A mixing height climatology for the western U.S.

Climatology information of mixing layer height can be extremely beneficial for air quality decision-making and planning. The Desert Research Institute (DRI) Program for Climate, Ecosystem and Fire Applications (CEFA) has been developing a mixing height forecast product based on the National Centers for Environmental Prediction Eta model (32km resolution). Though initially produced for wildland fire managers, the forecasts are also useful to anyone requiring meteorological information related to air quality. A deterministic method incorporating virtual potential temperature profiles is used to compute mixing height for 6-hourly forecast periods out to 48 hours. The model’s 00 and 12 UTC initialization runs can be used to establish a daytime and nighttime mixing height climatology. We have begun to develop a mixing height climatology over the western U.S. by computing monthly and seasonal mixing height values at each Eta model grid point using the 00 and 12 UTC daily initialization runs for 1998 and 1999. At the moment, this short period is due in part to concerns about model algorithm consistency during the course of its operational use. Though two years would be considered insufficient for many climatological purposes, it does begin to provide relevant background information for the decision-maker. In this presentation, a brief background of the method, results of the climatological analysis and its value to decision-makers will be discussed.