陕北地区植被治理与退化对一次区域降水过程影响的数值模拟

A Numerical Simulation of the Impact of Afforestation and Desertification on Summer Rainfall in Northern Shaanxi

针对陕北地区一次区域性降雨个例 ,运用中尺度模式MM5V3 5进行了陕北地区植被治理和退化的敏感性试验。结果表明 ,植被生态治理后 ,能够使区域的平均降水量增加 ,使地表净盈余水分 7 6% ;植被退化使降水量减少 ,地表亏失水分 3 6%。植被变化对降水的影响有热力和动力两方面原因 :一方面 ,植被改善后 ,地气之间的热通量增大 ,地表对大气的增温作用增强 ,使低层大气更趋于不稳定 ;另一方面 ,植被改善增大了地表的非均一性 ,能够激发出一定强度的局地次级环流叠加于天气尺度系统上。这两种作用 ,使系统加深并发展 ,增加到达地面的降水量。植被退化则产生与上述相反的作用 ,导致局地降雨量的减小 ,使地面进一步干旱化。

The meso-scale model (MM5V3 5) is employed to investigate the effect on a summ er rainfall case of afforestation and desertification in northern Shaanxi The results indicated that the surface rain water would be increased 7 6 percent by afforestation and be decreased 3 6 percent by desertification The reasons ca n be came down to two aspects: on the one hand, afforestation would be respons ible for the strengthening of thermal flux and the increase of atmospheric insta bility near surface; on the other hand, the surface inhomogeneity is enhanced af ter afforestation, and it would inspire rather intense secondary circulation imp osing on the synoptic circulation system, as the results, the circulation system is developed and the surface rain water is increased Reversal would happen in the presence of desertification, which would lead to farther more drought and d eterioration