Effects Of Vegetation Change On Air Temperature And Precipitation In The Loess Plateau Based On CLM Model

Loess Plateau region locates in the second step of China with a complex geographical environment and fragile ecological environment. This paper aims to investigate the relationships between vegetation cover and climate in Loess Plateau region by diagnostic analysis and numerical simulation tests using GIMMS NDVI and stationary observed datasets. The main results are shown as following.(1) The results of statistical analysis indicate that NDVI, temperature and precipitation of Loess Plateau region exhibit obvious seasonal variation characteristics; from1982to2006, the regional slope of average NDVI, temperature and precipitation is0.004/10a,0.6℃/10a and-10.8mm/10a respectively, and there are space difference among them; The anomaly average correlation coefficient of NDVI&temperature and NDVI&precipitation in the same period is not significant, and with obvious spatial difference.(2) By using CLM and CAM model to simulate temperature and precipitation in Loess Plateau region, the model can simulate the space distribution of temperature and precipitation, with the parameterization scheme improved by LAI remote sensing data, the simulation of temperature and precipitation reaches a certain degree of improvement. To carry out a sensitivity test, we change the vegetation types of Loess Plateau region from crops to temperate deciduous broad-leaved forest, and expand the leaf area index. The simulation results show that vegetation coverage changes have lead to temperature decrease and rainfall increase, and summer performs an obvious change.(3) By using the offline simulation of CLM, we discuss the effects on the energy balance of the earth atmosphere system whenever the vegetation cover has changed. When the vegetation coverage increases, net absorbing shortwave radiation of the study area were significantly increased, and net long-wave radiation decreased. When vegetation coverage increased, the sensible heat flux and latent heat flux were all increased, and latent heat flux increases stronger than sensible heat flux, which may take a certain impact on the significantly decreasing of temperature when the vegetation coverage has increased. When vegetation type changed from crops to temperate deciduous broad-leaved forest and leaf area index expanded, while the soil moisture content of the area increased, and evapotranspiration increased, this may cause some enhancement in precipitation in the study area.