| In this paper, we analyzed characteristics of the change in surface air temperature and its elevation dependency over Tibetan Plateau by using the five ensemble average of CCSM4 models data. and analyzed the trend of surface temperature change and elevation dependence on surface warming over Tibetan plateau under RCP2.6 and RCP8.5 scene of the 21 st century. The main conclusions are as follows:(1) From 1951 to 2000, the average and winter half-year maximum temperature, average temperature, minimum temperature was stronger in the mid and Midwest on Tibetan Plateau and the warming rate reached about 0.4℃/10 a, respectively. It is getting warming over high elevation regions. The increase in average minimum temperature is the most significant compared to the maximum or average temperature. the minimum temperature warming is stronger at 3.5km below, and the maximum temperature is more significant warming at the 3.5km above.(2)The warming trend of maximum, average and minimum temperature over Tibetan Plateau is obvious under RCP2.6 scenario. but there are differences in the magnitude of warming in different regions, and the warming of the mid on Tibetan Plateau is stronger; the largest Warming magnitude on Midwest of Tibetan Plateau is stronger than the same period of the annual average, while the temperature of the cooling trend was significantly expanded the scope of the area. Different heights within the highest range, average, average warming rate of minimum temperatures were increased with increasing altitude, showing a significant elevation dependence. The warming trend of average and winter year in 2016-2055 is warming stronger than 2056-2100.(3)Under RCP8.5 scenario, half of the 21 st century, the annual mean maximum, average, minimum temperature warming was stronger than the 21 th Century; winter half year of the first 21 st century,the midwest of the plateau warming is larger even more than the next 21 half of the century. the maximum, average, minimum temperature with increasing altitude have a positive correlation in year and winter half year. After the first half of the 21 st century plateau warming is stronger than the annual average temperature in 2016-2100.(4)From 1951 to 2000, the surface upward long-wave radiation and the ground temperature was bigger on the central area of western Plateau. In addition to the Plateau northeastern edge region, the average of the sum of heat and latent heat is increased in the whole plateau, especially in the central of plateau. The ground temperature,the surface upward long-wave radiation and the sum of heat and latent heat range generally increases with the elevation, there is a significant elevation dependence. we can assume that they are responsible for altitude-dependent warming of the Tibetan Plateau.(5)The surface upward long-wave radiation and the ground temperature show an increasing trend on the central and western area of Plateau, the trend is stronger in winter year. The rate of them were increased with increasing altitude, showing an significant elevation dependence under RCP2.6 scenario form 2016 to 2055.(6) Compared with RCP2.6 scenario, under RCP8.5 scenario in 2016-2055, the surface upward long-wave radiation, the ground temperature and the sum of heat and latent heat also have an increasing trend on the central and western area of Plateau, and they have a greater magnitude and change range generally increases with the elevation., especially in winter half year. Under RCP8.5 scenario, the surface warming generally strengthens with the elevation increasing over the Tibetan Plateau, especially for winter half year. Surface long-wave radiation, ground temperature and the sum of sensible heat and latent heat like the surface temperature showed altitude dependence, especially in winter half year, Then we can think that the earth’s surface absorb the net radiation flux, conveying the sense heat and latent heat into the atmosphere,they are impact factors that influence elevation dependence on surface warming over Tibetan Plateau. |
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