1 00:00:09,240 --> 00:00:04,170 [Music] 2 00:00:12,959 --> 00:00:09,250 I guess what's what's on my slide lawyer 3 00:00:16,339 --> 00:00:12,969 okay so thanks for the introduction 4 00:00:18,600 --> 00:00:16,349 and so this talk is kind of a shift from 5 00:00:21,120 --> 00:00:18,610 pre-op pretty bad pretty biotic 6 00:00:25,260 --> 00:00:21,130 chemistry to atmospheric dynamics so 7 00:00:26,460 --> 00:00:25,270 let's all take a deep breath and we're 8 00:00:28,380 --> 00:00:26,470 gonna kind of get back into the 9 00:00:31,019 --> 00:00:28,390 headspace we were in the small thing and 10 00:00:32,100 --> 00:00:31,029 maybe yesterday and Tuesday so I'll be 11 00:00:33,720 --> 00:00:32,110 talking about the atmospheric 12 00:00:35,459 --> 00:00:33,730 circulation and climate of terrestrial 13 00:00:37,259 --> 00:00:35,469 planets orbiting both sun-like stars and 14 00:00:38,790 --> 00:00:37,269 M dwarf stars so this is kind of falling 15 00:00:41,669 --> 00:00:38,800 off of one of our town slides from this 16 00:00:43,349 --> 00:00:41,679 morning and kind of one theme I'll come 17 00:00:45,660 --> 00:00:43,359 back on again again is the effect of 18 00:00:47,579 --> 00:00:45,670 rotation on atmospheric circulation of 19 00:00:49,290 --> 00:00:47,589 terrestrial planets and so here I'm 20 00:00:51,270 --> 00:00:49,300 showing you a plot from Adam Sherman's 21 00:00:53,250 --> 00:00:51,280 review paper from a few years ago on 22 00:00:55,229 --> 00:00:53,260 terrestrial planets and it's showing you 23 00:00:57,720 --> 00:00:55,239 the distinction between tropical regions 24 00:00:59,970 --> 00:00:57,730 which are regions where rotation doesn't 25 00:01:01,229 --> 00:00:59,980 matter in the overall force balance so 26 00:01:03,389 --> 00:01:01,239 the Coriolis force is relatively 27 00:01:04,710 --> 00:01:03,399 unimportant and extra tropical regions 28 00:01:06,600 --> 00:01:04,720 where the Coriolis force does matter 29 00:01:08,280 --> 00:01:06,610 rotation is really important and how 30 00:01:10,560 --> 00:01:08,290 that changes with planetary rotation 31 00:01:12,690 --> 00:01:10,570 period so this goes from an earth-like 32 00:01:14,520 --> 00:01:12,700 rotation period of one day where we have 33 00:01:16,350 --> 00:01:14,530 tropical regions and we have extra 34 00:01:18,320 --> 00:01:16,360 tropical regions and as we go to a 35 00:01:20,610 --> 00:01:18,330 longer rotation periods the tropical 36 00:01:22,560 --> 00:01:20,620 regions the width of them widens and 37 00:01:25,410 --> 00:01:22,570 once you hit a rotation period of about 38 00:01:27,990 --> 00:01:25,420 10 days the entire planet is now in all 39 00:01:29,850 --> 00:01:28,000 tropics world or rotation is relatively 40 00:01:32,310 --> 00:01:29,860 unimportant in overall force balance and 41 00:01:33,900 --> 00:01:32,320 so you can characterize this by the roz 42 00:01:35,190 --> 00:01:33,910 be number of the planet and so if the 43 00:01:37,950 --> 00:01:35,200 roz be number which is the ratio of 44 00:01:40,050 --> 00:01:37,960 effective to Coriolis forces is large 45 00:01:43,080 --> 00:01:40,060 then the Coriolis force this can be 46 00:01:44,550 --> 00:01:43,090 neglected and a global sense and so you 47 00:01:45,570 --> 00:01:44,560 can see this directly in general 48 00:01:47,820 --> 00:01:45,580 circulation models of terrestrial 49 00:01:51,060 --> 00:01:47,830 planets and so here I'm showing you to 50 00:01:52,740 --> 00:01:51,070 GCM results from Ravi Kapoor so the top 51 00:01:54,900 --> 00:01:52,750 panel is showing your simulations of a 52 00:01:57,540 --> 00:01:54,910 earth-like planet around a sun-like star 53 00:01:58,800 --> 00:01:57,550 with a 24-hour rotation period and you 54 00:02:01,590 --> 00:01:58,810 can see that the planet has a hot 55 00:02:03,600 --> 00:02:01,600 equator and a cold pole at a large 56 00:02:06,450 --> 00:02:03,610 equator to pole temperature contrast and 57 00:02:07,800 --> 00:02:06,460 the circulation the atmosphere is trying 58 00:02:08,880 --> 00:02:07,810 to erase this equator to pull 59 00:02:11,130 --> 00:02:08,890 temperature contrast let's switch 60 00:02:13,709 --> 00:02:11,140 driving the large-scale circulation of 61 00:02:15,839 --> 00:02:13,719 the Hadley cells and the Farrell cell 62 00:02:17,300 --> 00:02:15,849 I'll be talking about a bit later but 63 00:02:18,770 --> 00:02:17,310 for the M dwarf 64 00:02:20,150 --> 00:02:18,780 star shown on the bottom here which is 65 00:02:21,680 --> 00:02:20,160 slowly rotating because it's tally 66 00:02:24,440 --> 00:02:21,690 locked with the rotation period of about 67 00:02:25,699 --> 00:02:24,450 58 days you can see that the dayside is 68 00:02:27,229 --> 00:02:25,709 really really hot because that's where 69 00:02:29,210 --> 00:02:27,239 you're seeing the radiation and the 70 00:02:31,070 --> 00:02:29,220 night Sun is cold but the equator to 71 00:02:32,510 --> 00:02:31,080 pole temperature contrast is really tiny 72 00:02:34,339 --> 00:02:32,520 relative to the planner around a 73 00:02:36,080 --> 00:02:34,349 sun-like star and this is because the 74 00:02:39,020 --> 00:02:36,090 entire day side of the planet is