植被变化对中国区域气候的影响Ⅰ:初步模拟结果

THE EFFECTS OF VEGETATION CHANGE ON REGIONAL CLIMATE Ⅰ:SIMULATION RESULTS

利用区域气候模式（RegCM2）对中国植被变化的气候影响进行了模拟研究,结果表明:江淮流域洪涝灾害增多及华北干旱的加剧可能是北方草原沙漠化与南方长绿阔叶林退化共同影响的结果,而且南方植被退化对其的影响似乎更严重。严重的植被退化会导致降水与植被退化之间的正反馈,易使退化区不断向外扩展且退化难以恢复。而程度较轻的植被退化,退化与降水减少之间是一种负反馈,当人为压力减弱后,退化较易恢复,但由于地表径流的增加,易导致洪涝灾害的发生。植被退化使气候变得更加恶劣,而北方草原植被增加使气候变得温和。但植树区外围的降水减少,易使新栽树林由外向内退化,说明目前的北方草原区气候似乎不支持在该地区出现大面积的森林。

In the context of a regional climate model (RegCM2) , simulation is undertaken of climatic effects of changed vegetation over China, reaching results which show that the increase in flood events over the Changjiang Huaihe River Valleys and the aggravation of North China droughts are likely to be under the joint action of desertification of the northern grassland and southern degradation of evergreen broadleaf trees, the latter seeming to be the primary factor. Severe vegetation degeneration leads to a positive feedback between rainfall reduction and degradation with the consequence that the disaster expands steadily outward and the hit-area is difficult to turn back into farmland. In contrast, less heavy degeneration causes a negative feedback between deterioration and rainfall reduction. And the stricken sector is likely to reclaim when human damages are decreased or removed. However, degeneration strengthens surface runoff, allowing flood occurrence. Vegetation deterioration makes the climate even more inhospitable. On the other hand, experiments show that the vegetation enlargement of northern grassland will lead to a mild climate, responsible for precipitation reduction in the outer belts of afforestation, which is possible to cause newly-planted trees to die stepwise inward, a result that means the current climate in the grassy land does not seem to support a plan on large-scale afforestation there.