Radiometers Due for Checkup

 
Published: 15 November 2006

During the MWR Intercomparison Study at the SGP site, a liquid nitrogen-filled blackbody target (shown on top of the MWR in the foreground) is used for calibration.

Between October and November, six 2-channel microwave radiometers (MWRs) are collocated at the Southern Great Plains (SGP) Central Facility for a 2-month intercomparison study. The purpose of the intercomparison is to quantify the current operational accuracy of these instruments, as they have been in continuous service for 10 to 14 years, and several have recently required repair by the manufacturer. The MWRs provide estimates of the amounts of integrated water vapor and cloud liquid water overhead, which are critical inputs to many models and value-added products.

This is the first intercomparison of the instruments since the first Water Vapor IOP in September 1996. That 3-week campaign focused on optimizing the capabilities of the SGP site’s instrumentation for characterizing atmospheric water vapor, particularly emphasizing measurements of water vapor in the lowest kilometer (especially the lower 200 m) of the atmosphere. It also provided an overall calibration for the site’s Raman lidar. In the current study, the radiometers will once again be compared against each other for accuracy. In addition, their calibrations will be checked, and calibration algorithms reviewed for possible improvement.