acting 75 00:02:42,080 --> 00:02:39,030 like the tropics and one consequence of 76 00:02:43,370 --> 00:02:42,090 this is the cloud coverage in these two 77 00:02:44,449 --> 00:02:43,380 models which is something that Martin 78 00:02:46,490 --> 00:02:44,459 talked about and something that was very 79 00:02:47,740 --> 00:02:46,500 important and potentially an early Venus 80 00:02:51,080 --> 00:02:47,750 of microwave was talking about yesterday 81 00:02:52,610 --> 00:02:51,090 so for the planet around a sun-like star 82 00:02:54,320 --> 00:02:52,620 that has an earth-like rotation rate we 83 00:02:56,509 --> 00:02:54,330 have lots of clouds as you can see here 84 00:02:59,270 --> 00:02:56,519 near the equator which are driven by 85 00:03:01,250 --> 00:02:59,280 deep deep convection in the tropics this 86 00:03:04,039 --> 00:03:01,260 makes all those thunderstorms that are 87 00:03:06,680 --> 00:03:04,049 famous in the tropics and you have less 88 00:03:08,330 --> 00:03:06,690 clouds as you go to higher latitudes in 89 00:03:09,620 --> 00:03:08,340 a general sense but for the planet 90 00:03:11,180 --> 00:03:09,630 orbiting an M dwarf star that's slowly 91 00:03:14,449 --> 00:03:11,190 rotating because there's deep convection 92 00:03:16,009 --> 00:03:14,459 throughout the dayside there's now a 93 00:03:17,839 --> 00:03:16,019 side cloud correction that's relatively 94 00:03:19,520 --> 00:03:17,849 high throughout the day side and this 95 00:03:21,770 --> 00:03:19,530 hide a side cloud fraction as we saw 96 00:03:23,870 --> 00:03:21,780 earlier today in March on stock acts to 97 00:03:25,729 --> 00:03:23,880 affect the hable zone so it makes the 98 00:03:27,410 --> 00:03:25,739 habitable zone potentially wider for 99 00:03:29,000 --> 00:03:27,420 planets orbiting M dwarf stars that are 100 00:03:32,000 --> 00:03:29,010 tightly locked so this is work of 101 00:03:33,920 --> 00:03:32,010 joon-young this is his GCM results for 102 00:03:36,530 --> 00:03:33,930 it slowly rotating planets and the red 103 00:03:38,059 --> 00:03:36,540 line rapidly rotating plants and the in 104 00:03:40,759 --> 00:03:38,069 the black line and then the other two 105 00:03:42,590 --> 00:03:40,769 solid lines show previous 1d models for 106 00:03:43,880 --> 00:03:42,600 the inner edge of the habitable zone as 107 00:03:44,479 --> 00:03:43,890 a function of the temperature of the 108 00:03:46,220 --> 00:03:44,489 host star 109 00:03:48,199 --> 00:03:46,230 so later type stars going down an 110 00:03:49,640 --> 00:03:48,209 incident solar flux so higher stellar 111 00:03:51,650 --> 00:03:49,650 flux is going to the left here on this 112 00:03:53,990 --> 00:03:51,660 diagram and you can see down near the 113 00:03:55,699 --> 00:03:54,000 bottom of the domain here in the M dwarf 114 00:03:57,289 --> 00:03:55,709 region the inner edge of the habitable 115 00:03:59,270 --> 00:03:57,299 zone for the slowly rotating and tightly 116 00:04:01,430 --> 00:03:59,280 locked models is about 50% or more 117 00:04:03,559 --> 00:04:01,440 closer to the host star and instant 118 00:04:06,559 --> 00:04:03,569 solar flux then in the rapidly rotating 119 00:04:08,360 --> 00:04:06,569 models so this is just one example of 120 00:04:10,309 --> 00:04:08,370 how rotation effects 121 00:04:12,559 --> 00:04:10,319 circulation and protection potentially 122 00:04:14,449 --> 00:04:12,569 affects habitability and rotation 123 00:04:16,009 --> 00:04:14,459 affects circulation in other ways but 124 00:04:17,360 --> 00:04:16,019 also there's a broad range right of 125 00:04:19,039 --> 00:04:17,370 planetary parameters that can affect 126 00:04:20,810 --> 00:04:19,049 circulation you can think of things like 127 00:04:23,210 --> 00:04:20,820 the instance of a flux of course the 128 00:04:25,880 --> 00:04:23,220 surface pressure the gravity of the 129 00:04:28,219 --> 00:04:25,890 planet the planetary radius and so I ran 130 00:04:29,930 --> 00:04:28,229 a large grid of simulations of Tresh of 131 00:04:31,080 --> 00:04:29,940 planets orbiting both sun-like stars and 132 00:04:32,820 --> 00:04:31,090 M dwarf stars 133 00:04:34,260 --> 00:04:32,830 that you can see in this paper that was 134 00:04:35,909 --> 00:04:34,270 published earlier this year and so there 135 00:04:36,780 --> 00:04:35,919 they use a kind of idealized model set 136 00:04:39,120 --> 00:04:36,790 up even though they're using a 137 00:04:41,280 --> 00:04:39,130 relatively complex GCM which is EXO cam 138 00:04:42,540 --> 00:04:41,290 which was the same GCM from the 139 00:04:44,580 --> 00:04:42,550 simulations I just showed you earlier 140 00:04:46,590 --> 00:04:44,590 robbery cover-up ooh and so I'm using an 141 00:04:49,530 --> 00:04:46,600 aqua planet set up with a nitrogen water 142 00:04:52,409 --> 00:04:49,540 atmosphere around stars that are either 143 00:04:54,600 --> 00:04:52,419 late type M dwarf stars kind of late K 144 00:04:56,100 --> 00:04:54,610 early M dwarf stars or some like stars 145 00:04:59,159 --> 00:04:56,110 and I'm assuming towel locking if the 146 00:05:01,350 --> 00:04:59,169 plants are orbiting M dwarf stars and so 147 00:05:02,730 --> 00:05:01,360 