黄土高原植被恢复引发区域气温下降

Cooling effect induced by vegetation restoration on the Loess Plateau

黄土高原退耕还林(草)等生态恢复工程促进了地表植被覆盖增加,进而通过影响地表-大气之间热量交换影响区域气候过程。基于黄土高原1998—2000年和2008—2010年SPOT卫星反演的植被覆盖资料、54个地面气象站气温资料及EIN-Interim地表热通量数据,采用空间分析交叉验证及地表热量平衡分析的方法,从站点尺度探讨了退耕还林(草)工程初期和10年后黄土高原植被变化与气温和地表热通量变化之间的关系。研究表明,退耕还林(草)工程开展10年后,黄土高原气温最小值、最大值与平均值均有下降,植被覆盖增加与气温变量降低在空间上呈正相关。同时,植被覆盖增加与潜热通量增加、感热通量与大气下行长波辐射下降在空间上也呈正相关关系。这些结果表明,植被恢复可通过增加地表蒸散发作用对区域气候产生降温效应,会减缓气温升高对黄土高原生态系统的影响。

A large-scale re-vegetation with regional ecological engineering on the Loess Plateau, including the Grain for Green Project （GGP）, has already greatly impacted the heating and energy flux between the land and atmosphere, which induces regional climate. We used two methods, the cross-checking of spatial change and surface heat balance analysis to detect the relationships among the vegetation change, temperature change, and surface heat flux change during the GGP at the station scale over the Loess Plateau. The 10 days normalized difference vegetation index （NDVI） derived from SPOT data was used to indicate the vegetation. The monthly temperature data from 54 weather stations within or nearby the Loess Plateau were used to describe the temperature change. The EIN-Interim surface heat fluxes were analyzed to determine the surface heat condition. Two stages, the initial stage （1998-2000, Stage I） of GGP and 10 years after （2008-2010, Stage Ⅱ） were compared. The minimum, maximum, and mean temperatures were lower in Stage Ⅱ, and the increase of vegetation was spatially positively correlated to the decrease in all temperature variables. Meanwhile, the increase in vegetation was spatially positively correlated to the increase in latent heat flux, and the decrease of sensible heat flux and the atmospheric downward longwave heat flux. These results indicated that vegetation restoration may lower the temperatures through an increase in surface evapotranspiration, and thereby mitigate the climate warming effect on the ecological system of the Loess Plateau.