Abstract

A fast-forward radiative transfer (RTF) model is presented that includes cloud-radiation interaction for any number of cloud layers. Layer cloud fraction and transmittance are treated separately and combined with that of gaseous transmittances. RTF is tested against a reference procedure that uses line-by-line gaseous transmittances and solves the radiative transfer equation by use of the adding-doubling method to handle multiple-scattering conditions properly. The comparison is carried out for channels 8, 12, and 14 of the High Resolution Infrared Radiation Sounder (HIRS/2) and for the geostationary satellite METEOSAT thermal infrared and water vapor channels. Fairly large differences in simulated radiances by the two schemes are found in clear conditions for upper- and mid-tropospheric channels; the cause of the differences is discussed. For cloudy situations an improved layer source function is shown to be required when rapid changes in atmospheric transmission are experienced within the model layers. The roles of scattering processes are discussed; results with and without scattering, both obtained by use of a reference code, are compared. Overall, the presented results show that the fast model is capable of reproducing the cloudy results of the much more complex and time-consuming reference scheme.

© 2002 Optical Society of America

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References

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  1. J.-J. Morcrette, “Evaluation of model generated cloudiness: satellite observed and model generated diurnal variability of brightness temperature,” Mon. Weather Rev. 119, 1205–1224 (1991).
    [CrossRef]
  2. R. Rizzi, “Raw HIRS/2 radiances and model simulations in the presence of clouds,” Tech. Rep. TR-73 (European Centre for Medium Range Weather Forecasts, Reading, UK, 1994).
  3. F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).
  4. F. Chevallier, G. Kelly, “Model clouds as seen from space: comparison with geostationary imagery in the 11 µm window channel,” Mon. Weather Rev. (to be published).
  5. L. C. J. Van de Berg, J. Schmetz, J. Whitlock, “On the calibration of the METEOSAT water vapour channel,” J. Geophys. Res. 100, 21,069–21,076 (1995).
    [CrossRef]
  6. Intergovernmental Panel on Climate Change, “WG I climate change 2001: the scientific basis, summary for policy makers,” Third Assessment Rep. (Intergovernmental Panel on Climate Changes, Geneva, Switzerland, 2001).
  7. European Space Agency, “The five candidate Earth Explorer core missions—EarthCARE—Earth clouds, aerosols and radiation explorer,” ESA SP-1257(1) (ESA Publications Division, European Space Research and Technology Center, Noordwijk, The Netherlands, 2001).
  8. J. R. Eyre, “A fast radiative transfer model for satellite sounding systems,” Res. Dept. Tech. Memo 176. (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1991).
  9. R. W. Saunders, M. Matricardi, P. Brunel, “An improved fast radiative transfer model for assimilation of satellite radiance observations,” Q. J. R. Meteorol. Soc. 125, 1407–1425 (1999).
  10. R. W. Saunders, M. Matricardi, P. Brunel, “A fast radiative transfer model for assimilation of satellite radiance observations-RTTOV5,” Res. Dept. Tech. Memo 282 (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1999).
  11. R. Rizzi, M. Matricardi, F. Miskolczi, “Simulation of uplooking and downlooking high-resolution radiance spectra with two different radiative transfer models,” Appl. Opt. 41, 1–17 (2002).
    [CrossRef]
  12. R. Rizzi, J. A. Smith, P. di Pietro, G. Loffredo, “Comparison of measured and modeled stratus cloud infrared spectral signatures,” J. Geophys. Res. (to be published).
  13. W. Wiscombe, “Mie scattering calculations: advances in technique and fast, vector-speed computer codes,” Tech. Note TN-140+STR (National Center for Atmospheric Research, Boulder, Colo., 1979).
  14. D. J. Segelstein, “The complex refractive index of water,” M.S. thesis (University of Missouri, Kansas City, Mo., 1984).
  15. S. G. Warren, “Optical constants of ice from the ultraviolet to the microwave,” Appl. Opt. 23, 1206–1225 (1984).
    [CrossRef] [PubMed]
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    [CrossRef]
  17. J. E. Hansen, “Multiple scattering of polarized light in planetary atmosphere. II. Sunlight reflected by terrestrial water clouds,” J. Atmos. Sci. 28, 120–125 (1971).
    [CrossRef]
  18. J. E. Hansen, L. D. Travis, “Light scattering in planetary atmospheres,” Space Sci. Rev. 16, 527–610 (1974).
    [CrossRef]
  19. K. F. Evans, G. L. Stephens, “A new polarized atmospheric radiative transfer model,” J. Quant. Spectrosc. Radiat. Transfer 46, 412–423 (1991).
    [CrossRef]
  20. L. Tian, J. A. Curry, “Cloud overlap statistics,” J. Geophys. Res. 94, 9925–9935 (1989).
    [CrossRef]
  21. R. Rizzi, M. Matricardi, “The use of TOVS clear radiances for NWP using an updated forward model,” Q. J. R. Meteorol. Soc. 124, 1293–1312 (1998).
    [CrossRef]
  22. L. M. McMillin, H. E. Fleming, M. L. Hill, “Atmospheric transmittance of an absorbing gas. 3. A computationally fast and accurate transmittance model for absorbing gas with variable mixing ratios,” Appl. Opt. 18, 1600–1606 (1979).
    [CrossRef] [PubMed]
  23. J. R. Eyre, H. M. Woolf, “Transmittance of atmospheric gases in the microwave region: a fast model,” Appl. Opt. 27, 3244–3249 (1988).
    [CrossRef] [PubMed]
  24. P. Räisänen, “Effective longwave cloud fraction and maximum-random overlap of clouds: a problem and a solution,” Mon. Weather Rev. 126, 3336–3340 (1998).
    [CrossRef]
  25. S. A. Clough, M. J. Iacono, J. L. Moncet, “Line-by-line calculations of atmospheric fluxes and cooling rates: application to water vapor,” J. Geophys. Res. 97, 15761–15785 (1992).
    [CrossRef]
  26. G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

