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Air‐sea sensible and latent heat fluxes are fundamental to tropical cyclone (TC) energetics, yet the impacts of seastate‐dependent sea spray heat fluxes on TC structure and intensity remain poorly understood. To explore these impacts, we implement a recently developed parameterization of seastate‐dependent spray heat fluxes into a fully coupled atmosphere‐wave‐ocean model, the Unified Wave INterface–Coupled Model (UWIN‐CM). We conduct UWIN‐CM experiments, both with and without spray, for four TCs covering a broad spectrum of intensities and structural characteristics. Overall, we find that spray evaporation hinders intensification of weak TCs, while direct heating from warm spray droplets promotes intensification of major hurricanes. The effects of spray on open ocean TCs can be summarized in three stages: (1) In tropical storms and weak hurricanes (≤Category 1), spray evaporation cools the boundary layer (BL) throughout the storm, hindering intensification. (2) In stronger TCs, increasing spray production leads to stronger direct heating that warms the eyewall BL, partly offsetting the storm‐scale BL cooling. However, storms remain relatively weaker due to structural inefficiency of cooler BL inflow. (3) With further intensification and even stronger spray production, BL warming eventually overcomes the structural inefficiency and promotes intensification, particularly in major hurricanes (>Category 3), including rapid intensification. The shift in spray heat flux characteristics is initiated by a significant increase in spray production linked to seastate conditions occurring at 10‐m windspeed ≈30 m s−1. Additionally, our results indicate that enhanced spray generation from breaking waves in the coastal zone may strengthen landfalling TCs.
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Assessing the destructiveness of tropical cyclones induced by anthropogenic aerosols in an atmosphere–ocean coupled framework
Abstract. 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.
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- Award ID(s):
- 2103820
- PAR ID:
- 10520632
- Publisher / Repository:
- EGU
- Date Published:
- Journal Name:
- Atmospheric Chemistry and Physics
- Volume:
- 23
- Issue:
- 21
- ISSN:
- 1680-7324
- Page Range / eLocation ID:
- 13835 to 13852
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.5194/acp-23-13835-2023