beaut I'm I'm mostly to be focusing on 148 00:05:04,290 --> 00:05:02,740 rotation period and let's talk a little 149 00:05:05,460 --> 00:05:04,300 bit about surface pressure but if you 150 00:05:07,710 --> 00:05:05,470 want to learn more you can check out the 151 00:05:09,360 --> 00:05:07,720 paper so first I'll talk about the 152 00:05:11,219 --> 00:05:09,370 circulation of planets orbiting sun-like 153 00:05:13,469 --> 00:05:11,229 stars and then move on to planets 154 00:05:15,390 --> 00:05:13,479 orbitting M dwarf stars so here I'm 155 00:05:17,580 --> 00:05:15,400 showing you results from simulations on 156 00:05:20,159 --> 00:05:17,590 the left-hand panel of a planet with a 157 00:05:21,420 --> 00:05:20,169 one-day rotation period same as Earth on 158 00:05:23,400 --> 00:05:21,430 the right-hand panel of planet with an 159 00:05:25,080 --> 00:05:23,410 eight-day rotation period these are 160 00:05:27,030 --> 00:05:25,090 zonal mean temperatures in the colors 161 00:05:28,830 --> 00:05:27,040 and the contours of showing the zonal 162 00:05:30,210 --> 00:05:28,840 mean potential temperature the potential 163 00:05:31,740 --> 00:05:30,220 temperature is a measure of entropy in 164 00:05:33,150 --> 00:05:31,750 the atmosphere and we'll come back to 165 00:05:35,550 --> 00:05:33,160 why this is important in a little bit 166 00:05:36,810 --> 00:05:35,560 and so the y-axis of these panels is the 167 00:05:38,250 --> 00:05:36,820 pressure normalized by the surface 168 00:05:39,990 --> 00:05:38,260 pressure so the bottom of the panels is 169 00:05:42,270 --> 00:05:40,000 the surface and then the x-axis is 170 00:05:43,890 --> 00:05:42,280 latitude and so you can see that in the 171 00:05:46,230 --> 00:05:43,900 1-day case the equator to pole 172 00:05:48,270 --> 00:05:46,240 temperature contrast is larger than in 173 00:05:49,560 --> 00:05:48,280 the eight-day case and additionally in 174 00:05:51,510 --> 00:05:49,570 the 1-day case if you look at the 175 00:05:54,450 --> 00:05:51,520 spacing of the contours they're 176 00:05:55,980 --> 00:05:54,460 relatively more closely spaced and as a 177 00:05:58,620 --> 00:05:55,990 result the potential temperature lapse 178 00:06:00,540 --> 00:05:58,630 rate also increases with increasing 179 00:06:02,040 --> 00:06:00,550 rotation rate and I'll come back to this 180 00:06:04,740 --> 00:06:02,050 later and talk about why it's important 181 00:06:06,990 --> 00:06:04,750 so this is how the climate changes when 182 00:06:08,490 --> 00:06:07,000 you change rotation rate go to floor 183 00:06:11,100 --> 00:06:08,500 rotation rates than Earth but what 184 00:06:13,320 --> 00:06:11,110 happens to the dynamics so this is kind 185 00:06:14,969 --> 00:06:13,330 of alluded to in previous talks so the 186 00:06:17,640 --> 00:06:14,979 dynamics also greatly changes so here 187 00:06:19,500 --> 00:06:17,650 I'm showing you the same parameter space 188 00:06:21,779 --> 00:06:19,510 on the axes but now I'm plotting and the 189 00:06:23,430 --> 00:06:21,789 colors the stream function of the 190 00:06:25,170 --> 00:06:23,440 circulation so the stream function tells 191 00:06:27,570 --> 00:06:25,180 you which direction the circulation goes 192 00:06:29,460 --> 00:06:27,580 so if it's red it's a clockwise 193 00:06:31,350 --> 00:06:29,470 circulation rising at the equator and 194 00:06:32,550 --> 00:06:31,360 descending at higher latitudes and if 195 00:06:34,710 --> 00:06:32,560 it's blue it's showing a 196 00:06:36,300 --> 00:06:34,720 counterclockwise circulation again in 197 00:06:37,830 --> 00:06:36,310 this case because it's a Hadley cell 198 00:06:40,230 --> 00:06:37,840 resident at the equator and descending 199 00:06:42,410 --> 00:06:40,240 at higher latitudes and so you can see 200 00:06:44,030 --> 00:06:42,420 as we vary the rotation period the 201 00:06:46,430 --> 00:06:44,040 with the Hadley cell changes in these 202 00:06:48,290 --> 00:06:46,440 two models as we decrease the rotation 203 00:06:49,700 --> 00:06:48,300 rate increase the rotation period the 204 00:06:51,920 --> 00:06:49,710 Hadley cell becomes wider and 205 00:06:53,690 --> 00:06:51,930 additionally I'm also putting in the 206 00:06:55,250 --> 00:06:53,700 contours here the zonal mean zonal wind 207 00:06:57,050 --> 00:06:55,260 speed in the atmosphere so this is 208 00:06:59,420 --> 00:06:57,060 showing you the east-west Jets in the 209 00:07:01,760 --> 00:06:59,430 atmosphere and so you can see that the 210 00:07:03,650 --> 00:07:01,770 east-west Jets occur at about plus at 211 00:07:05,420 --> 00:07:03,660 minus thirty degree latitude and the 212 00:07:06,860 --> 00:07:05,430 earth light case and these are the same 213 00:07:08,750 --> 00:07:06,870 jets that you know if you flew here from 214 00:07:10,040 --> 00:07:08,760 the USA made your trip a little bit 215 00:07:12,200 --> 00:07:10,050 faster and will make your trip a little 216 00:07:16,130 --> 00:07:12,210 bit slower going back it's gonna be 217 00:07:18,110 --> 00:07:16,140 annoying and you can see that if our 218 00:07:20,090 --> 00:07:18,120 planet was a slower repeater these Jets 219 00:07:22,100 --> 00:07:20,100 would occur