A comparison of atmospheric temperature over China between radiosonde observations and multiple reanalysis datasets

The quality controlled (RAW) and homogenized (ADJ) radiosonde temperatures at 850—30 hPa collected at 118 stations in China are compared, on a monthly mean basis, with the temperatures extracted from 8 reanalysis datasets (REA) including NCEPv1, NCEPv2, ERA-40 (ECMWF 45-yr Reanalysis), ERA-Interim, JRA55 (Japanese 55-yr Reanalysis), 20CR (20th Century Reanalysis), MERRA (Modern Era Retrospective-Analysis), and CFSR (Climate Forecast System Reanalysis). Average differences, correlations, standard deviations, and linear trends among RAW, ADJ, and REA for the period 1981-2010 are analyzed. The results reveal significant inhomogeneity in the time series of RAW radiosonde temperature in China; an overall negative adjustment was thus applied to obtain the ADJ temperatures, and the effect the negative adjustment is the most significant within 200—100 hPa. Such a homogenization rocess has removed the system errors in RAW possibly caused by radiosonde instrument changes and observation system upgrades. Hence, the correlation is higher between ADJ and REA than that between RAW and REA. The mean difference between ADJ and REA is about 1℃ during 1981-2010, while REA are mostly cooler in the troposphere and warmer in the stratosphere than ADJ; nonetheless, they have a high positive significant correlation and their annual varialility is notably consistent annual variability. Furthermore, the trends in REA and ADJ both demonstrate warming in the lower－mid troposphere and cooling in the mid stratosphere, with large uncertainties found in the upper troposphere and lower stratosphere. In general, ERA-Interim, JRA55, and MERRA are more consistent with ADJ than other reanalysis datasets.