1 00:00:05,480 --> 00:00:08,760 Speaker 1: Kielder. I'm Chelsea Daniels and this is a bonus episode 2 00:00:08,880 --> 00:00:12,520 Speaker 1: of The Front Page, a daily podcast presented by the 3 00:00:12,520 --> 00:00:19,640 Speaker 1: New Zealand Herald. Over the last year, the term atmospheric 4 00:00:19,800 --> 00:00:23,840 Speaker 1: river has entered our daily vocabulary as New Zealand sees 5 00:00:23,920 --> 00:00:28,360 Speaker 1: more intense rainfall hit our shores. From the Auckland Anniversary 6 00:00:28,400 --> 00:00:31,880 Speaker 1: floods to two months worth of rain heading the East 7 00:00:31,960 --> 00:00:35,239 Speaker 1: coast in just one day. The whole country seems to 8 00:00:35,240 --> 00:00:39,000 Speaker 1: be susceptible to increase rainfall. But is this really the 9 00:00:39,040 --> 00:00:42,920 Speaker 1: case and if so, what's the cause. Today on the 10 00:00:42,920 --> 00:00:47,360 Speaker 1: Front Page, doctor Daniel Kingston from Otago University joins us 11 00:00:47,640 --> 00:00:51,199 Speaker 1: to discuss their latest research into the cause and effect 12 00:00:51,400 --> 00:00:58,640 Speaker 1: of rainfall in this country. Daniel, we've heard this word 13 00:00:58,800 --> 00:01:01,920 Speaker 1: a lot in recent years, or this phrase rather, but 14 00:01:02,000 --> 00:01:05,319 Speaker 1: can you explain what our atmospheric rivers? 15 00:01:05,640 --> 00:01:08,919 Speaker 2: Well, the areas in the atmosphere where we see really strong, 16 00:01:09,000 --> 00:01:13,040 Speaker 2: really intense transport of moisture vapor through the atmosphere in 17 00:01:13,600 --> 00:01:16,760 Speaker 2: a long, thin section. So it looks a bit like 18 00:01:16,800 --> 00:01:18,720 Speaker 2: a river when you look at a weather map of this, 19 00:01:19,080 --> 00:01:21,480 Speaker 2: although it's not actually a river like we think of 20 00:01:21,520 --> 00:01:22,880 Speaker 2: on the land surface. 21 00:01:22,880 --> 00:01:25,760 Speaker 1: Right so literally, if we were looking at it from above, 22 00:01:25,880 --> 00:01:28,080 Speaker 1: it would be kind of like a river above us. 23 00:01:28,240 --> 00:01:30,440 Speaker 2: Yeah, it would certainly look like that in the sense 24 00:01:30,440 --> 00:01:32,880 Speaker 2: that it's long and it's thin, and it's carrying an 25 00:01:32,920 --> 00:01:36,280 Speaker 2: awful lot of water, but it's water vapor rather than 26 00:01:36,280 --> 00:01:37,520 Speaker 2: liquid water itself. 27 00:01:37,959 --> 00:01:40,560 Speaker 1: They seem to bring a lot of rain to New Zealand. 28 00:01:40,640 --> 00:01:45,040 Speaker 1: But how much do these rivers of the sky contribute 29 00:01:45,080 --> 00:01:46,160 Speaker 1: to our rainfall? 30 00:01:46,280 --> 00:01:49,600 Speaker 2: It varies a little bit around the country. So in 31 00:01:49,760 --> 00:01:52,920 Speaker 2: places like the west coast of the South Island, then 32 00:01:53,200 --> 00:01:56,440 Speaker 2: we might be looking up up to eighty percent of 33 00:01:56,600 --> 00:02:00,720 Speaker 2: our annual rainfall comes through these atmospheric river events. Places 34 00:02:00,760 --> 00:02:04,000 Speaker 2: on the eastern side of the country maybe like Dunidan 35 00:02:04,280 --> 00:02:06,960 Speaker 2: or christ Church a bit less, so maybe you know, 36 00:02:07,000 --> 00:02:10,200 Speaker 2: we're talking less than fifty percent here. So it varies 37 00:02:10,200 --> 00:02:13,240 Speaker 2: a bit around the country, but they're really important in 38 00:02:13,280 --> 00:02:16,040 Speaker 2: some parts. And then particularly when we start to look 39 00:02:16,080 --> 00:02:20,720 Speaker 2: at our heaviest rainfall events, then these do generally come 40 00:02:20,800 --> 00:02:22,640 Speaker 2: from atmospheric river events. 