三江源地区干旱指数时空演变及成因分析

Spatiotemporal Variation Characteristics of Aridity Index and Its Possible Causes in the “Three-River Headwaters” Region

基于1966-2017年三江源区11个气象台站的逐日气象资料,运用彭曼公式(Penman Monteith)计算潜在蒸散量(ET0)并进一步分析干旱指数(aridity index,AI)对于气候因子的敏感性.结果表明:三江源地区1966-2017年干旱指数总体呈明显下降趋势(0.1/10 a),年均值为1.76,属于半干旱区;研究区5年的干旱指数距平值于1990年后为负值,表明该区域气候于1990年后趋于湿润化,Mann-Kendall突变检验结果表明干旱指数分别在1988年和1992年发生突变;根据干旱指数的空间分布特征,将三江源区划分为东南湿润区、中部半湿润区和北部干旱区,其余大部分地区属于半干旱区和半湿润区;干旱指数对日照时数和相对湿度响应较为敏感,敏感系数分别为9.3和6.4,但对平均温度极为不敏感.相对贡献分析结果表明,三江源地区的干旱指数主要受相对湿度和平均风速的控制.

Based on daily meteorological data of 11 meteorological stations in the“Three-River Headwaters”region during 1966-2017,the potential evapotranspiration(ET0)and aridity index(AI)were calculated by Penman-Monteith formula.The temporal and spatial distribution characteristics and trends of drought change in the“Three-River Headwaters”region were analyzed by means of climatic tendency rate method and Mann-Kendall catastrophe analysis,and the sensitivity of drying index to climate factors was analyzed.The AI in the study region showed a remarkable downward trend(0.1/10 a)during 1966-2017,with an annual average value of 1.76,suggesting that the study area belonged to semi-arid area.The anomaly value of 5-year AI in this area was negative after 1990,indicating that the climate tended to be humid after 1990.Mann-Kendall mutation test of AI showed that AI suddenly changed in 1988 and 1992.According to the spatial distribution of AI,the study region were divided into the southeast humid area,the middle semi-humid area and the northern arid area,and most of the remaining regions belonged to semi-humid areas and semiarid areas;The AI was sensitive to sunshine hours and relative humidity,with sensitivity coefficients of 9.3 and 6.4,respectively.But it was insensitive to average temperature.Combined with the relative contribution rate of each meteorological factor to the AI in the study area,it showed that the AI in the“Three-River Headwaters”region was mainly affected by relative humidity and average wind speed.