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arXiv · 2107.06193

Large-eddy simulations of marine boundary-layer clouds associated with cold air outbreaks during the ACTIVATE campaign-part 1: Case setup and sensitivities to large-scale forcings

Xiang-Yu Li·Hailong Wang·Jingyi Chen·Satoshi Endo·Geet George·Brian Cairns·Seethala Chellappan·Xubin Zeng·Simon Kirschler·Christiane Voigt·Armin Sorooshian·Ewan Crosbie·Gao Chen·Richard Anthony Ferrare·William I. Gustafson·Johnathan W Hair·Mary M Kleb·Hongyu Liu·Richard Moore·David Painemal·Claire Robinson·Amy Jo Scarino·Michael Shook·Taylor J Shingler·Kenneth Lee Thornhill·Florian Tornow·Heng Xiao·Luke D Ziemba·Paquita Zuidema
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Abstract

Large-eddy simulation (LES) is able to capture key boundary-layer (BL) turbulence and cloud processes. Yet, large-scale forcing and surface turbulent fluxes of sensible and latent heat are often poorly prescribed for LES simulations. We derive these quantities from measurements and reanalysis obtained for two cold air outbreak (CAO) events during Phase I of the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) in February-March 2020. We study the two contrasting CAO cases by performing LES and test the sensitivity of BL structure and clouds to large-scale forcings and turbulent heat fluxes. Profiles of atmospheric state and large-scale divergence and surface turbulent heat fluxes obtained from the reanalysis data ERA5 agree reasonably well with those derived from ACTIVATE field measurements for both cases at the sampling time and location. Therefore, we adopt the time evolving heat fluxes, wind and advective tendencies profiles from ERA5 reanalysis data to drive the LES. We find that large-scale thermodynamic advective tendencies and wind relaxations are important for the LES to capture the evolving observed BL meteorological states characterized by the hourly ERA5 reanalysis data and validated by the observations. We show that the divergence (or vertical velocity) is important in regulating the BL growth driven by surface heat fluxes in LES simulations. The evolution of liquid water path is largely affected by the evolution of surface heat fluxes. The liquid water path simulated in LES agrees reasonably well with the ACTIVATE measurements.This study paves the path to investigate aerosol-cloud-meteorology interactions using LES informed and evaluated by ACTIVATE field measurements.

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Xiang-Yu Li, Hailong Wang, Jingyi Chen, Satoshi Endo, Geet George, Brian Cairns, Seethala Chellappan, Xubin Zeng, Simon Kirschler, Christiane Voigt, Armin Sorooshian, Ewan Crosbie, Gao Chen, Richard Anthony Ferrare, William I. Gustafson, Johnathan W Hair, Mary M Kleb, Hongyu Liu, Richard Moore, David Painemal, Claire Robinson, Amy Jo Scarino, Michael Shook, Taylor J Shingler, Kenneth Lee Thornhill, Florian Tornow, Heng Xiao, Luke D Ziemba, Paquita Zuidema. 2021-07-13. Large-eddy simulations of marine boundary-layer clouds associated with cold air outbreaks during the ACTIVATE campaign-part 1: Case setup and sensitivities to large-scale forcings. https://doi.org/10.1175/jas-d-21-0123.1

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