基于连续无有效降水日数指标的中国南方作物干旱时空特征

利用中国南方15个省(市、区)气象台站1959-2009年逐日降水资料,以连续无有效降水日数(Dnp)为干旱指标,完善了指标中有效降水临界值和干旱分级标准,利用改进后的连续无有效降水日数干旱指标计算了南方地区春播夏收作物、春播秋收作物、夏播秋收作物、越冬作物近50a的干旱指数,得到干旱频率和干旱持续天数的空间分布特征,并分析其年际变化;同时引入逐日干旱频率,研究作物生育期内逐日干旱动态变化。研究结果表明:春播夏收作物在西南地区西部和淮北地区常发生春旱;春播秋收作物在长江中下游地区多发夏秋旱,在华南东北部多发秋旱,在西南地区东部伏旱明显;夏播秋收作物在长江中下游地区秋旱多发、华南东部秋旱高发;越冬作物在西南地区西部秋冬春旱高发且持续时间长,江北和华南地区也多秋旱和春旱。从年际变化趋势看,春播秋收作物干旱范围略有增大,夏播秋收作物干旱范围显著增大、强度略有增强,越冬作物干旱范围呈较明显增大;其他各作物干旱范围和强度呈不同程度减少、减弱的趋势。

Spatio-temporal characteristics of crop drought in southern China based on drought index of continuous days without available precipitation

Abstract: This study was based on daily precipitation data from standard meteorological stations in the 15 provinces (municipalities, or autonomous regions) in southern China. We adopted continuous days without available precipitation (Dnp) as drought index, also improved the critical values of available precipitation and drought classification standard during the data process, then calculated drought index values for crop ( spring sowing-summer harvesting crop, spring sowing-autumn harvesting crop, summer sowing-autumn harvesting crop, and overwintering crop ) during the most recent 50 years(from 1959 to 2009) in southern China. We analyzed the spatial distribution characteristics and inter-annual variation of crop drought frequency and crop drought duration days. In addition, we introduced daily drought frequency to study dynamic change of crop drought during the growing period. The results showed: spring sowing-summer harvesting crop drought occurred sometimes in the west of Southwest China and part of Huaibei Area during spring; spring sowing-autumn harvesting crop drought often affected the middle and lower reaches of Yangtze River, as well as the northeast of South China and the east of Southwest China during summer and autumn; summer sowing-autumn harvesting crop drought often occurred in the middle and lower reaches of Yangtze River during autumn, as well as the east and north of South China; overwintering crop drought took place in the north of Yangtze River and South China during autumn and spring , especially drought occurred frequently in the west of Southwest China during autumn to next spring. Generally, the distribution of drought duration days without available precipitation was basically consistent with the distribution of drought frequency, which meant drought lasted relatively longer in drought-prone area.The characteristics of drought change trend in southern China showed that: spring sowing-summer harvesting crop drought showed a decreasing trend in covering area as well as a reducing trend in intensity; spring sowing-autumn harvesting crop drought showed a slightly increasing trend in covering area yet a slightly reducing trend in intensity; summer sowing-autumn harvesting crop drought showed a significantly increasing trend in covering area and a slightly increasing trend in intensity with an exception of the Southwest China showing a reducing trend in intensity; overwintering crop drought showed a relatively more significantly increasing trend in covering area and an reducing trend in intensity with an exception of South China showing a increasing trend in intensity. From the perspective of daily drought frequency, early spring in the south and west of South China as well as the north of Yangtze River, together with spring in the west of Southwest China, showed a relatively higher drought frequency, hence affected spring sowing crops; midsummer drought in July and August in the middle and lower reaches of Yangtze River, autumn drought in September and October in South China, together with midsummer and autumn drought in the east of Southwest China mainly affected autumn harvesting crops; overwintering crop showed a relatively higher drought frequency in the whole study area, and the main drought period was in autumn and wintering period, however, early spring in the north of Yangtze River, as well as the south of South China, and Southwest China showed a relatively higher drought frequency.