41 00:02:22,840 --> 00:02:25,480 Speaker 3: Meanwhile, heavy rain and strong winds have seen a state 42 00:02:25,480 --> 00:02:29,359 Speaker 3: of emergency declared for part of Hastings after three breaches 43 00:02:29,400 --> 00:02:32,520 Speaker 3: of the Home wan Sea Wall. Police are knocking on 44 00:02:32,600 --> 00:02:37,240 Speaker 3: doors of affected residences to evacuate. The town of de Kataka, 45 00:02:37,280 --> 00:02:40,720 Speaker 3: thirty kilometers from Gisbon, is cut off in both directions 46 00:02:41,040 --> 00:02:44,200 Speaker 3: in State Highway thirty five between Gisbon and Tolika Bay 47 00:02:44,360 --> 00:02:46,240 Speaker 3: is closed due to surface flooding. 48 00:02:49,480 --> 00:02:52,400 Speaker 1: So this one's a new one for me. IVT or 49 00:02:52,560 --> 00:02:57,680 Speaker 1: vertically integrated water vapor transport. Not quite as catchy as 50 00:02:57,840 --> 00:03:00,799 Speaker 1: atmospheric river, is it? What does that mean? 51 00:03:01,400 --> 00:03:05,480 Speaker 2: No? Not quite. Well, that's basically described how we measure 52 00:03:05,639 --> 00:03:09,280 Speaker 2: how much water is being transported through the atmosphere. So 53 00:03:09,320 --> 00:03:12,360 Speaker 2: when we're looking to say whether an atmospheric river is 54 00:03:12,360 --> 00:03:16,679 Speaker 2: occurring or not, we look at this IVT variable vertically 55 00:03:16,680 --> 00:03:22,320 Speaker 2: integrated water vapor transport. And so if that IVT is 56 00:03:22,360 --> 00:03:26,000 Speaker 2: above a certain threshold and the kind the spatial pattern 57 00:03:26,040 --> 00:03:29,160 Speaker 2: of IVT kind of matches what we expect of an 58 00:03:29,160 --> 00:03:31,800 Speaker 2: atmospheric river, then we can say, well, this is an 59 00:03:31,800 --> 00:03:35,120 Speaker 2: atmospheric river. And so if it's too low or if 60 00:03:35,160 --> 00:03:36,960 Speaker 2: the shape isn't quite right, then it's not. 61 00:03:37,560 --> 00:03:41,240 Speaker 1: Now I'm assuming that atmospheric rivers aren't anything new. Why 62 00:03:41,280 --> 00:03:44,200 Speaker 1: do you reckon it's come into the public's consciousness. 63 00:03:44,240 --> 00:03:48,600 Speaker 2: Now, Yeah, people first started researching them in the nineteen 64 00:03:48,680 --> 00:03:52,440 Speaker 2: nineties and it didn't get picked up a huge amount initially, 65 00:03:52,800 --> 00:03:56,160 Speaker 2: but kind of from the two thousands onwards, people started 66 00:03:56,240 --> 00:04:00,000 Speaker 2: paying increased attention to it. Partly, it's just a catchy name, 67 00:04:00,240 --> 00:04:03,160 Speaker 2: like you said, so it's something that people latch onto 68 00:04:03,600 --> 00:04:05,160 Speaker 2: and gets a bit more recognition. 69 00:04:05,400 --> 00:04:06,839 Speaker 1: It's visceral, isn't it. 70 00:04:06,920 --> 00:04:09,520 Speaker 2: Yes, it is that everyone knows what a river's like. 71 00:04:10,320 --> 00:04:12,920 Speaker 2: So yeah, it kind of really gives you a clear 72 00:04:12,960 --> 00:04:15,840 Speaker 2: idea of what's going on. And then I think probably 73 00:04:16,160 --> 00:04:18,640 Speaker 2: as people have become more and more aware of climate 74 00:04:18,760 --> 00:04:22,760 Speaker 2: change and we've seen the effects that climate change has 75 00:04:22,839 --> 00:04:26,040 Speaker 2: on some of our more extreme weather events, then you know, 76 00:04:26,279 --> 00:04:29,600 Speaker 2: as we start getting more and more floods and damages 77 00:04:29,640 --> 00:04:32,760 Speaker 2: from floods, then people naturally want to know what's causing it. 78 00:04:32,839 --> 00:04:35,680 Speaker 2: And so there's kind of two things allided to give 79 00:04:35,760 --> 00:04:38,159 Speaker 2: us this increased attention on atmospheric rivers. 