18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Monday, 30 July 2001
Evaluating convective momentum fluxes using remotely sensed data
John R. Mecikalski, CIMSS/Univ. of Wisconsin, Madison, WI
With the advent of the Tropical Rainfall Measuring Mission (TRMM), and airborne and upward/downward-looking Doppler radar instruments (disdrometers), which can sense the (sub-)cumulus scale aspects of convective systems, the time is right to begin assessing momentum transport qualities using remotely-sensed datasets. As TRMM and Doppler measurements observe convection over a range of scales, from 4 km to 10's of meters, a cloud-resolving numerical model becomes a necessary tool when attempting to construct a parameterization of convective momentum flux driven by remotely-sensed data sources.

This poster will address the following: 1) Use TRMM Precipitation Radar (PR), TRMM Visible and Infrared Scanner (VIRS) and vertically-looking disdrometer data, along with numerical model simulations of the large scale environment, to determine the momentum transport characteristics of tropical convective systems, and 2) Use these data to formalize a momentum transport scheme which relies on remotely-sensed data as the main inputs.

For this study, TRMM PR data is analyzed to identify the tilts and orientiations of convective updrafts during the TExas-FLorida UNderflights (TEFLUN-A/B) experiments. Using a cloud-resolving model of the same convection to obtain a complete momentum budget, the relative contributions of updrafts to the momentum budget (measureable with TRMM PR) are determined. This is followed by an analysis of disdrometer data to obtain further information on the modeled convection's real structure at fine resolution (~30-50 m). A parameterization scheme for momentum flux which relies on TRMM PR as input, in addition to information from the large scale environment (i.e vertical wind shear, inertial stability), will be the end result. Such a parameterization will be validated and refined using real observations collected during recent field experiments (e.g., CAMEX-3), and by numerical simulations. Constructing a parameterization in the context of the cumulus friction approach is the plan.

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