The vertical correlation of surface parameter errors has long been a dilemma for assimilation of surface observations. While surface observations are relatively dense, there are almost no high-frequency observations of the vertical profile above the surface. Thus, a technique has been developed to use the background planetary boundary layer depth to provide an estimate of the depth over which the observation-minus-background values of temperature, moisture, and wind are likely to be applicable. This technique has been in real-time testing of the RUC for over a year, showing an overall improvement in temperature and dewpoint forecast statistical accuracy, and improvements in convective available ppotential energy (CAPE) forecasts for convection forecasts. This was shown most notably for the 10 November 2002 tornado outbreak case. Further revisions are currently in testing to improve the robustness of this technique. This improvement is important given the sensitivity of the CAPE estimate to small changes in moisture and temperature profiles.
Results will be shown both for overall statistical improvement and important case studies using this PBL-based technique for assimilation of METAR observations.
Supplementary URL: http://ruc.fsl.noaa.gov