at higher latitudes because 220 00:07:23,900 --> 00:07:22,110 these Jets occur at the edge of the 221 00:07:25,390 --> 00:07:23,910 Hadley cell and they're formed by a 222 00:07:28,280 --> 00:07:25,400 mixture of angular momentum conservation 223 00:07:33,730 --> 00:07:28,290 leading to Jets plus any interactions 224 00:07:36,110 --> 00:07:33,740 feeding into the Zola mean flow okay so 225 00:07:37,280 --> 00:07:36,120 that's going to slow rotation periods on 226 00:07:39,170 --> 00:07:37,290 earth but what happens if you make it 227 00:07:41,900 --> 00:07:39,180 rotate faster than Earth so here I'm now 228 00:07:43,040 --> 00:07:41,910 comparing maps of the circulation so on 229 00:07:45,170 --> 00:07:43,050 the left hand panel I'm showing the 230 00:07:46,490 --> 00:07:45,180 zonal wind so this is the east-west wind 231 00:07:47,810 --> 00:07:46,500 and the right-hand panel is I'm showing 232 00:07:50,300 --> 00:07:47,820 the eddies on the wind so this is the 233 00:07:52,820 --> 00:07:50,310 deviation of the east-west wind from the 234 00:07:54,590 --> 00:07:52,830 zonal mean east-west wind so the 235 00:07:57,230 --> 00:07:54,600 deviation from the east-west average of 236 00:07:59,330 --> 00:07:57,240 the east-west wind that's a mouthful 237 00:08:01,100 --> 00:07:59,340 so you can see again our subtropical 238 00:08:03,800 --> 00:08:01,110 jets at plus or minus 30 degree latitude 239 00:08:05,750 --> 00:08:03,810 and you can see large-scale Eddie's that 240 00:08:07,340 --> 00:08:05,760 are driven by instabilities 241 00:08:08,480 --> 00:08:07,350 near the jet and you can also see 242 00:08:10,280 --> 00:08:08,490 large-scale Eddie's in the tropical 243 00:08:11,810 --> 00:08:10,290 regions as well and for the fast 244 00:08:14,240 --> 00:08:11,820 rotating case you can see that we no 245 00:08:15,620 --> 00:08:14,250 longer just have to eastward Jets one in 246 00:08:17,750 --> 00:08:15,630 each hemisphere we now have many many 247 00:08:19,190 --> 00:08:17,760 eastward Jets and additionally you can 248 00:08:21,620 --> 00:08:19,200 see that the life skill of Eddie's 249 00:08:23,750 --> 00:08:21,630 decrease with increasing rotation rate 250 00:08:25,040 --> 00:08:23,760 this was alluded to earlier today and so 251 00:08:27,380 --> 00:08:25,050 for faster rotating plants we have 252 00:08:28,940 --> 00:08:27,390 smaller Eddy length scales we can fit in 253 00:08:30,440 --> 00:08:28,950 more zonal Jets and also I'm not showing 254 00:08:32,990 --> 00:08:30,450 it here but the equator to pole 255 00:08:36,320 --> 00:08:33,000 temperature contrast also increases with 256 00:08:39,920 --> 00:08:36,330 increasing rotation rate so the question 257 00:08:41,719 --> 00:08:39,930 is is can we explain this how the 258 00:08:44,960 --> 00:08:41,729 large-scale circulation changes in a 259 00:08:46,580 --> 00:08:44,970 simple analytic way and so I just want 260 00:08:48,890 --> 00:08:46,590 to introduce a concept here that I'll be 261 00:08:50,420 --> 00:08:48,900 referring back to so what I'm plotting 262 00:08:52,430 --> 00:08:50,430 on this diagram these different lines 263 00:08:53,990 --> 00:08:52,440 they're ice and Tropes so they're 264 00:08:55,890 --> 00:08:54,000 contours of constant potential 265 00:08:58,260 --> 00:08:55,900 temperature in the atmosphere or 266 00:08:59,850 --> 00:08:58,270 contours of constant entropy and the y 267 00:09:02,460 --> 00:08:59,860 axis here is height going from the 268 00:09:04,320 --> 00:09:02,470 surface to the tropopause and the x-axis 269 00:09:06,900 --> 00:09:04,330 is latitude going from the equator to 270 00:09:09,300 --> 00:09:06,910 the pole and so I'm plotting here one 271 00:09:11,430 --> 00:09:09,310 line the red line which has a slope that 272 00:09:13,680 --> 00:09:11,440 I'm defining as a slope of one so it's a 273 00:09:15,630 --> 00:09:13,690 isin't rope that rises from the surface 274 00:09:18,360 --> 00:09:15,640 at the equator through the tropopause at 275 00:09:22,290 --> 00:09:18,370 the pole and this is where earth lies on 276 00:09:24,630 --> 00:09:22,300 this diagram it has a slope such that a 277 00:09:25,710 --> 00:09:24,640 nice intrepid rise from the surface of 278 00:09:28,410 --> 00:09:25,720 the equator to the tropopause of the 279 00:09:30,440 --> 00:09:28,420 pole and so the reason why earth is that 280 00:09:32,820 --> 00:09:30,450 this kind of this kind of state has been 281 00:09:35,820 --> 00:09:32,830 kind of debated over the past 50 years 282 00:09:38,550 --> 00:09:35,830 since the 70s so people think that earth 283 00:09:40,140 --> 00:09:38,560 once Earth's atmosphere if in a 284 00:09:43,320 --> 00:09:40,150 radiative convective sense without 285 00:09:45,380 --> 00:09:43,330 dynamics would be in an unstable state 286 00:09:48,300 --> 00:09:45,390 where the slope is greater than 1 and 287 00:09:49,950 --> 00:09:48,310 the planet would be unstable to so 288 00:09:52,019 --> 00:09:49,960 called bear clinic instabilities which 289 00:09:54,060 --> 00:09:52,029 are the large-scale fluid instabilities 290 00:09:56,820 --> 00:09:54,070 that lead to weather and storms and Arce 291 00:09:58,740 --> 