The Estimation of Extratropical Cyclone Parameters from Satellite Radiation Measurements

William E. Shenk Goddard Space Flight Center, Greenbelt, Md.

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Herbert E. Hunter Avco Corporation, Wilmington, Mass.

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Frederick V. Menkello USAF Environmental Technical Applications Center, Washington, D.C.

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Robert Holub USAF Environmental Technical Applications Center, Washington, D.C.

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Vincent V. Salomonson Goddard Space Flight Center, Greenbelt, Md.

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Abstract

An objective statistical procedure has been developed using satellite infrared window radiation measurements to estimate the central pressure (Pc), the deviation of the central pressure from the climatological normal (ΔP), the intensity (I = ∇2P), and the deepening or filling rate (dP/dt) of extratropical cyclones. The independent variables for 40 cylones over the North Atlantic and Pacific Oceans were the Nimbus 2 High Resolution Infrared Radiometer (HRIR) measurements at 79 locations surrounding the center of each cyclone, the date, and the geographical location of the center. Optimum empirical orthogonal functions were used to reduce the dimensionality and establish the regression relationship between the cyclone parameters and the radiation measurements for 30 of the cyclones. The remaining 10 cyclones were used to test the accuracy of the regression relationship. When the test cyclones were well represented by the cyclones in the sample employed to establish the relationship, a standard error of estimate for Pc of 6 mb was achieved for the test cyclones with slightly lower percentage accuracies for ΔP and I. An a priori decision could be made for each test cyclone regarding the probable success of parameter estimation. This was dependent on how well the test cyclone was represented by the orthogonal functions derived by the cyclones used to establish the regression equation.

Abstract

An objective statistical procedure has been developed using satellite infrared window radiation measurements to estimate the central pressure (Pc), the deviation of the central pressure from the climatological normal (ΔP), the intensity (I = ∇2P), and the deepening or filling rate (dP/dt) of extratropical cyclones. The independent variables for 40 cylones over the North Atlantic and Pacific Oceans were the Nimbus 2 High Resolution Infrared Radiometer (HRIR) measurements at 79 locations surrounding the center of each cyclone, the date, and the geographical location of the center. Optimum empirical orthogonal functions were used to reduce the dimensionality and establish the regression relationship between the cyclone parameters and the radiation measurements for 30 of the cyclones. The remaining 10 cyclones were used to test the accuracy of the regression relationship. When the test cyclones were well represented by the cyclones in the sample employed to establish the relationship, a standard error of estimate for Pc of 6 mb was achieved for the test cyclones with slightly lower percentage accuracies for ΔP and I. An a priori decision could be made for each test cyclone regarding the probable success of parameter estimation. This was dependent on how well the test cyclone was represented by the orthogonal functions derived by the cyclones used to establish the regression equation.

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