基于改进失水模式和增加建模站点的Palmer旱度模式

Modification of Palmer Drought Severity Model Based on Improving Water Loss Pattern and Increasing Sample Stations

根据1965年Palmer旱度模式的思路,在1986年修正版及2003年修正版的基础上,为了使Palmer旱度模式更适用于我国北方干旱、半干旱地区,通过改进2003年修正的Palmer旱度模式在建模时表层失水模式的假设以及增加建模站点个数两个方面对Palmer旱度模式进行进一步修正。将计算的Palmer指数值与2003年计算的Palmer指数值及一些文献记载的实际旱涝灾情相对照进行验证,结果表明:新修正的Palmer旱度模式能更好地评估旱涝情况,扩大其在我国干旱地区的适用性。

After the modification of Palmer Drought Severity Model in 2003, it is found that the soil water loss pattern needs to be improved according to the actual soil water loss process. Also, in order to apply the Palmer Drought Severity Model more practical and more suitable in most arid and semi-arid regions in north parts of China, Palmer Drought Severity Model is once again modified from the aspect of optimizing the soil water loss pattern and increasing the sample numbers of modeling stations. From the aspect of soil water loss pattern, in consideration that in most arid and semi-arid regions in north parts of China, evapotranspiration will stop when soil water content in 0--20 cm layer is about 5 % of available water consumption （Caw）. Thus in the soil water loss pattern in modeling Palmer Drought Severity, it is supposed that the soil water loss in upper soil layer will be no less than 5 % of Caw. Besides Jinan, Zhengzhou, and Taiyuan stations, Qiqihaer station in Heilongjiang Province and Haiyuan station in Ningxia Province are selected and added to the modeling process. Totally 25 stations in north parts of China are used to modify the weight factors （4 new selected stations, in addition to 21 stations in modeling in 2003）. The drought index calculated by latest modified Palmer Drought Severity Model is compared with that modified in 2003 and the actual drought and wetting records in history. The result indicates that the latest modified Palmer Drought Severity Model can better evaluate the drought and wetting situations, especially in describing the extreme drought and extreme wet development processes, and can be better applied in most arid and semiarid regions in north parts of China.