaker 1: moved in and low pressure the little metal box. The
Speaker 1: air type metal metal box expands and this ends up
Speaker 1: pushing against the spring, which means that the dial will
Speaker 1: move toward the other side, showing a low pressure uh
Speaker 1: system has moved in. So the dial turning to the
Speaker 1: left or right is all dependent upon whether or not
Speaker 1: this metal box is compressed or expanded. It's actually incredibly
Speaker 1: simple when you think about it, and thus I think
Speaker 1: a pretty elegant way of measuring air pressure. Mercury barometers
Speaker 1: are more accurate than aneroid barometers, but there's a disadvantage
Speaker 1: to mercury barometers, which is that stuff's poison. Y'all, mercury
Speaker 1: is toxic, so aneroid barometers are safer to have around.
Speaker 1: They also are more portable, so you could put them
Speaker 1: on stuff like sailing ships and not have to worry
Speaker 1: about mercury spilling out all over the place because they
Speaker 1: were mechanical didn't depend upon mercury at all. But if
Speaker 1: you wanted something that had more precision and accuracy. You
Speaker 1: wanted a mercury barometer, not an aneroid barometer. Uh. However,
Speaker 1: we can go with microelectronics too. We don't have to
Speaker 1: use mercury or anneroid, although the microelectronics version uses a
Speaker 1: very similar approach to aneroid barometers. So we do have
Speaker 1: barometric pressure sensors which rely on the piezo resistant of effect. Now,
Speaker 1: this is kind of similar to what we were talking
Speaker 1: about with thermistors, only in this case we're not talking
Speaker 1: about temperature. We're talking about stuff that's under pressure. Do
Speaker 1: you remember that has that same baseline as ice ice baby? Anyway,
Speaker 1: you may have heard about the piezo electric effect, right.
Speaker 1: Piezo electric effect refers to the tendency of certain materials
Speaker 1: um certain types of crystals in particular like quartz, that
Speaker 1: when you put a mechanical stress on those materials, such
Speaker 1: as you mush mush mushed them up in some way,
Speaker 1: these materials would generate an electric charge or there's a
Speaker 1: reverse piece of electric effect. If you were to subject
Speaker 1: these materials to an applied electric field, they would produce
Speaker 1: a mechanical force like they vibrate and stuff. The crystal
Speaker 1: courts are the quartz crystals. I guess I should say
Speaker 1: in old watches. That's why they're used. It's has this
Speaker 1: piezo electric effect. Piezo resistive materials are similar to that,
Speaker 1: except that, as you would expect, their electrical resistance changes
Speaker 1: as mechanical force applied to them changes. So typically you'd
Speaker 1: put this piezo resistive material around a hermetically sealed cavity
Speaker 1: similar to what you'd find in an aneroid barometer. So
Speaker 1: you have this little area that you have hermetically sealed
Speaker 1: and it's lined with this piezo resistive material, and as
Speaker 1: the cavity reacts to changes in the air pressure, it
Speaker 1: places mechanical stresses on the piezo resistive material inside, and
Speaker 1: that again changes its electrical resistance. A microprocessor will measure
Speaker 1: fluctuations in current passing through this piezo resistive material and
Speaker 1: then convert those changes in current into a digital signal
Speaker 1: that can be used to approximate pressure. All right, So
Speaker 1: now we've got temperature and air pressure out of the way,
Speaker 1: two of the big ones. But man, there's so much more.
Speaker 1: So I'm gonna try and summarize some of the other
Speaker 1: many sensors that are used by meteorological observation stations UH
Speaker 1: today in order to gather information about the weather. But
Speaker 1: I am going to summarize because otherwise this episode is
Speaker 1: gonna last six hours long, and I got stuff to do, y'all.
Speaker 1: So let's get another basic measurement out of the way,
Speaker 1: and that would be wind, something I generate a lot
Speaker 1: of from multiple ends. As it turns out, you want
Speaker 1: to know where wind is coming from, and you want
Speaker 1: to know how strong the wind is because this will
Speaker 1: inform lots of other stuff like incoming changes to weather
Speaker 1: such as storms, et cetera. For wind direction, we use
Speaker 1: something that's been around for hundreds of years, weather vain.
