Elucidating the Spatial Scaling Behavior of Cloud Embedded Convection and Rainfall Patterns in Complex Terrain Using Idealized WRF Simulations

It is often observed a situation where a stratiform orographic cloud develops shallow embedded convective structures, which change the rainfall pattern and amounts considerably and can lead to localized extreme values of rainfall. These localized extremes are responsible for mountain hazards including landslides, debris flows and flashfloods. Although the basic mechanism responsible for orographic precipitation is well known, the triggering and dynamics of embedded convective structures is still poorly understood. An interesting idea is that the development of these cloud embedded convective structures results from the unstable growth of small scale disturbances inside the cloud, with upstream lee wave generation by small scale topography being a very important source of such disturbances. Linear stability analysis has been used previously with promising results to gain insight on the dominant spatial scales of the convective structures when a wide range of disturbance modes are present, as it is expected in the atmosphere. But the ability of such models to explain more realistic situations is still unclear and there is no consensus on the governing physics. These issues are assessed using a population of idealized cloud resolving high resolution simulations performed with the Weather Research and Forecasting (WRF) model for various configurations of small scale terrain. Here, we report on the relationships among the spatial scaling behavior of cloud embedded convective structures and associated precipitation patterns, small scale terrain features, and dynamical regimes described by moist stability, advective time scale, mean wind intensity and mean wind shear.