Comparison of Ceiling and Visibility Observation for NWS Manned Observation Sitesand Asos Sites

摘要

The National Weather Service modernization program involves, among other things,a shift from manned weather observation to automated, unmanned instrument sensing. The Automated Surface Observing System (ASOS) is the device that will replace the conventional manned weather observation in use today. ASOS observations of ceiling and visibility were compared to the standard manual observations at 16 sites having at least four months of overlap data. The 16 sites were located in the central plains states of Colorado, Nebraska, Missouri, Kansas, Oklahoma, and Texas. The period of study was confined to the precommissioning period of the sites when both conventional data and ASOS data were available. The study spans from mid September of 1991 to late July 1992, with the greatest amount of data collected between February and June 1992. The overall results show that ASOS ceiling reports were within 1000 ft of conventional ceiling reports 92.7% of the time. Similarly, ASOS derived visibility was within one reportable category of conventionally derived visibility 93.7% of the time. These percentages were determined from a data base composed of approximately 64,000 observations.