11th Conference on Satellite Meteorology and Oceanography

Tuesday, 16 October 2001: 11:30 AM
Satellite-based Tropical Cyclone Intensity Estimation Using NOAA-KLM Series Advanced Microwave Sounding Unit (AMSU).(Invited Presentation)
Kurt F. Brueske, U.S. Air Force Academy, U.S. Air Force Academy, CO; and C. S. Velden
Poster PDF (732.3 kB)
Satellite-borne passive microwave radiometers are well suited to monitor tropical cyclones (TCs) by virtue of their ability to assess changes in tropospheric warm core structure in the presence of clouds. The temporal variability in TC warm core size, structure, and magnitude provide vital information on changes in kinematic structure and minimum sea level pressure (MSLP) through implicit thermodynamic and dynamic constraints. In this study, the efficacy of a hybrid-statistical algorithm capable of estimating MSLP using Advanced Microwave Sounding Unit (AMSU) temperature (AMSU-A) and moisture sounder (AMSU-B) data is demonstrated. The proposed AMSU TC intensity estimation algorithm addresses tropospheric warm anomaly (UTWA) sub sampling through explicit convolution of an analytic function approximating the horizontal distribution of the TC UTWA and the AMSU-A antenna gain pattern. Differences between observed AMSU-A 54.94 GHz upper tropospheric limb corrected brightness temperatures (Tb) and those of a forward model based on the convolution function are minimized through maximum likelihood regression using known and estimated radiometric noise, position and TC structure function errors.

Dependent data set results using 1999 Atlantic (ATL) and eastern Pacific (EPAC) basin aircraft reconnais-sance and AMSU-A observation pairs (n=22) indicate significantly increased correlation between scan geometry/diffraction-corrected AMSU-A 54.94 GHz TC UTWA and MSLP (R2=0.9) vs. using no correction (R2=0.7). Linear least squares regression coefficients derived from the 1999 dependent sample were used to predict TC MSLP using a fully automated, objective processing scheme in multiple ocean basins during 2000 and a limited number of cases in early 2001. ATL/EPAC independent test results (n=31) indicate that substantial improvements in correlation between AMSU-A TC UTWA and MSLP (R2=0.94 vs. 0.80), predicted MSLP mean error of 6.2 hPa vs. 7.5 hPa, and reduced standard deviation of 8.0 hPa vs. 9.9 hPa) are possible using the proposed hybrid AMSU intensity estimation scheme. Comparison of AMSU ATL/EPAC independent test results with subjective Dvorak MSLP estimate mean error and standard deviation (7.8 hPa +/- 7.6 hPa, n=31) analyses demonstrates superior AMSU TC intensity estimation technique performance with reductions in both mean error and variance. Further extending statistical analysis of AMSU TC intensity estimate performance to include western North Pacific Ocean (NWPAC), Southern Indian Ocean (SIO) and Southern Pacific Ocean (SPAC) validation candidates, the aforementioned results are roughly equivalent albeit slightly improved (i.e., mean error of 5.3 hPa vs. 7.4 hPa and standard deviations 7.2 hPa vs. 9.7 hPa).

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