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Fig. 10.5 Radial-height cross sections for Hurricane Gert on 16 Sept. 1999 of AMSU-retrieved
( a ) temperature anomalies (8 C), showing the warm core at a height of approximately 12 km, and
( b ) gradient winds (kt), showing that the MSW occurs at approximately 175 km from the storm
center (From Demuth et al. 2004 )
Although the retrieved wind structure in Fig. 10.5 is qualitatively similar to a
tropical cyclone with cyclonic tangential winds decreasing with height and a larger
scale anticyclone at upper levels, the inner core is still not represented well. The
low-level radius of maximum wind is about 175 km, which is much too large, and
the retrieved maximum wind of about 60 kts is much lower than what was observed
for Hurricane Gert at this time. To help correct for the lack of resolution, a statistical
bias correction is applied to several parameters from the retrieved fields (Demuth
et al. 2006 ) to improve the accuracy of the method. A scale correction is also
applied to the AMSU retrieval method described by Brueske and Velden ( 2003 ).
That algorithm also makes use of the AMSU-B moisture channels, which have a
footprint size about 1/3 that of AMSU-A, to provide an eye-size estimate. The eye-
size information is used to help correct for the low resolution of the AMSU-A
channels. Both of the TC intensity estimation techniques described above have been
used operationally by the National Hurricane Center and the Joint Typhoon Warn-
ing Center for the past several years. The average accuracy of the AMSU methods
is not quite as good as the Dvorak method, especially for very small cyclones, but it
provides an independent estimate of intensity.
10.3.2 Microwave Imagery Applications
Microwave imagery has been available from LEO satellite systems for the past few
decades, including Special Sensor Microwave/Imager (SSMI), Special Sensor Micro-
wave Imager Sounder (SSMIS), Tropical Rainfall Measuring Mission (TRMM)
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