Accession Number:

ADA518985

Title:

Measuring Overcast Colors with All-Sky Imaging

Descriptive Note:

Journal article

Corporate Author:

NAVAL ACADEMY ANNAPOLIS MD MATHEMATICS AND SCIENCES DIV

Personal Author(s):

Report Date:

2008-04-01

Pagination or Media Count:

11.0

Abstract:

Digital images of overcast skies as seen from the earths surface open new windows onto the angular details of overcast colors and visible-wavelength spectra. After calibration with a spectroradiometer, a commercial CCD camera equipped with a fisheye lens can produce colorimetrically accurate all-sky maps of overcast spectra. Histograms and azimuthally averaged curves of the resulting chromaticities show consistent, but unexpected, patterns in time-averaged overcast colors. Although widely used models such as LOWTRAN7 and MODTRAN4 cannot explain these characteristic patterns, a simple semiempirical model based on the radiative transfer equation does, and it provides insights into the visible consequences of absorption and scattering both within and beneath overcasts.

Subject Categories:

  • Meteorology
  • Electrical and Electronic Equipment
  • Test Facilities, Equipment and Methods
  • Miscellaneous Detection and Detectors
  • Atomic and Molecular Physics and Spectroscopy
  • Astronomy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE