基于SPEI的云南省夏玉米生长季干旱时空特征分析

The Temporal and Spatial Distribution of Droughts During Summer Corn Growth in Yunnan Province Based on SPEI

基于云南省29个典型气象站1953年-2011年的气象资料和16个州(市)1979年-2011年的玉米生产资料,分析云南省夏玉米生长季4个时间尺度的干旱风险时空变化特征,计算其标准化降水蒸散指数(Standardized Precipitation Evapotranspiration Index,SPEI),并验证了其与玉米减产率的正相关性。结果表明,SPEI能够较好地反映云南省历史干旱变化的时空特征和夏玉米的产量变化情况:①随着时间尺度的增加,SPEI值变化幅度减小,干旱频率降低、持续时间增长。3个月尺度的SPEI-3和6个月尺度的SPEI-6可体现干湿季节变化,12个月尺度的SPEI-12更能反映干旱年际变化情况;②从云南夏玉米不同生长期的干旱频率看,播种期>花丝期>成熟期;③从干旱频率空间分布特征看,总体上是滇东北>滇中>滇西南;④从年代际变化特征看,云南省玉米全生育期干旱呈加重趋势,以昆明市为例,玉米全生育期干旱指数Sep-SPEI-6最小值出现在2010年;⑤从统计分析结果看,云南省16个州(市)SPEI与玉米减产率均呈正相关关系,其中年均SPEI-3、年均SPEI-6、玉米全生育期干旱指数Sep-SPEI-6与玉米减产率相关性较大,表明了玉米生长季的干湿情况对玉米产量的影响较大。

Monthly precipitation, average temperature and sunshine data from 1953 to 2011 for 29 typical weather stations, and corn production data from 1979 to 2011 for 16 cities in Yunnan province were analysed to determine temporal and spatial characteristics. The correlation coefficient of the SPEI index at different time scales and corn yield reduction was also calculated. The results showed that variation in SPEI has declined, and the frequency of droughts has reduced but the duration has increased. Changes in the wet and dry seasons were reflected by SPEI-3 and SPEI-6, and annual changes were verified by SPEI-12. From the perspective of drought frequency during the different stages of com growth, the highest is the sowing period, which is followed by filaments period, and finally, the maturity period. There were three extreme droughts and 28 severe droughts in Kunming during the corn sowing period from 1951 to 2011, and the drought frequency was up to 51%. The frequency of drought was highest in central Yunnan. Drought tended to be seasonal and worse during the summer com growth season： the minimum Sep-SPEI-6 drought index of Kunming was in 2010. The SPEI drought indices in the 16 cities of Yunnan were positively correlated with com yield reduction. The SPEI value of the Kunming com growth season and corn yield reduction was positively correlated, and the correlation coefficient of Sep-SPEI-6 drought index and com yield reduction is equal to 0.58. Overall, droughts in the summer com growth season affect com production greatly and SPEI drought index can be applied to drought monitoring during the com growing season in Yunnan.