Increasing precipitation on the Antarctic Ice Sheet (AIS) in a warming climate has the potential to partially mitigate Antarctica’s contribution to sea level rise. We show that a simple, physically motivated change to the shallow convective cloud phase in the Community Earth System Model (CESM)—improving a long-standing bias in shortwave cloud forcing over the Southern Ocean—leads to an enhanced response of precipitation when the model is forced with realistic stratospheric ozone depletion, with other radiative forcing remaining constant. We analyze two ozone-forced ensemble experiments with the CESM version 1.1: one using the standard version of the model and the other using the cloud-modified version. The standard version exhibits a precipitation increase on the AIS of 34 gigatons year⁻¹; the cloud-modified version shows an increase of 109 Gt year⁻¹. The cloud-modified version shows a more robust, year-round poleward shift in the westerly jet and storm tracks, which brings more precipitation to the AIS, compared to the standard version. Greater surface warming and larger-amplitude stationary waves further increase the Antarctic precipitation response. The enhanced warming in the cloud-modified version is explained by larger positive shortwave cloud feedbacks, while the enhanced poleward jet shift is associated with a stronger meridional temperature gradient in the upper troposphere—lower stratosphere. These results illustrate (1) the sensitivity of forced changes in Antarctic precipitation to the mean state of a climate model and (2) the strong role of atmospheric dynamics in driving that forced precipitation response.

在气候变暖的情况下，南极冰原（AIS）上降水的增加有可能部分缓解南极洲对海平面上升的影响。我们显示，在社区地球系统模型（CESM）中，一个简单的，出于物理动机的对浅层对流云阶段的改变-改善了南海短波云强迫中长期存在的偏见-当该模型导致降雨响应增强时在现实的平流层臭氧消耗中被强迫，而其他辐射强迫保持恒定。我们使用CESM 1.1版分析了两个臭氧强迫的整体实验：一个使用模型的标准版，另一个使用云修改版。标准版本的AIS的AIS降水量增加了34吉比特- ^1年; 经云修改的版本显示增加了109 Gt年^-1。经云修改的版本显示出西风急流和风暴轨道全年更强的极移，与标准版本相比，这为AIS带来了更多的降水。更大的表面变暖和更大振幅的驻波进一步增加了南极的降水响应。在云修正版本中，变暖的增强是由较大的短波云正反馈所解释的，而增强的极向射流偏移与对流层上方（平流层下部）更强的子午温度梯度有关。这些结果说明（1）南极降水强迫变化对气候模式平均状态的敏感性，以及（2）大气动力学在驱动强迫降水响应中的强大作用。