Decoding Precipitation Dynamics in High-Elevation Complex Terrain: Bridging Satellite Radar Gaps with Large Eddy Simulation

Precipitation dynamics in high-elevation regions are profoundly shaped by complex terrain, influencing processes that drive precipitation formation and distribution. In valleys flanked by mountain ridges, satellite-based precipitation radar signals are often obscured by ground clutter up to 2 km above the surface, masking critical near-surface processes. To address this limitation, this study employs a Large Eddy Simulation (LES) model with an advanced microphysics scheme, resolving eddies on scales of hundreds of meters, to investigate the vertical structure and dynamics of a precipitating system characterized by convective elements embedded within stratiform precipitation in a high-altitude valley in the Central Andes of Peru. Such kind of system, is frequently observed in satellite and in-situ Ka-band radar measurements. Two simulations were conducted: a control case with flat terrain and a realistic case incorporating actual topography. The simulation with topography revealed deep convection initiated along eastern ridges, vertically transporting moisture and generating ice and snow particles. These particles were advected into the valley by easterly winds, producing stratiform precipitation with a bright band consistent with radar observations. In contrast, the flat-terrain simulation exhibited only shallow convection without a bright band. Analysis of wind vortices linked to convective activity showed comparable vortex sizes in both simulations, with no significant enhancement in the valley’s semi-flat central region, suggesting shallow convection dominates there. However, the interplay between stratiform precipitation originating at the ridges and this shallow convection resulted in a stratiform system with embedded convective cells. These findings underscore the capability of LES to dissect the interplay of deep and shallow convection in complex terrain, offering valuable insights to refine satellite-derived precipitation estimates in regions where radar observations are challenged by topography.