Speaker 1: We have lots of fancy ones today, but they all
Speaker 1: are still working on the same general principle. I mean,
Speaker 1: you can use more high tech ways to detect wind direction,
Speaker 1: but it's really not necessary. So whether veins typically consist
Speaker 1: of a counterweight on one end of a rotating UH
Speaker 1: peace on the weather vein. On the other end, you
Speaker 1: have some sort of thin that is covering a much
Speaker 1: larger area than the counterweight is. So when wind blows,
Speaker 1: it hits against the fin the weather vein because this
Speaker 1: part of it can rotate freely along its axis. UH.
Speaker 1: In the horizontal plane, it will rotate so that the
Speaker 1: area being hit by the wind is facing away from
Speaker 1: the wind. The counterweight will point into the wind. Often
Speaker 1: the counterweight is in the form of an arrow, so
Speaker 1: it might be the point of an arrow, and the
Speaker 1: back may look like the fletching of an arrow, and
Speaker 1: this tells you where the wind is coming from. So
Speaker 1: if you have a traditional weather vein and the arrow
Speaker 1: is pointing northeast, that tells you wind is coming from
Speaker 1: the northeast. It is not blowing to the northeast. It
Speaker 1: it's coming from the northeast. The counterweight is needed so
Speaker 1: that there's equal mass on either ends of this rotating
Speaker 1: part of the weather vein. But you also want to
Speaker 1: make sure that there is an unequal area. In other words,
Speaker 1: the back half of the weather vein of that rotating
Speaker 1: piece needs to have more area to it so that
Speaker 1: the wind pushes it in the right way. You want
Speaker 1: more area on one side so that you can get
Speaker 1: that into the right position, and that indicates where the
Speaker 1: wind is coming from. UH. Once you look at where
Speaker 1: the counterweight is, wind direction can give you a general
Speaker 1: idea of what sort of weather you might encounter based
Speaker 1: upon what's going on in that direction. So let's say
Speaker 1: that you are in Georgia, the state that's where I'm in,
Speaker 1: and you are in the winter, and you see that
Speaker 1: the wind is coming from the northwest. You're looking at
Speaker 1: a weather vein, it's pointing to the northwest. That's where
Speaker 1: winds are coming from. And you happen to know that
Speaker 1: there's a cold air mass that was moving down from
Speaker 1: Canada through the United States. So you would say, well,
Speaker 1: based upon the fact that wind is coming from the northwest,
Speaker 1: that's the direction where if you were to go that way,
Speaker 1: you hit Canada. And I happen to know that there's
Speaker 1: a cold air mass moving down. I suspect that means
Speaker 1: that pretty soon our temperatures are going to drop further
Speaker 1: and we're going to get what is called the Devil's
Speaker 1: dan droff down here in Georgia. Thank you, Saturday Night Live.
Speaker 1: Most people know it as snow. We know it as
Speaker 1: the stuff what shuts down our entire infrastructure at a
Speaker 1: given heartbeat. Anyway, that's why wind direction is important, because
Speaker 1: if you know what's going on elsewhere, then you can
Speaker 1: and you know that the wind is coming from that
Speaker 1: direction you, you can expect to get some of it yourself.
Speaker 1: By the way, if you hear that winds are let's say, northeasterly,
Speaker 1: that tells you where the winds are coming from, that
Speaker 1: they're coming from the northeast. But if you hear the
Speaker 1: suffix ward ended at the end of a direction, that
Speaker 1: tells you the direction the winds are blowing toward, So
Speaker 1: an eastward wind or eastward wind if you prefer, I
Speaker 1: don't eastward wind that means winds are blowing to the east,
Speaker 1: and easterly wind means winds are blowing from the east,
Speaker 1: clear as mud, right. But wind direction is just one thing.
Speaker 1: It's also useful to know wind speed. Now. Traditionally wind
Speaker 1: speed was measured in knots or nautical miles per hour.
Speaker 1: But was it not? I'll tell you, but not right now.
Speaker 1: I'll tell you after we take another quick break to
Speaker 1: thank our sponsors. So you want to measure wind speed
Speaker 1: wind speed, you would measure and knots. Knots stands for
Speaker 1: a nautical mile, although it's spelled like a knot like
Speaker 1: you would tie and a thread. A nautical mile is
Speaker 1: equal to one point one five miles per hour or
Speaker 1: one point nine kilometers per hour. So if you hear
Speaker 1: there's a northeasterly wind blowing at fifteen knots, you know
Speaker 1: that the wind is coming from the northeast, and you
Speaker 1: know that it's blowing at seventeen point to five miles
Speaker 1: per hour or twenty eight and a half kilometers per hour.
