Comparison between the Spatial Distribution of Surface Humidity in Winter and Summer over East China

Based on the monthly mean surface dataset from 315 weather stations during 1963-2012, the spatial distribution characteristics of specific humidity (SH) and relative humidity (RH) over East China are analyzed. The results are as follows: 1) In winter months, the mean values of SH (0.4-7 g kg^-1) show zonal spatial distribution decreasing with latitude, while the mean values of RH (41%-82%) present the feature of a lower value in the central than in the northern and southern sides of the region. The relative variability of SH and RH are also discussed, revealing higher values of relative variability in areas with a lower value of SH and RH during the winter months. 2) In summer months, the values of SH (7-20 g kg^-1) are generally higher than in winter months, but the RH values (44%-89%) have little changes. Both SH and RH decrease from the southeast coast to northwest inland over East China. The spatial distribution of relative variability in summer months shows the lower mean values of surface humidity denoting lower mean values of SH or RH denoting higher values of SH or RH relative variability. 3) The spatial distribution of surface humidity in winter is deeply affected by the geographical location over East China. Specifically, surface humidity in winter is mainly dependent on latitude, but longitude also plays a role. However, surface humidity is not sensitive to elevation. Moreover, the distribution characteristics of SH are more dependent on the geography than RH in winter. 4) In contrast, the influence of geographical factors on the surface humidity distribution is more obvious in summer than in winter. In summer, surface humidity is also largely dependent on latitude, but the influence of elevation on SH and longitude on RH becomes more significant in summer than in winter. The geographical characteristics of the SH distribution are also stronger than for RH in summer.