Ceilometer Comparisons March 1998 - April 1999

The Automated Surface Observing System (ASOS) uses the Vaisala Model CT12K ceilometer for cloud height detection up to 12,000 feet. Using the information from the Vaisala CT12K, the sky condition algorithm processes ceilometer data to formulate cloud amounts and heights. The ASOS program initiated a concept exploration effort in August 1996 to test and evaluate new cloud height detection technologies. Laser beam ceilometers that detect clouds up to 25,000 feet were selected to compare against the Vaisala CT12K at heights below 12,000 feet.

Intensive ceilometer performance testing began on March 2, 1998 and ended on April 19, 1999. Twenty-five thousand foot ceilometers from three manufacturers were under test and evaluation at Sterling, Virginia. The purpose was to determine whether the 25,000 foot ceilometer technology could replace the Vaisala CT12K ceilometer, which is now out of production. This paper provides analyses of test results, including a discussion of 25,000 foot ceilometer performance as compared to the Vaisala CT12K ceilometer in all weather conditions, and recommendations for future work.