关键词: 标准化前期降水指数, 气象干旱指标, 旱日

Abstract: According to the definition of meteorological drought, considering cumulative effect of drought, a daily meteorological drought indicator is presented based on the standardized antecedent precipitation index (SAPI), and the applicability of SAPI were examined by using daily precipitation data of 632 meteorological stations in China from1961 to 2010. SAPI shows a typical “jagged fluctuation pattern” and decreases steadily during rainless periods, thereby overcoming the “unreasonable drought aggravation” problem of the comprehensive meteorological drought index based on equal weight accumulation due to the antecedent precipitation moving out of the calculation window. SAPI is able to describe the processes of occurrence, development and end of drought accurately. Sensitivity analysis show that the needed rainless days to increase one drought level are more in areas or seasons with less rainfall than in those with more rainfall, and the needed daily rainfall to reduce one drought level is less in areas or seasons with less rainfall than in those with more rainfall. In general, drought days of various levels are consistent with their theoretical frequencies. Light and moderate drought days are slightly more in areas or seasons with more rainfall than in those with less rainfall, and the opposite is true for severe and extreme drought days. During 1961-2010, national-averaged drought days of each level all show decreasing trends, among which the trends in extreme drought days are most obvious but with complex spatial-temporal characters. Drought days of each level increase significantly in September-November, however decrease in most of the rest months. Drought days of each level overall decrease in the west but increase in the east of China.

Key words: standardized antecedent precipitation index (SAPI), meteorological drought indicator, drought days