TITLE:
Study of Weak Intensity Cyclones over Bay of Bengal Using WRF Model
AUTHORS:
Radhika D. Kanase, P. S. Salvekar
KEYWORDS:
WRF-ARW Model, BMJ-YSU-WSM6 Combination, Pre and Post Monsoon Severe Cyclonic Storms
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.4 No.4,
September
18,
2014
ABSTRACT: Numerical
simulations of four weak cyclonic storms [two cases of pre-monsoon cyclones:
Laila (2010), Aila (2009) and two cases of post-monsoon cyclones: Jal (2010),
SCS (2003)] are carried out using WRF-ARW mesoscale model. Betts-Miller-Janjic
(BMJ) as cumulus parameterization (CP) scheme, Yonsei University(YSU) planetary
boundary layer (PBL) scheme and WRF single moment 6 class (WSM6) microphysics
(MP) scheme is kept same for all the cyclone cases. Three two-way interactive
nested domains [60 km,20 kmand6.6 km] are used with initial and boundary conditions
from NCEP Final Analysis data. The model integration is performed to evaluate
the track, landfall time and position as well as intensity in terms of Central
Sea Level Pressure (CSLP) and Maximum Surface Wind speed (MSW) of the storm. The
track and landfall (time and position) of almost all cyclones are well
predicted by the model (except for SCS cyclone case) which may be because of
the accurate presentation of the steering flow by CP scheme. Irrespective of
season, the intensity is overestimated in all the cases of cyclone, mainly
because of the lower tropospheric and mid-tropospheric parameters are
overestimated. YSU PBL scheme used here is responsible for the deep convection
in and above PBL. Concentration of frozen hydrometeors at the mid-tropospheric
levels and thus the latent heat released during auto conversion of hydrometeors
is also responsible for overestimation of intensity.