2002 (1)

R. Rizzi, M. Matricardi, F. Miskolczi, “Simulation of uplooking and downlooking high-resolution radiance spectra with two different radiative transfer models,” Appl. Opt. 41, 1–17 (2002).
[CrossRef]

1999 (1)

R. W. Saunders, M. Matricardi, P. Brunel, “An improved fast radiative transfer model for assimilation of satellite radiance observations,” Q. J. R. Meteorol. Soc. 125, 1407–1425 (1999).

1998 (2)

P. Räisänen, “Effective longwave cloud fraction and maximum-random overlap of clouds: a problem and a solution,” Mon. Weather Rev. 126, 3336–3340 (1998).
[CrossRef]

R. Rizzi, M. Matricardi, “The use of TOVS clear radiances for NWP using an updated forward model,” Q. J. R. Meteorol. Soc. 124, 1293–1312 (1998).
[CrossRef]

1995 (1)

L. C. J. Van de Berg, J. Schmetz, J. Whitlock, “On the calibration of the METEOSAT water vapour channel,” J. Geophys. Res. 100, 21,069–21,076 (1995).
[CrossRef]

1992 (2)

P. Chylek, P. Damiano, E. P. Shettle, “Infrared emittance of water clouds,” J. Atmos. Sci. 49, 1459–1472 (1992).
[CrossRef]

S. A. Clough, M. J. Iacono, J. L. Moncet, “Line-by-line calculations of atmospheric fluxes and cooling rates: application to water vapor,” J. Geophys. Res. 97, 15761–15785 (1992).
[CrossRef]

1991 (2)

K. F. Evans, G. L. Stephens, “A new polarized atmospheric radiative transfer model,” J. Quant. Spectrosc. Radiat. Transfer 46, 412–423 (1991).
[CrossRef]

J.-J. Morcrette, “Evaluation of model generated cloudiness: satellite observed and model generated diurnal variability of brightness temperature,” Mon. Weather Rev. 119, 1205–1224 (1991).
[CrossRef]

1989 (1)

L. Tian, J. A. Curry, “Cloud overlap statistics,” J. Geophys. Res. 94, 9925–9935 (1989).
[CrossRef]

1988 (1)

1984 (1)

1979 (1)

1974 (1)

J. E. Hansen, L. D. Travis, “Light scattering in planetary atmospheres,” Space Sci. Rev. 16, 527–610 (1974).
[CrossRef]

1971 (1)

J. E. Hansen, “Multiple scattering of polarized light in planetary atmosphere. II. Sunlight reflected by terrestrial water clouds,” J. Atmos. Sci. 28, 120–125 (1971).
[CrossRef]

Anderson, G. P.

G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

Bauer, P.

F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).

Brunel, P.

R. W. Saunders, M. Matricardi, P. Brunel, “An improved fast radiative transfer model for assimilation of satellite radiance observations,” Q. J. R. Meteorol. Soc. 125, 1407–1425 (1999).

R. W. Saunders, M. Matricardi, P. Brunel, “A fast radiative transfer model for assimilation of satellite radiance observations-RTTOV5,” Res. Dept. Tech. Memo 282 (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1999).

Chetwynd, J. M.

G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

Chevallier, F.

F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).

F. Chevallier, G. Kelly, “Model clouds as seen from space: comparison with geostationary imagery in the 11 µm window channel,” Mon. Weather Rev. (to be published).

Chylek, P.

P. Chylek, P. Damiano, E. P. Shettle, “Infrared emittance of water clouds,” J. Atmos. Sci. 49, 1459–1472 (1992).
[CrossRef]

Clough, S. A.

S. A. Clough, M. J. Iacono, J. L. Moncet, “Line-by-line calculations of atmospheric fluxes and cooling rates: application to water vapor,” J. Geophys. Res. 97, 15761–15785 (1992).
[CrossRef]

G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

Curry, J. A.

L. Tian, J. A. Curry, “Cloud overlap statistics,” J. Geophys. Res. 94, 9925–9935 (1989).
[CrossRef]

Damiano, P.

P. Chylek, P. Damiano, E. P. Shettle, “Infrared emittance of water clouds,” J. Atmos. Sci. 49, 1459–1472 (1992).
[CrossRef]

Evans, K. F.

K. F. Evans, G. L. Stephens, “A new polarized atmospheric radiative transfer model,” J. Quant. Spectrosc. Radiat. Transfer 46, 412–423 (1991).
[CrossRef]

Eyre, J. R.

J. R. Eyre, H. M. Woolf, “Transmittance of atmospheric gases in the microwave region: a fast model,” Appl. Opt. 27, 3244–3249 (1988).
[CrossRef] [PubMed]

J. R. Eyre, “A fast radiative transfer model for satellite sounding systems,” Res. Dept. Tech. Memo 176. (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1991).

Fleming, H. E.

Hansen, J. E.

J. E. Hansen, L. D. Travis, “Light scattering in planetary atmospheres,” Space Sci. Rev. 16, 527–610 (1974).
[CrossRef]

J. E. Hansen, “Multiple scattering of polarized light in planetary atmosphere. II. Sunlight reflected by terrestrial water clouds,” J. Atmos. Sci. 28, 120–125 (1971).
[CrossRef]

Hill, M. L.

Iacono, M. J.

S. A. Clough, M. J. Iacono, J. L. Moncet, “Line-by-line calculations of atmospheric fluxes and cooling rates: application to water vapor,” J. Geophys. Res. 97, 15761–15785 (1992).
[CrossRef]

Jakob, C.

F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).

Kelly, G.

F. Chevallier, G. Kelly, “Model clouds as seen from space: comparison with geostationary imagery in the 11 µm window channel,” Mon. Weather Rev. (to be published).

F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).

Kneizys, F. X.

G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

Loffredo, G.

R. Rizzi, J. A. Smith, P. di Pietro, G. Loffredo, “Comparison of measured and modeled stratus cloud infrared spectral signatures,” J. Geophys. Res. (to be published).

Matricardi, M.

R. Rizzi, M. Matricardi, F. Miskolczi, “Simulation of uplooking and downlooking high-resolution radiance spectra with two different radiative transfer models,” Appl. Opt. 41, 1–17 (2002).
[CrossRef]

R. W. Saunders, M. Matricardi, P. Brunel, “An improved fast radiative transfer model for assimilation of satellite radiance observations,” Q. J. R. Meteorol. Soc. 125, 1407–1425 (1999).

