• Allmen, M. C., , and Kegelmeyer W. P. , 1996: The computation of cloud-base height from paired whole-sky imaging cameras. J. Atmos. Oceanic Technol., 13 , 97113.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Buch, K. A., , Sun C-H. , , and Thorne L. R. , 1995: Cloud classification using whole-sky imager data. Proc. Fifth Atmospheric Radiation Measurement (ARM) Science Team Meeting, San Diego, CA, U.S. Dept. of Energy, 35–39.

  • Calbó, J., , Pagès D. , , and González J. A. , 2005: Empirical studies of cloud effects on UV radiation: A review. Rev. Geophys., 43 .RG2002, doi:10.1029/2004RG000155.

    • Search Google Scholar
    • Export Citation
  • Carslaw, K. S., , Harrison R. G. , , and Kirkby J. , 2002: Cosmic rays, clouds, and climate. Science, 298 , 17321737.

  • Chen, Z., , Zen D. , , and Zhang Q. , 1994: Sky model study using fuzzy mathematics. J. Illum. Eng. Soc., 23 , 5258.

  • Crawford, J., , Shetter R. E. , , Lefer B. , , Cantrell C. , , Junkermann W. , , Madronich S. , , and Calvert J. , 2003: Cloud impacts on UV spectral actinic flux observed during the International Photolysis Frequency Measurement and Model Intercomparison (IPMMI). J. Geophys. Res., 108 .8545, doi:10.1029/2002JD002731.

    • Search Google Scholar
    • Export Citation
  • Duchon, C. E., , and O’Malley M. S. , 1998: Estimating cloud type from pyranometer observations. J. Appl. Meteor., 38 , 132141.

  • Garand, L., 1988: Automated recognition of oceanic cloud patterns. Part I: Methodology and application to cloud climatology. J. Climate, 1 , 2039.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gedzelman, S. D., 1989: Cloud classification before Luke Howard. Bull. Amer. Meteor. Soc., 70 , 381395.

  • González, R. C., , Woods R. E. , , and Eddins S. L. , 2004: Digital Image Processing Using MATLAB. Prentice Hall, 609 pp.

  • Goodman, A. H., , and Henderson-Sellers A. , 1988: Cloud detection and analysis: A review of recent progress. Atmos. Res., 21 , 203228.

  • Houghton, J. T., , Ding Y. , , Griggs D. J. , , Noguer M. , , Van Der Linden P. J. , , Dai X. , , Maskell K. , , and Johnson C. A. , 2001: Climate Change 2001: The Scientific Basis. Cambridge University Press, 881 pp.

    • Search Google Scholar
    • Export Citation
  • Johnson, R. W., , Hering W. S. , , and Shields J. E. , 1989: Automated visibility and cloud cover measurements with a solid-state imaging system. Tech. Rep., University of California, San Diego, Scripps Institution of Oceanography, Marine Physical Laboratory, SIO Ref. 89-7, GL-TR-89-0061, 128 pp.

  • Kassianov, E., , Long C. N. , , and Christy J. , 2005: Cloud-base-height estimation from paired ground-based hemispherical observations. J. Appl. Meteor., 44 , 12211233.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Long, C. N., 2005: Accounting for circumsolar and horizon cloud determination errors in sky image inferral of sky cover. Proc. 15th Atmospheric Radiation Measurement (ARM) Science Team Meeting, Daytona Beach, FL, U.S. Dept. of Energy. [Available online at http://www.arm.gov/publications/proceedings/conf15/extended_gbs/long_cn2.pdf].

  • Long, C., , Sabburg J. , , Calbó J. , , and Pagès D. , 2006: Retrieving cloud characteristics from ground-based daytime color all-sky images. J. Atmos. Oceanic Technol., 23 , 633652.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lu, D., , Huo J. , , and Zhang W. , 2004: All-sky visible and infrared images for cloud macro characteristics observation. Proc. 14th Int. Conf. on Clouds and Precipitation, Bologna, Italy, Institute of Atmospheric Sciences and Climate, 1127–1129.

  • Martins, F. R., , Souza M. P. , , and Pereira E. B. , 2003: Comparative study of satellite and ground techniques for cloud cover determination. Adv. Space Res., 32 , 22752280.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mason, N., , and Hughes P. , 1998: An Introduction to Environmental Physics. Taylor and Francis, 463 pp.

  • Pagès, D., , Calbó J. , , Long C. N. , , González J-A. , , and Badosa J. , 2002: Comparison of several ground-based cloud detection techniques. Proc. XXVII General Assembly, Nice, France, European Geophys. Soc.

  • Parisi, A. V., , Sabburg J. , , and Kimlin M. J. , 2004: Scattered and Filtered Solar UV Measurements. Advances in Global Change Research Series, Vol. 17, Kluwer Academic, 195 pp.

