Abstract

This paper discusses new atmospheric cloud algorithms that we have developed to detect the presence and location of clouds in images of the sky acquired by day/night whole sky imagers, and to categorize the clouds by opacity. The day/night whole sky imagers that we developed are ground-based sensors that acquire digital imagery of the full sky down to the horizon in several visible spectral bands and a near-infrared spectral band. The instruments acquire accurate data under daylight, moonlight, and starlight conditions. This paper discusses the previously unpublished day and night cloud algorithms. The day cloud algorithm identifies opaque clouds using a red/blue ratio and identifies thin clouds by comparing current red/blue ratios with the ratios anticipated for clear skies. The clear sky ratios include an image-to-image adaptive algorithm feature to adjust for haze amount. The night cloud algorithms are based on determinations of earth-to-space beam transmittances and on comparisons of current radiances with radiance distributions for clear skies and for opaque clouds. They also include an adaptive algorithm feature to adjust for changes in haze amount. In addition, these new night algorithms report the Earth-to-space beam transmittance in selected directions. The algorithms provide a pixel-by-pixel determination of the cloud results with excellent accuracy. This paper discusses the new day and night cloud algorithms and an assessment of their accuracy, as well as a short discussion of the pros and cons of using these wave bands versus other wave bands.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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References

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  1. J. E. Shields, M. E. Karr, R. W. Johnson, and A. R. Burden, “Day/night whole sky imagers for 24-h cloud and sky assessment: history and overview,” Appl. Opt. 52, 1605–1616 (2013).
    [Crossref]
  2. J. E. Shields and M. E. Karr, “Radiometric calibration methods for day/night whole sky imagers and extinction imagers,” Appl. Opt. 58, 5663–5673 (2019).
    [Crossref]
  3. J. E. Shields and M. E. Karr, “Extinction imagers for measurements of atmospheric beam transmittance,” Appl. Opt. 58, 5486–5495 (2019).
    [Crossref]
  4. R. W. Johnson, W. S. Hering, and J. E. Shields, “Automated visibility and cloud cover measurements with a solid state imaging system,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 1989, https://apps.dtic.mil/docs/citations/ADA216906 .
  5. J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .
  6. U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.
  7. U. Feister and J. Shields, “Cloud and radiance measurements with the VIS/NIR Daylight Whole Sky Imager at Lindenberg (Germany),” Meteorol. Z. 14, 627–639 (2005).
    [Crossref]
  8. U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
    [Crossref]
  9. C. N. Long and J. J. DeLuisi, “Development of an automated hemispheric sky imager for cloud fraction retrievals,” in Tenth Symposium on Meteorological Observations and Instrumentation, Phoenix, Arizona (American Meteor Society, 1998), pp. 171–174.
  10. G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
    [Crossref]
  11. A. Cazorla, F. J. Olmo, and L. Alados-Arboledas, “Development of a sky imager for cloud cover assessment,” J. Opt. Soc. Am. A 25, 29–39 (2008).
    [Crossref]
  12. C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
    [Crossref]
  13. R. Pérez-Ramírez, R. J. Nemiroff, and J. B. Rafert, “nightskylive.net: the Night Sky Live project,” Astron. Nachr. 325, 568–570 (2004).
    [Crossref]
  14. D. J. Klege, R. D. Blatherwick, and V. R. Morris, “Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties,” Atmos. Meas. Tech. 7, 637–645 (2014).
    [Crossref]
  15. P. W. Nugent, J. A. Shaw, and S. Piazzolla, “Infrared cloud imager development for atmospheric optical communication,” Opt. Express 17, 7862–7872 (2009).
    [Crossref]
  16. B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
    [Crossref]
  17. J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .
  18. J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
    [Crossref]
  19. I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
    [Crossref]
  20. I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
    [Crossref]
  21. E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
    [Crossref]
  22. W. S. Hering, R. W. Johnson, W. S. Hering, and R. W. Johnson, The FASCAT odel performance under fractional cloud conditions and related studies,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1984, https://apps.dtic.mil/docs/citations/ADA169894 .
  23. S. Q. Duntley, R. W. Johnson, and J. I. Gordon, “Airborne measurements of optical atmospheric properties in Southern Illinois,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1973, https://apps.dtic.mil/docs/citations/AD0774597 .
  24. J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).
  25. B. Thurairajah and J. A. Shaw, “Cloud statistics measured with the infrared cloud imager (ICI),” IEEE Trans. Geosci. Remote Sens. 43, 2000–2007 (2007).
    [Crossref]
  26. E. D. Hoffleit and W. H. Warren, The Bright Star Catalogue, 5th ed. (Astronomical Data Center and Yale University Observatory, 1991).

