未来气候情景下西藏地区的干湿状况变化趋势

旱灾是西藏地区重要的气象灾害之一,每年均有不同程度的发生,对农牧业生产的影响极大,气候变化背景下开展西藏地区干湿状况变化趋势的预测研究对于预防和减轻该区干旱所造成的损失具有重要意义。选取区域气候模式PRECIS输出的未来A2气候情景（2011-2050年）以及基准气候条件（1961-1990年）逐日资料,利用联合国粮农组织（FAO）推荐的Penman-Monteith方法计算了参考作物蒸散量,基于湿润指数,按照中国气候区划中的干湿指标把西藏分为干旱、半干旱、半湿润、湿润4个气候区,预估了西藏地区2011-2050年干湿状况时空变化趋势。结果表明：与基准气候条件相比,未来A2气候变化背景下,除零星地区外,2011-2050年西藏地区降水量、参考作物蒸散量均呈增加趋势,且参考作物蒸散量增加的幅度小于降水量增加的幅度,但地区间差异都很显著;未来40a西藏气候总体上呈暖湿化趋势,干旱、半干旱区的缩小趋势非常明显,且年平均气温上升的幅度远远大于湿润指数增加的幅度,环境水热要素相对提高,干旱化程度在逐步减小,较利于生态环境的改善;但是,不同气候区在不同时段干湿状况变化趋势不同。2021-2030年干旱、半干旱地区的缩小趋势以及湿润、半湿润的扩大趋势都很明显;2031-2040年、2041-2050年,干旱、湿润区的缩小趋势以及半干旱、半湿润的扩大趋势均很明显。

Trends Of Tibet's Dry-Wet Condition under Future Climate Scenario

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.