Research And Applications In The Field Of Tropical Cyclones

With its unmistakable spiral shape and central eye, the tropical cyclone is the most memorable feature on any satellite image. Indeed, if weather satellites detected nothing else besides these monster storms, they would be worth the money invested in them. A number of techniques have been developed to estimate the movement and intensity of tropical cyclones. One of the most widely accepted is the Dvorak (1984) technique which assigns an intensity based on the size and shape of the dense cloud mass adjacent to the centre of the circulation of the storm. TC intensity is estimated using VIS and IR imagery. Fixes are also made using scatterometer, TRMM, multispectral and special sensor microwave imager (SSM/I) data. IR imagery is the workhorse of the TC analysis because of its 24 hours availability. VIS imagery provides the highest resolution and is the best channel available for detection of surface features that may not be seen in the IR or WV imagery. Multispectral imagery which highlights features both at low and high levels is used to determine TC intensity and position. Satellite fixes of position are added to the fixes data base along with fixes from other sources. This is used to develop a Working Best Track and for input of TC bogus into numerical models. A lot of insight has been gained into physical and dynamical progress shaping development of TCs. Satellite imagery has also been very exhaustively used for the analysis of TCs developing in the north Indian Ocean (Kalsi 1999 & 2002). The satellite based observations have opened up new research areas for improved forecasting of intensity and track. Some of the emerging research areas are:

• The 'warm core approach' using MSU sounding data to analyse warm temperature anomalies in upper troposphere and correlate to central pressure fall and maximum winds (DeMuth et al., 2001).

• The objective Dvorak technique (ODT) for intense cyclones (Velden et al., 1998) and Advanced Objective Dvorak technique (AODT) for weak systems.

• Storm surge prediction using satellite derived radius of maximum winds, intensity, direction and speed of cyclones.

• Use of satellite data for synthetic vortex generation in numerical models.

• Assimilation of satellite data as mentioned under section 8 below.

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