Effects of land-atmosphere coupling strength on coupled WRF/Noah model 0-24 h forecasts of warm-season precipitation in the central United States
In the current study we examine 0-24 h coupled WRF/Noah convection-resolving precipitation forecasts using different specifications of Czil for a six-day retrospective period within the International H20 (IHOP_2002) field program. Results indicate strong sensitivity in the timing of simulated afternoon convection initiation and subsequent precipitation amounts to the strength of the Czil-related variations in the strength of land-atmosphere coupling. Over the western high plains (105-100 W longitude), where deep convection is often locally generated, simulations using empirically derived values for Czil that varied with type (i.e., height) of vegetation produced a diurnal cycle of forecasted precipitation amounts in better agreement with Stage-4 precipitation observations than simulations that used single values of Czil. In this talk we present statistics of the relationship between Czil and forecasted precipitation for this six-day IHOP retrospective period and provide illustrative case studies of the mechanisms by which land-atmosphere coupling strength influences convection initiation and evolution.