| In the context of 1981-2002 GIMMS-NDVI data, snow depth data, surface heat flux and geopotential height data from ECMWF, and summer precipitation data at observational stations of China, it is investigated for the possible relationship of the variation of summer rainfall over China to the land surface conditions of Tibetan Plateau (TP) in April, by using correlate, composite and partial analysis and introducing the concept of inter-annual increment to reflect the inter-annual variation of these variables. The results suggest that:(1) The main features of land surface conditions of vegetation NDVI and climatology of snow decrease from south to north. The tendency of the first mode of two variables is unanimous on spatial and temporal distribution.(2) The vegetation has significant correlation with the snow cover by correlation analysis over TP in April. In order to remove the relationship between the two, the partial correlative relationship is carried out to find out that:The vegetation has negative correlation with the land surface heating and sensible heat while positive with the latent heating generally; The snow has negative correlation with the land surface heating and latent heating, and little correlation with the sensible heating; The correlation distribution between vegetation and land surface heating was similar with that between vegetation with land surface sensible heat; The correlation distribution between snow and land surface heating effected by the correlation of snow with sensible heat and latent heat simultaneous.(3) The apparent correlation between the surface heating of TP in April and inter-annual variation of summer rainfall over China is mainly located in Yangtze River, Yellow River, and north-eastern region of Inner Mongolia; and the correlation is more significant and the regions are broader from the perspective of inter-annual increment. The main distribution features are as follows:In June, the evident negative correlation covers the south of Yangtze River, part of Yellow River and the most regions of Northeast China, but positive correlation in Southwest China; In July and August, most regions of north Yangtze River show clear negative correlation, but positive correlation in South China.(4) The significant correlation between the height fields of Northern. Hemisphere in summer and the surface heating of TP in April is mainly located in middle and high latitudes, the Western Pacific subtropical region and Indian-Burma region. The distribution of correlation may explain the reason for the relation between the surface heating over TP in April and summer precipitation in China, because the region of significant correlation is important for effect of circulation system on summer rainfall.(5) Inter-annual increment could describe the inter-annual change for land surface conditions over TP and summer rainfall in China and the relationship between two. If the relationship between vegetation and snow is removed, when the vegetation vary over TP, surface heating will appear abnormal by the sensible heating of change to lead to the unusual atmospheric circulation in Northern Hemisphere, so that summer precipitation in China have contact with the vegetation over TP, while the snow depth is contact with the summer rainfall by the sensible heating. |
