32nd Conference on Broadcast Meteorology/31st Conference on Radar Meteorology/Fifth Conference on Coastal Atmospheric and Oceanic Prediction and Processes

Monday, 11 August 2003
Mantle echoes associated with deep convection during IHOP: Observations and numerical simulations
Roger M. Wakimoto, UCLA, Los Angeles, CA; and H. V. Murphey, R. G. Fovell, and W. C. Lee
Poster PDF (310.9 kB)
There have been numerous laboratory and numerical simulations of thermal or buoyant plumes. Detailed observations in the atmosphere, however, have been limited to shallow thermals and cumulus clouds. Indeed, to the authors’ knowledge, there have been no radar observations of the vertical structure of deep convection during the early stages of development. This lack of data is surprising in light of the numerous years that radars have been used to probe convection.

A large, multiagency and international program called IHOP (International H2O Project) was held during the spring and summer of 2002 in Texas, Oklahoma, and Kansas. One of the primary objectives of the program was to better understand the processes leading to initiation of convection along convergence boundaries within the convective boundary layer. On two days during the experiment, unique vertical cross sections of the early stages of deep convection were collected by ELDORA onboard a Navy P-3. In both cases, the aircraft flew beneath the developing echo revealing weak echo vaults and well-defined ‘mantle echoes’. On one of the days, maximum radar reflectivities were only ~13 dBZ at a height of 10 km AGL. Maximum updrafts based on the single Doppler velocities measured by the vertically pointing radar exceeded 30 ms-1.

The radar observations of these echoes provided the verification for a series of numerical simulations using the ARPS model. Early results for both cases showed that the bulk cloud microphysical parameterization as typically configured converts cloud water into precipitation too quickly. Conversion rates and fallspeeds were reduced based on microphysical arguments proposed by other investigators and were found to produce more realistic results. Preliminary conclusions suggest that the shape of the mantle echo is a sensitive function of the thermal ascent rate and whether gravity waves are produced during (or as a consequence of) the thermal ascent. The effect of these microphysical alterations on longer time scales should be investigated.

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