Estimation of Centre and Intensity of Tropical Cyclones over the North Indian Ocean Using Microwave Imageries - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 189

Microwave is powerful electromagnetic radiation for atmospheric sounding
which is transparent to dense cloud due to high weighting function in middle
atmospheric region (Meeks and Lilley, 1963; Veldon and Smith, 1983). Several
studies have been made to convert microwave-based brightness temperature
of the cloud into rain rate and surface wind associated with tropical cyclones
(Evans and Stephans, 1993; Kummerow et al., 1996). The brightness
temperature is used to determine Estimated Central Pressure (ECP) and
Maximum Sustained Wind (MSW) of the storm (Goodberlet et al., 1989 and
Bessho et al., 2006). Considering the importance of the microwave imageries
and the availability of tools to analyse them, the microwave imageries have
been operationally introduced for monitoring of CDs over NIO from 2010. In
this application, the ECP and MSW estimated by the National Ocean and
Atmospheric Administration (NOAA) are utilized.
To overcome this difficulty microwave imageries from NOAA series,
Metop-A, Defense Meteorological Satellite Program (DMSP) satellites are used
to analyze the inner structure of tropical cyclones. Several authors (Veldon
and Smith, 1983) have shown a potential usefulness of microwave image
products for the detection of the TC centre. However, the use of microwave
data in this regard has been limited upto recently primarily because of the low
spatial and temporal resolution of the microwave products. Furthermore these
methods use a limited number of channels, usually the 85.5 GHz channel which
is sensitive to the ice particles, but has a higher spatial resolution than lower
frequency channels, for the determination of TC centre. Recent development
of the web based TC information distribution system by Hawkins et al. (2001)
shows the many advantages of microwave data over the current visible/IR data
specially when the TC is in the development stage.
Velden et al. (1989) found an objective way for centre determination of
TCs using multispectral satellite imagery called the Automated Rotational
Centre Hurricane Eye Retrieved (ARCHER). The algorithm finds the centre
of rotation using spirally oriented brightness temperature gradients along the
ring shaped edge of a possible eye. JMA is using microwave imageries for (i)
MSW estimation using multi-channel microwave imager data, (ii) centre
pressure estimation using multi-channel microwave sounder data based on the
study of Beisho et al. (2010) as a method of detecting warm core, (iii) converting
warm core values to centre pressure data based on CIMSS AMSU intensity
algorithm and (iv) implementation of a method for estimating 30 and 50 knots
radii and MSW using 7 and 10 GHz band imagery for AMSU-I band.
In this study, microwave cloud imageries and derived products in the
frequency of 85 GHz have been examined for six TCs that occurred during
FDP period (15 October- 30 November) of 2009-2011 over the Bay of Bengal.
The location of centre and intensity (T number) as estimated by various
operational centres like Satellite Division of IMD New Delhi, Satellite Service
Division (SSD) of NOAA and National Research Laboratory (NRL) of US
Navy based on microwave imageries of various polar orbiting satellites