Accession Number : ADA260175


Title :   RTNEPH Total Cloud Cover: Validation Study


Descriptive Note : Project rept.


Corporate Author : AIR FORCE ENVIRONMENTAL TECHNICAL APPLICATIONS CENTER SCOTT AFB IL


Personal Author(s) : Lowther, Ronald P ; Surmeier, Mark T ; Hartman, Richard W ; Coffin, Charles R ; Warren, Anthony J


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a260175.pdf


Report Date : Oct 1991


Pagination or Media Count : 51


Abstract : In 1983, the United States Air Force Global Weather Central (AFGWC) implemented a new model to map and store an analysis of worldwide cloud-cover derived from surface and satellite data. This model, the designated the Real- Time Nephanalysis (RTNEPH) model, contains analyses of total sky cover, cloud bases, and cloud heights. Studies assessing the accuracy of the RTNEPH database have, up to now, been limited. In this work, the RTNEPH total sky-cover database is evaluated against independent surface observations. Since the RTNEPH algorithm heavily weights available surface observations, this was not a simple task; more than 500,000 independent surface and RTNEPH observations had to be matched and evaluated. Frequency distributions of the differences in these two sources were computed and stratified by latitude, season, time of day (day versus night), and age. Finally, statistical tests were run to obtain quantitative assessments of the results. In general, the RTNEPH total sky cover compared favorably with the surface reports, but there were differences. Certain biases in the RTNEPH were also identified, most notably the underestimation of cloud cover in arctic regions and the poor resolution of RTNEPH in regions where the airways surface observation code is used.


Descriptors :   *CLOUD COVER , TEST AND EVALUATION , DATA BASES , ALGORITHMS , FREQUENCY , CLOUDS , GLOBAL , WEATHER , MODELS , REAL TIME , DISTRIBUTION , STATISTICAL TESTS , OBSERVATION , METEOROLOGICAL DATA , ARTIFICIAL SATELLITES , METEOROLOGY , DATA STORAGE SYSTEMS , MAPS , LATITUDE , SEASONS , ARCTIC REGIONS , ATMOSPHERE MODELS , HEIGHT , CLIMATOLOGY


Subject Categories : Meteorology


Distribution Statement : APPROVED FOR PUBLIC RELEASE