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Intense tropical cyclones (TCs) can cause catastrophic damage to coastal regions after landfall. Recent studies have linked the devastation associated with TCs to climate change, which induces favorable conditions, such as increasing sea-surface temperature, to supercharge storms. Meanwhile, environmental factors, such as atmospheric aerosols, also impact the development and intensity of TCs, but their effects remain poorly understood, particularly coupled with ocean dynamics. Here, we quantitatively assess the aerosol microphysical effects and aerosol-modified ocean feedbacks during Hurricane Katrina using a cloud-resolving atmosphere–ocean coupled model: Weather Research and Forecasting (WRF) in conjunction with the Regional Ocean Model System (ROMS). Our model simulations reveal that an enhanced storm destructive power, as reflected by larger integrated kinetic energy, heavier precipitation, and higher sea-level rise, is linked to the combined effects of aerosols and ocean feedbacks. These effects further result in an expansion of the storm circulation with a reduced intensity because of a decreasing moist static energy supply and enhancing vorticity Rossby wave outward propagation. Both accumulated precipitation and storm surge are enhanced during the mature stage of the TC with elevated aerosol concentrations, implying exacerbated flood damage over the polluted coastal region. The ocean feedback following the aerosol microphysical effects tends to mitigate the vertical mixing cooling in the ocean mixing layer and offsets the aerosol-induced storm weakening by enhancing cloud and precipitation near the eyewall region. Our results highlight the importance of accounting for the effects of aerosol microphysics and ocean-coupling feedbacks to improve the forecast of TC destructiveness, particularly near the heavily polluted coastal regions along the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) with a high Saffir-Simpson scale can cause catastrophic damages to coastal regions after landfall. Recent studies have linked the TC's devastation to climate change that induces favorable environmental conditions, such as increasing sea-surface temperature, to supercharge the storms. Also, atmospheric aerosols likely impact the development and intensity of TCs, but their effects remain poorly understood, particularly coupled with the ocean dynamics. Here we quantitatively assess the aerosol microphysical effects and aerosol-modified ocean feedbacks during Hurricane Katrina using a cloud-resolving atmosphere-ocean coupled model - Weather Research and Forecasting (WRF) in conjunction with the Regional Ocean Model System (ROMS). Our model simulations reveal that an enhanced destructive power of the storm, as reflected by larger integrated kinetic energy, heavier precipitation, and higher sea-level rise, is linked to the combined effects of aerosols and ocean feedbacks. These effects further result in an expansion of the storm circulation with a reduced intensity because of decreasing moist static energy supply and enhancing vorticity Rossby wave outward propagation. Both accumulated precipitation and storm surge are enhanced during the mature stage with elevated aerosol concentrations, implying exacerbated flooding damage over the coastal region. The ocean feedback following the aerosol microphysical effects tends to mitigate the Ekman upwelling cooling and offsets the aerosol-induced storm weakening, by invigorating cloud and precipitation near the eyewall region. Our results highlight the importance of accounting for the effects of aerosol microphysics and ocean-coupling feedbacks to improve the forecast of TC destructiveness, particularly near the heavily polluted coastal regions along the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

The destructive power of tropical cyclones is driven by latent heat released from water condensation and is inevitably linked to the abundance of aerosols as cloud condensation nuclei. However, the aerosol effects are unaccounted for in most operational hurricane forecast models. We combined multisource measurements and cloud‐resolving model simulations to show fundamentally altered cloud microphysical and thermodynamic processes by anthropogenic aerosols during Hurricane Harvey. Our observational analyses reveal intense lightning and precipitation in the proximity of Houston industrial areas, and these hot spots exhibit a striking geographic similarity to a climatological maximum of lightning flash density in the south‐central United States. Our ensemble cloud‐resolving simulations of Hurricane Harvey indicate that aerosols increase precipitation and lightning by a factor of 2 in the Houston urban area, unraveling the key anthropogenic factor in regulating flooding during this weather extreme. Plain Language Summary: The catastrophic flooding during Hurricane Harvey has received major attention, but the cause remains mysterious. The destructive power of tropical cyclones is produced by the latent heat release from phase change of water, which is linked to airborne particles emitted from vehicles and petrochemical plants. By combining observation and model simulations, our work provides microphysical and thermodynamic insights into the cause of the catastrophic flooding during Hurricane Harvey by the aerosols from industrial sources. Our discovery underscores the importance of representing the effects of anthropogenic aerosols for accurate short‐term forecast and climate projection of tropical cyclones to minimize future catastrophic destruction along the highly industrialized Gulf of Mexico region. Key Points: Aerosol increases accumulative precipitation by a factor of 2T and invigorates lightning activities in Houston during Hurricane HarveyObservations show intense lightning over Houston which exhibits geographic similarity to climatological maximum lightning flash densityTo better forecast extreme weather events, it is essential to account for aerosol effects in operational weather forecast models [ABSTRACT FROM AUTHOR]