Retrievals of low integrated water vapor using MIR and SSM/T-2 measurements

Satellite radiometric measurements at 150, 183.3/spl plusmn/3, and 183.3/spl plusmn/7 GHz have previously been used to retrieve integrated water vapor <1 g/cm/sup 2/ over Antarctica. The effects of the frequency dependence of surface emissivity and the variation of surface temperature on the retrieval, which have not been closely examined in the studies, are analyzed. Using four days of near-concurrent airborne and satellite radiometric measurements, it is shown that the previously derived retrieval algorithm could overestimate or underestimate integrated water vapor by up to 0.1 g/cm/sup 2/, depending on whether the surface emissivity increases or decreases with frequency. The average of the absolute value of the bias for each flight case studied is /spl les/0.04g/cm/sup 2/. Additionally, surface skin temperature is shown to vary substantially over a range from 240-270 K during these four days of measurements; the corresponding effect on the retrieval of integrated water vapor is comparable to that due to frequency dependence on surface emissivity. The quantitative correction needed for this effect is dependent upon the magnitude of integrated water vapor. At high values of integrated water vapor of 0.6-0.8 g/cm/sup 2/, the corrections are as large as 0.1 g/cm/sup 2/ for changes of surface temperature of /spl plusmn/10 K. A simple procedure is implemented to correct for this error, which significantly improves the retrieval. Correction for the frequency dependence of surface emissivity is nontrivial when using currently available satellite measurements; in order to properly correct this effect, an additional channel of measurements, e.g., at 220 GHz, is required.

[1]  D. H. Staelin,et al.  A method for estimation of atmospheric water vapor profiles by microwave radiometry , 1982 .

[2]  Dorothy K. Hall,et al.  Comparison of snow mass estimates from a prototype passive microwave snow algorithm, a revised algorithm and a snow depth climatology , 1997 .

[3]  Jungang Miao,et al.  Atmospheric water vapor over Antarctica derived from Special Sensor Microwave/Temperature 2 data , 2001 .

[4]  Dorothy K. Hall,et al.  Snow parameters derived from microwave measurements during the BOREAS winter field campaign , 1997 .

[5]  Fuzhong Weng,et al.  A microwave land emissivity model , 2001 .

[6]  Dorothy K. Hall,et al.  Detection of Snow Cover Using Millimeter-Wave Imaging Radiometer (MIR) Data , 1999 .

[7]  S. A. Snyder,et al.  Determination of oceanic total precipitable water from the SSM/I , 1990 .

[8]  Paul Racette,et al.  An Airborne Millimeter-Wave Imaging Radiometer for Cloud, Precipitation, and Atmospheric Water Vapor Studies , 1996 .

[9]  L. R. Dod,et al.  Retrieval of total precipitable water over high latitude regions using radiometric measurements near 90 and 183 GHz , 1992 .

[10]  Will Manning,et al.  Near concurrent MIR, SSM/T-2, and SSM/I observations over snow-covered surfaces , 2003 .

[11]  Paul Racette,et al.  Retrieval of precipitable water vapor by the millimeter-wave imaging radiometer in the arctic region during FIRE-ACE , 2001, IEEE Trans. Geosci. Remote. Sens..

[12]  James R. Wang.  A comparison of the MIR-estimated and model-calculated fresh water surface emissivities at 89, 150, and 220 GHz , 2002, IEEE Trans. Geosci. Remote. Sens..

[13]  Tim J. Hewison,et al.  Airborne retrievals of snow and ice surface emissivity at millimeter wavelengths , 1999, IEEE Trans. Geosci. Remote. Sens..

[14]  W. Paul Menzel,et al.  Airborne Scanning Spectrometer for Remote Sensing of Cloud, Aerosol, Water Vapor, and Surface Properties , 1996 .

[15]  Paul Racette,et al.  Retrievals of column water vapor using millimeter-wave radiometric measurements , 2002, IEEE Trans. Geosci. Remote. Sens..

[16]  Donald J. Cavalieri,et al.  Satellite passive microwave observations and analysis of Arctic and Antarctic sea ice, 1978–1987 , 1993, Annals of Glaciology.

[17]  Thomas T. Wilheit,et al.  Profiling atmospheric water vapor by microwave radiometry , 1977 .

[18]  Donald J. Cavalieri,et al.  Arctic and Antarctic Sea Ice, 1978-1987: Satellite Passive-Microwave Observations and Analysis , 1992 .

[19]  J. R. Wang,et al.  Retrieval of total precipitable water using radiometric measurements near 92 and 183 GHz , 1989 .

[20]  C. J. Drummond,et al.  Computing the Atmospheric Absorption for the DMSP Operational Linescan System Infrared Channel , 1999 .

[21]  Ramesh K. Kakar,et al.  Retrieval of Clear Sky Moisture Profiles using the 183 GHz Water Vapor Line , 1983 .

[22]  A. Gruber,et al.  Atmospheric Water Content over the Tropical Pacific Derived from the Nimbus-6 Scanning Microwave Spectrometer , 1980 .

[23]  Stephenson Moore,et al.  Determination of integrated water vapor over Antarctica utilizing special sensor microwave temperature-2 (SSM/T- 2) data , 1997 .

[24]  T. T. Wilheit,et al.  A passive microwave technique for profiling of atmospheric water vapor , 1979 .

[25]  John Turner,et al.  Antarctic Meteorology and Climatology , 1998 .