Speaker 1: But how do you determine wind speed? How do you
Speaker 1: know how fast the wind is blowing? Well, meteorologists use
Speaker 1: an instrument called an anemometer. The old anemometers had moving
Speaker 1: parts in them that made them sort of look like
Speaker 1: pin wheels. Uh. They had arms extending out from a hub,
Speaker 1: with each arm ending in a little cup to catch
Speaker 1: the wind, and then they would rotate along their axis
Speaker 1: on the horizontal plane. So think of like a windmill,
Speaker 1: but on its side, so it's the fans are not
Speaker 1: standing up vertically, they're spread out horizontally and instead of
Speaker 1: it being ends or fins, some some of them were,
Speaker 1: but most of them ended with these cups that would
Speaker 1: catch the wind. So the wind would blow and force
Speaker 1: the hub to rotate along its axis in that horizontal plane.
Speaker 1: And then it just depended on the type of anemometer
Speaker 1: you're looking at. A lot of them worked in a
Speaker 1: very similar way to an electric generator. So you might
Speaker 1: remember this from our discussion about the history of electricity.
Speaker 1: It's based on electro magnetism. If you have a magnet
Speaker 1: and you turn it and it's surrounded by a conductive material,
Speaker 1: or it's itself around a conductive material like a coil
Speaker 1: of insulated copper wire, it will induce current to flow
Speaker 1: through that conductor. Right. That's the basis of the electric generator.
Speaker 1: So let's say you've got this spinning anemometer and it's
Speaker 1: turning a magnet around a conductive material, and this creates
Speaker 1: a current flowing through that duct of material. You have
Speaker 1: then a electronic circuit that's specifically designed to measure how
Speaker 1: much current has been produced and then converts that to
Speaker 1: a digital readout that indicates wind speed. So you calibrate it.
Speaker 1: You first have to calibrate this device so that it
Speaker 1: quote unquote knows how much current relates to which you
Speaker 1: know what the wind speed is. But once you've calibrated it,
Speaker 1: that's how you can measure wind speed. You just look
Speaker 1: at how much electric current is generated in one of
Speaker 1: these devices. And now there are also other anemometers that
Speaker 1: do not use this approach, they don't resemble an electric
Speaker 1: generator in that way. They instead will count the number
Speaker 1: of rotations of the cups within a given amount of
Speaker 1: time in order to convert that to a wind speed.
Speaker 1: So you might look at how many times per minute
Speaker 1: did this rotate based upon the you know, the speed
Speaker 1: of the wind, we're going to say that that means
Speaker 1: it's blah blah blah. Typically these anemometers have a simple
Speaker 1: switch that gets activated upon each rotation, and the switch
Speaker 1: makes a notation, and you just look at the number
Speaker 1: of notations per minute or per whatever unit of time
Speaker 1: you're using to measure, and you convert that information over
Speaker 1: to create the figure for miles per hour or knots
Speaker 1: of wind speed. Or you could have a light sensor,
Speaker 1: so imagine an anemometer. It still is one of these
Speaker 1: pinwheel like devices. It's still spinning in the horizontal plane,
Speaker 1: but it has a little disc that can cover up
Speaker 1: a hole that otherwise leads down to a light sensor.
Speaker 1: When the anemometer rotates, this disc ends up being pulled
Speaker 1: away from the sensor so light can hit it, and
Speaker 1: then as it continues to rotate, it covers the sensor. Again,
Speaker 1: it just does the circular path where it is covering
Speaker 1: and uncovering the sensor. Doing this, the sensor counts the
Speaker 1: number of times that light is hitting the sensor. It's
Speaker 1: very similar to that other electronic switch I was just
Speaker 1: talking about. And again it makes a notation. And again
Speaker 1: you just look at the number of notations per unit
Speaker 1: of time and you use that to convert it over
Speaker 1: two miles per hour for wind speed. But that's not all.
