Determination of an Amazon Hot Reference Target for the On-Orbit Calibration of Microwave Radiometers

Shannon T. Brown Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan

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Christopher S. Ruf Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan

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Abstract

A physically based model is developed to determine hot calibration reference brightness temperatures (TBs) over depolarized regions in the Amazon rain forest. The model can be used to evaluate the end-to-end calibration of any satellite microwave radiometer operating at a frequency between 18 and 40 GHz and angle of incidence between nadir and 55°. The model is constrained by Special Sensor Microwave Imager (SSM/I) TBs measured at 19.35, 22.2, and 37.0 GHz at a 53° angle of incidence and extrapolates/interpolates those measurements to other frequencies and incidence angles. The rms uncertainty in the physically based model is estimated to be 0.57 K. For instances in which coincident SSM/I measurements are not available, an empirical formula has been fit to the physical model to provide hot reference brightness temperature as a function of frequency, incidence angle, time of day, and day of year. The empirical formula has a 0.1-K rms deviation from the physically based model for annual averaged measurements and at most a 0.6-K deviation from the model for any specific time of day or day of year.

Corresponding author address: Chris Ruf, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143. Email: cruf@umich.edu

Abstract

A physically based model is developed to determine hot calibration reference brightness temperatures (TBs) over depolarized regions in the Amazon rain forest. The model can be used to evaluate the end-to-end calibration of any satellite microwave radiometer operating at a frequency between 18 and 40 GHz and angle of incidence between nadir and 55°. The model is constrained by Special Sensor Microwave Imager (SSM/I) TBs measured at 19.35, 22.2, and 37.0 GHz at a 53° angle of incidence and extrapolates/interpolates those measurements to other frequencies and incidence angles. The rms uncertainty in the physically based model is estimated to be 0.57 K. For instances in which coincident SSM/I measurements are not available, an empirical formula has been fit to the physical model to provide hot reference brightness temperature as a function of frequency, incidence angle, time of day, and day of year. The empirical formula has a 0.1-K rms deviation from the physically based model for annual averaged measurements and at most a 0.6-K deviation from the model for any specific time of day or day of year.

Corresponding author address: Chris Ruf, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109-2143. Email: cruf@umich.edu

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  • Benoit, A., 1968: Signal attenuation due to neutral oxygen and water vapor, rain and clouds. Microwave J., 11 , 7380.

  • Colton, M. C., and Poe G. A. , 1999: Intersensor calibration of DMSP SSM/I’s: F-8 to F-14, 1987–1997. IEEE Trans. Geosci. Remote Sens., 37 , 418439.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cruz Pol, S., Ruf C. , and Keihm S. , 1998: Improved 20–32 GHz atmospheric absorption model. Radio Sci., 22 , 13191333.

  • Ferrazzoli, P., and Guerriero L. , 1996: Passive microwave remote sensing of forests: A model investigation. IEEE Trans. Geosci. Remote Sens., 34 , 433443.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Grody, N. C., 1993: Remote sensing of the atmosphere from satellites using microwave radiometry. Atmospheric Remote Sensing by Microwave Radiometry, M. A. Janssen, Ed., Wiley, 259–314.

    • Search Google Scholar
    • Export Citation
  • Hiltbrunner, D., Matzler C. , and Wiesmann A. , 1994: Monitoring land surfaces with combined DMSP-SSM/I and ERS-1 scatterometer data. Proc. IEEE Int. Geosci. Remote Sens. Symp., Pasadena, CA, IGARSS, 1945–1947.

    • Search Google Scholar
    • Export Citation
  • Isaacs, R., Jin Y. , Worsham R. , Deblonde G. , and Falcone V. , 1989: The RADTRAN microwave surface emission models. IEEE Trans. Geosci. Remote Sens., 27 , 433440.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Janssen, M., Ruf C. , and Keihm S. , 1995: TOPEX/Poseidon Microwave Radiometer (TMR): II. Antenna pattern correction and brightness temperature algorithm. IEEE Trans. Geosci. Remote Sens., 33 , 138146.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Keihm, S. J., Janssen M. A. , and Ruf C. S. , 1995: TOPEX/Poseidon Microwave Radiometer (TMR): III. Wet troposphere range correction algorithm and pre-launch error budget. IEEE Trans. Geosci. Remote Sens., 33 , 147161.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Macelloni, G., Paloscia S. , Pampaloni P. , and Ruisi R. , 2001: Airborne multifrequency L- to Ka-band radiometric measurements over forests. IEEE Trans. Geosci. Remote Sens., 39 , 25072513.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Piepmeier, J. R., and Gasiewski A. J. , 2001: High-resolution passive polarimetric microwave mapping of ocean surface wind vector fields. IEEE Trans. Geosci. Remote Sens., 39 , 606622.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Prigent, C., Rossow W. , and Matthews E. , 1997: Microwave land surface emissivities estimated from SSM/I observations. J. Geophys. Res., 102 , 2186721890.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rosenkranz, P., 1993: Absorption of microwaves by atmospheric gases. Atmospheric Remote Sensing by Microwave Radiometry, M. A. Janssen, Ed., Wiley, 37–79.

    • Search Google Scholar
    • Export Citation
  • Ruf, C., Keihm S. , Subramanya B. , and Janssen M. , 1994: TOPEX/POSEIDON microwave radiometer performance and in-flight calibration. J. Geophys. Res., 99 , C12,. 2491524926.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ruf, C., Keihm S. , and Janssen M. , 1995: TOPEX/Poseidon Microwave Radiometer (TMR): I. Instrument description and antenna temperature calibration. IEEE Trans. Geosci. Remote Sens., 33 , 125137.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ruf, C. S., 2000: Detection of calibration drifts in spaceborne microwave radiometers using a vicarious cold reference. IEEE Trans. Geosci. Remote Sens., 38 , 4452.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ulaby, F., Moore R. , and Fung A. , 1982: Microwave Remote Sensing, Active and Passive. Volume II: Radar Remote Sensing and Surface Scattering and Emission Theory. Artech House, 608 pp.

    • Search Google Scholar
    • Export Citation
  • Ulaby, F., Moore R. , and Fung A. , 1986: Microwave Remote Sensing, Active and Passive. Volume III: From Theory to Applications. Artech House, 1098 pp.

    • Search Google Scholar
    • Export Citation
  • Walcek, C., and Taylor G. , 1986: A theoretical method for computing vertical distributions of acidity and sulfate production within cumulus clouds. J. Atmos. Sci., 43 , 339355.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wentz, F. J., 1991: User’s manual SSM/I antenna temperature tapes. Revision 1, Remote Sensing Systems Tech. Rep. 120191, 9–14.

  • Wilheit, T. T., and Fowler M. G. , 1977: Microwave radiometric determination of wind speed at the surface of the ocean during BESEX. IEEE Trans. Geosci. Remote Sens., 25 , 111120.

    • Search Google Scholar
    • Export Citation
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