R. Rizzi, M. Matricardi, “The use of TOVS clear radiances for NWP using an updated forward model,” Q. J. R. Meteorol. Soc. 124, 1293–1312 (1998).
[CrossRef]

R. W. Saunders, M. Matricardi, P. Brunel, “A fast radiative transfer model for assimilation of satellite radiance observations-RTTOV5,” Res. Dept. Tech. Memo 282 (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1999).

McMillin, L. M.

McNally, T.

F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).

Miskolczi, F.

R. Rizzi, M. Matricardi, F. Miskolczi, “Simulation of uplooking and downlooking high-resolution radiance spectra with two different radiative transfer models,” Appl. Opt. 41, 1–17 (2002).
[CrossRef]

Moncet, J. L.

S. A. Clough, M. J. Iacono, J. L. Moncet, “Line-by-line calculations of atmospheric fluxes and cooling rates: application to water vapor,” J. Geophys. Res. 97, 15761–15785 (1992).
[CrossRef]

Morcrette, J.-J.

J.-J. Morcrette, “Evaluation of model generated cloudiness: satellite observed and model generated diurnal variability of brightness temperature,” Mon. Weather Rev. 119, 1205–1224 (1991).
[CrossRef]

Pietro, P. di

R. Rizzi, J. A. Smith, P. di Pietro, G. Loffredo, “Comparison of measured and modeled stratus cloud infrared spectral signatures,” J. Geophys. Res. (to be published).

Räisänen, P.

P. Räisänen, “Effective longwave cloud fraction and maximum-random overlap of clouds: a problem and a solution,” Mon. Weather Rev. 126, 3336–3340 (1998).
[CrossRef]

Rizzi, R.

R. Rizzi, M. Matricardi, F. Miskolczi, “Simulation of uplooking and downlooking high-resolution radiance spectra with two different radiative transfer models,” Appl. Opt. 41, 1–17 (2002).
[CrossRef]

R. Rizzi, M. Matricardi, “The use of TOVS clear radiances for NWP using an updated forward model,” Q. J. R. Meteorol. Soc. 124, 1293–1312 (1998).
[CrossRef]

R. Rizzi, J. A. Smith, P. di Pietro, G. Loffredo, “Comparison of measured and modeled stratus cloud infrared spectral signatures,” J. Geophys. Res. (to be published).

R. Rizzi, “Raw HIRS/2 radiances and model simulations in the presence of clouds,” Tech. Rep. TR-73 (European Centre for Medium Range Weather Forecasts, Reading, UK, 1994).

Saunders, R. W.

R. W. Saunders, M. Matricardi, P. Brunel, “An improved fast radiative transfer model for assimilation of satellite radiance observations,” Q. J. R. Meteorol. Soc. 125, 1407–1425 (1999).

R. W. Saunders, M. Matricardi, P. Brunel, “A fast radiative transfer model for assimilation of satellite radiance observations-RTTOV5,” Res. Dept. Tech. Memo 282 (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1999).

Schmetz, J.

L. C. J. Van de Berg, J. Schmetz, J. Whitlock, “On the calibration of the METEOSAT water vapour channel,” J. Geophys. Res. 100, 21,069–21,076 (1995).
[CrossRef]

Segelstein, D. J.

D. J. Segelstein, “The complex refractive index of water,” M.S. thesis (University of Missouri, Kansas City, Mo., 1984).

Shettle, E. P.

P. Chylek, P. Damiano, E. P. Shettle, “Infrared emittance of water clouds,” J. Atmos. Sci. 49, 1459–1472 (1992).
[CrossRef]

G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

Smith, J. A.

R. Rizzi, J. A. Smith, P. di Pietro, G. Loffredo, “Comparison of measured and modeled stratus cloud infrared spectral signatures,” J. Geophys. Res. (to be published).

Stephens, G. L.

K. F. Evans, G. L. Stephens, “A new polarized atmospheric radiative transfer model,” J. Quant. Spectrosc. Radiat. Transfer 46, 412–423 (1991).
[CrossRef]

Tian, L.

L. Tian, J. A. Curry, “Cloud overlap statistics,” J. Geophys. Res. 94, 9925–9935 (1989).
[CrossRef]

Travis, L. D.

J. E. Hansen, L. D. Travis, “Light scattering in planetary atmospheres,” Space Sci. Rev. 16, 527–610 (1974).
[CrossRef]

Van de Berg, L. C. J.