Speaker 1: You don't even have to have a rotating element at
Speaker 1: all to calculate wind speed these days, because you can
Speaker 1: use what are called sonic anemometers. Now these are more
Speaker 1: or less the standard for a lot of observation uh
Speaker 1: points these days. For meteorological observations, they use ultrasonic signal
Speaker 1: emitters and receivers mounted at right angles to each other.
Speaker 1: So from the top it might look like a square.
Speaker 1: You have receivers and transmitters that are mounted in a
Speaker 1: square in relation to one another. And it's it's important
Speaker 1: to remember sound as physical phenomenon, right. Sound is all
Speaker 1: about molecules bashing into each other, vibrations spreading across a medium.
Speaker 1: So when we're hearing things, we're hearing the sense of
Speaker 1: hearing is all based upon air moving, vibrating at oscillating
Speaker 1: at the speed of whatever caused it to move in
Speaker 1: the first place, and it continues to make other air
Speaker 1: molecules do this same thing until some of them end
Speaker 1: up hitting the ear drums in our ears, which transfers
Speaker 1: this uh this vibration to some very tiny bones in
Speaker 1: our ears in our ears, which then transmit that vibration
Speaker 1: to the cochlea, which ultimately interprets this as sound. That's
Speaker 1: how how we perceive it. But that means that sound
Speaker 1: itself is a physical thing, and you can affect it
Speaker 1: by changing things in the air, like if wind is blowing,
Speaker 1: it affects how sound travels. And if you've ever tried
Speaker 1: to talk to someone on a windy day, then you've
Speaker 1: probably experienced this at least a little bit. So the
Speaker 1: way these ultrasonic wind anemometers work is that they transmit
Speaker 1: signals at an ultrasonic frequency. It's too high for humans
Speaker 1: to hear, but the receivers can pick up on it.
Speaker 1: When wind is blowing, it's going to affect the timing
Speaker 1: of when a transmission is sent out and when it
Speaker 1: gets received by the other side this timing. It's super
Speaker 1: super subtle. Uh, It's not like it's something that we
Speaker 1: humans could detect, but these instruments can detect it, and
Speaker 1: by detecting those changes, it can convert that into an
Speaker 1: interpretation of how fast the wind is blowing. It's really
Speaker 1: the difference that the it took for the sound to
Speaker 1: get from its point of origin to its destination impaired
Speaker 1: against what it normally would take under still conditions with
Speaker 1: no wind present. If you ever look at technical readouts
Speaker 1: of wind speed and direction, you might notice that there's
Speaker 1: a lot of symbols that are used. Typically, you would
Speaker 1: see what's called wind barbs. So first you start with
Speaker 1: two lines representing north, south and east west in a
Speaker 1: crosshair layout, you know, your typical north southeast west compass
Speaker 1: rose sort of thing. And from the center, you would
Speaker 1: have a line that would extend out towards the direction
Speaker 1: where wind is coming from. So let's say it's coming
Speaker 1: from the northwest. This line would extend out halfway between
Speaker 1: north and west. If it was truly coming from the northwest.
Speaker 1: From that line, you might notice one or more short barbs,
Speaker 1: or even what is called a pennant. It looks like
Speaker 1: a little flag at the end of it. Those barbs
Speaker 1: actually represent wind speed, and the number of barbs on
Speaker 1: there tell you how strong the wind is blowing. So
Speaker 1: a line that has in short barb extending from it
Speaker 1: indicates calm winds that approximately five knots. If you have
Speaker 1: the opposite, If you have a line with has a
Speaker 1: pennant on the end of it and two barbs extending
Speaker 1: from it out to the side, that would indicate very
Speaker 1: strong winds at like sixty five knots now. One of
Speaker 1: the simpler tools in the meteorological tool kit is the
Speaker 1: precipitation gauge. This is telling you how much precipitation has
Speaker 1: fallen over a given amount of time. Essentially, this comes
Speaker 1: down to a container designed to catch precipitation, so you
Speaker 1: can see how much has fallen in that area. Now,
Speaker 1: your basic rain gage consists of a funnel which can
Speaker 1: capture precipitation falling precipitation. It has a measuring tube that
Speaker 1: the funnel feeds into, and the measuring tube itself tends
Speaker 1: to be fairly you know, not like maybe like an
Speaker 1: inch in diameter, maybe about eight inches long. Typically, um,
Speaker 1: it's it's a tube, it's open at the top and
Speaker 1: close at the bottom. Then that itself is inside a
Speaker 1: larger collecting vessel, and the collecting vessel's mouth is the
Speaker 1: same diameter as the funnel that's at the very top,
Speaker 1: so the funnel prevents water from falling directly into the
Speaker 1: containment vessel. Instead it funnels the water into the tube
Speaker 1: that's inside the collecting vessel. The tubes are calibrated to
Speaker 1: measure the amount of rainfall based upon the diameter of
Speaker 1: that collecting vessel's mouth, so each one is very specific
Speaker 1: to the collecting vessel, and the scale that you will
Speaker 1: see on these tubes has been written out to reflect
Speaker 1: that collecting vessel. That's why if you pick up one
Speaker 1: of these measuring tubes that's using the big funnels, and
Speaker 1: you look on it and it looks like there's maybe
Speaker 1: six inches of water inside the tube, but the tube
Speaker 1: breeds that as b being uh, three quarters of an
Speaker 1: inch of rain. You're like, well, why is that? I mean,
Speaker 1: there's there's six inches of water inside the tube. How
Speaker 1: can it be three quarters of an inch of rain?
Speaker 1: It's because the funnel that's catching all that rain and
Speaker 1: funneling it down into the tube. It's a larger diameter,
Speaker 1: it's got more surface area, so more rain is hitting
Speaker 1: that funnel than would have hit the tube just on
Speaker 1: its own. Now, the reason why you have the collecting
Speaker 1: vessel there is that sometimes you get more rain than
Speaker 1: what the tube can handle. If the tube is calibrated
Speaker 1: so that it can hold up to one inch of
Speaker 1: rain compared based upon the size of the collecting vessel,
Speaker 1: it is in what happens if you get more than
Speaker 1: an inch of rain, well, water will start to overflow
Speaker 1: from the top of the tube and pour into the
Speaker 1: collecting vessel. When rain is done and you're wanting to
Speaker 1: see how much rain has fallen, you go out, you
Speaker 1: remove the funnel, you remove the tube, and you say,
Speaker 1: all right, we start with one inch of rain. Because
Speaker 1: this tube is full, that means that it rained at
Speaker 1: least an inch. You pour that out it. Then you
Speaker 1: take the water from the collecting vessel, you pour that
Speaker 1: back into the tube, and you use that to measure
Speaker 1: how much in addition to one inch has fallen. So
Speaker 1: that's the reason for the collecting vessel and for the calibration.
Speaker 1: Otherwise you would just have to keep building tubes that
Speaker 1: are taller and taller and taller, and you know, if
Speaker 1: they're narrow enough, it can give you an unrealistic account
Speaker 1: for how much rain has fallen. That's your basic rain gage.
Speaker 1: Um there there are other types of rain gages beyond
Speaker 1: the basic one. There's one called the tipping bucket rain gage.
Speaker 1: I love these. If you've ever seen fountains where there's
Speaker 1: a small container that gradually fills up with water and
Speaker 1: when it fills up to the top, it tips over,
Speaker 1: dumping all the water out into the base of the fountain,
Speaker 1: and then it tips back up again because now the
Speaker 1: water's gone, that that counterweight has gone, so the bucket
Speaker 1: returns to its normal, uh normal orientation. That's exactly the
Speaker 1: way these tipping bucket rain gage is work. They work
Speaker 1: as they have two buckets, typically on a see saw
Speaker 1: like device, so they swivel on the seesaw device as
Speaker 1: one fills up. It gets heavy enough once it reaches
Speaker 1: a certain point for it to tip, pouring its water
Speaker 1: out into a containment vessel below. The other bucket is
Speaker 1: then tilted upward to catch the water from that point
Speaker 1: forward until it fills up, and then it tilts again
Speaker 1: and dumps its water. These buckets hold a very small
Speaker 1: amount of water, typically one an inch of rain essentially,
Speaker 1: and you have a switch that is connected to this
Speaker 1: see saw like device, and every time it tilts, the
Speaker 1: switches registers it. And because it registers that, it makes
Speaker 1: a mark on the device, makes a mark on a
Speaker 1: piece of paper or otherwise activates a counter, and that
Speaker 1: tells you that an inch of rain has just been
Speaker 1: uh registered counted. And then you just add up all
Speaker 1: the different one one hundreds of an inch, and you
Speaker 1: can tell within a hundredth of an inch how much
Speaker 1: rain has fallen in that given area. There are even
Speaker 1: versions of this that are heated, where they have little
Speaker 1: heating elements, typically coils of wire that will heat up
Speaker 1: as current passes through them, and the purpose of that
Speaker 1: is so that they can measure frozen precipitation. As frozen
Speaker 1: precipitation hits the buckets, that heats up, it converts into water,
Speaker 1: and also it prevents the gauge itself from freezing over
Speaker 1: in cold weather, something that we don't get a whole
Speaker 1: lot of in my neck of the woods, but I
Speaker 1: think it's a pretty cool way of measuring rainfall. There
Speaker 1: are other types of rain gages. They are weighing gauges.
