关键词: 西藏, 气候变化, 湿润指数, 干湿状况, 未来气候情景

Abstract: The drought is one of the important meteorological disasters in Tibet,and occurs in varying degrees each year.The drought has a great impact on the agriculture and livestock production.It has an important significance that forecasting the trends of Tibet′s dry-wet condition under future climate scenario for prevention and reduction of losses caused by drought in the region.Based on the daily data of A2 climate scenario(2011-2050) and baseline climate condition(1961-1990) from the regional climate model PRECIS with resolution of 50km×50km,reference crop evapotranspiration was calculated according to Penman-Monteith equation recommended by FAO.In terms of grades of wetness index from Chinese Climate Classification Criterion,Tibet is classified into arid,semi-arid,semi-humid and humid zones,respectively.The possible temporal-spatial changes of dry-wet condition in Tibet from 2011 to 2050 were analyzed based on wetness index.The results showed that: the amount of precipitation and reference crop evapotranspiration in the most regions of Tibet would increase from 2011 to 2050 compared with the baseline climate conditions from 1961 to 1990.The increase range of reference crop evapotranspiration was less than that of precipitation.However,the inter-regional differences were both significant;in the next 40 years,Tibet′s climate showed a warming and wetting trend in general.The reducing trends in arid and semi-arid areas were clear.And the increase range of average temperature was far greater than that of wetness index.Environmental water and heat factors were higher and drought gradually decreased.It was more conducive to the improvement of ecological environment;however,the different climatic zones in dry-wet conditions at different times showed different trends.The area′s reducing trend in the arid and semi-arid region and the expanding trend in the humid and semi-humid region during 2021 to 2030 would be obvious compared with the baseline climatic conditions.And the area′s reducing trend in the arid and humid region and the expanding trend in the semi-arid and semi-humid region during 2031 to 2050 would be obvious compared with the baseline climatic conditions.

Key words: Tibet, Tibet, Climate change, Wetness index, Dry-wet condition, Future climatic scenario