Further Modification And Application Of The Palmer Drought Severity Model

Drought is one of the most serious meteorological disaster in China.There are different definition and index of drought in different field.Because of the complexity of drought and the universality of its influence,most of the existent drought indexes have limitation in speciality and regionally application. Meteorological drought is the foundation of other kinds of drought.The objective of this research is to develop a meterological drought severity model considering climate factor comprehensively,which reflecting the beginning,end, the cause of formation and the severity of drought ,and is comparable in space and time.On the base of the Palmer Drought Severity Model of America and the modificated Palmer Drought Severity Model(1986),we further modificate the Palmer Drought Severity Model in the following aspects;?4 stations were chosen to develope the model and adjust the weighting factor; ㏕he potential evapotranspiration for an each month was computed by the Penman-Monteith equation commended by FAO;(3) The getting of available water capacity of the soil(AWC) in each station was based on the data of AWC that we can find and the characteristic of soil in each station.The monthly Palmer Drought Index of 160 stations from 1961 to 2000 were computed based on the further modified Palmer Drought Severity Model Compared the computed Palmer Drought Index with the actual drought and waterlog,it shows that the further modified Palmer Drought Severity Model can reflect the severity of meteorological drought or waterlog better and is more applicable for china than the Palmer Drought Severity Model modified in 1986.The computed Palmer Drought Index of 124 stations in the north of china are used to analyse some charactersin this region,including the main drouthy years and its severity,the drought range,etc..we also analyse the main drouthy periods,the frequency of each drought degree,the main area and the drought cycle in northwest china,north china and northeast china.On the base of the Further Modification of Palmer Drought Severity Model,a daily Palmer Drought Severity Model are developed.lt indicated that the daily drought index is accordant with the monthly drought index,and can reflect the change of severity in detail.