00:09:56,830 mid latitudes where we are not and so 292 00:10:00,390 --> 00:09:58,750 basically these instabilities will lead 293 00:10:02,460 --> 00:10:00,400 to an adjustment social that the planet 294 00:10:04,980 --> 00:10:02,470 would go from this unstable state back 295 00:10:06,990 --> 00:10:04,990 to the stable state and so there's a 296 00:10:09,180 --> 00:10:07,000 wide range of literature on this but 297 00:10:11,340 --> 00:10:09,190 relatively recently multi Anson 298 00:10:13,890 --> 00:10:11,350 developed a simple theory to explain 299 00:10:15,690 --> 00:10:13,900 that in principle if the forcing regimes 300 00:10:18,120 --> 00:10:15,700 are very different than Earth the 301 00:10:20,100 --> 00:10:18,130 atmosphere can stay in an unstable state 302 00:10:23,579 --> 00:10:20,110 it doesn't necessarily have to adjust 303 00:10:26,160 --> 00:10:23,589 back so in that in that case it just 304 00:10:27,990 --> 00:10:26,170 kind of happens to be in this slope 305 00:10:29,400 --> 00:10:28,000 equals one state and note that if the 306 00:10:31,019 --> 00:10:29,410 slope is less than one then the 307 00:10:32,940 --> 00:10:31,029 atmosphere is on a large scale sense 308 00:10:36,449 --> 00:10:32,950 stable to bear a clinic instabilities 309 00:10:38,310 --> 00:10:36,459 and so know that if you understand if 310 00:10:40,110 --> 00:10:38,320 you have some sort of theory for this 311 00:10:42,210 --> 00:10:40,120 slope and principle you should 312 00:10:44,790 --> 00:10:42,220 understand how the equator to pole 313 00:10:45,990 --> 00:10:44,800 temperature contrasts and the surface of 314 00:10:48,510 --> 00:10:46,000 tropopause potential temperature 315 00:10:50,760 --> 00:10:48,520 contrast depend on planetary parameters 316 00:10:53,280 --> 00:10:50,770 because this criticality parameter is 317 00:10:54,329 --> 00:10:53,290 directly related to the ratio of the 318 00:10:55,980 --> 00:10:54,339 horizontal potential temperature 319 00:10:57,390 --> 00:10:55,990 contrast in the vertical potential 320 00:10:59,310 --> 00:10:57,400 temperature contrast in the atmosphere 321 00:11:02,220 --> 00:10:59,320 and so I just kind of want to show you 322 00:11:03,449 --> 00:11:02,230 in a basic sense what these two 323 00:11:04,829 --> 00:11:03,459 parameters the horizontal in the 324 00:11:07,500 --> 00:11:04,839 vertical potential temperature contrast 325 00:11:09,950 --> 00:11:07,510 mean and in in terms of the climate of 326 00:11:12,920 --> 00:11:09,960 an exoplanet so here I'm showing you 327 00:11:14,510 --> 00:11:12,930 of zonal mean potential temperature so 328 00:11:16,610 --> 00:11:14,520 these were the contours of my earlier 329 00:11:19,010 --> 00:11:16,620 plot showing the climate and I'm 330 00:11:21,050 --> 00:11:19,020 highlighting the horizontal potential 331 00:11:22,460 --> 00:11:21,060 temperature contrast in the red so this 332 00:11:23,990 --> 00:11:22,470 is basically just the equator to pole 333 00:11:25,850 --> 00:11:24,000 temperature contrast at the surface 334 00:11:27,830 --> 00:11:25,860 because at the surface potential 335 00:11:30,290 --> 00:11:27,840 temperature and normal temperature are 336 00:11:31,520 --> 00:11:30,300 the same and the vertical potential 337 00:11:32,600 --> 00:11:31,530 temperature contrast is just the 338 00:11:34,760 --> 00:11:32,610 difference of the potential temperature 339 00:11:38,630 --> 00:11:34,770 from the surface to the tropopause 340 00:11:40,880 --> 00:11:38,640 in the mid latitudes and so we can try 341 00:11:42,050 --> 00:11:40,890 to figure out what the slope of a nice 342 00:11:43,880 --> 00:11:42,060 and trope would be in this kind of 343 00:11:46,940 --> 00:11:43,890 atmosphere so if we basically just 344 00:11:48,890 --> 00:11:46,950 connect the lines from where a nice and 345 00:11:51,080 --> 00:11:48,900 trope or a contour of constant potential 346 00:11:53,330 --> 00:11:51,090 temperature is at the surface at the 347 00:11:55,310 --> 00:11:53,340 equator to the pole you can see that it 348 00:11:57,020 --> 00:11:55,320 rises up to about here so not quite the 349 00:11:59,270 --> 00:11:57,030 tropopause in this case so this 350 00:12:01,010 --> 00:11:59,280 atmosphere is stable and a large-scale 351 00:12:03,560 --> 00:12:01,020 bulk sense to bear clinic instabilities 352 00:12:08,660 --> 00:12:03,570 because the slope of a sites and tropes 353 00:12:12,740 --> 00:12:08,670 across a hemisphere is less than one and 354 00:12:14,180 --> 00:12:12,750 so multi Anton developed a simple theory 355 00:12:15,380 --> 00:12:14,190 to try to explain how the criticality 356 00:12:17,600 --> 00:12:15,390 parameter should depend on planar 357 00:12:18,980 --> 00:12:17,610 Triplanetary parameters it should 358 00:12:20,900 --> 00:12:18,990 increase with increasing rotation rate 359 00:12:21,830 --> 00:12:20,910 because bare clinic instabilities should 360 00:12:23,000 --> 00:12:21,840 increase with the increase in the 361 00:12:25,100 --> 00:12:23,010 strength of a cushioned rotation rate 362 00:12:26,750 --> 00:12:25,110 because deformation scales decrease with 363 00:12:28,370 --> 00:12:26,760 increasing rotation rate and it should 