2019 (2)

2018 (1)

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

2014 (2)

D. J. Klege, R. D. Blatherwick, and V. R. Morris, “Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties,” Atmos. Meas. Tech. 7, 637–645 (2014).
[Crossref]

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

2013 (1)

2011 (1)

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

2010 (1)

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

2009 (1)

2008 (2)

A. Cazorla, F. J. Olmo, and L. Alados-Arboledas, “Development of a sky imager for cloud cover assessment,” J. Opt. Soc. Am. A 25, 29–39 (2008).
[Crossref]

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

2007 (2)

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

B. Thurairajah and J. A. Shaw, “Cloud statistics measured with the infrared cloud imager (ICI),” IEEE Trans. Geosci. Remote Sens. 43, 2000–2007 (2007).
[Crossref]

2005 (2)

U. Feister and J. Shields, “Cloud and radiance measurements with the VIS/NIR Daylight Whole Sky Imager at Lindenberg (Germany),” Meteorol. Z. 14, 627–639 (2005).
[Crossref]

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

2004 (1)

R. Pérez-Ramírez, R. J. Nemiroff, and J. B. Rafert, “nightskylive.net: the Night Sky Live project,” Astron. Nachr. 325, 568–570 (2004).
[Crossref]

2003 (1)

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

Agassi, E.

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

Alados-Arboledas, L.

Altaratz, O.

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

Baker, J. G.

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .

Blatherwick, R. D.

D. J. Klege, R. D. Blatherwick, and V. R. Morris, “Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties,” Atmos. Meas. Tech. 7, 637–645 (2014).
[Crossref]

Burden, A. R.

J. E. Shields, M. E. Karr, R. W. Johnson, and A. R. Burden, “Day/night whole sky imagers for 24-h cloud and sky assessment: history and overview,” Appl. Opt. 52, 1605–1616 (2013).
[Crossref]

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).

Cazorla, A.

Chow, C. W.

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Clark, R. T.

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

Dehne, K.

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

DeLuisi, J. J.

C. N. Long and J. J. DeLuisi, “Development of an automated hemispheric sky imager for cloud fraction retrievals,” in Tenth Symposium on Meteorological Observations and Instrumentation, Phoenix, Arizona (American Meteor Society, 1998), pp. 171–174.

Dominguez, A.

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Duntley, S. Q.

S. Q. Duntley, R. W. Johnson, and J. I. Gordon, “Airborne measurements of optical atmospheric properties in Southern Illinois,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1973, https://apps.dtic.mil/docs/citations/AD0774597 .

Feingold, G.

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

Feister, U.

U. Feister and J. Shields, “Cloud and radiance measurements with the VIS/NIR Daylight Whole Sky Imager at Lindenberg (Germany),” Meteorol. Z. 14, 627–639 (2005).
[Crossref]

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

Feister, U. H.

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

Forgan, B. W.

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

Gordon, J. I.

S. Q. Duntley, R. W. Johnson, and J. I. Gordon, “Airborne measurements of optical atmospheric properties in Southern Illinois,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1973, https://apps.dtic.mil/docs/citations/AD0774597 .

