Oral Presentation AMOS Annual Meeting and International Conference on Tropical Meteorology and Oceanography

Thermodynamic control of convection in a high resolution model of tropical cyclones (#22)

David Raymond 1 , Gerard Kilroy 2
  1. New Mexico Tech, Socorro, NEW MEXICO, United States
  2. Physics, Ludwig Maximillian University, Munich, Bavaria, Germany

Recent modeling work suggests that the statistical characteristics of
convection over tropical oceans are controlled by a combination of the
thermodynamic environment and the surface latent and sensible heat
fluxes. This result was obtained by analyzing repeated invocations of
a weak temperature gradient convective model with many different
temperature and humidity profiles as well as a variety of surface wind
speeds and sea surface temperatures. Recently we performed a similar
analysis on developing tropical cyclones simulated in a
high-resolution, stretched-grid model. Mean convective
characteristics were calculated in two domains, a central core 50 km
in radius containing the developing eyewall and an outer ring with
inner and outer radii of 50 km and 100 km. Three different
simulations were used, one with warm rain cloud physics, a second with
ice cloud physics, and a third with warm rain physics but with surface
friction turned off. In order to account for the possible effects of
frictional convergence, an additional control parameter related to the
convective inhibition was included. This factor, taken together with
measures of moist convective instability, column water vapor, and
surface fluxes, explains a large fraction of the variance in lower
tropospheric vertical mass flux (a surrogate for precipitation rate)
in both the inner cores and outer rings of these simulations.
Furthermore, the results are in close agreement with those obtained in
the earlier weak temperature gradient modeling work. These results
may help us better understand intensity change in tropical cyclones.