Speaker 1: Weight gauges you could say that estimate the amount of
Speaker 1: rain based upon the weight change. And UH, those are
Speaker 1: the major types of precipitation gauges. Then you have various
Speaker 1: devices that can detect electrical storms. UH. Basically what you
Speaker 1: need is an antenna. Meteorologists use thunderstorm detectors. That our
Speaker 1: antenna that registers spikes of electro magnetic radiation or lightning strikes.
Speaker 1: So if you've ever listened to a m radio during
Speaker 1: a thunderstorm, you may have noticed that there's this burst
Speaker 1: of static whenever there's a lightning strike somewhere in the area.
Speaker 1: Thunderstorm detectors pick up electrical discharges, typically within a couple
Speaker 1: of hundred miles of the detectors, so it doesn't have
Speaker 1: to be that close in order to pick up on it.
Speaker 1: It just is this little spike of electric discharge that
Speaker 1: the antenna can pick up on. Your basic system is
Speaker 1: a simple receiver. There's no transmitter, it just records it
Speaker 1: and using several of those sensors across the region will
Speaker 1: help you determine where and not just when lightning strikes.
Speaker 1: You can use triangulation using three or well really three
Speaker 1: points to figure out where did the lightning strike These
Speaker 1: three different detectors picked it up. Based on the timing
Speaker 1: of the three detections, we can say the lightning strike
Speaker 1: must have happened at these coordinates. It's a very simple
Speaker 1: way of doing it. But there are also mobile lightning
Speaker 1: detectors that you are typically would put in an aircraft.
Speaker 1: You fly a plane around a weather plane and look
Speaker 1: for these electra electric discharges. These will use attenuation signal
Speaker 1: attenuation to determine the location of lightning strikes, but that
Speaker 1: is not um not always accurate because it is dependent
Speaker 1: upon some other factors that can confound the device. But yeah,
Speaker 1: there's a couple of different ways of doing it. Other
Speaker 1: devices that meteorologists might use might include paranometers or pyranometers
Speaker 1: if you prefer um pyra to indicate heat that measures
Speaker 1: a solar radiation actually or how much sun exposure a
Speaker 1: place will receive over a given amount of time. These
Speaker 1: are also used not just for weather forecasts, but also
Speaker 1: when you want to figure out the best place to locate,
Speaker 1: say a solar panel farm, you might use a pyranometer
Speaker 1: to see how much solar radiation that area actually receives.
Speaker 1: Does it make sense to put a solar panel farm
Speaker 1: there or are you not going to maximize your efficiency
Speaker 1: if you place it there. Typically, they measure sun exposure
Speaker 1: by using thermopiles, which are sensors that generate electricity as
Speaker 1: they heat up from absorbing light. So these things absorb
Speaker 1: lots of light. They're very dark, they tend to be black.
Speaker 1: Absorbed light, they generate electricity, and then by measuring the
Speaker 1: electricity you understand how much sun exposure you got. Then
Speaker 1: there are devices called celo meters which are used to
Speaker 1: measure clouds, like the ceiling spelled like that. Celo meters
Speaker 1: they can measure cloud height and thickness. And the one
Speaker 1: I was looking at specifically does this in a pretty
Speaker 1: cool way. It shoots lasers at clouds. So the lasers
Speaker 1: hit the clouds, and then the laser lights starts to
Speaker 1: scatter as it encounters the various particles that are in
Speaker 1: clouds like water, vapor, and that kind of stuff. And
Speaker 1: then you use backscatter technology to measure that dispersal of
Speaker 1: light within the clouds. So you fire laser into the cloud.