Görsdorf, U.

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

Güldner, J.

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

Hering, W. S.

R. W. Johnson, W. S. Hering, and J. E. Shields, “Automated visibility and cloud cover measurements with a solid state imaging system,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 1989, https://apps.dtic.mil/docs/citations/ADA216906 .

W. S. Hering, R. W. Johnson, W. S. Hering, and R. W. Johnson, The FASCAT odel performance under fractional cloud conditions and related studies,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1984, https://apps.dtic.mil/docs/citations/ADA169894 .

W. S. Hering, R. W. Johnson, W. S. Hering, and R. W. Johnson, The FASCAT odel performance under fractional cloud conditions and related studies,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1984, https://apps.dtic.mil/docs/citations/ADA169894 .

Hirsch, E.

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

Hodgkiss, W. S.

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).

Hoffleit, E. D.

E. D. Hoffleit and W. H. Warren, The Bright Star Catalogue, 5th ed. (Astronomical Data Center and Yale University Observatory, 1991).

Johnson, R. W.

J. E. Shields, M. E. Karr, R. W. Johnson, and A. R. Burden, “Day/night whole sky imagers for 24-h cloud and sky assessment: history and overview,” Appl. Opt. 52, 1605–1616 (2013).
[Crossref]

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .

W. S. Hering, R. W. Johnson, W. S. Hering, and R. W. Johnson, The FASCAT odel performance under fractional cloud conditions and related studies,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1984, https://apps.dtic.mil/docs/citations/ADA169894 .

W. S. Hering, R. W. Johnson, W. S. Hering, and R. W. Johnson, The FASCAT odel performance under fractional cloud conditions and related studies,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1984, https://apps.dtic.mil/docs/citations/ADA169894 .

S. Q. Duntley, R. W. Johnson, and J. I. Gordon, “Airborne measurements of optical atmospheric properties in Southern Illinois,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1973, https://apps.dtic.mil/docs/citations/AD0774597 .

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

R. W. Johnson, W. S. Hering, and J. E. Shields, “Automated visibility and cloud cover measurements with a solid state imaging system,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 1989, https://apps.dtic.mil/docs/citations/ADA216906 .

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).

Karr, M. E.

J. E. Shields and M. E. Karr, “Extinction imagers for measurements of atmospheric beam transmittance,” Appl. Opt. 58, 5486–5495 (2019).
[Crossref]

J. E. Shields and M. E. Karr, “Radiometric calibration methods for day/night whole sky imagers and extinction imagers,” Appl. Opt. 58, 5663–5673 (2019).
[Crossref]

J. E. Shields, M. E. Karr, R. W. Johnson, and A. R. Burden, “Day/night whole sky imagers for 24-h cloud and sky assessment: history and overview,” Appl. Opt. 52, 1605–1616 (2013).
[Crossref]

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

Kaufman, Y. J.

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

Klege, D. J.

D. J. Klege, R. D. Blatherwick, and V. R. Morris, “Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties,” Atmos. Meas. Tech. 7, 637–645 (2014).
[Crossref]

Kleissl, J.

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Koren, I.

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

Lave, M.

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Levin, Z.

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

Liley, J. B.

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

Long, C. N.

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

C. N. Long and J. J. DeLuisi, “Development of an automated hemispheric sky imager for cloud fraction retrievals,” in Tenth Symposium on Meteorological Observations and Instrumentation, Phoenix, Arizona (American Meteor Society, 1998), pp. 171–174.

Martins, J. V.

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

McKenzie, R. L.

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

Mikuls, V. W.

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

Möller, H.

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

Morris, V. R.

D. J. Klege, R. D. Blatherwick, and V. R. Morris, “Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties,” Atmos. Meas. Tech. 7, 637–645 (2014).
[Crossref]

Nemiroff, R. J.

