Cross Comparison of Three Kinds of Upper Air Temperature and Humidity Data over China
In this study, the differences of temperature and humidity profiles over China obtained from L band sounding system, COSMIC occulation observation system and ERAInterim reanalysis data during the period 2011-2013 are compared. Time series comparisons show a good positive linear correlation among these three data sets. In addition to a few levels above 10 hPa, L band, COSMIC occultation and ERAInterim reanalysis temperature data accord well with each other, with the temperature bias ranging within ±0.4℃, and the standard deviation between 1℃ and 2℃. L band temperature is higher due to the great influence by solar radiation in the middle to upper troposphere, with the maximum bias of 0.64℃ when compared with COSMIC occultation. As for relative humidity, things are strikingly different. L band relative humidity data exhibit a varying degree of dry bias between the lower troposphere and the upper troposphere. Moreover, there are obvious diurnal, seasonal and climate regional differences, and the differences become even more evident during daytime, spring/summer period, and over south moisture climate areas. Generally, the dry bias is more obvious in the region near the top of troposphere; L band relative humidity turns to wet bias at above 200 hPa atmospheric pressure layer. L band and COSMIC occultation sounding relative humidity, ERAInterim relative humidity have positive correlations obviously below the top of troposphere. Nevertheless, there is a negative correlation above the tropopause.