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analysis technique have capability to be applied for assimilation of radar data
in Weather Research and Forecasting (WRF) Model.
Installation of DWRs in India has motivated to test and evaluate the Bratseth
successive correction technique and cloud analysis package of ADAS for
assimilation of Indian DWR data in WRF Model. Warning Decision Support
System Integrated Information (WDSS-II) is installed in India Meteorological
Department (IMD) for real time quality control of radar data, analysis,
visualizing and nowcasting of weather using remotely sensed weather radar
data. Roy Bhowmik et al. (2011) showed the applicability of WDSS-II software
for generation of quality control radar data. Technical details about the
customization of ADAS over Indian region are documented by Srivastava et
al. (2011a, 2011b).
In this study DWR observation taken by Kolkata Radar are assimilated for
numerical simulation of a land-falling TC Aila (2009) over the Bay of Bengal
(BoB). The quality-controlled radar data from WDSS-II are assimilated into
the WRF Model through ADAS and Cloud Analysis procedure. Experiments
are conducted to study the thermal and hydrometeor structures of cyclone Aila
at the time of landfall. Apart from that impact of radar data on the divergence/
convergence conditions of cyclone inner-core area is also studied.
2. Description of Cyclone Aila
A depression formed over the southeast BoB at 0600 UTC of 23 May, 2009.
Under favourable conditions like warmer sea surface temperature, low to
moderate vertical wind shear and upper level divergence, it intensified into a
cyclonic storm (CS) “Aila”
at 1200 UTC of 24 May and into a severe cyclonic
storm (SCS) at 0600 UTC of 25 May. The system moved in a northerly direction
and crossed West Bengal coast close to Sagar Island between 0800 and 0900
UTC of 25 May. It caused loss of about 100 lives and left several injured in
West Bengal. It also caused about 175 human deaths and several injured in
adjoining Bangladesh. The system moved in a near-northerly direction
throughout its life span. It intensified into SCS only a few hours before landfall.
The system maintained the intensity of the cyclone (T2.5) even up to 15 hours
after the landfall. Satellite visible image and DWR max (Z) plot at the time of
landfall are shown in Fig. 1.
3. Data and Methodology
Reflectivity and Radial Wind from Kolkata Doppler Weather Radar data
(latitude 22.60 deg N, longitude. 88.40 deg E) are assimilated in WRF model
through ADAS. Figure 2 shows number of radar observation at different vertical
levels at the 0900 UTC 25 May 2009. It is apparent that most of the radar data
are distributed between the altitudes of 1 and 14 km. For all the experiments,
model domain consists of 15° to 30° N and 80° to 95° E with horizontal
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