Enhanced Predictability of Himalayan Orographic Precipitation Extremes Using a Kilometer-Scale Convection-Permitting Multi-Physics Ensemble

Orographic interactions of intense western disturbances (WDs) with western Himalayan (WH) topography often drive persistent extreme precipitation events (EPEs) in the region during the winter season, contributing to significant socio-economic losses. Accurate predictions of such events remain challenging due to the sparse gauge network and complex multi-scale interactions of dynamical and microphysical processes with the region’s heterogenous orography. Numerical weather prediction models, such as the Weather Research and Forecasting (WRF) model, are widely utilized tools for simulating extreme precipitation with high-resolution and physically informed configurations. Kilometer-scale convection-permitting hold potential for improved representation of sub-grid processes, such as orographic effects and land-surface interactions, thus offering more scope for enhancing predictability. The present study investigates the predictability of intense WD-associated EPEs using convection-permitting (3 km) dynamically downscaled WRF simulations and a multi-physics ensemble (ENSM) approach, initialized using ERA5 reanalysis and validated with high resolution IMDAA (12 km) regional reanalysis. Ten persistent EPEs (lasting 3 or more consecutive days) were analyzed to assess sensitivity to sea surface temperature (SST) forcings and eight microphysical parameterization (MP) schemes (Single-moment: WSM7, Thompson8; Double-moment: WDM7, Thompson28, Morrison, P3). The findings reveal minimal variations from SST forcings at 3–4-day time scales, highlighting the dominant role of atmospheric processes at shorter time scales during winter EPEs. Both single- and double-moment MPs exhibited comparable performance, with minor spatial variations. The ENSM demonstrated enhanced prediction skill (>0.6) and accurately captured precipitation characteristics, including diurnal variations and dynamics like atmospheric baroclinicity, vertical wind shear, and stability driven by meridional temperature gradients. Overall, the findings underscore the potential of a convection-permitting multi-physics ensemble frameworks in enhancing the predictability of extreme winter precipitation over the orographic WH region.

Keywords: Convection-Permitting Simulations, WRF Model, Mountain Precipitation Extremes, Prediction, Microphysical Parameterization