Speaker 1: The particles in the cloud cause the laser light to
Speaker 1: scatter at different levels depending upon the density and composition
Speaker 1: of those particles, and you measure that backscattered light to
Speaker 1: allow you to define the parameters of the cloud and
Speaker 1: it's density, and even be able to tell whether or
Speaker 1: not precipitation is likely to fall because of those clouds.
Speaker 1: You've also got visibility sensors that can measure how transparent
Speaker 1: the air is, which might sound kind of silly until
Speaker 1: you remember that fog is totally a thing. Uh So
Speaker 1: these devices measure light attenuation and use backscatter technologies similar
Speaker 1: to the cealimeters I just talked about in order to
Speaker 1: measure visibility. So you can use optical sensors to measure
Speaker 1: of visibility as well, in other words, like cameras and stuff,
Speaker 1: and you can get a firsthand look at visibility, but
Speaker 1: these are looking at it on a more precise level
Speaker 1: than just does it look clear out there. Oh and
Speaker 1: Doppler radar. I can't finish this episode without talking about
Speaker 1: Doppler radar. If you've watched a weather report, you've likely
Speaker 1: heard this term bandied about when it comes to measuring
Speaker 1: rainstorm systems and their movements. So Doppler radar measures not
Speaker 1: just the presence of something but it's movement either toward
Speaker 1: or away from the radar station. So your basic radar
Speaker 1: is pretty simple. You beam out a signal in a direction.
Speaker 1: That signal encounters other stuff and bounces off of it,
Speaker 1: some of it coming back to you, and it gets
Speaker 1: to the starting location. If you look at the time
Speaker 1: between when you sent the signal out and when the
Speaker 1: signal came back, you can then use that to extrapolate
Speaker 1: how far away that thing is. And if it's stationary,
Speaker 1: then you're not going to see any difference in the
Speaker 1: frequency of the signal coming back as the one you
Speaker 1: sent out. Right, it should be pretty much identical, and
Speaker 1: you'd say, all right, there's a stationary object that's ten
Speaker 1: miles away. Godzilla is taking a nap now. Uh. You
Speaker 1: can do this, by the way, because those radio waves,
Speaker 1: the radar waves, are traveling at the speed of light
Speaker 1: right there. It's a constant speed, so you don't have
Speaker 1: to worry about anything else. You just say, well, I
Speaker 1: know how fast light travels. I know how long it
Speaker 1: took the returning wave to get back to me. Because
Speaker 1: I've got a timer. It tells me that this much
Speaker 1: time passed between transmission and receiving the echo. Then I
Speaker 1: can say, well, how far away, how far did the
Speaker 1: signal have to travel in order to get there and back? Um,
Speaker 1: And that will tell you how far away the object is.
Speaker 1: But you can also tell if the object is moving
Speaker 1: toward you or away from you, because the signals coming
Speaker 1: back to you will be affected by this. Uh. It
Speaker 1: is the Doppler effect, something that is pretty easy to
Speaker 1: encounter out in the real world, just on your own.
Speaker 1: If you've ever heard a like a police car blaring
Speaker 1: a siren and the police cars coming toward you and
Speaker 1: then it passes you, you've probably noticed that the sound
Speaker 1: of the siren changed as the police car passed you.
Speaker 1: So when the cars coming towards you, it's actually compressing
Speaker 1: those sound waves that are emitted by the siren. Uh.
Speaker 1: And because it's compressing the sound waves, UH, it means
Speaker 1: that it's increasing the frequency. It's like physically compressing, not
Speaker 1: digitally compressing. We're talking about physically compressing those waves so
Speaker 1: that the frequency is increased. That means the pitch goes up,
Speaker 1: so you hear a higher pitch noise as the cars
Speaker 1: moving away. It's along gating those sound waves, it's stretching
Speaker 1: them out which means decreasing the frequency and us decreasing
Speaker 1: the pitch, making it a lower pitch. Well, radar has
Speaker 1: the same shifts with its signals if it hits something
Speaker 1: that's moving toward it. So you've got a radar station
Speaker 1: shoots out a little radar beam. The radar beam comes
Speaker 1: back and the frequency is shorter like it's it's the
Speaker 1: or the frequency has been increased. The wavelength is shorter.