80 00:04:38,560 --> 00:04:43,280 Speaker 1: Well, you've absolutely segued perfectly into my next question. So 81 00:04:43,320 --> 00:04:46,880 Speaker 1: you've recently worked on a study, hey, looking into the 82 00:04:46,880 --> 00:04:50,440 Speaker 1: relationship between rainfall and climate change in New Zealand. What 83 00:04:50,440 --> 00:04:51,960 Speaker 1: did your team investigate there? 84 00:04:52,279 --> 00:04:54,600 Speaker 2: Ah? Yeah, So this is work done by a PhD 85 00:04:54,680 --> 00:04:59,040 Speaker 2: student here at a tigo niftin Krishna and he's well, 86 00:04:59,080 --> 00:05:02,880 Speaker 2: what we've been doing to together is looking for the 87 00:05:02,920 --> 00:05:06,520 Speaker 2: trends in IVT over New Zealand and then trying to 88 00:05:06,600 --> 00:05:11,280 Speaker 2: unpick what's caused those trends. So is it just that 89 00:05:11,800 --> 00:05:15,279 Speaker 2: there's more water in the atmosphere and that's leading to 90 00:05:15,839 --> 00:05:18,440 Speaker 2: a higher IVT or is it changes in the wind 91 00:05:18,600 --> 00:05:22,200 Speaker 2: so it's wind speed getting stronger or weaker. You know, 92 00:05:22,240 --> 00:05:25,360 Speaker 2: where's it coming from. So that's kind of been the 93 00:05:25,480 --> 00:05:28,680 Speaker 2: key things that we've been asking and what we seem 94 00:05:28,720 --> 00:05:31,760 Speaker 2: to have found is that certainly over the southern part 95 00:05:31,800 --> 00:05:35,920 Speaker 2: of the country we are seeing higher IVT, so more 96 00:05:36,600 --> 00:05:38,800 Speaker 2: moisture being transported over the country. 97 00:05:39,360 --> 00:05:45,280 Speaker 1: If I whip out my year seven science knowledge, if 98 00:05:45,320 --> 00:05:49,920 Speaker 1: the world is getting warmer, wouldn't that then mean that 99 00:05:49,960 --> 00:05:53,640 Speaker 1: there is more water in the atmosphere because it gets evaporated. 100 00:05:54,200 --> 00:05:56,840 Speaker 2: Yeah, that's right, No, you're exactly right. You know, we've 101 00:05:56,839 --> 00:05:59,360 Speaker 2: got a warming planet, so that means that there's more 102 00:05:59,480 --> 00:06:02,719 Speaker 2: energy at the surface that could be used to evaporate water. 103 00:06:03,200 --> 00:06:06,240 Speaker 2: So as it gets hotter, we have more evaporation. But 104 00:06:06,320 --> 00:06:09,799 Speaker 2: also as the air gets hotter, it can hold more moisture. 105 00:06:10,200 --> 00:06:13,840 Speaker 2: So you know, if you keep evaporating, eventually the atmosphere 106 00:06:13,839 --> 00:06:17,279 Speaker 2: will saturate and the water will have to fall out. 107 00:06:17,560 --> 00:06:20,360 Speaker 2: But what we're doing to the atmosphere is increasing its 108 00:06:20,400 --> 00:06:24,239 Speaker 2: capacity to hold that moisture, so the air can hold 109 00:06:24,279 --> 00:06:27,719 Speaker 2: more moisture, so when a rain event does happen, there's 110 00:06:27,800 --> 00:06:30,360 Speaker 2: more moisture in there that can be rained out. And 111 00:06:30,400 --> 00:06:33,360 Speaker 2: that's why we expect to see and why we are 112 00:06:33,400 --> 00:06:36,640 Speaker 2: seeing heavier rain events as climate change progresses. 