Precipitation changes in full response to CO₂ increase are widely studied but confidence in future projections remains low. Mechanistic understanding of the direct radiative effect of CO₂ on precipitation changes, independent from CO₂-induced SST changes, is therefore necessary. Utilizing global atmospheric models, we identify robust summer precipitation decreases across North America in response to direct CO₂ forcing. We find that spatial distribution of CO₂ forcing at land surface is likely shaped by climatological distribution of water vapor and clouds. This, coupled with local feedback processes, changes in convection, and moisture supply resulting from CO₂-induced circulation changes, could determine North American hydroclimate changes. In central North America, increasing CO₂ may decrease summertime precipitation by warming the surface and inducing dry advection into the region to reduce moisture supply. Meanwhile, for the southwest and the east, CO₂-induced shift of subtropical highs generates wet advection, which might mitigate the drying effect from warming.

中文翻译：

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CO2增加对北美夏季降水的直接辐射效应


完全响应 CO ₂ 增加的降水变化已得到广泛研究，但对未来预测的信心仍然很低。因此，有必要了解 CO ₂ 对降水变化的直接辐射影响（独立于 CO ₂ 引起的海温变化）的机制。利用全球大气模型，我们发现北美夏季降水量因直接二氧化碳 ₂ 强迫而大幅减少。我们发现陆地表面 CO ₂ 强迫的空间分布可能是由水蒸气和云的气候分布决定的。这与局部反馈过程、对流变化以及 CO ₂ 引起的循环变化引起的水分供应相结合，可以决定北美水文气候的变化。在北美中部，增加的二氧化碳 ₂ 可能会通过使地表变暖并诱导干燥平流进入该地区来减少夏季降水，从而减少水分供应。同时，对于西南和东部地区，CO ₂ 引起的副热带高压移动会产生湿平流，这可能会减轻变暖带来的干燥效应。