塔里木盆地灌溉对局地干旱气候影响的数值模拟研究

Numerical Simulation of the Effects of Irrigation on Local Arid Climate in Tarim Basin

塔里木盆地气候干燥,其农业主要依赖灌溉,灌溉必将对局地气候产生重要影响。为了更好地了解农田灌溉如何改变新疆干旱地区的局地气候以及量化灌溉农田在局地气候系统中的作用,以中国西北地区的塔里木盆地为典型研究区域,首先在区域气候模型WRF(Weather Research and Forecasting)的CLM(Community Land Model)陆面模式中加入合理的灌溉方案,然后设计2组试验(分别为考虑和不考虑灌溉),连续模拟10 a(2006-2015年)的作物生长季(5-9月),通过模型模拟结果与观测比较来研究塔里木盆地灌溉的局地气候效应。研究结果表明:改进后的模型能够模拟出与观测相近的地表温度、近地面气温和降水,不仅显著地降低了原模式在灌区内的热偏差,而且灌溉引起的冷却和增湿效应导致灌区降水误差变小。此外,灌溉导致灌区的降水略微增加,在灌区周边的降水却显著增加。因此,由灌溉增加的降水量能够缓解干旱地区的灌溉需求压力,对当地的干旱气候也会产生重要影响。

The climate in Tarim Basin is dry,and its agriculture mainly relies on irrigation,which will definitely have an important impact on the local climate.In order to better understand how farmland irrigation can change the local climate in arid regions of Xinjiang and quantify the role of irrigated farmland in the local climate system,we chose the Tarim Basin in northwest China as a typical study area.This study firstly added a reasonable irrigation scheme to the CLM(Community Land Model)land surface model in the regional climate model WRF(Weather Research and Forecasting),and then designed two sets of experiments(with and without irrigation),and simulates them continuously for 10 years(2006-2015)in the crop growing seasons(May-September).The effects of irrigation on local climate in Tarim Basin were studied by comparisons with observations through model simulations.The results indicated that the modified model can simulate land surface temperature,near-surface air temperature,and precipitation similar to the observations.Not only the warm biases of the original model over irrigated areas are significantly reduced,but also the cooling and wetting effects induced by irrigation lead to a reduction of precipitation bias.In addition,the irrigation caused a slight increase in precipitation over irrigated areas,but precipitation around irrigated areas increased significantly.Therefore,the increase of precipitation induced by irrigation can alleviate the pressure of irrigation demand in arid regions,and it will also have an important impact on the local arid climate.