Diurnal Cycle Variability of Surface Temperature Inferred From AIRS Data

The diurnal cycle of the Earth surface temperature is investigated using the daily range of the satellite skin temperature data (DTR) provided by measurements of Atmospheric Infrared Sounder (AIRS) in 2002-2015. The AIRS is on the Aqua satellite, which is in a polar orbit with two crossing times per day at every location on the Earth. Its measurements from the ascending (day) and descending (night) orbits can serve as a proxy for the diurnal cycle. The spatial pattern of the DTR of the skin temperature and its time variability for 14 years of the AIRS operation allows to evaluate the diurnal cycle change on the decadal time scale. Using the empirical mode decomposition of the data time series, it is found that the DTR of the surface (skin) temperature over the global Earth has a temporal small positive trend in the decade of the AIRS measurements indicating that the day temperatures grew slightly more rapidly than the night temperatures. A possible cause of the observed DTR increase is a decrease of the low cloud fraction at nighttime found for the same time period from the AIRS retrievals. Plain Language Summary The diurnal cycle (day-night difference) of the Earth surface temperature is investigated using the daily range of the satellite skin temperature data (DTR) provided by measurements of Atmospheric Infrared Sounder (AIRS) instrument in 2002-2015. The AIRS is on the Aqua satellite, which is in a polar orbit with two crossing times per day at every location on the Earth. Its measurements from the ascending (day) and descending (night) orbits can serve as a proxy for the diurnal cycle. It is found that the DTR of the surface temperature over the global Earth has a small positive trend in the decade of the AIRS measurements indicating that the day temperatures grew slightly more rapidly than the night temperatures. A possible cause of the observed DTR increase is a decrease of the low cloud fraction at nighttime found for the same time period from the AIRS retrievals.