Distribution Characteristics of Yunnan Province Atmospheric Water Resource

Using the monthly precipitation and temperature of Yunnan 124 stations from 1961 to 2004, the water resource components, such as the evaporation (E) and utilizable rainfall (P-E), are calculated by means of Takahashi's evaporation equation. The temporal and spatial features of water resource components and their periods are also analyzed. Results indicate that components (P, E, P-E) of water resource in southern area are higher than that of northern area. The grads in southern area are big and that in northern area are small. 44-year average P-E and have very similar spatial and temporal distribution. The biggest and smallest center of P-E are unanimously corresponding with P, but the value of P-E is smaller than P. The components (P, E, P-E) of water resource in Yunnan have obvious seasonal changes. The biggest value of the components (P, E, P-E) appears in summer. Their annual average values are 548 mm, 236 mm, 313 mm respectively and their ratios to the whole year are respectively 55%, 45% and 67%. The smallest value of the components (P, E, P-E) appears in winter and their ratios to the whole year are respectively 5%, 7%and 2%. The components (P, E, P-E) of water resource in Yunnan also have obvious inter-monthly, interannual and interdecadal changes. The biggest value appears in July and the smallest appears in January or December. The difference between the maximum and the minimum of components (P, E, P-E) of water resource is very large. At the same time, the interdecadal difference of components (P, E, P-E) of water resource is also very obvious. P and P-E are relatively abundant from 1960s to the middle of 1970s, they are less from mid 1970s to mid 1990s and more after mid 1990s. By the power spectrum period analysis method, it is revealed that there is a significant period of 2.6 years in total annual rainfall and total annual utilizable rainfall and there is a significant period of 2.9 years in total annual evaporation. The water resource of Yunnan Province is divided into three regions:abundant region, poor region and general region. There are very obvious differences among regional and annual mean utilizable rainfall, evaporation and rainfall of the three regions.