    • Search Google Scholar
    • Export Citation
  • Pfister, G., , McKenzie R. L. , , Liley J. B. , , Thomas A. , , Forgan B. W. , , and Long C. N. , 2003: Cloud coverage based on all-sky imaging and its impact on surface solar irradiance. J. Appl. Meteor., 42 , 14211434.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sabburg, J., , and Wong J. , 1999: Evaluation of a ground-based sky camera system for use in surface irradiance measurement. J. Atmos. Oceanic Technol., 16 , 752759.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sabburg, J., , and Long C. N. , 2004: Improved sky imaging for studies of enhanced UV irradiance. Atmos. Chem. Phys., 4 , 25432552.

  • Salvador, R., , Calbó J. , , and Millán M. M. , 1999: Horizontal grid size selection and its influence on mesocale model simulations. J. Appl. Meteor., 38 , 13111329.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Seiz, G., , Baltsavias E. P. , , and Gruen A. , 2002: Cloud mapping from the ground: Use of photogrammetric methods. Photogramm. Eng. Remote Sens., 68 , 941951.

    • Search Google Scholar
    • Export Citation
  • Shields, J. E., , Johnson R. W. , , Karr M. E. , , Burden A. R. , , and Baker J. G. , 2003: Daylight visible/NIR whole sky imagers for cloud and radiance monitoring in support of UV research programs. Proc. SPIE, 5156 , 155166.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Singh, M., , and Glennen M. , 2005: Automated ground-based cloud recognition. Pattern Anal. Applic., 8 .doi:10.1007/s10044-005-0007-5.

  • Souza-Echer, M. P., , Pereira E. B. , , Bins L. S. , , and Andrade M. A. R. , 2006: A simple method for the assessment of the cloud cover state in high-latitude regions by a ground-based digital camera. J. Atmos. Oceanic Technol., 23 , 437447.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tooman, T. P., 2003: Whole sky imager retrieval guide. Atmospheric Radiation Measurement Program Tech. Rep. ARM TR-011.1, 109 pp. [Available online at http://www.arm.gov/publications/tech_reports/arm-tr-011-1.pdf.].

  • WMO, 1975: International Cloud Atlas. Vol. I. World Meteorological Organization, 155 pp.

  • WMO, 1987: International Cloud Atlas. Vol. II. World Meteorological Organization, 212 pp.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 216 216 50
PDF Downloads 138 138 36

Feature Extraction from Whole-Sky Ground-Based Images for Cloud-Type Recognition

View More View Less
  • 1 Department of Physics, and Institute of the Environment, University of Girona, Girona, Spain
  • | 2 Department of Biological and Physical Sciences, Faculty of Sciences, University of Southern Queensland, Toowoomba, Queensland, Australia
© Get Permissions
Restricted access

Abstract

Several features that can be extracted from digital images of the sky and that can be useful for cloud-type classification of such images are presented. Some features are statistical measurements of image texture, some are based on the Fourier transform of the image and, finally, others are computed from the image where cloudy pixels are distinguished from clear-sky pixels. The use of the most suitable features in an automatic classification algorithm is also shown and discussed. Both the features and the classifier are developed over images taken by two different camera devices, namely, a total sky imager (TSI) and a whole sky imager (WSC), which are placed in two different areas of the world (Toowoomba, Australia; and Girona, Spain, respectively). The performance of the classifier is assessed by comparing its image classification with an a priori classification carried out by visual inspection of more than 200 images from each camera. The index of agreement is 76% when five different sky conditions are considered: clear, low cumuliform clouds, stratiform clouds (overcast), cirriform clouds, and mottled clouds (altocumulus, cirrocumulus). Discussion on the future directions of this research is also presented, regarding both the use of other features and the use of other classification techniques.

Corresponding author address: Dr. Josep Calbó, Dept. of Physics, University of Girona, Campus Montilivi, EPS-II, 17071 Girona, Spain. Email: josep.calbo@udg.es

Abstract

Several features that can be extracted from digital images of the sky and that can be useful for cloud-type classification of such images are presented. Some features are statistical measurements of image texture, some are based on the Fourier transform of the image and, finally, others are computed from the image where cloudy pixels are distinguished from clear-sky pixels. The use of the most suitable features in an automatic classification algorithm is also shown and discussed. Both the features and the classifier are developed over images taken by two different camera devices, namely, a total sky imager (TSI) and a whole sky imager (WSC), which are placed in two different areas of the world (Toowoomba, Australia; and Girona, Spain, respectively). The performance of the classifier is assessed by comparing its image classification with an a priori classification carried out by visual inspection of more than 200 images from each camera. The index of agreement is 76% when five different sky conditions are considered: clear, low cumuliform clouds, stratiform clouds (overcast), cirriform clouds, and mottled clouds (altocumulus, cirrocumulus). Discussion on the future directions of this research is also presented, regarding both the use of other features and the use of other classification techniques.

Corresponding author address: Dr. Josep Calbó, Dept. of Physics, University of Girona, Campus Montilivi, EPS-II, 17071 Girona, Spain. Email: josep.calbo@udg.es

Save