Report Chilly Higher Mesospheric Temperatures Recommend One other Good Noctilucent Cloud Viewing Season
From Dr Roy Spencer’s Weblog
Might 31st, 2020 by Roy W. Spencer, Ph. D.
Noctilucent clouds (NLCs) are sometimes seen within the excessive higher ambiance (80-85 km altitude) effectively after sundown within the late spring and summer time at excessive northern latitudes. They type from ice condensing on meteoric mud at extraordinarily chilly temperatures (beneath 150 Kelvin or -190 deg. F). The chilly temperatures are because of adiabatic cooling from dynamic uplift mixed with little ozone to soak up the solar’s ultraviolet radiation.
Noctilucent clouds on Might 31, 2020 (Alan Robust, Scotland)
With present photo voltaic minimal circumstances lowering photo voltaic heating by ultraviolet radiation, and slowly growing CO2 within the ambiance inflicting enhanced infrared cooling to outer area, report low temperature are occurring. This has prolonged the southernmost viewing alternative for NLCs from the standard ~60 deg. N latitude to as little as 35N latitude final 12 months, with NLC sightings close to Los Angeles and Las Vegas in 2019.
This current article by Dr. Tony Phillips steered that 2020 is shaping as much as be one other good NLC viewing season. An earlier article by Tony included this good plot of April-Might temperatures at 80 N latitude from this 12 months in comparison with earlier years, exhibiting the overall cooling development in the course of the present photo voltaic minimal circumstances.
Knowledge plot courtesy of Dr. Lynn Harvey, U. of Colorado.
We downloaded some newer Aura satellite tv for pc Microwave Limb Sounder information, and plotted it as a operate of latitude. Notice how briskly temperatures dropped in solely 6 days… 1-2 deg. C per day relying upon latitude.
Higher mesospheric temperatures at 83 km altitude on two totally different days in Might, 2020 as a operate of latitude. Strains are 2nd order polynomial matches to the info, offering common temperatures as a operate of latitude.
The 141 Ok common temperature on Might 27 (Day 148) at 80N latitude seems to be a brand new report low if we evaluate it to the info within the earlier plot by Dr. Harvey.
I’ll attempt to hold monitor of those temperatures because the NLC season progresses within the coming weeks. Thus far, NLC sightings have been largely in northern Europe and the UK.
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