R. Pérez-Ramírez, R. J. Nemiroff, and J. B. Rafert, “nightskylive.net: the Night Sky Live project,” Astron. Nachr. 325, 568–570 (2004).
[Crossref]

Nugent, P. W.

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

P. W. Nugent, J. A. Shaw, and S. Piazzolla, “Infrared cloud imager development for atmospheric optical communication,” Opt. Express 17, 7862–7872 (2009).
[Crossref]

Olmo, F. J.

Oreopoulos, L.

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

Pérez-Ramírez, R.

R. Pérez-Ramírez, R. J. Nemiroff, and J. B. Rafert, “nightskylive.net: the Night Sky Live project,” Astron. Nachr. 325, 568–570 (2004).
[Crossref]

Pfister, G.

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

Piazzolla, S.

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

P. W. Nugent, J. A. Shaw, and S. Piazzolla, “Infrared cloud imager development for atmospheric optical communication,” Opt. Express 17, 7862–7872 (2009).
[Crossref]

Rafert, J. B.

R. Pérez-Ramírez, R. J. Nemiroff, and J. B. Rafert, “nightskylive.net: the Night Sky Live project,” Astron. Nachr. 325, 568–570 (2004).
[Crossref]

Redman, B. J.

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

Remer, L. A.

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

Rudich, Y.

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

Sattler, T.

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

Shaw, J. A.

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

P. W. Nugent, J. A. Shaw, and S. Piazzolla, “Infrared cloud imager development for atmospheric optical communication,” Opt. Express 17, 7862–7872 (2009).
[Crossref]

B. Thurairajah and J. A. Shaw, “Cloud statistics measured with the infrared cloud imager (ICI),” IEEE Trans. Geosci. Remote Sens. 43, 2000–2007 (2007).
[Crossref]

Shields, J.

U. Feister and J. Shields, “Cloud and radiance measurements with the VIS/NIR Daylight Whole Sky Imager at Lindenberg (Germany),” Meteorol. Z. 14, 627–639 (2005).
[Crossref]

Shields, J. E.

J. E. Shields and M. E. Karr, “Radiometric calibration methods for day/night whole sky imagers and extinction imagers,” Appl. Opt. 58, 5663–5673 (2019).
[Crossref]

J. E. Shields and M. E. Karr, “Extinction imagers for measurements of atmospheric beam transmittance,” Appl. Opt. 58, 5486–5495 (2019).
[Crossref]

J. E. Shields, M. E. Karr, R. W. Johnson, and A. R. Burden, “Day/night whole sky imagers for 24-h cloud and sky assessment: history and overview,” Appl. Opt. 52, 1605–1616 (2013).
[Crossref]

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

R. W. Johnson, W. S. Hering, and J. E. Shields, “Automated visibility and cloud cover measurements with a solid state imaging system,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 1989, https://apps.dtic.mil/docs/citations/ADA216906 .

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

Streeter, J. R.

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

Thomas, W.

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

Thurairajah, B.

B. Thurairajah and J. A. Shaw, “Cloud statistics measured with the infrared cloud imager (ICI),” IEEE Trans. Geosci. Remote Sens. 43, 2000–2007 (2007).
[Crossref]

Urquhart, B.

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Warren, W. H.

E. D. Hoffleit and W. H. Warren, The Bright Star Catalogue, 5th ed. (Astronomical Data Center and Yale University Observatory, 1991).

Washom, B.

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Woldt, M.

