[Characteristics and adaptation of seasonal drought in southern China under the background of global climate change. IV. Spatiotemporal characteristics of drought for maize based on crop water deficit index].

Based on the 1959-2008 meteorological data from 249 meteorological stations in southern China, and by using crop water deficit index (CWDI) as the agricultural drought index, this paper calculated the drought frequency and drought stations ratio in this region, and analyzed the spatiotemporal distribution characteristics of drought for spring maize and summer maize during their growth periods. As for the spatial pattern of drought frequency, the drought for spring maize was more severe in the north of Huaihe River, northern Yunnan, and southern South China, but was lighter in the other regions. Except that the drought for summer maize at its late developmental stage was more severe in the middle-lower reaches of Yangtze River, northern South China, and eastern Southwest China, the drought for summer maize at its other developmental stages within southern China was lighter. As for the variation trend of drought intensity and drought area, the drought intensity of spring maize from its seven-leaf stage to jointing stage in the middle-lower reaches of Yangtze River increased obviously, while the drought intensity and drought area of the spring maize from its late spinning stage to milky maturity stage presented a decreasing trend. The drought of summer maize from its late jointing stage to tasseling stage and from late spinning stage to milky maturity stage all showed a decreasing trend. In Southwest China, the drought intensity and drought area for spring maize and summer maize had no clear trend. From the viewpoint of the inter-annual and decadal variability of drought intensity and drought area, there was a larger variation for the summer maize in the middle-lower reaches of Yangtze River, but less difference in Southwest China.