Sensitivity of WRF cloud microphysics to simulations of a severe thunderstorm event over Southeast India

  • Rajeevan M
  • Kesarkar A
  • Thampi S
 et al. 
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Abstract

In the present study, we have used the Weather Research and Forecasting (WRF) model to simulate the fea-tures associated with a severe thunderstorm observed over Gadanki (13.5 • N, 79.2 • E), over southeast India, on 21 May 2008 and examined its sensitivity to four different micro-physical (MP) schemes (Thompson, Lin, WSM6 and Mor-rison). We have used the WRF model with three nested do-mains with the innermost domain of 2 km grid spacing with explicit convection. The model was integrated for 36 h with the GFS initial conditions of 00:00 UTC, 21 May 2008. For validating simulated features of the thunderstorm, we have considered the vertical wind measurements made by the In-dian MST radar installed at Gadanki, reflectivity profiles by the Doppler Weather Radar at Chennai, and automatic weather station data at Gadanki. There are major differences in the simulations of the thun-derstorm among the MP schemes, in spite of using the same initial and boundary conditions and model configura-tion. First of all, all the four schemes simulated severe con-vection over Gadanki almost an hour before the observed storm. The DWR data suggested passage of two convec-tive cores over Gadanki on 21 May, which was simulated by the model in all the four MP schemes. Comparatively, the Thompson scheme simulated the observed features of the updraft/downdraft cores reasonably well. However, all the four schemes underestimated strength and vertical extend of the updraft cores. The MP schemes also showed problems in simulating the downdrafts associated with the storm. While the Thompson scheme simulated surface rainfall distribution closer to observations, the other three schemes overestimated observed rainfall. However, all the four MP schemes simu-lated the surface wind variations associated with the thun-derstorm reasonably well. The model simulated reflectivity Correspondence to: M. Rajeevan (rajeevan@narl.gov.in) profiles were consistent with the observed reflectivity pro-file, showing two convective cores. These features are con-sistent with the simulated condensate profiles, which peaked around 5–6 km. As the results are dependent on initial condi-tions, in simulations with different initial conditions, differ-ent schemes may become closer to observations. The present study suggests not only large sensitivity but also variability of the microphysical schemes in the simulations of the thunder-storm. The study also emphasizes the need for a comprehen-sive observational campaign using multi-observational plat-forms to improve the parameterization of the cloud micro-physics and land surface processes over the Indian region.

Author-supplied keywords

  • Meteorology and atmospheric dynamics (Mesoscale meteorology)

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