基于区域气候模式的流域农业干旱成因分析

以湄公河流域为研究区,采用区域气候模式RegCM3为模拟工具,以根系层土壤含水量为代表性指标,对A1B情景下未来研究区月尺度农业干旱进行了预估。基于地表能量平衡原理,系统分析了降水、蒸发、地表温度和根系层土壤含水量等农业干旱主要影响因素与区域气候模式模拟的大气环流、地表感热通量、地表潜热通量、地表净通量之间的联系和变化规律,从气陆间能量和水汽通量平衡角度,对农业干旱发生机理进行了识别。预估结果表明:从年内各月地表净通量和地表温度变化来看,未来春末(6月)和秋末(10月)湄公河流域温度增加明显,且土壤含水量减少也较为明显;同时,这两个时段蒸发旺盛和降水减少的趋势,有可能导致流域局部地区(尤其是非灌溉农业区)农业干旱的发生。

Driving forces analysis and estimation of agriculture drought in river basins using regional climate model

Taking the Mekong River basin as the study area,this paper analyzed and estimated the changes of agricultural drought on a monthly scale in terms of the typical index of soil water content in the root layer.The regional climate model(RegCM3) under the A1B scenario is used in the simulation of soil water content and other surface variables.Based on the theory of surface energy balance,it systematically analyzed the relationship and variation between the main factors of agricultural drought(such as precipitation,evaporation,surface temperature and soil water content of root layer) and atmosphere circulation,surface energy fluxes(such as sensible flux,latent heat flux,surface net flux) simulated by RegCM3.Through land surface water and energy fluxes balance,this paper identified preliminarily the occurrence mechanism of agriculture drought in the Mekong River basin.The estimation indicated that the surface temperature would increase obviously,but the soil moisture could decrease remarkably in late spring(June) and autumn(October).During the latter two periods,the study area is likely to experience a reduction in precipitation and an intensification of evapotranspiration,which could lead to the occurrence of agricultural drought in the study area especially in the non-irrigated agricultural regions.