The Drought Characteristics In The Regions Of China Based On The Standardized Precipitation Evapotranspiration Index

Based on the monthly precipitation and monthly-mean temperature data of160stations in China from1951to2010, which is provided by China Meteorological Administration, the applicability of the standardized precipitation evapotranspiration index(SPEI) is examined. The results are as the followings:(1) The SPEI at multiple time scales could be used to drought examining in the area which the annual precipitation is greater than200mm in China; In the other area, only the SPEI at the time scales which are longer than12months could be used to drought examining, especially for the12-month SPEI.(2) Because of many zero values (no precipitation and evapotranspiration cases) during winter months, it would reduce the confidence of the SPEI values when applying1-,3-,6-month SPEIs in arid climatic regimes which the annual precipitation is less than200mm.(3) Time series of the three indices, include SPEI, SPI and H index, were compared for four observatories with different climate characteristics, located in different parts of China. Relative to the SPI and H index, only the SPEI can identify an increase in drought severity associated with higher water demand as a result of evapotranspiration under the global warming, and can tell the start/end of drought events. So the SPEI takes the advantage for drought analysis and monitoring.(4) According to the SPEI, since the end of last century, an increase in drought severity occurred in the area which the annual precipitation is less than800mm in China. And in the area which the annual precipitation is greater than1200mm, the increase in drought severity occurred since the beginning of this century.(5) Since1997, the increase in drought is caused by the temperature rise in the area which the annual precipitation is less than200mm in China, and in the other area, precipitation is primary factors to affect the surface water resource.(6) Temperature rise aggravated drought in the area which the annual precipitation is200～400mm in China. Because of the precipitation is much more than the evapotranspiration which is calculated using the temperature data, the warming impact can never be ignored in the area which the annual precipitation is greater than400mm in China.