Climate Change And Its Influence Oh NDVI Over The Qinghai-Tibet Plateau

As the global warming, the region climate has changed unceasingly. The regional land surface processes related to the theory of the regional ecological environment and economic development is of great significance under the background of global warming. The research indicated that, the area within the scope of the ground process characteristics and laws are more easily grasp, because of the spatial and temporal characteristics of regional climate and its change rule than to global climate change is more obvious.I choose the Qinghai-Tibet plateau as study area, and based on the Long term vegetation index dataset of China—Pathfinder AVHRR NDVI (the data produced through funding from the Earth Observing System Pathfinder Program of NASA’s Mission to Planet Earth in cooperation with National Oceanic and Atmospheric Administration, and were provided by EOSDIS, distributed Active Archive Center at Goddard Space Flight Center which archives, manages, and distributes this data set), Long term vegetation index dataset of China—SPOT VEGETATION NDVI(source for this dataset was the VITO),and the meteorological data gathered from68weather stations in Qinghai-Tibet plateau, variation of the vegetation in Qinghai-Tibet plateau and its growth season NDVI in the period of1970～2010, and their relations with major climate factor(temperature, relative humidity, precipitation, wind velocity and sunshine duration),were analyzed.The results show that:(1) Due to the effects of global warming, temperature over Qinghai-Xizang Plateau in recent40years showed a significant upward trend, warming rate reaches0.44℃/10a, and in the last20years the increasing range of intensified, warming rate up to0.64℃/10a, warming rate decreases from south to the north of progressively trend, through the calculation shows the increasing range and vegetation coverage degree of negative correlation between; precipitation and relative humidity in the past40years rising trend is not significant, nearly20rainfall amplitude rises somewhat, overall increase a rate of6.65mm/10a, while the humidity rate decreased year by year, in recent40years humidity rise rate of0.099%/10a, the Tibetan Plateau precipitation and relative humidity amplitude appears West High East low posture; through the analysis of nearly40years of Qinghai-Tibet Plateau wind and sunshine hours showed a significant downward trend, and in the nearly20years of decline has slowed.(2)Through the statistics,it shows a gradually rising trend durning1982-2010years the average NDVI of Qinghai-Tibet Plateau, as the rising rate of0.026/10a, however, change rate is not clear. The NDVI of montane evergreen broad-leaved forest in south side of eastern Himalayas shows a rate of rise, reaching0.1/10a, the second is montane coniferous forest in western Sichuan and eastern Tibet, shows the rising rate of0.05/10a, but the remaining part of rising rate is not obvious, remained at the0.01-0.025/10a. What’s more, based on the AVHRR_PathFinder vegetation index data sets and SPOT_Vegetation vegetation index data base and combining with the research and analysis of the Qinghai-Tibet Plateau and the regional vegetation growing season threshold. And it shows that, the NDVI in the Qinghai-Tibet plateau increased in the past30years, with the rate of0.013/10a. The largest increase was at the south side of the eastern Himalayas, with a rate of0.02-0.08/10a. Small regions distributed throughout the desert in Qaidam, the montane coniferous forest in Changdu in eastern Tibet and the alpine shrub in Naqu had a decreasing trend with a change rate of0-0.04/10a.(3) Regarding all types of vegetation across the Qinghai-Tibet plateau, the response of NDVI to temperature and precipitation showed a time lag effect. The accumulated time lag periods of NDVI and corresponding temperature is45and10to25days for the alpine desert areas, and cold meadow, alpine cold grassland, alpine cold brush, periglacial cushion vegetation areas. Expect cold meadow and desert areas, the time lag as to responses of NDVI to precipitation and relative humidity of different types of vegetation are around2to3months and1to2months or so, respectively.(4) Climate change influenced the NDVI in the Qinghai-Tibet plateau mainly through temperature, precipitation and wind velocity. The changes in temperature, precipitation and wind velocity mostly influenced NDVT, and the relative humidity and sunshine hours exerted less influence on NDVI. In all, the changes in NDVI in the Qinghai-Tibet plateau belong to the temperature-precipitation driving type, of which temperature was the dominant driving factor. At the same time, the relationship between NDVI and climate factors shows a regional difference. Precipitation was the main reason for the NDVI change in south Qinghai, west Sichuan and east Tibet, Ali and the south side of the eastern Himalayas. The remnant parts were mainly influenced by temperature-precipitation.(5) By using R/S analysis of Qinghai-Tibet plateau climate factors since relative to taller, this represents various climate change continued strong. With nearly40years of Qinghai-Tibet Plateau several regional climate change and the overall rate, Qinghai-Tibet Plateau climate more conducive to warm and humid, vegetation growth.