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April 30, 2019 at 04:18PM
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April 30, 2019 at 04:18PM
I have previously addressed the NASA study that concluded the AIRS satellite temperatures “verified global warming trends“. The AIRS is an infrared temperature sounding instrument on the NASA Aqua satellite, providing data since late 2002 (over 16 years). All results in that study, and presented here, are based upon infrared measurements alone, with no microwave temperature sounder data being used in these products.
That reported study addressed only the surface “skin” temperature measurements, but the AIRS is also used to retrieve temperature profiles throughout the troposphere and stratosphere — that’s 99.9% of the total mass of the atmosphere.
Since AIRS data are also used to retrieve a 2 meter temperature (the traditional surface air temperature measurement height), I was curious why that wasn’t used instead of the surface skin temperature. Also, AIRS allows me to compare to our UAH tropospheric deep-layer temperature products.
So, I downloaded the entire archive of monthly average AIRS temperature retrievals on a 1 deg. lat/lon grid (85 GB of data). I’ve been analyzing those data over various regions (global, tropical, land, ocean). While there are a lot of interesting results I could show, today I’m going to focus just on the United States.
Because the Aqua satellite observes at nominal local times of 1:30 a.m. and 1:30 p.m., this allows separation of data into “day” and “night”. It is well known that recent warming of surface air temperatures (both in the U.S. and globally) has been stronger at night than during the day, but the AIRS data shows just how dramatic the day-night difference is… keeping in mind this is only the most recent 16.6 years (since September 2002):
The AIRS surface skin temperature trend at night (1:30 a.m.) is a whopping +0.57 C/decade, while the daytime (1:30 p.m.) trend is only +0.15 C/decade. This is a bigger diurnal difference than indicated by the NOAA Tmax and Tmin trends (triangles in the above plot). Admittedly, 1:30 a.m. and 1:30 pm are not when the lowest and highest temperatures of the day occur, but I wouldn’t expect as large a difference in trends as is seen here, at least at night.
Furthermore, these day-night differences extend up through the lower troposphere, to higher than 850 mb (about 5,000 ft altitude), even showing up at 700 mb (about 12,000 ft. altitude).
This behavior also shows up in globally-averaged land areas, and reverses over the ocean (but with a much weaker day-night difference). I will report on this at some point in the future.
If real, these large day-night differences in temperature trends is fascinating behavior. My first suspicion is that it has something to do with a change in moist convection and cloud activity during warming. For instance more clouds would reduce daytime warming but increase nighttime warming. But I looked at the seasonal variations in these signatures and (unexpectedly) the day-night difference is greatest in winter (DJF) when there is the least convective activity and weakest in summer (JJA) when there is the most convective activity.
One possibility is that there is a problem with the AIRS temperature retrievals (now at Version 6). But it seems unlikely that this problem would extend through such a large depth of the lower troposphere. I can’t think of any reason why there would be such a large bias between day and night retrievals when it can be seen in the above figure that there is essentially no difference from the 500 mb level upward.
It should be kept in mind that the lower tropospheric and surface temperatures can only be measured by AIRS in the absence of clouds (or in between clouds). I have no idea how much of an effect this sampling bias would have on the results.
Finally, note how well the AIRS low- to mid-troposphere temperature trends match the bulk trend in our UAH LT product. I will be examining this further for larger areas as well.
via Watts Up With That?
April 30, 2019 at 04:15PM
Temperatures below the climatic norm
1) Night frosts and snow in central Europe (Russia)
After a 20°C heat, night frosts returned. In the Volga-Vyatka region and the Middle Volga region snow fell.
The lowest temperature (up to −6 …− 8ºC) is registered in the Yaroslavl, Kirov, Penza and Ulyanovsk regions.
2) Snow cover will remain in the Middle Urals – IA “Meteonovosti”
The active cyclone, which brought inclement weather to the Urals last weekend, goes to the northeast, bringing arctic air.
On Sunday, 11 mm of precipitation fell in Yekaterinburg, and 8 mm more on Monday night. By morning, snow cover up to 15 cm high was formed in the city.
On Tuesday, with the increasing influence of the anticyclone from the west, in some places small precipitation in the daytime in the form of wet snow will be observed. At night, the frost will get stronger to -5 ..- 10°C, in the Sverdlovsk region with clearing up to -15°C.
3) This week in Moscow is dry and sunny, but with frosts.
On the last day of April, with variable cloudiness, still without precipitation, with a weak northeastern wind at night in Moscow 1..3°C, in low relief areas, on ramps and bridges to -1°C, in the region from -2 to +3°C. By day, due to solar warming, the temperature will rise to 14..16°C. The average daily temperature will be below the climatic norm by 2 degrees.
Thanks to Martin Siebert for these links
via Ice Age Now
April 30, 2019 at 02:17PM