Geoscience Reference
In-Depth Information
Simulation of Pre-monsoon Cyclones
of Two Contrasting Monsoon Years
Using Mesoscale Model WRF (ARW)
Surireddi S.V.S. Ramakrishna*, C.V. Srinivas 1 , A. Sravani,
N. Nanaji Rao, V. Lakshmana Rao and N. Vijaya Saradhi
Department of Meteorology and Oceanography
Andhra University, Visakhapatnam
1 Indira Gandhi Centre for Atmospheric Research, Kalpakkam, Chennai
*e-mail: ssvs_rk@yahoo.co.in
1. Introduction
Tropical cyclones are known for their devastation in tropical regions over the
whole globe. The devastation is mainly due to high winds, intense rains and
the associated storm surge. The life cycle of a tropical cyclone is dependent on
a number of environmental factors (Gray, 1968) which are frequently present
in the Inter Tropical Convergence Zone (ITCZ). These include a warm ocean
surface (above 26 o C) and several physical parameters contributing to a deep
humid and unstable atmosphere. It is a well established fact that SST>26.6 o C
is a prerequisite for tropical cyclone formation in the Bay of Bengal. The
formation process begins in an area of low pressure coinciding with vigorous
convective cloud in the tropics between 5 o and 22 o latitude. Usually the cloud
cluster drifts slowly towards the west as the convection increases and winds
begin spiralling in towards the centre of the system. There are two cyclonic
seasons in the North Indian Ocean (NIO), pre-monsoon (April and May) and
post-monsoon (October and November). Tropical cyclones form in the NIO
during pre-monsoon season of which most of these cyclones develop in the
Bay of Bengal and hit the Bangladesh or Myanmar coast. Cyclonic disturbances
that develop during this season have a high probability of reaching a severe
cyclonic stage (Singh et al., 2000).
In the recent years mesoscale models are extensively used for simulation
of genesis, intensification and movement of tropical cyclones in the Bay of
Bengal (Mohanty et al., 2004; Bhaskar Rao and Hariprasad, 2006; Ramakrishna
et al., 2012). Rao et al. (2008) showed that if the decreasing trend of Tropical
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