2002 Annual

Thursday, 17 January 2002: 9:00 AM
Sunshine sensor testing for ASOS Product Improvement
Lynn J. Winans, SAIC, Sterling, VA
Poster PDF (2.1 MB)
The National Weather Service (NWS) has directed testing of a proposed sunshine sensor for the Automated Surface Observing System (ASOS) over the past 5 years. One of the measurements routinely archived by human observers at designated stations is sunshine duration. Since 1953, these measurements have been made at approximately 100 NWS offices using the Foster-Foskett sunshine switch. However, the Foster-Foskett sensor was found to be impractical for use in ASOS because the sensor's potentiometer requires frequent adjustment (perhaps daily) to maintain a consistent voltage threshold for sunshine.

Digital EKO sensors (MS-092) with ASOS compatible electronic interface enclosures were tested at Sterling, VA between September, 1999 and July, 2001 against the Eppley Normal Incidence Pyrheliometer (the national standard) using new performance requirements. Daily minutes of sunshine comparisons were expanded under the new requirements to include cumulative direct solar radiation over a 30-day interval. Hourly average direct solar radiation during cloud-free periods was an additional requirement and test metric.

This paper presents the data analysis and results of this test and discusses a proposed reporting algorithm.

Supplementary URL: