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Mixed-phase Convective Clouds in the Polar Marine Boundary Layer
项目编号DE-SC0018927
Geerts, Bart
项目主持机构University of Wyoming
开始日期2018-08-15
结束日期2021-08-14
英文摘要Mixed-phase Convective Clouds in the Polar Marine Boundary LayerBart Geerts, University of Wyoming (PI)Yonggang Wang, Texas Tech University (co-I)The cold-air outbreak (CAO) cloud regime is commonly encountered over high-latitude oceansand adjacent coastal regions when a cold air mass becomes exposed to a sufficient fetch of open water.Cold-air outbreak clouds are generally convective, mixed-phase, and even though they are rather shallow, they canproduce heavy snowfall. Their structure is fetch-dependent, evolving from narrow bands into open orclosed cells as the marine boundary layer (MBL) deepens. Cold-air outbreak convection and associated marine boundary layercirculations effectively transfer heat into an otherwise highly stratified environment and involveinteractions between sea-surface, boundary layer, cloud microphysical, and radiative processes. Theseinteractions remain poorly understood given the hostile environment in which these clouds occur, bothoffshore and near-shore.This proposal, a collaboration between two universities, firstly aims to describe the high-latitudecold-air outbreak cloud regime using the array of instruments at the NSA (Barrow, Alaska) and at two mobile Atmospheric Radiation Measurement (ARM)sites (MARCUS 2017-18, and COMBLE 2020). These ARM data, and the multi-sensor variables wepropose to derive, allow detailed descriptions of mesoscale organization of precipitation, thermodynamicprofiles, vertical velocity, cloud depth, and cloud and precipitation properties. These observations are keyfor our second goal, which is to use output from validated cloud- and eddy-resolving simulations to gaininsights into the linkages between microphysical processes, the marine boundary layer vertical structure, and the marine boundary layerdynamics that control cloud macrostructure. Specifically, the two linked objectives of this proposal are: to document the cold-air outbreak cloud regime in three regions with DOE ARM facilities, in particular the vertical structure of stability and shear, vertical velocity, clouds, and precipitation, in the context of observed surface fluxes and cloud macrostructure; and to explore the role of clouds and precipitation on the boundary-layer circulations that control the cloud macrostructure, through high-resolution model simulations for specific cases in the three regions, specifically focusing on the feedbacks between microphysical processes and dynamics through the novel piggybacking technique. Intellectual merit: Both dynamical and microphysical processes controlling shallow convection incold air masses are fundamentally different from those in warm marine boundary layer clouds, which are relatively well-documented. The cold-air outbreak cloud regime is not adequately represented in weather and climate modelsbecause the dominant scale of vertical motion and precipitation growth is unresolved. The proposed studyis deeply anchored in observations thanks to the rich array of sensors at the NSA site and at the twomobile ARM sites. These data, combined with well-constrained numerical simulations, enable, for thefirst time, the testing of the hypothesis that cloud microphysical processes, especially precipitation,control the mesoscale organization of the cold-air outbreak cloud regime.Broader impact: Cold-air outbreak clouds are ubiquitous in high-latitude regions in the cold season. Thiscloud regime (and thus the processes controlling it) matter, given their significance in the global climatesystem, and, more generally, given the potential role that the polar regions (especially the Arctic) play inamplifying global climate change, and interacting with weather and climate in the lower latitudes (NRC2014).
学科分类09 - 环境科学;06 - 生物科学
资助机构US-DOE
项目经费605455
项目类型Grant
国家US
语种英语
文献类型项目
条目标识符http://gcip.llas.ac.cn/handle/2XKMVOVA/69302
推荐引用方式
GB/T 7714
Geerts, Bart.Mixed-phase Convective Clouds in the Polar Marine Boundary Layer.2018.
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