研究人员表明，在全球范围内，云量，特别是低层云量，在气候变暖的情况下，呈现出不对称的日趋势。白天的平均云分下降幅度大于夜间。气候模型表明，昼夜不对称云量变化主要受对流层稳定性降低的趋势驱动，并在很大程度上被归因于温室气体的增加而非自然变率。因此，这种不对称通过减少白天云的短波反照率效应和增加夜间云的长波温室效应，而被证明是地表变暖的放大器。
据研究人员介绍，地表气温(SAT)是气候变化的重要指标。云量的变化通过与辐射的相互作用影响SAT。在白天，云通过阻挡阳光使地表降温，而夜间云通过捕获长波辐射使地表变暖。
附：英文原文
Title: Diurnally asymmetric cloud cover trends amplify greenhouse warming
Author: Hao Luo, Johannes Quaas, Yong Han
Issue&Volume: 2024-06-21
Abstract: Surface air temperature (SAT) is a key indicator of climate change. Variations in cloud cover affect SAT by interacting with radiation. During daytime, clouds tend to cool the surface by blocking sunlight, while nighttime clouds warm the surface by trapping longwave radiation. Here, we show that, on the global scale, cloud cover, particularly low-level cloudiness, exhibits diurnally asymmetric trends in a warming climate. Cloud fraction on average decreases more during the day than at night. Climate models indicate that the diurnally asymmetric cloud cover variation is mainly driven by trends in the lower tropospheric stability and is largely attributed to the increasing greenhouse gases rather than natural variability. This asymmetry, therefore, turns out to be an amplifier of surface warming, by both decreasing the daytime cloud shortwave albedo effect and increasing the nighttime cloud longwave greenhouse effect.
DOI: ado5179
Source: https://www.science.org/doi/10.1126/sciadv.ado5179