Simulating Stratiform Precipitation With Embedded Convection in High‐Elevation Valleys Using LES: The Role of Topographic Detail

Abstract

Precipitation dynamics in high‐elevation valleys of the central Andes are strongly modulated by complex terrain, which alters local circulation and cloud development. Here, we use the Cloud Model 1 (CM1) in large‐eddy simulation (LES) mode with a two‐moment microphysics scheme to examine the role of topographic detail on the spatial distribution of precipitation in the Mantaro Valley, Peru. Three terrain resolutions (450, 1,050, and 1,650 m) were tested under identical thermodynamic conditions derived from in situ soundings. In all cases, anabatic winds transported moisture upslope, but the fine‐resolution case generated larger amounts of ice, snow, and graupel within vortical structures, yielding rainfall that matched Ka‐band radar reflectivity profiles. In contrast, smoother terrains delayed cloud formation by 30–60 min and reduced ice‐phase particle production, confining precipitation to the eastern slopes. Wind vortex analysis revealed smaller upper level eddies (above 2 km AGL) in the high‐resolution case, promoting enhanced mixing and hydrometeor growth. These results demonstrate that subtle variations in terrain detail critically influence convection and stratiform precipitation processes in Andean valleys, underscoring the need for subkilometer representation of topography in high‐mountain rainfall modeling.