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Corresponding Author
Randall Alliss
Randall Alliss Northrop Grumman IT - TASC
Session3 (Approaches for modeling atmospheric optical turbulence.)
Title'A Ten Year Cloud Climatology of the Hawaiian Islands as Derived by GOES'
AbstractCloud retrieval algorithms have been developed and applied to the current generation of National Oceanic and Atmospheric Administration (NOAA) Geostationary Environmental Operational Satellite (GOES) imagery to produce a twelve year climatology of cloudiness over the Continental United States (CONUS) and ten years over the state of Hawaii. The database contains cloud no cloud decisions at approximately fifteen minute and four kilometer resolution, respectively. Over 350,000 images have been processed over this twelve year period.
The GOES imager includes multi-spectral chan¬nels including one visible and four infrared. Cloud detec¬tion is accomp¬lished by modeling the radiance of the ground in the absence of clouds and comparing with the actual radiance values from the imagery. A composite cloud decision is formed by objectively com¬bining the results of the tests from the individual channels. The strength of using all bands as opposed to using a single band was demonstrated very early in the development. For example, low clouds radiating at a similar temperature to the earth are detectable at night with the use of the shortwave infrared channel. A combination of the visible and shortwave infrared channels helps to distinguish low and high clouds from snow cover.
To date, this database has been used to study the impacts of clouds on optical communications for the NASA – Jet Propulsion Laboratory. Since clouds adversely affect the trans¬mission of an optical communications link, a reliable communication system is only possible through the use of multiple geographically diverse ground stations. The relatively high spatial and temporal resolution of this GOES database makes it possible to study the cloud correlations between different locations.
Results produced by this database indicate a measurable variability in cloudiness over many reporting stations across CONUS as well as Hawaii during the 1995 – 2006 time period. Mean cloudiness varies from less than 30% in the dessert regions and the mountain peaks of Maui and the Big Island to greater than 70% in the Great Lakes region and Pacific Northwest. Results have been compared with cloudiness derived from a ground based Whole Sky Imager (WSI) for select locations and have produced very good agreement. This paper will present a climatology of cloudiness over the Hawaiian Islands including the summits of Mauna Kea and Haleakala.

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