Climatology of Wind and Mixing Height in the United States

We are developing a 40-year time series of 0 UTC and 12 UTC surface wind and mixing height at 2.5 minute latitude-longitude spatial resolution for the United States. The data will replace existing climate summaries that are inadequate for many applications because they are either point specific or coarsely interpolated over space and time. Development of the new time series is supported by the interagency Joint Fire Science Program to help assess the impact of smoldering smoke from wildland fire. Because wind is so strongly influenced by small undulations in topography and land use, it often is inappropriate to spatially interpolate point observations. Therefore, we are generating the surface wind data with a one-level hydrostatic flow model. The flow model uses upper-air data from the NCEP Reanalysis project to resolve temperature, pressure, and resulting wind fields around surface topography. The simplicity of the model allows calculations of long time series and large domains with modest computing resources. Hourly surface observations from NWS primary observing sites are used for verifying wind speed and direction. In addition, output from our simple flow model compares well to data generated by the non-hydrostatic model, MM5, that are available at similar resolutions for a 5-year time period in the Pacific Northwest. Mixing heights are calculated from raobs using Holzworth's algorithms and mapped according to topographic constraints. Maps of cold-air drainage patterns are integrated to enhance the morning mixing height patterns. Air pollution and boundary layer experiments reported in literature and some limited field observations provide data to help verify mixing height calculations. Prelimary results show realistic patterns in wind and mixing height that can be used for a variety of applications.