Total Column Water Vapor over Chinese Mainland Based on Different Datasets

The spatial distribution characteristics and linear trends of total column water vapor (TCWV) are compared between radiosonde data, NCEP/NCAR reanalysis data and ERA-40 reanalysis data over Chinese Mainland from 1971 to 2001. The TCWV is also used to investigate how water vapor changes under the context of climate change. The radiosonde data are used to calculate TCWV, which is integrated vertically from surface to 300 hPa, TCWV of NCEP/NCAR and ERA-40 reanalysis data also restricts from surface to 300 hPa. Considering the missing rate and integrity, 78 stations are selected and the analyzed. The result shows that the climatological annual mean and seasonal mean spatial distribution features of TCWV between those data are consistent. TCWV decreases gradually from southeast to northwest, but the decreasing rate derived from the two reanalysis data are smaller than that of radiosonde data. Seasonal variations of TCWV is distinct, the largest TCWV occurs in summer and the smallest in winter. For linear trend of annual mean, TCWV is increasing in northeast of China, the coastal regions of Southern China, northern regions of Southwest China and northern Xinjiang region in all three data. The most evident differences in three data are in southern Xinjiang region and parts of north and east China. In southern Xinjiang region, TCWV of NCEP/NCAR reanalysis data shows decreasing trend, it is increasing according to the other two datasets. In parts of north and east China, TCWV of the two reanalysis datasets both show decreasing trend, but according to the radiosonde data, TCWV may increase slightly rather than decrease. The linear trend of TCWV by all three datasets is not significant at 95% confidence level in this region. Radiosonde data also shows that the largest relative trends are in higher latitudes. Six stations are selected to compare time series of anomaly TCWV between the three datasets, indicating that anomaly TCWV of three datasets have similar variation tendency at the same station, though not equal. The variation tendency of TCWV is different from station to station, which illustrates water vapor responds differently to climate change in different regions.