Shaik Darga Saheb

The onset of the Southwest Monsoon (SWM) over Karnataka marks a critical transition from hot, dry pre-monsoon conditions to a period of high convective activity, bringing thunderstorms along with heavy rainfall and strong gusty winds. The study investigates the characteristics of thunderstorms and associated key synoptic and thermodynamic factors during the onset of monsoon for the year of 2024. The monsoon advanced over Karnataka on 1st June 2024 and covered the entire state by 6th June 2024. Thunderstorm activities were observed in the entire Karnataka region with isolated extremely heavy rainfall at a few locations (e.g., rainfall ~11 cm in Bengaluru on 3rd June). Synoptic analysis revealed a persistent shear zone along 8°N over South Peninsular India (3.1– 4.5 km altitude) and cyclonic circulations over the Arabian Sea, enhancing the moisture transport over the region. A low-pressure system over the Bay of Bengal and mid-tropospheric circulations over coastal Karnataka further intensified convective instability during the study period. Based on the upper air sounding data, the thermodynamic indices indicated that strong moisture convergence, high Convective Available Potential Energy (CAPE) ~2501 J/Kg and vertical wind shear are fostering thunderstorm genesis. The study highlights the complex interplay of large-scale dynamics and localized processes in thunderstorm formation during monsoon onset of 2024. Improved understanding of these mechanisms can enhance predictive accuracy, disaster preparedness and mitigate the socio-economic impacts in the Karnataka region.

The study examines the long-term (2011-2023) analysis of thunderstorm and lightning activities and their impacts on local meteorology and air pollutants over Bengaluru. The diurnal thunderstorm events occur mainly in the late evening hours (1900–2100 IST) and on monthly maximum in May while minimum in January. Annually, Bengaluru experiences an average of 41 thunderstorms and 157 lightning strikes, both of which have shown a statistically significant upward trend at a 95% confidence level. The rate of increase is 3.41% per year for thunderstorms and 3.3% per year for lightning events. Local temperatures coupled with abundant moisture supply from the southwest/northeast monsoon creates a favourable condition for the initiation of thunderstorms over the region. This study also focused on the trend analysis of meteorological parameters and atmospheric compositions, a rising trend were found in rainfall (1.44 mm year–1), RH (0.74% year–1) & pressure (0.03 hPa year–1) whereas a slight declining trends in temperature (0.06 0C year-1) & wind speed (-0.02 ms-1 year–1). As the availability of heat and humidity are two main prerequisites for the occurrence of thunderstorm and hence the probability of severe thunderstorms may increase in future. The AOD, NO2 & O3 showed a significant increasing trend while no trend for SO2. The Pearson correlations showed the AOD, NO2 & SO2 concentrations are significant negatively correlated with wind speed but positively correlated with atmospheric pressure. A further study indicated a significant impact of thunderstorm on the air pollutants has also been quantified and it was observed that PM2.5 concentration gradually decreases after the commencement of thunderstorm while quick increase response (less than 1 hour) was observed in O3 and delay response (after 2:30 hours) in NO2 which may linked to lightning activities. The results reveal that thunderstorms can affect both the local meteorology as well as atmospheric pollutants and vice-versa from regional to global.

This study investigates the impacts of summer monsoon activity on aerosols over the Indian region. We analyze the variability of aerosols during active and break monsoon phases, as well as strong and weak monsoon years, using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Our findings show a clear distinction in aerosol distribution between active and break phases. During active phases, the Aerosol Optical Depth (AOD) and aerosol extinction are lower across the Indian region, while break phases are associated with higher AOD and extinction. Furthermore, we observed a significant increase in AOD over Central India during strong monsoon years, compared to weak monsoon years. Utilizing the vertical feature mask (VFM) data from CALIPSO, we identified polluted dust and dusty marine aerosols as the dominant types during both active/break phases and strong/weak monsoon years. Notably, the contributions of these pollutants are significantly higher during break phases compared to during active phases. Our analysis also reveals a shift in the origin of these aerosol masses. During active phases, the majority originate from the Arabian Sea; in contrast, break phases are associated with a higher contribution from the African region.

Study aims to conduct a synoptic and thermodynamic analysis of significant rainfall events that happened during the break monsoon season. During the investigation of meteorological events, it was observed that the monsoon trough at mean sea level passed along the foothills of the Himalaya. On August 31, 2023, there was a cyclonic circulation observed in the northeast Bay of Bengal as well as adjacent areas, reaching an altitude of 5.8 km above mean sea level (AMSL). This circulation tilted southwestward with height. During the period of August 31-September 2, 2023, there was a cyclonic circulation persistent that occurred inside a particular geographical area. This phenomenon extended up to a height of 4.5 km AMSL and exhibited a south-westward tilt as the altitude increased. On August 31, 2023, the Convective Available Potential Energy (CAPE) was measured to be 2153 J/kg, whereas the Convective Inhibition Energy (CINE) was recorded as 0 J/kg. INSAT-3D satellite image showed a cloud top temperature of – 40 °C to – 60 °C. The Doppler Weather Radar (DWR) pictures also showed convective clouds to support this phenomenon. The synoptic and thermodynamic indices indicate a high likelihood of significant precipitation occurring over Bengaluru and its surrounding regions.