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<p>The height of the atmospheric boundary layer (ABLH) along the west coast of India varies with strong diurnal amplitudes over land, and plays a seminal role in convection initiation. A case study of a typical post-monsoon thunderstorm event over a coastal urban city in India explored the characteristic role of the ABL in initiating storm development. The diurnal variation in the ABLH was investigated using data from a 205&#xa0;MHz VHF radar, revealing a gradual and substantial deepening of the ABLH ~ 2&#xa0;h prior to the storm, with an afternoon peak of 2.13&#xa0;km. The weather research and forecasting (WRF-ARW) model successfully simulated the diurnal evolution of ABLH in a reasonable manner with a peak height of 2.15&#xa0;km, albeit with a lead time of ~ 1–2&#xa0;h compared to observations. The convective mass fluxes and convective available potential energy necessary for storm development were amplified by warm, humid air within an exceedingly buoyant and unstable boundary layer. The significant vertical gradients in equivalent potential temperature (dθ<sub>e</sub>/dz) just prior to the storm development suggests that the atmosphere was primed for convection. Furthermore, the large difference (~ 50&#xa0;K) between θ<sub>e</sub> and θ near the surface indicates high moisture convergence and latent heat content which enhance buoyancy and create strong conditional instability supporting deep convection and thunderstorm development. This highlights the critical role boundary layer processes play in initiating local convection and thunderstorms over tropical regions with complex terrain and a land-sea interface, thereby contributing to improved understanding and prediction of thunderstorms through radar observation and simulations.</p>

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Boundary layer evolution and thermodynamics in a tropical thunderstorm: insights from VHF radar observations and numerical simulation

  • 期刊论文

  • 发表日期：

    2025年5月10日

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  • Angel Anita Christy,
  • M. G. Manoj,
  • Ashish Shaji,
  • Kavya Johny,
  • Rona Maria Sunil,
  • Reshma Thampy,
  • Rakesh V.,
  • Sudeep Kumar B. L.

摘要

The height of the atmospheric boundary layer (ABLH) along the west coast of India varies with strong diurnal amplitudes over land, and plays a seminal role in convection initiation. A case study of a typical post-monsoon thunderstorm event over a coastal urban city in India explored the characteristic role of the ABL in initiating storm development. The diurnal variation in the ABLH was investigated using data from a 205 MHz VHF radar, revealing a gradual and substantial deepening of the ABLH ~ 2 h prior to the storm, with an afternoon peak of 2.13 km. The weather research and forecasting (WRF-ARW) model successfully simulated the diurnal evolution of ABLH in a reasonable manner with a peak height of 2.15 km, albeit with a lead time of ~ 1–2 h compared to observations. The convective mass fluxes and convective available potential energy necessary for storm development were amplified by warm, humid air within an exceedingly buoyant and unstable boundary layer. The significant vertical gradients in equivalent potential temperature (dθe/dz) just prior to the storm development suggests that the atmosphere was primed for convection. Furthermore, the large difference (~ 50 K) between θe and θ near the surface indicates high moisture convergence and latent heat content which enhance buoyancy and create strong conditional instability supporting deep convection and thunderstorm development. This highlights the critical role boundary layer processes play in initiating local convection and thunderstorms over tropical regions with complex terrain and a land-sea interface, thereby contributing to improved understanding and prediction of thunderstorms through radar observation and simulations.