Atmospheric Lakes of Vapor Drifting Over the East Coast of Africa

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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.