The Importance of Atmospheric Temperature on the Size and Structure of Tropical Cyclones

During the course of their lives, tropical cyclones can travel long distances and move through environments of varying temperature, moisture, and underlying sea-surface temperatures, which result in, sometimes dramatic, changes in their size and structure (e.g., Hurricane Katrina 2005). This modeling study was designed to investigate the effects that changing the environment profile has on the size and structure of a tropical cyclone. Using the WRF-ARW model, a control atmospheric profile and underlying sea-surface temperature is modified in a systematic fashion to explore how and why the size and structure of tropical cyclones change under different environmental conditions. It is found that for the same sea-surface temperature and static stability, the size of the tropical cyclone increases with every incremental decrease in the atmospheric temperature profile.

Upon analyzing the surface moisture fluxes, a correlation between enhanced moisture fluxes and expansion of the wind field and radar reflectivity is found, which is directly associated with the decreasing atmospheric temperature profile. As the atmospheric temperature profile decreases, the difference between the surface air and ocean temperature increases, which results in increased sensible and latent heat fluxes. The results indicate that the increased latent heat fluxes from the underlying ocean are essential to the growth of a tropical cyclone.