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<p>Monsoon convection plays a crucial role in regional climate dynamics, influencing precipitation patterns, radiation budget, and tropospheric-stratospheric exchange processes. Understanding the morphological, dynamical, and microphysical characteristics of monsoon convection over the gateway of the Indian summer monsoon, i.e., Kerala, is essential, as it dictates the propagation of the monsoon system over the entire country. The present study hence deals with the morphological characteristics of convective storms (CS), their propagation, and the diurnal cycle during the Indian summer monsoon using C-band weather radar from Thumba (8.5°N, 76.9°E) over a seven-year (2017–2023) period. The study also investigates the large-scale dynamics and its interaction with the convective systems. The Thunderstorm Identification, Tracking, Analysis, and Nowcasting, a lagrangian based approach, is employed for the identification of CS. Higher occurrences of CS are observed on the leeward side of the Western Ghats. The percentage occurrence of congestus, deep, and overshooting is 60%, 39%, and 1%, respectively. Maximum reflectivity (Max-Z) is observed for overshooting storms, with a higher rain rate compared to congestus and deep, although its occurrence is considerably less. The occurrence of D, C, and B/C scale CS is found to be 89.5%, 10%, and 0.5%, respectively. We observed a single modal distribution for C and D and a bimodal for B/C with a small peak at 5&#xa0;km and another at 10&#xa0;km. The distribution is broader (5–10&#xa0;km) for D and C-type CS compared to B/C. D scale CS are more dominant with duration of ~ 40&#xa0;min. The CS are relatively intense over the land compared to oceans. Diurnal progression shows that during early morning (00–03 LT), the CS form over the southwest Arabian Sea, and as time progresses, the occurrence increases towards the coast and maximizes between 06 and 09 LT. The CS then progresses towards the inland region and shows a maximum between 09 and 15 LT. The CS peaks again over the oceans from 18 LT, and subsequently the occurrence decreases over the land. A prominent peak in the afternoon over the land and a dominant peak in the early morning, followed by two weak peaks in the afternoon and midnight, are observed over the ocean. The interaction with the background stability, moisture, and dynamics showed that the mid-tropospheric moistening is responsible for intense CS coupled with large-scale advection.</p>

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Characteristics of monsoon convection and its interaction with the large-scale environment over the gateway of the Indian summer monsoon: insights from radar observations and reanalysis

  • 期刊论文

  • 发表日期：

    2025年10月13日

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  • K. N. Uma,
  • Bukya Sama

摘要

Monsoon convection plays a crucial role in regional climate dynamics, influencing precipitation patterns, radiation budget, and tropospheric-stratospheric exchange processes. Understanding the morphological, dynamical, and microphysical characteristics of monsoon convection over the gateway of the Indian summer monsoon, i.e., Kerala, is essential, as it dictates the propagation of the monsoon system over the entire country. The present study hence deals with the morphological characteristics of convective storms (CS), their propagation, and the diurnal cycle during the Indian summer monsoon using C-band weather radar from Thumba (8.5°N, 76.9°E) over a seven-year (2017–2023) period. The study also investigates the large-scale dynamics and its interaction with the convective systems. The Thunderstorm Identification, Tracking, Analysis, and Nowcasting, a lagrangian based approach, is employed for the identification of CS. Higher occurrences of CS are observed on the leeward side of the Western Ghats. The percentage occurrence of congestus, deep, and overshooting is 60%, 39%, and 1%, respectively. Maximum reflectivity (Max-Z) is observed for overshooting storms, with a higher rain rate compared to congestus and deep, although its occurrence is considerably less. The occurrence of D, C, and B/C scale CS is found to be 89.5%, 10%, and 0.5%, respectively. We observed a single modal distribution for C and D and a bimodal for B/C with a small peak at 5 km and another at 10 km. The distribution is broader (5–10 km) for D and C-type CS compared to B/C. D scale CS are more dominant with duration of ~ 40 min. The CS are relatively intense over the land compared to oceans. Diurnal progression shows that during early morning (00–03 LT), the CS form over the southwest Arabian Sea, and as time progresses, the occurrence increases towards the coast and maximizes between 06 and 09 LT. The CS then progresses towards the inland region and shows a maximum between 09 and 15 LT. The CS peaks again over the oceans from 18 LT, and subsequently the occurrence decreases over the land. A prominent peak in the afternoon over the land and a dominant peak in the early morning, followed by two weak peaks in the afternoon and midnight, are observed over the ocean. The interaction with the background stability, moisture, and dynamics showed that the mid-tropospheric moistening is responsible for intense CS coupled with large-scale advection.