113 00:06:37,279 --> 00:06:40,040 Speaker 1: From your research, which areas of the country are most 114 00:06:40,120 --> 00:06:43,840 Speaker 1: at risk from bearing the brunt of increased rainfall, it 115 00:06:43,880 --> 00:06:44,280 Speaker 1: would be. 116 00:06:44,320 --> 00:06:47,679 Speaker 2: The southern half of the country, particularly the western side 117 00:06:47,680 --> 00:06:50,760 Speaker 2: of it. So in a general sense, our weather comes 118 00:06:50,760 --> 00:06:52,960 Speaker 2: from the west. You know, it might be a bit 119 00:06:53,000 --> 00:06:56,360 Speaker 2: more southwesterly or northwesterly, but generally it's from the west. 120 00:06:56,839 --> 00:06:59,279 Speaker 2: So that means that the west coast of the South 121 00:06:59,320 --> 00:07:03,560 Speaker 2: Island and the North Island experience those weather systems first, 122 00:07:03,880 --> 00:07:06,640 Speaker 2: and so that's where the rain falls initially. That's why 123 00:07:06,680 --> 00:07:10,800 Speaker 2: we know that the West Coast, as you know, wetter locations. 124 00:07:12,480 --> 00:07:15,440 Speaker 3: Remaining Westport residents may be forced to evacuate this evening 125 00:07:15,480 --> 00:07:18,840 Speaker 3: with serious flooding expectant to peak overnight. The rain delivered 126 00:07:18,960 --> 00:07:22,360 Speaker 3: is predicted two months worth falling in just the last 127 00:07:22,440 --> 00:07:24,600 Speaker 3: three days, with more on the way. 128 00:07:29,360 --> 00:07:32,240 Speaker 1: So I'm here to say that global heating and climate 129 00:07:32,320 --> 00:07:34,560 Speaker 1: change is really having an impact on rainfall. 130 00:07:34,960 --> 00:07:39,840 Speaker 2: Yes, would be a simple answer. It gets a bit 131 00:07:39,880 --> 00:07:44,320 Speaker 2: more complicated rainfall because it's so episodic in nature, it 132 00:07:44,440 --> 00:07:47,600 Speaker 2: varies a lot from place to place. It makes it 133 00:07:47,640 --> 00:07:50,680 Speaker 2: a lot harder to pick out a signal compared to temperature. 134 00:07:50,760 --> 00:07:54,120 Speaker 2: Let's say there's always a temperature, we can always measure it, 135 00:07:54,360 --> 00:07:58,520 Speaker 2: and it doesn't vary quite so much from place to place. 136 00:07:58,760 --> 00:08:01,600 Speaker 2: It's much easier to pick out trends in temperature than 137 00:08:01,640 --> 00:08:05,320 Speaker 2: it is in rainfall. But still we expect to see 138 00:08:05,560 --> 00:08:10,720 Speaker 2: those extremes increase with climate change. But at the same time, 139 00:08:11,120 --> 00:08:14,440 Speaker 2: we might expect our dry periods to increase as well, 140 00:08:14,960 --> 00:08:19,320 Speaker 2: because if we've got higher temperatures, then that water will 141 00:08:19,320 --> 00:08:22,200 Speaker 2: evaporate from the surface, will dry out more quickly, and 142 00:08:22,240 --> 00:08:24,760 Speaker 2: then if the atmosphere can hold more moisture, there might 143 00:08:24,800 --> 00:08:28,360 Speaker 2: be a longer time period between rain events, even if 144 00:08:28,400 --> 00:08:30,480 Speaker 2: those rain events actually end up being heavier. 145 00:08:30,880 --> 00:08:35,000 Speaker 1: I suppose dozens of atmospheric rivers make landfall here every year. 146 00:08:35,360 --> 00:08:37,360 Speaker 1: At what point should we be concerned? 