末次间冰期亚洲中部干旱区干湿变化的模拟研究

利用国际古气候模拟对比计划第四阶段的多模式结果，分析了末次间冰期亚洲中部干旱区的干湿变化及机制。多模式集合平均结果表明，末次间冰期亚洲中部干旱区年降水减少0.7％，其中中亚地区的年降水减少2.8％，新疆地区年降水增加1.8％。水汽收支方程表明，末次间冰期中亚地区在雨季（冬春季）的降水变化主要与垂直动力项有关，新疆地区在雨季（夏季）的降水变化主要与垂直动力与热力项有关。此外，基于Penman-Montieth方法计算的亚洲中部干旱区的干旱指数在末次间冰期减小约10.2％，表明末次间冰期亚洲中部干旱区气候明显变干且存在旱区扩张的现象，这主要受到潜在蒸散变化的调控。潜在蒸散的增加进一步受到有效能量增加与地面风速增大的调控。本研究从模拟的角度揭示了末次间冰期亚洲中部干旱区干湿变化的可能特征及机制，在一定程度上有助于理解旱区气候在增暖情景下对轨道参数的响应特征。

Deciphering the variations of wet-dry conditions over Arid Central Asia during the Last Interglacial based on PMIP4 models

Climate change over drylands in a warmer climate and its responses to Earth''s orbit can be better understood by an investigation of climate change across arid Central Asia during the Last Interglacial (LIG).Based on the Paleoclimate Modelling Intercomparison Project Phase 4 (PIMP4), we analyze variations in wet-dry conditions and associated mechanisms over arid Central Asia during the LIG.The results show that during the LIG, the annual precipitation is reduced by 0.7% over arid Central Asia, with precipitation decreasing by 2.8% over Central Asia while increasing by 1.8% over Xinjiang compared to the preindustrial period.Over Central Asia, the precipitation decreases by 1.8%, 1.3%, 1.5%, and 10.3% in the spring, summer, autumn, and winter, respectively, indicating that the reduced annual precipitation is mainly due to changes in winter.According to the moisture budget equation, variations in precipitation over Central Asia during the rainy season (winter and spring) are mainly caused by the vertical dynamic term.Moreover, precipitation over Xinjiang is reduced by 5.9% and 3.8% in spring and winter, respectively, and increased by 14.1% in summer and 8.6% in autumn, indicating that the majority of the rise in annual precipitation is a result of precipitation in summer.Consequently, the moisture budget analysis suggests that the vertical dynamic and thermodynamic terms contribute most to the variations in precipitation over Xinjiang.In addition, the aridity index over arid Central Asia decreases by approximately 10.2% during the LIG based on the Penman-Montieth method, which indicates that arid Central Asia experience a drier condition.Furthermore, drylands over arid Central Asia had expanded during that period, including the transition from semi-arid to arid regions, from sub-humid and semi-arid to arid regions, and from humid to sub-humid, semi-arid and arid regions.Hence, the reduced aridity index over arid Central Asia is a result of increased potential evaporation at that time.This increased evaporation is further linked with negative contributions from decreased surface air temperature and increased relative humidity, as well as positive contributions from enhanced surface wind speed and available energy.Our study provides a possible map for changes in wet-dry conditions over arid Central Asia in a warmer climate induced by the Earth''s orbit and sheds light on risk assessments for arid Central Asia in different warming scenarios.