An Inter-Comparison between the CL31, CT12K and Human Observations

Cloud hit data has been collected from six Department of Defense (DoD) sites from stand-alone CL31s and was compared with CT12K/V2.79D equipped ASOS observations and human observations. The DoD sites are staffed 24/7 with observers and the legacy ASOS configuration can be compared with what a CL31/V2.79Y equipped ASOS would report. Additionally, ASOS observations generated from collocated CT12K and CL31 sensors at Williston, ND, will be compared with ceiling light and 30g PIBAL observations. This will allow a more robust comparison to be made at Williston, ND. This evaluation will be conducted during times of MVFR and IFR ceilings (i.e. at or below 3000 feet), with emphasis on IFR conditions (i.e. ceilings at or below 1000 feet).