364 00:12:30,590 --> 00:12:28,380 also depend on the surface pressure of 365 00:12:32,030 --> 00:12:30,600 the planet the tropopause height or the 366 00:12:35,210 --> 00:12:32,040 scale height and many other parameters 367 00:12:36,800 --> 00:12:35,220 and so here's just that scaling so this 368 00:12:39,320 --> 00:12:36,810 is how the slope of ice and Tropes 369 00:12:41,540 --> 00:12:39,330 depend on rotation rate pressure and 370 00:12:43,040 --> 00:12:41,550 then H which is the minimum in this case 371 00:12:44,930 --> 00:12:43,050 of the scale height and the tropopause 372 00:12:46,340 --> 00:12:44,940 height note that Earth is in a state 373 00:12:47,990 --> 00:12:46,350 where the scale height is actually kind 374 00:12:49,370 --> 00:12:48,000 of similar to the tropopause height it's 375 00:12:50,930 --> 00:12:49,380 just a little bit smaller but in 376 00:12:53,590 --> 00:12:50,940 principle it can be larger for a 377 00:12:56,240 --> 00:12:53,600 different kind of atmosphere and so 378 00:12:57,620 --> 00:12:56,250 these are comparisons with my GCM 379 00:12:59,120 --> 00:12:57,630 results so the solid lines in these 380 00:13:01,340 --> 00:12:59,130 plots are showing you the GCM results 381 00:13:03,380 --> 00:13:01,350 and the dashed line is the scaling for 382 00:13:04,670 --> 00:13:03,390 the criticality parameter the slope as a 383 00:13:06,530 --> 00:13:04,680 function of rotation rate on the 384 00:13:08,510 --> 00:13:06,540 left-hand panel and surface pressure on 385 00:13:10,430 --> 00:13:08,520 the right panel and so you can see as a 386 00:13:12,140 --> 00:13:10,440 function of surface pressure but scaling 387 00:13:13,400 --> 00:13:12,150 does a really good job throughout the 388 00:13:15,530 --> 00:13:13,410 full range of surface pressures we 389 00:13:17,690 --> 00:13:15,540 considered as a function of rotation 390 00:13:20,480 --> 00:13:17,700 rate the scaling does a good job for the 391 00:13:21,860 --> 00:13:20,490 fast rotating cases around here but it's 392 00:13:23,950 --> 00:13:21,870 also do such a good job for the slowly 393 00:13:26,440 --> 00:13:23,960 rotating cases with appreciation period 394 00:13:28,570 --> 00:13:26,450 greater than about four days and the 395 00:13:31,030 --> 00:13:28,580 reason why is because these cases down 396 00:13:33,010 --> 00:13:31,040 here rotates slow enough that the Ralphy 397 00:13:34,870 --> 00:13:33,020 deformation radius is larger than the 398 00:13:36,130 --> 00:13:34,880 planetary radius and so Barry clinic 399 00:13:36,970 --> 00:13:36,140 instability shouldn't be very important 400 00:13:38,770 --> 00:13:36,980 these atmospheres and 401 00:13:40,180 --> 00:13:38,780 this theory wouldn't apply to these 402 00:13:41,860 --> 00:13:40,190 slowly rotating planets only applies to 403 00:13:43,270 --> 00:13:41,870 planets with the rotation rates it's 404 00:13:46,090 --> 00:13:43,280 kind of they're kind of like earth or 405 00:13:47,890 --> 00:13:46,100 faster and so I said before if we 406 00:13:49,630 --> 00:13:47,900 understand this slope of ice and ropes 407 00:13:50,950 --> 00:13:49,640 we should also understand the equator 408 00:13:52,900 --> 00:13:50,960 droople temperature contrast in the 409 00:13:54,850 --> 00:13:52,910 vertical potential temperature contrast 410 00:13:56,350 --> 00:13:54,860 and in principle the vertical potential 411 00:13:58,120 --> 00:13:56,360 temperature contrast can be related to 412 00:14:00,070 --> 00:13:58,130 the lapse rate of the atmosphere which 413 00:14:02,050 --> 00:14:00,080 is something that we could in principle 414 00:14:04,030 --> 00:14:02,060 with a really awesome giant light bucket 415 00:14:05,620 --> 00:14:04,040 actually constrained with with 416 00:14:07,840 --> 00:14:05,630 retrievals onto our selection planet 417 00:14:12,310 --> 00:14:07,850 atmospheres you know when I'm maybe 50 418 00:14:15,100 --> 00:14:12,320 or something so or older we'll see so 419 00:14:16,930 --> 00:14:15,110 here I'm plotting the scaling between 420 00:14:18,820 --> 00:14:16,940 the GCM in theory for the equator pole 421 00:14:20,350 --> 00:14:18,830 temperature contrast on the left-hand 422 00:14:21,760 --> 00:14:20,360 panel and the bulk lapse rate or the 423 00:14:23,290 --> 00:14:21,770 vertical potential temperature contrast 424 00:14:25,330 --> 00:14:23,300 on the right-hand panel and you can see 425 00:14:26,950 --> 00:14:25,340 the theory predicts that both of these 426 00:14:28,930 --> 00:14:26,960 should increase with increasing rotation 427 00:14:29,110 --> 00:14:28,940 rate and our GCM results do bear that 428 00:14:31,090 --> 00:14:29,120 out 429 00:14:32,200 --> 00:14:31,100 note that this is kind of more of a 430 00:14:34,240 --> 00:14:32,210 broad agreement than the criticality 431 00:14:35,380 --> 00:14:34,250 parameter but in general the scaling 432 00:14:37,210 --> 00:14:35,390 predicts that this should this should 433 00:14:39,340 --> 00:14:37,220 hold over a wide range of parameters and 434 00:14:43,780 --> 00:14:39,350 so we've also tested surface pressure 435 00:14:46,180 --> 00:14:43,790 gravity and plenty radius did you or 436 00:14:53,310 --> 00:14:46,190 you're holding up a sign I have 20 437 00:14:55,480 --> 00:14:53,320 seconds great all right so to the end I 438 00:14:57,340 --> 00:14:55,490 talked a lot slower than I know that I 439 00:14:59,290 --> 00:14:57,350 normally do but so I've also looked at 440 00:15:00,760 --> 00:14:59,300 planets orbiting M dwarf stars and so 441 00:15:02,620 --> 00:15:00,770 the one thing I kind of want to get 442 00:15:04,600 --> 00:15:02,630 across is that for planets orbiting M 443 00:15:05,920 --> 00:15:04,610 dwarf stars we know that they're cloud 444 00:15:08,440 --> 00:15:05,930 coverage should depend on the rotation 445 00:15:10,030 --> 00:15:08,450 period so slowly rotating planets have 446 00:15:12,340 --> 00:15:10,040 more dayside cloud covers than fast 447 00:15:13,750 --> 00:15:12,350 rotating planets and in principle with 448 00:15:15,400 --> 00:15:13,760 future observations phase curve 449 00:15:17,770 --> 00:15:15,410 observations of these planets we could 450 00:15:19,450 --> 00:15:17,780 actually distinguish between these so 451 00:15:21,640 --> 00:15:19,460 for rapid rotating planets which don't 452 00:15:23,470 --> 00:15:21,650 have a sight sitting civics significant 453 00:15:24,970 --> 00:15:23,480 day sight cloud coverage you can easily 454 00:15:26,650 --> 00:15:24,980 see the outgoing cluck-cluck from the 455 00:15:28,540 --> 00:15:26,660 day side peaking near the substellar 456 00:15:29,980 --> 00:15:28,550 point but for slowly rotating planets 457 00:15:31,660 --> 00:15:29,990 which have significant dayside cloud 458 00:15:33,520 --> 00:15:31,670 coverage you wouldn't be able to seek 459 00:15:35,050 --> 00:15:33,530 this outgoing flux peak near the some 460 00:15:36,900 --> 00:15:35,060 stellar point because clouds would 461 00:15:38,160 --> 00:15:36,910 inhibit the olr and 462 00:15:39,780 --> 00:15:38,170 so you would actually see an inverted 463 00:15:41,430 --> 00:15:39,790 face curve and so in principle we can 464 00:15:43,560 --> 00:15:41,440 test all of our theories for cloud 465 00:15:45,600 --> 00:15:43,570 coverage on Endor fresco planets by 466 00:15:47,250 --> 00:15:45,610 through infrared phase curves all right 467 00:15:59,510 --> 00:15:47,260 thank you 468 00:16:04,830 --> 00:16:02,640 hi Neil is from the University of Oxford 469 00:16:07,530 --> 00:16:04,840 I was just wondering in the scaling as 470 00:16:09,900 --> 00:16:07,540 you showed it why you had the presence 471 00:16:11,940 --> 00:16:09,910 of the rotation rate but not the radius 472 00:16:14,190 --> 00:16:11,950 because in a number of ways they come 473 00:16:17,010 --> 00:16:14,200 into the momentum equations in the same 474 00:16:18,600 --> 00:16:17,020 place and you know both say if you're 475 00:16:21,150 --> 00:16:18,610 thinking about the light equatorial 476 00:16:23,640 --> 00:16:21,160 deformation radius has like a feature in 477 00:16:26,340 --> 00:16:23,650 it which has a inside and although the 478 00:16:29,250 --> 00:16:26,350 Rose be number is like you over L which 479 00:16:30,540 --> 00:16:29,260 hasn't hey yeah so this scaling I didn't 480 00:16:32,010 --> 00:16:30,550 I purposely didn't talk about how it's 481 00:16:34,290 --> 00:16:32,020 derived it doesn't come from the 482 00:16:34,800 --> 00:16:34,300 momentum equation it's very very simple 483 00:16:37,020 --> 00:16:34,810 actually 484 00:16:38,730 --> 00:16:37,030 so it just comes from the slope of right 485 00:16:40,290 --> 00:16:38,740 the slope of a nice and trope is related 486 00:16:42,030 --> 00:16:40,300 to the scale height divided by the 487 00:16:44,010 --> 00:16:42,040 length of a nation trip and so what we 488 00:16:45,840 --> 00:16:44,020 do is we scale the length of isin't rope 489 00:16:48,210 --> 00:16:45,850 saying that the maximum like ninth 490 00:16:49,830 --> 00:16:48,220 length of a nice intro is basically 491 00:16:51,930 --> 00:16:49,840 related to an any diffusion parameter 492 00:16:53,130 --> 00:16:51,940 times the rate of timescale and so if 493 00:16:54,840 --> 00:16:53,140 you can relate that a t diffusion 494 00:16:56,610 --> 00:16:54,850 parameter to large-scale properties of 495 00:16:58,680 --> 00:16:56,620 the circulation so if you scale it with 496 00:17:01,350 --> 00:16:58,690 in this case the the Ryans the rhine 497 00:17:03,570 --> 00:17:01,360 scale then you can basically then relate 498 00:17:05,250 --> 00:17:03,580 that back out to planetary parameters 499 00:17:06,660 --> 00:17:05,260 doesn't make sense so it's very very 500 00:17:08,940 --> 00:17:06,670 simple it basically it's just a scaling 501 00:17:10,290 --> 00:17:08,950 for these slopes it's not necessarily 502 00:17:11,910 --> 00:17:10,300 like a full scaling of momentum 503 00:17:24,810 --> 00:17:11,920 equations like maybe Mark Hammonds done 504 00:17:28,170 --> 00:17:24,820 yeah Mark Hyman to University of Oxford 505 00:17:29,940 --> 00:17:28,180 are there any observational tests beyond 506 00:17:31,830 --> 00:17:29,950 face curbs or other ones that you 507 00:17:34,560 --> 00:17:31,840 thought of for these scaling relations 508 00:17:36,420 --> 00:17:34,570 Oh so for the scaling relations I don't 509 00:17:38,970 --> 00:17:36,430 know if face curves would necessarily be 510 00:17:40,230 --> 00:17:38,980 a great test so for terrestrial planets 511 00:17:41,640 --> 00:17:40,240 I'm thinking about treasure planets that 512 00:17:43,440 --> 00:17:41,650 are orbiting sun-like stars something 513 00:17:45,870 --> 00:17:43,450 about reflected light with like Louvois 514 00:17:48,990 --> 00:17:45,880 or high backs in the far future and so 515 00:17:50,710 --> 00:17:49,000 in principle if the planet is inclined 516 00:17:51,850 --> 00:17:50,720 you can back out 517 00:17:52,990 --> 00:17:51,860 and equator to pole brightness 518 00:17:54,700 --> 00:17:53,000 difference if you can make brightness 519 00:17:55,810 --> 00:17:54,710 match to the planet and so that would be 520 00:17:57,340 --> 00:17:55,820 really really challenging that would 521 00:17:59,560 --> 00:17:57,350 require face cream observations over a 522 00:18:00,519 --> 00:17:59,570 long time baseline but in principle you 523 00:18:02,529 --> 00:18:00,529 can constrain the equator to pole 524 00:18:04,629 --> 00:18:02,539 temperature contrast in that case but 525 00:18:06,399 --> 00:18:04,639 more directly one could constrain the 526 00:18:08,019 --> 00:18:06,409 bulk lapse rate through retrieval so if 527 00:18:09,009 --> 00:18:08,029 you have a spectra you understand right 528 00:18:10,299 --> 00:18:09,019 the brightness as a function of 529 00:18:11,889 --> 00:18:10,309 wavelength that tells you a bit about 530 00:18:14,080 --> 00:18:11,899 the bride this is function of pressure 531 00:18:18,210 --> 00:18:14,090 which lets you back out a lot rate and 532 00:18:20,470 --> 00:18:18,220 so cat things worked a lot on that yeah 533 00:18:21,909 --> 00:18:20,480 quick question Ted I mean if you're 534 00:18:23,259 --> 00:18:21,919 looking for reflected light with like 535 00:18:25,389 --> 00:18:23,269 the warned havoc studies aren't gonna be 536 00:18:27,220 --> 00:18:25,399 tidally locked anymore right then we 537 00:18:29,220 --> 00:18:27,230 won't have to actually observe them that 538 00:18:31,869 --> 00:18:29,230 long as you're looking for a rotation 539 00:18:33,909 --> 00:18:31,879 shoot so I didn't get this across so in 540 00:18:35,320 --> 00:18:33,919 the first half of the first part the the 541 00:18:36,820 --> 00:18:35,330 scaling theory is for planets around 542 00:18:40,659 --> 00:18:36,830 sun-like stars that aren't highly locked 543 00:18:41,169 --> 00:18:40,669 yeah so it would it's not doable in the 544 00:18:45,419 --> 00:18:41,179 near future 545 00:18:49,419 --> 00:18:45,429 okay yeah sorry hi Pam 546 00:18:51,009 --> 00:18:49,429 what no stay on in the back he gave me 547 00:18:54,970 --> 00:18:51,019 the microphone but that was it okay 548 00:19:00,970 --> 00:18:54,980 that's fine who are you again IVF emoji 549 00:19:02,980 --> 00:19:00,980 Oxford uh does that apply and can you 550 00:19:04,480 --> 00:19:02,990 give me a scaling for hot Jupiters for 551 00:19:07,149 --> 00:19:04,490 the equator support operator grad young 552 00:19:08,740 --> 00:19:07,159 because that's something emily is gonna 553 00:19:10,690 --> 00:19:08,750 tell you we can observe we sugandha 554 00:19:13,629 --> 00:19:10,700 replicate mapping pretty soon which i'm 555 00:19:16,720 --> 00:19:13,639 sorry i'm gonna be mysterious so that's 556 00:19:19,690 --> 00:19:16,730 a really really good question so i think 557 00:19:21,249 --> 00:19:19,700 most of us are a little unsure how 558 00:19:22,960 --> 00:19:21,259 relevant bear clinic instabilities are 559 00:19:25,180 --> 00:19:22,970 for the atmospheric circulation of hot 560 00:19:26,590 --> 00:19:25,190 Jupiters i think in a bulk sense most of 561 00:19:28,629 --> 00:19:26,600 the instabilities we've seen our GCMs 562 00:19:31,119 --> 00:19:28,639 are barotropic right like the shedding 563 00:19:33,909 --> 00:19:31,129 of the shedding of Eddie's from the from 564 00:19:35,379 --> 00:19:33,919 the equatorial jet right and so I'm not 565 00:19:36,909 --> 00:19:35,389 really sure if there's bear clinic 566 00:19:38,980 --> 00:19:36,919 instabilities on our simulations it's 567 00:19:40,869 --> 00:19:38,990 kind of in like a stick where maybe they 568 00:19:43,149 --> 00:19:40,879 would occur if we had the right like 569 00:19:45,340 --> 00:19:43,159 forcing setup or something but in 570 00:19:47,860 --> 00:19:45,350 principle I would expect that warm 571 00:19:49,060 --> 00:19:47,870 Jupiter's might might have might be more 572 00:19:50,680 --> 00:19:49,070 likely to have better clinic 573 00:19:52,240 --> 00:19:50,690 instabilities because they can be faster 574 00:19:53,740 --> 00:19:52,250 rotating and actually that's what I'm 575 00:19:55,180 --> 00:19:53,750 doing next right now there's a we have a 576 00:19:56,740 --> 00:19:55,190 summer student who's running warm 577 00:19:58,600 --> 00:19:56,750 Jupiter simulations and we're gonna see 578 00:19:59,889 --> 00:19:58,610 if the same idea applies to them so we 579 00:20:01,690 --> 00:19:59,899 can test this sooner which James Webb 580 00:20:03,970 --> 00:20:01,700 rather than having to wait till the 581 00:20:07,190 --> 00:20:03,980 2040s yeah