TITLE:
Seasonal Prediction of Indian Summer Monsoon Using WRF: A Dynamical Downscaling Perspective
AUTHORS:
Manas Ranjan Mohanty, Uma Charan Mohanty
KEYWORDS:
Dynamical Downscaling, Regional and Mesoscale Modeling, Diabatic Heating, WRF
JOURNAL NAME:
Open Journal of Modelling and Simulation,
Vol.12 No.1,
January
15,
2024
ABSTRACT: Seasonal forecasting of the Indian summer monsoon by
dynamically downscaling the CFSv2 output using a high resolution WRF model over
the hindcast period of 1982-2008 has been performed in this study. The April
start ensemble mean of the CFSv2 has been used to provide the initial and
lateral boundary conditions for driving the WRF. The WRF model is integrated
from 1st May through 1st October for each monsoon season. The analysis suggests
that the WRF exhibits potential skill in improving the rainfall skill as well
as the seasonal pattern and minimizes the meteorological errors as compared to
the parent CFSv2 model. The rainfall pattern is simulated quite closer to the observation
(IMD) in the WRF model over CFSv2 especially over the significant rainfall
regions of India such as the Western Ghats and the central India. Probability
distributions of the rainfall show that the rainfall is improved with the WRF.
However, the WRF simulates copious amounts of rainfall over the eastern coast
of India. Surface and upper air meteorological parameters show that the WRF
model improves the simulation of the lower level and upper-level winds, MSLP,
CAPE and PBL height. The specific humidity profiles show substantial
improvement along the vertical column of the atmosphere which can be directly
related to the net precipitable water. The CFSv2 underestimates the specific
humidity along the vertical which is corrected by the WRF model. Over the Bay
of Bengal, the WRF model overestimates the CAPE and specific humidity which may
be attributed to the copious amount of rainfall along the eastern coast of
India. Residual heating profiles also show that the WRF improves the
thermodynamics of the atmosphere over 700 hPa and 400 hPa levels which helps in improving the rainfall
simulation. Improvement in the land surface fluxes is also witnessed in the WRF
model.