Statistical Characteristics of Convective Clouds over the Western Ghats Derived from Weather Radar Observations

Abstract

X‐band radar observations at Mandhardev (18.04°N, 73.85°E) are used to investigate statistics of convective clouds over the Western Ghats during monsoon season (June–September 2014). Convective storms (cells) are identified using an objective‐tracking method to examine their spatiotemporal variability, thus quantifying the time‐continuous aspects of convective cloud population over the region for the first time. An increased frequency of storm location and initiation along the windward mountains compared to coastal and lee side highlights orographic response to southwesterly flow, with superimposed diurnal cycle. An eastward progression of convective activity from upstream the barrier through windward slopes of mountains over to the lee side is observed. Storm area, height, and duration follow lognormal distributions; wherein, small‐sized storms contribute more to total population and unimodal distribution of 35 dBZ top heights (peaking at 5.5 km) depicts the dominance of shallow convection. Storms exhibit a pronounced diurnal cycle with a peak in afternoon hours, while the convective area maximum is delayed by several hours to that of precipitation flux. Cell lifetime and propagation show that cells move with slow speeds and have mean duration of 46 min. They align east‐west nearly parallel to mountain ridges, and their direction of movement is steered mostly by large‐scale winds at lower levels. Based on top heights, convective cells are further classified into cumulus, congestus, and deep clouds. In general, congestus (deep) cells are most abundant in the windward (leeward) side. A lead‐lag relationship between congestus and deep cells indicates midtroposphere moistening by congestus cells prior to deep convection.

The dynamic and thermodynamic structure of the monsoon over southern India: New observations from the INCOMPASS IOP

“…Kumar and Bhat (2017) also showed that the TRMM convective/stratiform identification algorithm classified rainfall offshore from the Indian west coast as convective more frequently than in other similar regions. Utsav et al (2017) used ground-based weather radar observations at the northern end of the Western Ghats to show that this is most frequently congestus-type convection. While most rainfall upstream of the Western Ghats comes from convective clouds with tops below about 6 km, the most intense rainfall comes from organized large-scale features such as the northward propagation of the tropical convergence zone (Francis and Gadgil, 2006).…”

Observed Vertical Structure of Convection During Dry and Wet Summer Monsoon Epochs Over the Western Ghats

“…Recently, there have been few ground‐based studies on orographic convection documenting the radar divergence profiles (Deshpande et al, ) and drop size distributions (Das et al, ; Konwar et al, ). Utsav et al () derived the statistical characteristics of convective clouds over the WG during monsoon using the X‐band radar observations. Although these studies describe the orographic rainfall characteristics over this region, the vertical structure of convective clouds, especially during the monsoon intraseasonal phases, remains to be documented and is the focus of this study.…”

Statistical characteristics of raindrop size distribution over Western Ghats of India: wet versus dry spells of Indian Summer Monsoon

“…Konwar et al (2006) and Rao et al (2009) showed that stratiform precipitation dominates over Gadanki. However, shallow convection occurs frequently over WGs (Utsav et al, 2017). This indicates that the rain microphysical processes are different over WGs compared to other regions.…”

“…It receives a large amount of rainfall (~6000mm) during the Indian Summer Monsoon (ISM; , and references therein). The monsoon rainfall in this region is contributed by both shallow clouds on the windward side (Kumar et al, 2013;Utsav et al, 2017Utsav et al, , 2019 and deep convection in the leeward side (Utsav et al, 2017(Utsav et al, , 2019Maheskumar et al, 2014). In addition, thunderstorms also occur over WGs; however, they are very few during the monsoon period.…”