Convection, Clouds and Sea Surface Temperature

云对地球的能量收支有相互竞争的影响，因为云通过捕获外出的红外辐射使地球变暖，但它们也通过将阳光反射回太空而使地球变冷。对于热带地区的深层对流云，这些竞争效应之间的平衡非常接近，因此它们的净辐射效应接近于零。这种接近抵消的原因尚不清楚，全球变暖可能使净云辐射效应倾向于变暖或变冷，增强或减弱温室气体增加的变暖效应。该奖项下的工作将研究云加热和冷却之间的平衡，重点关注云生命周期不同阶段云辐射效应的差异，以及热带云与海洋表面温度之间的关系。云生命周期效应的研究是由PI最近对卫星数据的研究推动的，这些数据表明，伴随热带深层对流的高冰云是通过辐射和湍流之间的相互作用而自我维持的。对流云的近零辐射效应是由高空冰云的净冷却效应和产生它们的深层降水云的净变暖效应共同作用的结果。海温-云相互作用的研究是由海温与对流层翻转环流之间的关系推动的，对流层翻转环流将海温与深云和浅云联系起来。初步结果显示，随着海温变暖，翻转环流的强度意外增加，该项目探讨了这种增强的原因及其对云量的影响。这项工作是通过分析卫星和其他来源的观测数据以及理想化的模拟实验来进行的。由于云辐射效应在确定由于温室气体浓度增加而导致的变暖程度方面的作用，这项工作具有更广泛的影响。该项目还考虑了温室增温对热带海温对比的影响，这是一个重要的考虑因素，因为热带气候变化的区域影响受到海温对比的强烈影响。该项目还资助了两名研究生，并为教育材料的开发做出了贡献，包括首席研究员全球物理气候学教材的第三版。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Clouds have competing effects on Earth's energy budget, as clouds warm the Earth by trapping outgoing infrared radiation but they also cool by reflecting sunlight back to space. For deep convective clouds in the tropics the balance between these competing effect is very close, so that their net radiative effect is near zero. The reasons for the close cancellation are not known, and it is possible that global warming may tip the net cloud radiative effect to favor warming or cooling, enhancing or dimishing the warming effect of greenhouse gas increases.Work under this award examines the balance between cloud heating and cooling with a focus on differences in cloud radiative effects at different stages of the cloud lifecycle, and on the relationship between tropical clouds and sea surface temperatures (SSTs). The work on cloud lifecycle effects is motivated by the PI's recent examination of satellite data suggesting that the high ice clouds accompanying deep tropical convection are self-sustaining through an interaction between radiation and turbulence. The near-zero radiative effect of convective clouds would then result from a combination of the net cooling effect of the high ice clouds and the net warming effect of the deep precipitating clouds that generate them. The work on SST-cloud interactions is motivated by the relationship between SSTs and the tropospheric overturning circulations that connect them to both deep and shallow clouds. Preliminary results show an unexpected increase in the strength of the overturning circulations as SSTs warm, and the project explores the reasons for the strengthening and its implications for cloud cover. The work is conducted through analysis of observational data from satellites and other sources and idealized modeling experiments.The work has broader impacts due to the role of cloud radiative effects in determining the amount of warming that will occur as a result of increases in greenhouse gas concentrations. The project also considers the effect of greenhouse warming on tropical SST contrasts, an important consideration as the regional impacts of tropical climate change are strongly influenced by SST contrasts. The project also supports two graduate students and contribute to the development of educational materials including a third edition of the Principal Investigator's textbook on global physical climatology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.