A Filter for Using Mesonet Visibility Observations in Operations and Verification

Meteorological Terminal Aviation Routine Weather Reports (METARs) are often used for data assimilation into models as well as for model verification. Mesonet observations are an additional data set that can be useful both for data assimilation and model verification by providing reports of meteorological conditions in locations where METARs may not be available. Mesonet observations of visibility, however, are particularly problematic compared to other weather sensors because of the different reporting ranges of the instruments and the possibility of erroneous reports.

To mitigate this problem, a simple filter for mesonet visibility observations was developed for use in verification and data assimilation. The filter uses recent reports from each mesonet station to determine whether or not the reports fall into an acceptable distribution. The filter requires that a majority of observations be made at an unrestricted visibility range and that the station has recently reported a restricted visibility. This presentation will provide an overview of the filter criteria, example results from applying the filter, and also include correlations between METARs and closely located mesonet visibility observations.