FGOALS/RegCM动力降尺度对南亚夏季气候变化的预估

基于CORDEX计划的试验设计,利用区域气候模式Reg CM3对全球模式FGOALS-g2在RCP8.5情景下的预估结果进行动力降尺度,预估了南亚地区未来近期(2016~2035年)和远期(2080~2099年)的夏季气候变化特征。结果显示,未来两个时段的气候变化空间分布类似,只是远期的变化幅度更大。具体表现为:高低空急流减弱,低空急流中心向北移动。南亚地区整体降水减少,但其北部降水显著增加。降水变化的空间分布主要受降水频率的控制,且降水频率随强度分布的变化表现出明显的地域差异。降水的未来变化特征与水汽输送的变化有密切联系。在区域模式中,受低空急流减弱和北移的影响,水汽输送减弱,对应降水减少。而在全球模式中,虽然季风环流也在减弱,但可降水量增加起主导作用,使得预估的水汽输送增强、降水量增加。

Projected Summer Climate Changes over South Asia Based on the Nested FGOALS/RegCM Model

This paper presents a dynamical downscaling simulation of future summer climate over the CORDEX (COordinated Regional climate Downscaling EXperiment) South Asia domain using the regional climate model RegCM3 nested within FGOALS-g2 (Grid-point version 2 of Flexible Global Ocean-Atmospheric-Land System Model). The projection under the RCP8.5 scenario in the near term (2016-2035) and long term (2080-2099) shows that the spatial pattern of the climate change in the near term is similar to that in the long term, but the variation amplitude in the long term is greater. The main features are listed as follows: The strength of the low-level jet (LLJ) will be weakened and the position will shift northward. The average precipitation over South Asia will decrease, but precipitation over the northern part will increase. The spatial distribution of precipitation change over land is mainly controlled by precipitation frequency, and changes in the distribution of mean precipitation frequency show remarkable geographic differences. The precipitation change is directly related to the moisture transport change. In RegCM3, changes in moisture transport are mainly controlled by the weakening and northward shifting of the LLJ, and the weakening of the LLJ cannot be offset by the increase in precipitable water. Meanwhile, in FGOALS-g2, precipitation will increase as the increase in precipitable water can offset the weakening of the LLJ.