85th AMS Annual Meeting

Tuesday, 11 January 2005
Remote sensing of microphysical particles in hurricanes from aircraft observations
Cerese M. Albers, Florida State University, Tallahassee, FL; and G. Skofronick-Jackson
Poster PDF (1.7 MB)
In an effort to better understand the number concentration characteristics and particle size distributions of frozen hydrometeors in hurricanes, brightness temperatures were compared with observations of Hurricane Erin (2001) from CAMEX-4 radiometers on the ER-2 aircraft. Frozen hydrometeors and hurricane particle microphysics play a large role in the development and strength of tropical cyclones through the convective processes in the rain bands present. Previous studies have proven that it is difficult to select proper ice particle parameterizations and that in situ measurements and additional studies are key to defining appropriate parameterizations.

The observations from the Fourth Convection and Moisture Experiment (CAMEX-4) and ER-2 Doppler reflectivities were co-located with brightness temperatures from the High Altitude MIMC Sounding Radiometer (HAMSR) and the Advanced Precipitation Microwave Radiometer. In order to obtain atmospheric profile information for radiative transfer calculations along the flight line of interest, supporting temperature, relative humidity, and wind speeds were obtained from a Mesoscale Model-5 (MM5) simulation of Hurricane Erin. Of 250 slices of simulated data in each direction, one ideal slice needed to be selected for use with the observed flight line. The observations had a definitive eye, several convective rainbands, and anvil ice clouds. The slice of data that proved to be ideal was number 123 in the i-direction, and is taken at the latitudes between 32.0 to 33.2 degrees north, and the longitude of -64.7879 degrees. The maximum altitude of the data slice was 15 km, and the simulated temperature, relative humidity, density of cloud ice, density of graupel, density of cloud water, density of rain water, and density of snow profiles were extracted.

Bilinear interpolation was used to convert the model data in 250 points with a resolution of 2km to 200 points with a resolution of 2.5km in order to match the observed data for purposes of comparison. This observed data will be helpful in understanding whether the model slice is appropriate and if the accompanying parameterization is useful for these types of hydrometeors. There is a correlation between high frequencies (>= 85 GHz) and the accurate detection of frozen particles’ radiative signatures in storms. Higher frequencies are particularly sensitive to the frozen hydrometeors, and finding a multi-frequency retrieval algorithm for ice particle characteristics is the goal.

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