147 00:08:37,440 --> 00:08:39,559 Speaker 2: I guess you've really just got to listen to what 148 00:08:39,600 --> 00:08:42,559 Speaker 2: Met Service are saying, what the weather forecast is. And 149 00:08:43,160 --> 00:08:46,560 Speaker 2: a lot of these atmospheric rivers are actually beneficial, right. 150 00:08:46,640 --> 00:08:50,400 Speaker 2: They provide the water that we use to generate electricity. 151 00:08:50,840 --> 00:08:54,080 Speaker 2: They stock up our snowfield during winter so people can 152 00:08:54,160 --> 00:08:56,520 Speaker 2: go skiing. A lot of what they give us is 153 00:08:56,520 --> 00:09:01,320 Speaker 2: beneficial when it gets potentially dangerous. That when Met Service 154 00:09:01,360 --> 00:09:04,040 Speaker 2: will give us our weather watches or our orange or 155 00:09:04,040 --> 00:09:04,960 Speaker 2: red warnings. 156 00:09:07,040 --> 00:09:10,160 Speaker 4: A year ago, record rainfall hit the Upper North Island, 157 00:09:10,240 --> 00:09:13,920 Speaker 4: delivering devastating flash floods at the start of the Anniversary 158 00:09:13,960 --> 00:09:17,480 Speaker 4: weekend holiday. Amid the flooding and the slips, four people 159 00:09:17,679 --> 00:09:21,240 Speaker 4: lost their lives, thousands abandoned their homes, resulting in about 160 00:09:21,240 --> 00:09:23,720 Speaker 4: two billion dollars of insurance claims. 161 00:09:26,600 --> 00:09:29,680 Speaker 1: The Auckland Anniversary floods seemed to catch everyone of God, hey, 162 00:09:30,200 --> 00:09:33,319 Speaker 1: are we becoming better at predicting rainfall at all? 163 00:09:33,600 --> 00:09:38,079 Speaker 2: Yeah? I mean weather forecasting in general, it improves over time. 164 00:09:38,280 --> 00:09:40,680 Speaker 2: It improves as kind of people do more research, and 165 00:09:40,720 --> 00:09:43,960 Speaker 2: it improves as we get bigger and better computers. There 166 00:09:43,960 --> 00:09:47,360 Speaker 2: were various kind of unique characteristics. I think of that 167 00:09:47,480 --> 00:09:52,560 Speaker 2: anniversary weekend blood that led to its rapid intensification, and 168 00:09:52,600 --> 00:09:55,880 Speaker 2: that did catch forecasters out a little bit in terms 169 00:09:55,960 --> 00:09:58,600 Speaker 2: of not being able to provide the lead in time 170 00:09:58,960 --> 00:10:01,560 Speaker 2: that we might have hoped. But the contrast would be 171 00:10:01,720 --> 00:10:06,280 Speaker 2: as psychoon Gabriel, which is also incredibly damaging. But we 172 00:10:06,360 --> 00:10:08,839 Speaker 2: had a good idea that that was coming from more 173 00:10:08,880 --> 00:10:12,959 Speaker 2: than a week out and was forecast really well by comparison. 174 00:10:13,080 --> 00:10:17,120 Speaker 2: So you know, some events get really well forecast, others 175 00:10:17,440 --> 00:10:20,360 Speaker 2: not quite so much. But the gradual track over time 176 00:10:20,480 --> 00:10:22,800 Speaker 2: is yet that they get forecasts better and better. 177 00:10:23,280 --> 00:10:30,720 Speaker 1: Thanks for joining us, Daniel. That's it for this episode 178 00:10:30,720 --> 00:10:33,600 Speaker 1: of the Front Page. You can read more about today's 179 00:10:33,640 --> 00:10:37,200 Speaker 1: stories and extensive news coverage at enzed Herald dot co 180 00:10:37,480 --> 00:10:41,080 Speaker 1: dot nz. The Front Page is produced by Ethan Siles 181 00:10:41,120 --> 00:10:45,960 Speaker 1: with sound engineer Paddy Fox. I'm Chelsea Daniels. Subscribe to 182 00:10:46,000 --> 00:10:49,280 Speaker 1: The Front Page on iHeartRadio or wherever you get your podcasts, 183 00:10:49,600 --> 00:10:53,000 Speaker 1: and tune in tomorrow for another look behind the headlines.