Speaker 1: That tells you that the objects moving towards you. It
Speaker 1: is compressed the length the wavelength of that of that signal.
Speaker 1: If the wavelength is longer, tells you that the object
Speaker 1: is moving away from you. That the frequency has hit
Speaker 1: the object, but the objects moving away and thus the
Speaker 1: returning waves have an elongated wavelength. So Doppler radar is
Speaker 1: very cool and that it can tell you where a
Speaker 1: storm system is and whether or not it's moving toward
Speaker 1: you or away from you. Um and you use multiple
Speaker 1: observation stations with Doppler radar to get a full picture
Speaker 1: where is the system going. You can even detect things
Speaker 1: like precipitation using Doppler radar. The cool thing about Dopper
Speaker 1: radar in my mind is that it is a lazy,
Speaker 1: lazy worker. And by that I mean in a typical hour,
Speaker 1: the Doppler radar is actively sending out signals for about
Speaker 1: seven seconds total out of the entire hour, not all
Speaker 1: at once, but if you look at an entire hour
Speaker 1: and you measure the amount of time that the Dopper
Speaker 1: radar was sending signals out, it averages to about seven seconds.
Speaker 1: It's spending the other fifty nine minutes and fifty three
Speaker 1: seconds listening, Which seems like a great job to me
Speaker 1: to work for seven seconds and then just listen for
Speaker 1: fifty nine three seconds, But I guess it depends on
Speaker 1: what you're listening to. In this case, it's listening for
Speaker 1: those echoes, those returning frequencies for the rest of the hour.
Speaker 1: And again not all in one batch, it's spread throughout
Speaker 1: the hour, but collectively we're talking fifty nine minutes fifty
Speaker 1: three seconds of listening. Uh. It is scanning the sky
Speaker 1: in a series of angles. So think of a Doppler
Speaker 1: radar like a think of like a little satellite dish,
Speaker 1: and you start off at say forty five degree angle
Speaker 1: pointed at the sky, and then you move it up
Speaker 1: to seven degrees for the next scan and so on
Speaker 1: and so forth, and it's also rotating, so it's taking
Speaker 1: scans of different levels of elevation. In fact, they call
Speaker 1: these elevation slices in the Doppler radar gang and UH
Speaker 1: it gives the system a volume coverage pattern or VCP. Now,
Speaker 1: once it goes through all of its elevation slices and
Speaker 1: all of its rotations, it completes one volume scan, and
Speaker 1: it does this every five minutes or so during precipitation
Speaker 1: mode scans. The data that comes back can then be
Speaker 1: interpreted to build out a picture of weather systems where
Speaker 1: they are moving and how quickly they are moving. And
Speaker 1: that even includes active precipitation, which is pretty cool stuff.
Speaker 1: I think now that wraps up the basic tools and
Speaker 1: sensors that meteorologists used. Not keep in mind, there are
Speaker 1: other ones I didn't talk about, satellites, which are very important.
Speaker 1: Satellites also gather a lot of data about active weather
Speaker 1: systems on the Earth, and that data gets fed into
Speaker 1: computer models or weather forecasts. UH. There are other sensors
Speaker 1: and tools as well, but I wanted to cover the
Speaker 1: ones that you would find at your typical observation station
Speaker 1: on the ground. Keeping in mind there are others, So
Speaker 1: I hope I've given you an indication of how complex
Speaker 1: this is just from the types of information alone that
Speaker 1: have to be gathered and poured into these computer models
Speaker 1: so that we can get accurate weather forecasts. In our
Speaker 1: next episode, I'll talk specifically about how those weather models
Speaker 1: are constructed and how they generate forecasts, and the different
Speaker 1: models that are out there, and why are there different models,
Speaker 1: and what are the computer systems that are actually running
Speaker 1: these simulations, why are we using supercomputers? And will we
Speaker 1: ever get a computer model so comprehensive that we'll never
Speaker 1: be surprised by the weather again. Well, we'll talk about
Speaker 1: that in our next episode. Guys, if you have suggestions
Speaker 1: for future episodes of tech Stuff, let me know, would you.
Speaker 1: You can send me an email. The address is tech
Speaker 1: stuff at how stuff works dot com, or you can
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Speaker 1: You can also drop by Twitch dot tv slash tech stuff,
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Speaker 1: the audience I have watching me right now. I record
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