Aridity/humidity status of land surface in China during the last three decades

To clarify aridity/humidity status of land surface is helpful for studying environmental background and regional differences, seeking causes of environmental change, and providing a scientific basis for researches on climate change in the future. In this paper, the authors calculated potential evapotranspiration of China using data from 616 meteorological stations during the period of 1971-2000 with the Penman-Monteith model recommanded by FAO in 1998. Vysothkii’s model was used to calculate aridity/humidity index. Then the calculated results of sta-tions were interpolated to land surface using ArcGIS. Results show that the annual average potential evapotranspiration is 400-1500 mm in the whole country, 600-800 mm in most parts of it; and 350-1400 mm in growing season (April-Octobor), which is nearly 200 mm less than the annual average. According to the aridity/humidity indexes of 1.0, 1.5 and 4.0, the aridity/humidity status is categorized to four types, namely, humid, subhumid, semiarid and arid. A majority of stations (76%) are more humid in growing season than the annual average. Results of comprisons between the distribution map of aridity/humidity index with that of precipitation and vegetation indicate a good consistence of aridity/humidity status with natural environment. Therefore potential evapotranspiration calculated with modified FAO’s Penman-Monteith model in combination with aridity/humidity index that considers water balance can more reasonably explain the actual land surface aridity/humidity status of China.