Bruce W. Forgan

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Variations in solar radiation incident at Earth's surface profoundly affect the human and terrestrial environment. A decline in solar radiation at land surfaces has become apparent in many observational records up to 1990, a phenomenon known as global dimming. Newly available surface observations from 1990 to the present, primarily from the Northern(More)
There has been a long history of unexplained anomalous absorption of solar radiation by clouds. Collocated satellite and surface measurements of solar radiation at five geographically diverse locations showed significant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere than(More)
A general method for calibrating Sun photometers that relaxes the constraints on atmospheric conditions is described. Instead of requiring constant extinction conditions the method requires only that the relative aerosol size distribution remains constant during observations over a range of air masses during a morning or afternoon. Provided that the(More)
Cloud effects on UV Index (UVI) and total solar radiation (TR) as a function of cloud cover and sunny conditions (from sky images) as well as of solar zenith angle (SZA) are assessed. These analyses are undertaken for a southern-hemisphere mid-latitude site where a 10-years dataset is available. It is confirmed that clouds reduce TR more than UV, in(More)
A recent article by Schotland and Lea [Appl. Opt. 25, 2486 (1986)] discusses the errors in radiometer calibration by the Langley method and the detail required for very precise work. Their numerical methods on aerosol air mass can be simplified for use in the calibration of the worldwide sunphotometer network by using geometric considerations, assuming(More)
Monitoring ambient solar UVR levels provides information on how much there is in both real time and historically. Quality assurance of ambient measurements of solar UVR is critical to ensuring accuracy and stability and this can be achieved by regular intercomparisons of spectral measurement systems with those of other organizations. In October and November(More)
The basic requirement for any type of measurement in which comparisons are made in a scale, relative or absolute. The values used by the Committee on Solar Electromagnetic Radiation to derive the solar constant were in different radiometric scales. Assuming that only difference in radiometric references produced the wide scatter of individual values, an(More)
A technique for calibrating spectral radiometers measuring global (2π sr) irradiance using solar irradiance at the top of the atmosphere as the absolute irradiance reference is reported. In addition to providing a calibration at all measured wavelengths, the technique provides a direct measure of the angular response of the radiometer. For instruments that(More)
We present a new algorithm that simultaneously retrieves aerosol properties and land surface bidirectional reflectance distribution function (BRDF) over Australian from Advanced Along-Track Scanning Radiometer images. Three key components are addressed: (1) an analytical radiative transfer formulation, based on Green's function, linking top-of-atmosphere(More)
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