Geoscience Reference
In-Depth Information
The process of post-season analysis of CDs to determine the best estimate
of a CD's position and intensity along with other characteristics during its
lifetime is described as “best tracking”. The best tracking procedure has
undergone several changes world-over including NIO due to change in
definition and classification of TCs; monitoring and analysis tools and
procedure; and physical understanding of TCs. Hence, a study has been
undertaken by Mohapatra et al. (2012) to review the temporal changes in the
best track procedure including changes in observational network, monitoring
technique, area of responsibility for monitoring, terminology and classification
of the TCs etc. over the NIO and their impact on quality of best track parameters
over the NIO for the study of climate change impact on TCs. The problems
and prospective with the best track data over the NIO have been presented and
discussed by them.
Based on quality and availability, the whole period of best track information
may be broadly classified into four phases, viz., (i) pre-1877, (ii) 1877-1890,
(iii) 1891-1960 and (iv) 1961-2010 according to Mohapatra et al. (2012). The
period of 1961-2010 may be further classified into (a) 1961-1973, (b) 1974-
1990 and (c) 1991-2010. As optimum observational network including satellite
leading to better estimation of location and intensity without missing of CDs
was available since 1961, the climatology of TCs and interannual variation
can be best represented based on the data set of 1961-2010 and more so since
1974 and 1982 with the advent of geostationary satellites and Indian National
satellites (INSAT) respectively.
The best track developed by IMD is the consensus decision based on the
available observations including satellite, radar, ships, buoys, and coastal and
island observations. In this study, the characteristics of best track parameters
in the satellite era (1961-2010) and interannual variation of frequency and
intensity of CD over the NIO during the same period are analysed and discussed.
2. Characteristics of Best Tracks in Satellite Era
2.1 Satellite Observations of CDs
Satellites with meteorological instrumentation were first launched in the late
1950s. The first satellite completely dedicated to satellite meteorology was
launched on 1 April 1960. It was called the Television and Infrared Observational
Satellite (TIROS). The life span of this satellite was 79 days. The images,
however, generated much excitement in the meteorological community.
Nine additional TIROS satellites were subsequently launched through 1965.
Nimbus 1 was launched on 28 August, 1964. Six more Nimbus satellites were
subsequently launched and provided continuous coverage of the earth. This
meant that tropical storms could be closely monitored for the first time from
later part of 1964. The last Nimbus satellite was launched in 1978. The current
NOAA polar orbiting satellites are descendents of the original Nimbus satellites.
The 16 September, 1966 marked the launch of the first Defense Meteorological
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