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Title: Microwave and Millimeter-Wave Radiometric Studies of Temperature, Water Vapor and Clouds

Abstract

The importance of accurate measurements of column amounts of water vapor and cloud liquid has been well documented by scientists within the Atmospheric Radiation Measurement (ARM) Program. At the North Slope of Alaska (NSA), both microwave radiometers (MWR) and the MWRProfiler (MWRP), been used operationally by ARM for passive retrievals of the quantities: Precipitable Water Vapor (PWV) and Liquid Water Path (LWP). However, it has been convincingly shown that these instruments are inadequate to measure low amounts of PWV and LWP. In the case of water vapor, this is especially important during the Arctic winter, when PWV is frequently less than 2 mm. For low amounts of LWP (< 50 g/m{sup 2}), the MWR and MWRP retrievals have an accuracy that is also not acceptable. To address some of these needs, in March-April 2004, NOAA and ARM conducted the NSA Arctic Winter Radiometric Experiment - Water Vapor Intensive Operational Period at the ARM NSA/Adjacent Arctic Ocean (NSA/AAO) site. After this experiment, the radiometer group at NOAA moved to the Center for Environmental Technology (CET) of the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. During this 2004 experiment, a total of 220 radiosondes were launched,more » and radiometric data from 22.235 to 380 GHz were obtained. Primary instruments included the ARM MWR and MWRP, a Global Positioning System (GPS), as well as the CET Ground-based Scanning Radiometer (GSR). We have analyzed data from these instruments to answer several questions of importance to ARM, including: (a) techniques for improved water vapor measurements; (b) improved calibration techniques during cloudy conditions; (c) the spectral response of radiometers to a variety of conditions: clear, liquid, ice, and mixed phase clouds; and (d) forward modeling of microwave and millimeter wave brightness temperatures from 22 to 380 GHz. Many of these results have been published in the open literature. During the third year of this contract, we participated in another ARM-sponsored experiment at the NSA during February-March 2007. This experiment is called the Radiative Heating in Underexplored Bands Campaign (RHUBC) and the GSR was operated successfully for the duration of the campaign. One of the principal goals of the experiment was to provide retrievals of water vapor during PWV amounts less than 2 mm and to compare GSR data with ARM radiometers and radiosondes. A secondary goal was to compare the radiometric response of the microwave and millimeter wavelength radiometers to water and ice clouds. In this final report, we will include the separate progress reports for each of the three years of the project and follow with a section on major accomplishments of the project.« less

Authors:
Publication Date:
Research Org.:
University of Colorado
Sponsoring Org.:
USDOE
OSTI Identifier:
1015232
Report Number(s):
DE-05ER64015- Final Report
TRN: US201111%%730
DOE Contract Number:
FG02-05ER64015
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ACCURACY; ARCTIC OCEAN; BRIGHTNESS; CALIBRATION; CLOUDS; COMPUTERS; GLOBAL POSITIONING SYSTEM; HEATING; PROGRESS REPORT; RADIATIONS; RADIOMETERS; SIMULATION; SPECTRAL RESPONSE; WATER; WATER VAPOR; WAVELENGTHS

Citation Formats

Westwater, Edgeworth. Microwave and Millimeter-Wave Radiometric Studies of Temperature, Water Vapor and Clouds. United States: N. p., 2011. Web. doi:10.2172/1015232.
Westwater, Edgeworth. Microwave and Millimeter-Wave Radiometric Studies of Temperature, Water Vapor and Clouds. United States. doi:10.2172/1015232.
Westwater, Edgeworth. 2011. "Microwave and Millimeter-Wave Radiometric Studies of Temperature, Water Vapor and Clouds". United States. doi:10.2172/1015232. https://www.osti.gov/servlets/purl/1015232.
@article{osti_1015232,
title = {Microwave and Millimeter-Wave Radiometric Studies of Temperature, Water Vapor and Clouds},
author = {Westwater, Edgeworth},
abstractNote = {The importance of accurate measurements of column amounts of water vapor and cloud liquid has been well documented by scientists within the Atmospheric Radiation Measurement (ARM) Program. At the North Slope of Alaska (NSA), both microwave radiometers (MWR) and the MWRProfiler (MWRP), been used operationally by ARM for passive retrievals of the quantities: Precipitable Water Vapor (PWV) and Liquid Water Path (LWP). However, it has been convincingly shown that these instruments are inadequate to measure low amounts of PWV and LWP. In the case of water vapor, this is especially important during the Arctic winter, when PWV is frequently less than 2 mm. For low amounts of LWP (< 50 g/m{sup 2}), the MWR and MWRP retrievals have an accuracy that is also not acceptable. To address some of these needs, in March-April 2004, NOAA and ARM conducted the NSA Arctic Winter Radiometric Experiment - Water Vapor Intensive Operational Period at the ARM NSA/Adjacent Arctic Ocean (NSA/AAO) site. After this experiment, the radiometer group at NOAA moved to the Center for Environmental Technology (CET) of the Department of Electrical and Computer Engineering of the University of Colorado at Boulder. During this 2004 experiment, a total of 220 radiosondes were launched, and radiometric data from 22.235 to 380 GHz were obtained. Primary instruments included the ARM MWR and MWRP, a Global Positioning System (GPS), as well as the CET Ground-based Scanning Radiometer (GSR). We have analyzed data from these instruments to answer several questions of importance to ARM, including: (a) techniques for improved water vapor measurements; (b) improved calibration techniques during cloudy conditions; (c) the spectral response of radiometers to a variety of conditions: clear, liquid, ice, and mixed phase clouds; and (d) forward modeling of microwave and millimeter wave brightness temperatures from 22 to 380 GHz. Many of these results have been published in the open literature. During the third year of this contract, we participated in another ARM-sponsored experiment at the NSA during February-March 2007. This experiment is called the Radiative Heating in Underexplored Bands Campaign (RHUBC) and the GSR was operated successfully for the duration of the campaign. One of the principal goals of the experiment was to provide retrievals of water vapor during PWV amounts less than 2 mm and to compare GSR data with ARM radiometers and radiosondes. A secondary goal was to compare the radiometric response of the microwave and millimeter wavelength radiometers to water and ice clouds. In this final report, we will include the separate progress reports for each of the three years of the project and follow with a section on major accomplishments of the project.},
doi = {10.2172/1015232},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2011,
month = 5
}

