The Influences Of The Vegetation Degradation In The Qinghai-Tibet Plateau On The Atmospheric Circulation

The change of Qinghai-Tibet Plateau vegetation will influent the thermal action of the plateau. Using the remote sensing data of GIMMS NDVI and MODIS NDVI and the data from 6 meteorological stations of Qinghai-Tibet Plateau, as well as some statistical and calculation methods, we discuss the spatio-temporal variation of the vegetation of Qinghai-Tibet Plateau and its influence factors. Using the community atmosphere model (CAM5.1-CLM4.0), as well as the scope and degree of the Qinghai-Tibet Plateau vegetation degradation, by changing the leaf area index in the plateau. We discuss the influences of vegetation degradation in the Qinghai-Tibet plateau on the atmospheric circulation in the plateau and adjacent areas. The main results are as follows:(1) Some obvious differences exist in the space distribution of annual mean Qinghai-Tibet Plateau vegetation NDVI from 1982 to 2013; on the whole the space distribution is descending from southeast to northwest, furthermore, the time variation of vegetation in different areas are not exactly the same.(2) We further analyze the change rules of vegetation coverage according to the five areas which are divided from the NDVI of vegetation growing in June and September through EOF, the results show that the most sharply decreasing of Qinghai-Tibet Plateau NDVI lies in the area of Gar-Lake Bangong Gully as well as the region of the north qiangtang plateau; and the rise of Qinghai-Tibet Plateau vegetation NDVI lies in the eastern Qilian Mountain.(3) In the second partition of Qinghai-Tibet Plateau, both of the about double sunshine intensity compared with other areas and the low precipitation result in the vegetation degradation. The vegetation degradation in the forth partition of plateau is because of the limited precipitation, the high temperature and strong sunshine. In the fifth partition of Qinghai-Tibet Plateau, the precipitation is sufficient but sunshine is weak, which also cause the vegetation degradation.(4) The community atmosphere model (CAM5.1-CLM4.0) can well simulate the averaged summer characteristics of geopotential height and the location and intensity of the South Asia high, also with the plateau surface temperature field. However, the simulated South Asia high seems stronger and west back.(5) After the vegetation degradation, Qinghai-Tibet Plateau soil temperature rises, reference height temperature rises, surface sensible heat flux increases, surface latent heat flux decreases and which changes the Bowen ratio in plateau area. What’s more the surface sensible heat flux rises caused 500hPa height field reduces and 200hPa height field rises, result in the presence of strong anticyclonic circulation anomalies on 200hPa which make South Asia high increases and expansion to the north and east.(6) The increasing of surface sensible heat flux caused by vegetation degradation can lead to southern plateau airflow upward movement in the enhancement, northern plateau airflow upward movement in the less. Moreover the northern region outside the plateau sinking airflow range widen, the strength of the sinking airflow in subdued, these result in that expand the scope of drought the northern region outside the plateau, but drought degree of ease.