Cooperative Institute for Research in Environmental Sciences

Science Rendezvous > 2009 Posters
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Remote Sensing of Water Vapor, Cloud Liquid, and Temperature during RHUBC by Microwave nd Millimeter Wave Radiometers

E. R. Westwater, D. Cimini, V. Mattioli, M. Klein, V. Leuski, A. J. Gasiewski and D. Turner

The Radiative Heating in UnderExplored Bands Campaign (RHUBC) was held at the Atmospheric Radiation Measurement Program’s North Slope of Alaska site in Barrow, Alaska, during February 15 to March 15, 2007. One of the primary goals of RHUBC was to compare different techniques for measuring low amounts of water vapor during cold (Temperature < -30 °C) and dry (Precipitable Water Vapor < 2 mm) conditions. An important secondary goal was to compare the radiometric response to clouds, again during these cold conditions. During the experiment, several radiometers were operated, including: (A) The University of Colorado’s Ground-Based Scanning Radiometer (GSR). This is a 27 channel millimeter wavelength radiometer with frequencies ranging from 50 to 400 GHz. Channels include 11 in the 60 GHz O2 band for temperature profiling, dual-polarized window channels at 89 and 340 GHz for cloud sensing, and 7 and 5 channels, respectively near the 183.31 and 380.2 GHz lines of water vapor. (B) The ARM G-Band (183 GHz) Vapor Radiometer (GVR), a 4-channel double sideband radiometer with channels centered around the 183.31 GHz water vapor line. (C) The ARM Microwave Radiometer (MWR), the standard 2-channel microwave radiometer (D) Two ARM Atmospherically Emitted Radiance Interferometer, a 3300 to 400 cm^-1 wavenumber radiometer for measuring water vapor, temperature, and clouds.During the campaign, the ARM twice-a-day radiosondes were supplemented by additional Vaisala RS92 releases during very dry conditions. These SONDES provide ground truth for model-vs.-measurement comparisons of brightness temperatures, as well as the standard for retrievals of temperature and water vapor profiles and PWV. Data from the ARM ceilometer and Infrared Thermometer (IRT) are used to determine cloudy conditions. We compare LWP retrievals for several instruments and retrieval algorithms; of the GSR and combined MWR-AERI retrievals agree the best.We also show comparisons of retrievals of PWV and temperature and water vapor profiles from the GSR. Almost unprecedented accuracy was achieved in the GSR PWV retrievals.