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

Appl. Opt. (3)

Astron. Nachr. (1)

R. Pérez-Ramírez, R. J. Nemiroff, and J. B. Rafert, “nightskylive.net: the Night Sky Live project,” Astron. Nachr. 325, 568–570 (2004).
[Crossref]

Atmos. Chem. Phys. (2)

I. Koren, L. Oreopoulos, G. Feingold, L. A. Remer, and O. Altaratz, “How small is a small cloud?” Atmos. Chem. Phys. 8, 3855–3864 (2008).
[Crossref]

E. Hirsch, I. Koren, Z. Levin, O. Altaratz, and E. Agassi, “On transition-zone water clouds,” Atmos. Chem. Phys. 14, 9001–9012 (2014).
[Crossref]

Atmos. Meas. Tech. (1)

D. J. Klege, R. D. Blatherwick, and V. R. Morris, “Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties,” Atmos. Meas. Tech. 7, 637–645 (2014).
[Crossref]

Atmos. Res. (1)

U. H. Feister, H. Möller, T. Sattler, J. E. Shields, U. Görsdorf, and J. Güldner, “Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany,” Atmos. Res. 96, 395–407 (2010).
[Crossref]

Geophys. Res. Lett. (1)

I. Koren, L. A. Remer, Y. J. Kaufman, Y. Rudich, and J. V. Martins, “On the twilight zone between clouds and aerosols,” Geophys. Res. Lett. 34, L08805 (2007).
[Crossref]

IEEE Trans. Geosci. Remote Sens. (1)

B. Thurairajah and J. A. Shaw, “Cloud statistics measured with the infrared cloud imager (ICI),” IEEE Trans. Geosci. Remote Sens. 43, 2000–2007 (2007).
[Crossref]

J. Appl. Meteorol. (1)

G. Pfister, R. L. McKenzie, J. B. Liley, W. Thomas, B. W. Forgan, and C. N. Long, “Cloud coverage based on all-sky imaging and its impact on surface solar irradiance,” J. Appl. Meteorol. 42, 1421–1434 (2003).
[Crossref]

J. Opt. Express (1)

B. J. Redman, J. A. Shaw, P. W. Nugent, R. T. Clark, and S. Piazzolla, “Reflective all-sky thermal infrared cloud imager,” J. Opt. Express 26, 11276–11283 (2018).
[Crossref]

J. Opt. Soc. Am. A (1)

J. Sol. Energy (1)

C. W. Chow, B. Urquhart, M. Lave, A. Dominguez, J. Kleissl, J. E. Shields, and B. Washom, “Intra-hour forecasting with a total sky imager at the UC San Diego solar test bed,” J. Sol. Energy 85, 2881–2893 (2011).
[Crossref]

Meteorol. Z. (1)

U. Feister and J. Shields, “Cloud and radiance measurements with the VIS/NIR Daylight Whole Sky Imager at Lindenberg (Germany),” Meteorol. Z. 14, 627–639 (2005).
[Crossref]

Opt. Express (1)

Proc. SPIE (1)

J. E. Shields, A. R. Burden, R. W. Johnson, M. E. Karr, and J. G. Baker, “New cloud free line of sight statistics measured with digital Whole Sky Imagers,” Proc. SPIE 5891, 58910M (2005).
[Crossref]

Other (9)

E. D. Hoffleit and W. H. Warren, The Bright Star Catalogue, 5th ed. (Astronomical Data Center and Yale University Observatory, 1991).

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and J. G. Baker, “Analysis and measurement of cloud free line of sight and related cloud statistical behavior,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 2003, https://apps.dtic.mil/docs/citations/ADA425400 .

W. S. Hering, R. W. Johnson, W. S. Hering, and R. W. Johnson, The FASCAT odel performance under fractional cloud conditions and related studies,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1984, https://apps.dtic.mil/docs/citations/ADA169894 .

S. Q. Duntley, R. W. Johnson, and J. I. Gordon, “Airborne measurements of optical atmospheric properties in Southern Illinois,” , University of California, Scripps Institution of Oceanography, Visibility Laboratory, 1973, https://apps.dtic.mil/docs/citations/AD0774597 .

J. E. Shields, M. E. Karr, A. R. Burden, R. W. Johnson, and W. S. Hodgkiss, “Enhancement of near-real-time cloud analysis and related analytic support for whole sky imagers,” , ADA468076 (Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2007).

