[Characteristics and adaptation of seasonal drought in southern China under the background of climate change. III. Spatiotemporal characteristics of seasonal drought in southern China based on the percentage of precipitation anomalies].

To analyze the spatiotemporal characteristics and occurrence regularity of seasonal drought can provide theoretical basis for constituting the countermeasures of drought resistance and drought mitigation under the background of global climate change. Based on the 1959-2008 daily precipitation and atmospheric temperature data collected from the meteorological stations in 15 provinces (municipalities, and autonomous regions) of southern China, and using the percentages of precipitation anomalies (Pa) in the national standard "Meteorological Drought Classification", which were locally modified, the drought indices in southern China in 1959-2008 were calculated, and the spatial distribution characteristics of drought frequency in southern China in each year, each season, and each month, as well as the inter-annual changes of the drought intensity and the proportions of the stations with seasonal drought were analyzed. In the study period, the annual drought risk in southern China was generally low. There existed obvious seasonal differences in the spatial distribution characteristics of the drought. Autumn drought was most frequent and most intensive, mainly occurred in the middle and lower reaches of Yangtze River, South China and in the other major agricultural areas, winter drought was also frequent and intensive, mainly occurred in the west of Southwest China and the South China and other winter crop planting areas, while spring drought and summer drought were relatively less frequent or intensive. Spring drought mostly occurred in the southwest of Southwest China, the south of South China, and Huaibei area etc. , and summer drought mostly occurred in the middle and lower reaches of Yangtze River, southeastern coastal area of Fujian, and northeast of Southwest China. The area with drought frequently occurred showed an obvious monthly fluctuation and space transformation, which was decreased with time from November to next May, increased with time from May to November, in the smallest range from April to June, and in the widest range from November to December. The annual drought area showed a slight decrease while the drought intensity should a slight increase, but the situation differed with season, i. e. , spring drought area slightly decreased and the drought intensity weakened, summer drought area had an obvious decrease and the drought intensity weakened, autumn drought area increased obviously and the drought intensity increased, while winter drought area decreased and the drought intensity weakened.