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Description
Thunderstorms are among the most hazardous convective systems in the Indian subcontinent, and their occurrence is particularly frequent over the complex terrain of Northeast India. This study highlights the role of Very High Frequency (VHF) Stratosphere-Troposphere (ST) radar observations from Gauhati University in advancing the understanding of thunderstorm dynamics in Assam. A detailed analysis of the 20 April 2024 pre-monsoon thunderstorm is presented to illustrate the radar’s capabilities in capturing fine-scale temporal and vertical convective processes.
Key parameters such as vertical velocity, horizontal wind components (U and V), signal-to-noise ratio (SNR), and backscatter power are examined to describe the storm’s evolution The time-altitude evolution of vertical velocity indicates that prior to initiation, vertical air motions were weak, generally below ±1 m s⁻¹ throughout the troposphere. During the convective phase, strong mid-tropospheric updrafts developed, accompanied by downdrafts reaching nearly -4 ms⁻¹, coinciding with the onset of surface precipitation. To validate radar-derived convective signatures, rain data from a collocated disdrometer is incorporated, which aligns well with the radar observations and confirms the brief, low-intensity rainfall associated with the event.
The combined observations reveal the progression of updrafts, downdrafts, turbulent mixing, and refractive index fluctuations associated with convective activity. These results underscore the utility of ST radar in resolving fine-scale storm evolution over complex terrain. Finally, the study emphasizes the importance of integrating ST radar and ground-based precipitation measurements with satellite and numerical modelling approaches to improve thunderstorm forecasting and disaster preparedness in Northeast India.
