新疆地区未来气候变化的区域气候模式集合预估

本文基于一套在5个全球气候模式结果驱动下，RegCM4区域气候模式对东亚25 km水平分辨率的集合预估，分析了中、高温室气体典型排放路径（RCP4.5和RCP8.5）下，21世纪不同时期新疆地区的未来气候变化。对模式当代气候模拟结果的检验表明，区域模式的模拟集合（ensR）总体上能够很好地再现当代新疆平均气温、降水和极端气温、降水分布特征。ensR预估21世纪未来新疆平均气温和降水将不断升高或增加，RCP8.5下的变化大于RCP4.5。在21世纪末期RCP8.5下，区域年平均气温和降水将分别增加4.9°C和28%（102 mm），夏季（6～8月）的升温幅度略高于冬季（12～2月），降水则以冬季增加为主。极端温度以及高温日数同样将不断升高，其中年日最低气温最小值的增幅总体高于年日最高气温最大值，未来新疆地区的极端冷事件将减少，高温、热浪事件将增加。由极端降水指标日最大降水量反应的强降水事件将普遍增加，连续无降水日数总体以减少为主。积雪变化存在一定区域差异，具体表现为除塔里木盆地外的普遍减少。对总径流量和表层土壤湿度的预估分析表明，二者在新疆地区均以增加为主，但水文干旱在北疆会加重。ensR各模拟间无论是在当代模拟还是未来预估中都表现出较好的一致性，但在变化的具体数量及个别情况下符号均存在一定差异。最后，综合考虑ensR对各要素的预估发现，总体而言新疆未来更趋向于“暖湿化”，但这不会改变其干旱、半干旱气候的本质，而且水文干旱频率在一些地区会增加，未来新疆的水资源状况仍不容乐观。

Future Climate Change Projection over Xinjiang based on an Ensemble of Regional Climate Model Simulations

Based on a set of twenty-first-century climate change projections by a regional climate model (RegCM4) at a 25-km grid spacing driven by five global models, future climate change over Xinjiang in Northwest China under the middle and high representative concentration pathways of 4.5 and 8.5 (RCP4.5 and RCP8.5) is investigated. Results show the multi-RegCM4 ensemble (ensR) clearly determines both the spatial distributions and the amounts of mean temperature and precipitation, along with extreme temperature and precipitation. In the future, the temperature and precipitation over Xinjiang are projected to rise or increase continuously, especially under RCP8.5 compared with RCP4.5. Moreover, by the end of the twenty-first century under RCP8.5, the regional mean increases in annual temperature and precipitation will be as 4.9°C and 28% (102 mm), respectively. Increases of temperature and precipitation extremes are also reported as measured by different indices, indicating more heat waves, less cold spells, and more extreme precipitation in the future. Specifically, for temperature, greater increase of annual minimum of daily minimum temperature (TNn) is found compared to annual maximum of daily maximum temperature (TXx). By the end of the twenty-first century under RCP8.5, the increase of regional mean TXx and TNn over Xinjiang will be 4.9°C and 5.8°C, respectively. As for extreme precipitation indices, an increase of RX1day by 29% (5 mm) and a decrease of CDD by 10 days are found. The change of snow cover shows spatial differences, with a general decrease except a large percentage increase in the western Tarim Basin. A 13% reduction is reported for the regional mean snow coverage at the end of the twenty-first century under RCP8.5. The total runoff and soil moisture are projected to increase; however, more hydrological droughts in northern Xinjiang are projected to occur. The ensR show consistencies among the ensemble members, but there exist differences concerning the change of amount and the sign in some cases. Overall, considering the analyzed variables, a “warmer and more humid” tendency of climate as observed in the late decades will be expected in Xinjiang in the future. However, this may not change the fact of the dominance of arid and semiarid climate over the region. In addition, hydrological droughts are also projected to increase in the future. Thus, high attention still needs to be paid for the availability and risks on water resources over the region.