Some of the instruments collecting data during the Arctic Winter Water Vapor IOP include ARM's microwave radiometer profiler (left) and microwave radiometer (right), and NOAA's ground-based scanning radiometer (middle).

The Arctic Winter Water Vapor Intensive Operational Period (IOP), a collaborative effort with the National Oceanic and Atmospheric Administration (NOAA) Environmental Technology Laboratory, began on March 10 in Barrow, Alaska. The major goal of the Arctic Winter Water Vapor IOP is to demonstrate that millimeter wavelength radiometers can substantially improve water vapor and cloud liquid path observations during the Arctic winter, when conventional radiometers, lack the sensitivity required to accurately detect low water vapor and cloud amounts. The existing microwave radiometer, which has been operating routinely at the site for six years, provides information on cloud liquid and water vapor. The ability to obtain more accurate moisture measurements during the extremely cold and arid arctic winter will help ARM researchers to evaluate scaling of radiosonde humidity measurements by radiometer data. Similar scaling in the past has led to improved radiative transfer models from data at ARM’s Southern Great Plains and Tropical Western Pacific sites; the same is hoped for ARM’s North Slope of Alaska (NSA) site.

In support of the IOP, the microwave radiometer profiler (MWRP) was deployed permanently at the NSA site in Barrow. After completing installation, the instrument was calibrated with liquid nitrogen, and the computers were upgraded. The MWRP collects continuous, real-time vertical profiles of atmospheric temperature, water vapor, and cloud liquid water from the earth’s surface up to 6.2 miles into the atmosphere in nearly all weather conditions. This instrument joins a suite of other ARM and NOAA instruments contributing to the IOP, which also includes daily radiosonde and in-situ observations.