WEBVTT FILE 1 00:00:00.000 --> 00:00:03.940 Our lives are in sync with Earth's rotation. 2 00:00:03.940 --> 00:00:06.400 As our planet rotates on its axis, 3 00:00:06.400 --> 00:00:09.960 we shift from day to night and warm to cool.  4 00:00:09.960 --> 00:00:14.440 As a response, our weather follows a daily cycle. 5 00:00:14.440 --> 00:00:18.080 Now, the most detailed view of our daily weather has been created 6 00:00:18.080 --> 00:00:23.340 using a new NASA record that combines almost 20 years of rain and snow. 7 00:00:23.340 --> 00:00:26.440 By combining these two satellites, 8 00:00:26.440 --> 00:00:32.850 scientists calculated the changes in precipitation every 30 minutes for two decades. 9 00:00:32.850 --> 00:00:36.990 This is part of NASA's newest extended precipitation record 10 00:00:36.990 --> 00:00:43.410 known as the Integrated Multi-satellitE Retrievals for GPM, or IMERG analysis. 11 00:00:43.410 --> 00:00:44.860 From the vantage of space, 12 00:00:44.860 --> 00:00:50.080 IMERG shows the 24-hour pulse in weather known as the diurnal cycle. 13 00:00:50.080 --> 00:00:54.120 This cycle helps shape how and when our weather develops 14 00:00:54.120 --> 00:00:57.450 and is fundamental to regulating our climate. 15 00:00:57.450 --> 00:01:03.190 In the case of precipitation, one of the main questions is — the different main modes of variability. 16 00:01:03.190 --> 00:01:06.560 One main mode of variability is the seasonal variation. 17 00:01:06.560 --> 00:01:11.750 But on a much shorter time scale, the main mode of variability is the so-called diurnal cycle. 18 00:01:11.750 --> 00:01:14.830 That is the variation in precipitation over the day. 19 00:01:14.830 --> 00:01:18.690 IMERG not only shows us how much the rainfall shifts, 20 00:01:18.690 --> 00:01:21.640 it tells us what time it shifts and peaks. 21 00:01:21.640 --> 00:01:25.090 Over the U.S. we see a variety of patterns. 22 00:01:25.090 --> 00:01:33.130 This shows the average amount of rainfall every 30 minutes during the summer months of June, July, and August. 23 00:01:33.130 --> 00:01:37.300 In Florida, heat from the Sun builds up over the course of the day, 24 00:01:37.300 --> 00:01:39.410 driving rainfall over land. 25 00:01:39.410 --> 00:01:42.830 Sea breezes from the Gulf of Mexico and Atlantic Ocean 26 00:01:42.830 --> 00:01:47.300 feed the storms over land driving storms to peak in the afternoon. 27 00:01:47.300 --> 00:01:50.560 At night, rainfall moves over the ocean. 28 00:01:50.560 --> 00:01:55.430 Storms intensify offshore only to move inland during the day again. 29 00:01:55.430 --> 00:01:58.990 Over the midwest and the Great Plains, 30 00:01:58.990 --> 00:02:03.490 heating over the Rocky mountains forms storm systems during the day, 31 00:02:03.490 --> 00:02:05.770 which then roll eastward overnight. 32 00:02:05.770 --> 00:02:11.840 In the U.S. Northeast, heating over land causes rainfall during the day 33 00:02:11.840 --> 00:02:14.400 that moves over the ocean at night, 34 00:02:14.400 --> 00:02:17.590 because the water doesn’t cool down as quickly as over land. 35 00:02:17.590 --> 00:02:21.670 Due to this, you can clearly see the warm Gulf Stream water 36 00:02:21.670 --> 00:02:25.030 moving past the East Coast, on its way to the North Atlantic.  37 00:02:25.030 --> 00:02:29.690 During the winter months of December, January, and February along the West Coast, 38 00:02:29.690 --> 00:02:32.750 the daily patterns of rainfall every 30 minutes 39 00:02:32.750 --> 00:02:38.280 how how the coastal regions generally receive similar amounts of precipitation throughout the day. 40 00:02:38.280 --> 00:02:43.320 In the winter, precipitation is driven less from the daily heating of the Sun 41 00:02:43.320 --> 00:02:47.140 and more from the Pacific Ocean bringing in atmospheric rivers — 42 00:02:47.140 --> 00:02:51.040 corridors of intense water vapor in the atmosphere. 43 00:02:51.040 --> 00:02:54.210 By studying the diurnal variation, 44 00:02:54.210 --> 00:02:57.810 this gives us basic scientific understanding of what the atmosphere is doing,  45 00:02:57.810 --> 00:03:03.000 and it prepares us to look at models and understand what the relationship is 46 00:03:03.000 --> 00:03:06.790 between rainfall and these other variables, like air quality. 47 00:03:06.790 --> 00:03:11.180 Current climate models have difficulty accounting for the diurnal cycle, 48 00:03:11.180 --> 00:03:15.140 but the improved detail in IMERG could help fill in the gaps 49 00:03:15.140 --> 00:03:19.180 to create a more complete and accurate picture of daily precipitation, 50 00:03:19.180 --> 00:03:22.710 not just in the U.S. but around the world. 51 00:03:22.710 --> 00:03:33.099