Atmospheric Lakes of Vapor Drifting Over the East Coast of Africa

作为长期存在和孤立的潮湿空气团，“大气湖”被观察到从广阔的印度洋-太平洋暖池上方的大片潮湿空气中夹断后，缓慢地漂过赤道印度洋西部。这些湖泊孕育了大量的深对流降水，它们的登陆为通常干燥的非洲东部海岸带来了急需的降雨。到目前为止，对这些湖泊知之甚少，有关它们的新知识可能有助于管理当地的水资源，并改善对天气学研究很少的地区的天气预报。通过使用全球再分析数据，观测和业务预报和气候模式的输出，这项工作的目的是通过检查它们的管理过程，涉及对流，动力学，湍流和辐射的密切耦合来了解这些湖泊。作为潮湿热带大气的天然实验室，大气湖泊可能是地球上最接近对流自聚集的类似物，对流自聚集是一种需要观测试金石的热带气候的当代范式，已被广泛研究。在假设的指导下，研究人员将汇编湖泊以下的水蒸气和密切相关的（但更丰富的解释）湿静态能量的预算。MERRA-2再分析提供了封闭预算的所有条件，包括表明模型过程缺陷的分析趋势。将使用独立测量的卫星图像来确定云场的特征，包括对流系统的潜在聚集。由此产生的对湖泊维持和扩展过程的定量描述将成为该项目对天气预报和气候模拟模型数据进行比较研究的目标和挑战。登陆时出现的新过程也将被仔细审查，因为它们通过降雨影响东非及其人民。该奖项反映了NSF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。

As long-lived and isolated moist air masses, “atmospheric lakes” are observed to drift slowly across the western equatorial Indian Ocean after pinching off from the vast area of moist air over the broad Indo-Pacific warm pool. These lakes nurture clusters of precipitating deep convection, and their landfalls produce much-needed rain over the generally dry eastern African coast. To date, very little is known about these lakes, and new knowledge about them may help manage local water resource and improve weather forecasting over a region where synoptic meteorology is little studied. By using global reanalysis data, observations, and outputs from operational forecast and climate models, the work aims to understand these lakes by examining their governing processes that involve the intimately coupling of convection, dynamics, turbulence, and radiation. The work will train a graduate student.As natural laboratories of moist tropical atmosphere, atmospheric lakes may be Earth’s closest analogues to convective self-aggregation, a much-studied contemporary paradigm of tropical climate in need of observational touchstones. Guided by hypotheses, the investigators will compile lake-following budgets of water vapor and of the closely related (but more richly interpretable) moist static energy. The MERRA-2 reanalysis offers all terms for closed budgets, including analysis tendencies indicative of model process shortcomings. Independently measured satellite imagery will be used to characterize the cloud field, including the potential aggregation of convective systems. The resulting quantitative depiction of the lakes’ maintenance and propagation processes will serve as a target and challenge to the project’s comparative studies of weather-forecast and climate-simulation model data. New processes which come in at landfall will also be examined carefully, as they impact eastern Africa and its people through rainfall.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.