L. C. J. Van de Berg, J. Schmetz, J. Whitlock, “On the calibration of the METEOSAT water vapour channel,” J. Geophys. Res. 100, 21,069–21,076 (1995).
[CrossRef]

Warren, S. G.

Whitlock, J.

L. C. J. Van de Berg, J. Schmetz, J. Whitlock, “On the calibration of the METEOSAT water vapour channel,” J. Geophys. Res. 100, 21,069–21,076 (1995).
[CrossRef]

Wiscombe, W.

W. Wiscombe, “Mie scattering calculations: advances in technique and fast, vector-speed computer codes,” Tech. Note TN-140+STR (National Center for Atmospheric Research, Boulder, Colo., 1979).

Woolf, H. M.

Appl. Opt. (4)

J. Atmos. Sci. (2)

P. Chylek, P. Damiano, E. P. Shettle, “Infrared emittance of water clouds,” J. Atmos. Sci. 49, 1459–1472 (1992).
[CrossRef]

J. E. Hansen, “Multiple scattering of polarized light in planetary atmosphere. II. Sunlight reflected by terrestrial water clouds,” J. Atmos. Sci. 28, 120–125 (1971).
[CrossRef]

J. Geophys. Res. (3)

L. C. J. Van de Berg, J. Schmetz, J. Whitlock, “On the calibration of the METEOSAT water vapour channel,” J. Geophys. Res. 100, 21,069–21,076 (1995).
[CrossRef]

S. A. Clough, M. J. Iacono, J. L. Moncet, “Line-by-line calculations of atmospheric fluxes and cooling rates: application to water vapor,” J. Geophys. Res. 97, 15761–15785 (1992).
[CrossRef]

L. Tian, J. A. Curry, “Cloud overlap statistics,” J. Geophys. Res. 94, 9925–9935 (1989).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer (1)

K. F. Evans, G. L. Stephens, “A new polarized atmospheric radiative transfer model,” J. Quant. Spectrosc. Radiat. Transfer 46, 412–423 (1991).
[CrossRef]

Mon. Weather Rev. (2)

P. Räisänen, “Effective longwave cloud fraction and maximum-random overlap of clouds: a problem and a solution,” Mon. Weather Rev. 126, 3336–3340 (1998).
[CrossRef]

J.-J. Morcrette, “Evaluation of model generated cloudiness: satellite observed and model generated diurnal variability of brightness temperature,” Mon. Weather Rev. 119, 1205–1224 (1991).
[CrossRef]

Q. J. R. Meteorol. Soc. (2)

R. W. Saunders, M. Matricardi, P. Brunel, “An improved fast radiative transfer model for assimilation of satellite radiance observations,” Q. J. R. Meteorol. Soc. 125, 1407–1425 (1999).

R. Rizzi, M. Matricardi, “The use of TOVS clear radiances for NWP using an updated forward model,” Q. J. R. Meteorol. Soc. 124, 1293–1312 (1998).
[CrossRef]

Space Sci. Rev. (1)

J. E. Hansen, L. D. Travis, “Light scattering in planetary atmospheres,” Space Sci. Rev. 16, 527–610 (1974).
[CrossRef]

Other (11)

R. W. Saunders, M. Matricardi, P. Brunel, “A fast radiative transfer model for assimilation of satellite radiance observations-RTTOV5,” Res. Dept. Tech. Memo 282 (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1999).

R. Rizzi, J. A. Smith, P. di Pietro, G. Loffredo, “Comparison of measured and modeled stratus cloud infrared spectral signatures,” J. Geophys. Res. (to be published).

W. Wiscombe, “Mie scattering calculations: advances in technique and fast, vector-speed computer codes,” Tech. Note TN-140+STR (National Center for Atmospheric Research, Boulder, Colo., 1979).

D. J. Segelstein, “The complex refractive index of water,” M.S. thesis (University of Missouri, Kansas City, Mo., 1984).

R. Rizzi, “Raw HIRS/2 radiances and model simulations in the presence of clouds,” Tech. Rep. TR-73 (European Centre for Medium Range Weather Forecasts, Reading, UK, 1994).

F. Chevallier, P. Bauer, G. Kelly, C. Jakob, T. McNally, “Model clouds over the ocean as seen from space: comparison with HIRS/2 and MSU radiances,” J. Clim. (to be published).