C. N. Long and J. J. DeLuisi, “Development of an automated hemispheric sky imager for cloud fraction retrievals,” in Tenth Symposium on Meteorological Observations and Instrumentation, Phoenix, Arizona (American Meteor Society, 1998), pp. 171–174.

R. W. Johnson, W. S. Hering, and J. E. Shields, “Automated visibility and cloud cover measurements with a solid state imaging system,” , University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, 1989, https://apps.dtic.mil/docs/citations/ADA216906 .

J. E. Shields, M. E. Karr, A. R. Burden, V. W. Mikuls, J. R. Streeter, R. W. Johnson, and W. S. Hodgkiss, “Scientific report on whole sky imager characterization of sky obscuration by clouds for the Starfire Optical Range,” , Marine Physical Laboratory, Scripps Institution of Oceanography, University of California San Diego, 2010, https://apps.dtic.mil/docs/citations/ADA556222 .

U. Feister, J. E. Shields, M. E. Karr, R. W. Johnson, K. Dehne, and M. Woldt, “Ground-based cloud images and sky radiances in the visible and near infrared region from whole sky imager measurements,” in EUMP31, EUMETSAT Satellite Application Facility Workshop, Dresden, Germany, 20–22 November (2000), pp. 79–88.

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Figures (18)

Fig. 1.
Fig. 1. Raw WSI image, day with red filter showing clouds, clear sky, and solar/lunar occultor.
Fig. 2.
Fig. 2. Cloud decision image. Blue, no cloud; white, opaque cloud; yellow, thin cloud; black, no data (mask).
Fig. 3.
Fig. 3. Raw red image for case with contrails.
Fig. 4.
Fig. 4. Cloud decision image for case with contrails.
Fig. 5.
Fig. 5. N/B beta reference values versus SZA for several nearly cloud-free days at one site.
Fig. 6.
Fig. 6. Beta-beta line for a cloud-free but hazy image.
Fig. 7.
Fig. 7. Night image under no moon and cloud-free sky showing the Milky Way and lights from a nearby city.
Fig. 8.
Fig. 8. Sample cloud transmittance extraction result from an early version of the night algorithm. Red, star not detected; blue, purple, green, yellow, and orange correspond with transmittances of 0.8–1.0, 0.6–0.8, 0.4–0.6, 0.2–0.4, and 0–0.2, respectively.
Fig. 9.
Fig. 9. Typical no-moon clear-sky radiance levels for clear sky as a function of hour-angle (solid color curves), and for skies with opaque clouds under no-moon conditions (dashed line).
Fig. 10.
Fig. 10. Raw image for a no-moon case at night.
Fig. 11.
Fig. 11. Processed cloud decision image for the case in Fig. 10.
Fig. 12.
Fig. 12. Radiances along the center column for the clear and moon shells and the measured data for image in Fig. 13.
Fig. 13.
Fig. 13. Raw night image with thin clouds and moonlight.
Fig. 14.
Fig. 14. Cloud decision image corresponding with Fig. 13. Green represents pixels identified as thin cloud.
Fig. 15.
Fig. 15. Raw image for moonlight with broken clouds, with transmittance results superimposed. Orange, star not detected; blue, purple, green, and yellow correspond with transmittances of 0.8–1.0, 0.6–0.8, 0.2–0.6, and 0–0.2, respectively.
Fig. 16.
Fig. 16. Cloud decision image for case shown in Fig. 15.
Fig. 17.
Fig. 17. Day algorithm results showing percent of results from test bed assessed by the analyst to be correct in selected directions.
Fig. 18.
Fig. 18. Night algorithm results showing percent of results from test bed assessed by the analyst to be correct in selected directions.

Tables (1)

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Table 1. Summary of Results with New Blind Test Programs

Equations (1)

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N ( θ , φ , θ M , φ M , α ) = N B ( θ , φ ) + R N ( α ) * N M ( θ , φ , θ M , φ M , α max ) .

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