Three-Dimensional Variational Multi-Doppler Wind Retrieval over Complex Terrain

Airflow interactions with complex terrain can greatly enhance the potential for extreme precipitation events and alter the structure and intensity of the precipitating cloud systems, but these events are difficult to understand and forecast, partly due to limited direct in-situ measurements to sample wind and thermodynamic fields. Doppler radar can provide the capability to monitor extreme rainfall events over land, but our understanding of airflow modulated by orographic interactions remains limited. In this study, a new Doppler radar technique is developed to retrieve three-dimensional wind fields in precipitation over complex terrain. New boundary conditions are implemented in a variational multi-Doppler radar technique to represent the topographic forcing and surface impermeability.
A series of observing simulation sensitivity experiments using a full-physics model and radar emulator simulating rainfall from Typhoon Chanthu (2021) over Taiwan are conducted to evaluate the retrieval accuracy and parameter settings. Analysis from real radar observations from Chanthu demonstrates that the improved retrieval technique can advance scientific analyses for the underlying dynamics of orographic precipitation using radar observations.