Technical Report:

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  • Abstract - ProSensing Inc. has developed a G-band (183 GHz) water Vapor Radiometer (GVR) for long-term, unattended measurements of low concentrations of atmospheric water vapor and liquid water. Precipitable water vapor and liquid water path are estimated from zenith brightness temperatures measured from four double-sideband receiver channels, centered at 183.31 1, 3 and 7, and 14 GHz. A prototype ground-based version of the instrument was deployed at the DOE ARM program?s North Slope of Alaska site near Barrow AK in April 2005, where it collected data continuously for one year. A compact, airborne version of this instrument, packaged to operatemore » from a standard 2-D PMS probe canister, has been tested on the ground and is scheduled for test flights in the summer of 2006. This paper presents design details, laboratory test results and examples of retrieved precipitable water vapor and liquid water path from measured brightness temperature data.« less
  • Active and passive radiometric imaging techniques have been used at 1.4- and 3-mm wavelengths (220 and 100 GHz) to evaluate their potential use in detecting concealed objects. An evaluation of the techniques includes a particular study of their potential in detecting shielded nuclear materials and explosives carried covertly by personnel. We have previously reported images of metal objects and nuclear shielding materials that were detected when concealed under clothing. These images appear with the human body as background. Detection of contraband by radiometric imaging techniques depends upon the differences in emissivity and reflectivity of the contraband relative to human tissue.more » Explosives, unlike metals and metal composites, generally have high emissivities and low reflectivities that closely approximate those of human tissue making explosives difficult to detect. Samples of several common types of explosives (TNT, Detasheet, C4, and several types of water gels) have been examined at the 1.4- and 3-mm wavelengths using active and passive radiometric techniques.« less
  • The report describes Phase 2 of a research program to develop engineering design guidelines for the use of water spray curtains to disperse liquefied natural gas vapor clouds. Parametric experiments were conducted on model scale in a wind tunnel on the interaction of water sprays with simulated LNG vapor overflowing a 60m x 60m diked area. In addition, a few outdoor experiments with spray curtains were run, spilling LNG into a 3m x 3m diked area. Tests recently completed by the (British) Health and Safety Executive were also analyzed. Spray curtains with both upward and downward sprays were effective. Downwardmore » sprays had to be inclined toward the vapor source to be effective when the ground flow of vapor was dense. Spray curtain configurations tested, both upward and downward-inclined, reduced volumetric vapor concentrations downwind of the 60m x 60m dike model in the wind tunnel to well under 5%. A preliminary design guide has been drafted although the technical data base is inadequate.« less
  • This report represents the results of an investigation of dielectric resonators to be processed in GaAs substrates for application to microwave and millimeter-wave monolithic integrated circuits. Zeroth-and first order analyses are described. These analyses are applied to dielectric resonator structures to be formed in GaAs substrate material by etching an annular gap in the substrate, thereby effectively leaving a circular cylindrical disc of dielectric material to function as a resonator. Plots of geometric parameter variations with frequency are provided for these resonator structures. Tables are presented to show specific resonant structures for frequency-scaled microwave and non-scaled millimeter-wave resonators. Results aremore » discussed, conclusions drawn, and suggestions for further work set forth.« less