F. Chevallier, G. Kelly, “Model clouds as seen from space: comparison with geostationary imagery in the 11 µm window channel,” Mon. Weather Rev. (to be published).

Intergovernmental Panel on Climate Change, “WG I climate change 2001: the scientific basis, summary for policy makers,” Third Assessment Rep. (Intergovernmental Panel on Climate Changes, Geneva, Switzerland, 2001).

European Space Agency, “The five candidate Earth Explorer core missions—EarthCARE—Earth clouds, aerosols and radiation explorer,” ESA SP-1257(1) (ESA Publications Division, European Space Research and Technology Center, Noordwijk, The Netherlands, 2001).

J. R. Eyre, “A fast radiative transfer model for satellite sounding systems,” Res. Dept. Tech. Memo 176. (European Centre for Medium Range Weather Forecasts, Reading, U.K., 1991).

G. P. Anderson, S. A. Clough, F. X. Kneizys, J. M. Chetwynd, E. P. Shettle, “AFGL atmospheric constituent profiles (1–120 km),” Rep. AFGL-TR86-0110 (U.S. Air Force Geophysics Laboratory, Hanscom Air Force Base, Mass., 1986).

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Figures (10)

Fig. 1
Fig. 1

Differences in source functions L 1 and L τ with respect to L m , expressed as brightness temperature: (a) 850-m-thick layer with top temperature 218.8 K and bottom temperature 226.3 K; (b) 362-m-thick layer with top temperature 260.7 K and bottom temperature 257.2 K.

Fig. 2
Fig. 2

Tropical and arctic temperature profiles. The symbols denote the NWP model’s full levels, RTTOV gas levels, and the levels used for RT3X computations.

Fig. 3
Fig. 3

Weighting functions for HIRS/2 channels 8, 12 and 14 for tropical and arctic profiles.

Fig. 4
Fig. 4

Clear-sky brightness temperature difference (ΔT) between RTF and RT3X computations for some of the NOAA-12 HIRS/2 channels for the tropical and arctic profiles. RT3X standard computations (extending to 0.01 hPa) (filled symbols connected by solid curves) and computations with 0.1 hPa as the uppermost level (open symbols connected by dashed curves) are shown.

Fig. 5
Fig. 5

Extinction, scattering, and absorption optical depths for a 1-km layer with cloud water and cloud ice contents of 1 gm-3, computed with exact Mie theory (curves) and absorption optical depth used in fast computations: HIRS/2 channel 8, 12, and 14; IR and WV. Values for liquid water (Reff = 10 µm) and ice (Reff = 30 µm) are shown.

Fig. 6
Fig. 6

Brightness temperature difference T abs - T sca between a RT3X with only absorption T abs and a RT3X with the full scattering solution T sca for the tropical profile.

Fig. 7
Fig. 7

Brightness temperature difference T abs - T sca between a RT3X with only absorption T abs and a RT3X with the full scattering solution T sca for the arctic profile.

Fig. 8
Fig. 8

Brightness temperature difference between RTF and RT3X computations in cloudy conditions for HIRS/2 spectral channels 8, 12, and 14. Tropical and arctic profiles are shown. Cloud altitude and water and ice phases are listed in each figure.

Fig. 9
Fig. 9

Same as Fig. 8 but for METEOSAT (a) IR and (b) WV channels.

Fig. 10
Fig. 10

Scatter plots of the complete set of simulated RTF versus RT3X brightness temperatures for HIRS/2 channels 8, 12, and 14 and for METEOSAT channels IR and WV.

Tables (3)

Tables Icon

Table 1 Cloud Properties for Tropical Input Profiles

Tables Icon

Table 2 Cloud Properties for Arctic Input Profiles

Tables Icon

Table 3 Statistical Evaluation of the Complete Set of Results

Equations (7)

Equations on this page are rendered with MathJax. Learn more.

nr=Arα exp-βr.
N0=A Γα+1βα+1,
Reff=α+3β,
Veff=1α+3.
Trcλz, z=exp-Kabsλhμ,
L1=B0+B121-Trt,
Lτ=B0+B1-B0τ-B0+B1-B0τ1+τTrt,

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