Abstract:

The Upper Troposphere (UT) water vapor distribution has a very important influence on global energy and water cycle. The spatial-temporal distribution of water vapor in UT has been analyzed using humidity profile data retrieved from AIRS (Atmospheric Infrared Sounder) which is on board of Aqua satellite. In order to make sure that the accuracy of the humidity profile data meets the needs of the climate characteristics analyses, we run a validation on the relative humidity against the sounding observation data in JICA field campaign in 2008. The result shows that the two data sets have a good correlation, and the absolute error is within 5% in 200 hPa. Therefore, the AIRS relative humidity data in 200 hPa can be used for the climate characteristics analysis. Our analysis on the spatial-temporal characteristics of the relative humidity during the period of January 2003 through December 2013 prove that, with the impact of the summer monsoon, the relative humidity in China has significant seasonal and yearly variation characteristics. The relative humidity in UT is more in summer than that in winter in China, the high relative humidity area can move northward to 35°N in summer. There is a opposite distribution in Xinjiang province that more humidity in winter and less in summer. Over all, the relative humidity in UT over China is the highest in summer, lower in fall, and the lowest in winter. From 2003, the relative humidity has shown a significant elevating trend in South China Sea and Xinjiang province. In South China, North China, central and western of Inner Mongolia, relative humidity in UT also increased, but did not change significantly, and in the Tibetan Plateau and the Northeast China, water vapor in UT decreased slightly, but the changes were not significant. The increase of water vapor in the UT will have the potential to amplify the greenhouse effect, which should be paid more attention in the study of climate change.

Key words: AIRS, humidity profile, validation, spatial-temporal distribution characteristics, the upper troposphere