Contributions of Urban Land and Anthropogenic Aerosols of Houston to Convective intensity and Precipitation of a Deep Convective Storm

Monday, December 9, 2019 - 08:15
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During the summer time over Houston, frequent thunderstorms occur owing to air convergence over land and also possibly by urban heat island effect and sea breeze. Given warm cloud bases and humid conditions associated with those thunderstorms, it is anticipated that aerosols and clouds may exhibit a stronger correlation and interaction in this region. We conduct ensemble WRF-Chem simulations coupled with the spectral-bin microphysics (SBM) at 0.5 km grid spacing to simulate a thunderstorm occurring on 19 June 2013 and sensitivity tests to examine how urban land and anthropogenic aerosols over Houston impact the convective intensity and precipitation. We find that urbanization in Houston drastically enhances convective intensity and precipitation, primarily due to the urban aerosol effects. Urban land effect does not change precipitation much. but initiates mixed-phase regime 25 min earlier due to enhanced convergence as a result of urban heating. Urban aerosols fasten the development of convective cell into ice phase clouds, resulting from larger latent heat release. With the two-moment bulk microphysics, model does not show a significant aerosol impacts on convective intensity and precipitation, due to limitations in representation of aerosol-cloud interaction processes particularly aerosol activation and drop condensation.

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