Structure of pre-monsoon convective systems over a tropical coastal
region in southwest India using C-band polarimetric doppler weather
radar observations
Abstract
The structure of pre-monsoon convective systems over southern peninsular
India using polarimetric doppler weather radar (DWR) observations has
been analyzed. Convective-stratiform separation has been done for eleven
convective events during Mar-May, 2018. The mean vertical profile of
reflectivity shows peak reflectivity of 32 dBZ near 3 km height for
convective regions and the bright band signature over stratiform regions
was observed. The frequency distributions of reflectivity at 3 km height
over convective and stratiform regions are of bell-shaped nature with
peaks at 32 dBZ and 18 dBZ respectively. A comprehensive analysis has
been done on two prominent convective cases on 13th
and 25th May 2018. Strong convective regions
represented by high reflectivity (> 45 dBZ) were noticed in
the PPI diagrams. Specific differential phase (Kdp) has
been calculated from the slope of the filtered Φdp.
Heavy precipitation near surface is reflected in the high value of
Kdp (> 5° km-1). High
values of Zdr (> 3 dB) were measured at
lower levels due to the oblate bigger raindrops. A fuzzy logic-based
hydrometeor identification algorithm has been applied with five
variables (Zh, Zdr, ρhv,
Kdp, and T) to understand the bulk microphysical
processes at different heights within convective regions. The presence
of bigger graupel particles near the melting layer indicates strong
updrafts within the convective core regions. The vertical ice
hydrometeor might signify the existence of a strong electric field
causing them to align vertically and this could be linked to lightning
occurrence associated with such systems.