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Estimation of direct solar beam irradiance from measurements of the duration of bright sunshine
Author(s) -
Stanhill G.
Publication year - 1998
Publication title -
international journal of climatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.58
H-Index - 166
eISSN - 1097-0088
pISSN - 0899-8418
DOI - 10.1002/(sici)1097-0088(19980315)18:3<347::aid-joc239>3.0.co;2-o
Subject(s) - sunshine duration , irradiance , environmental science , solar irradiance , climatology , atmospheric sciences , meteorology , relative humidity , optics , geography , physics , geology
Measurements of the duration of bright sunshine, n , using the Campbell‐Stokes sunshine recorder are shown to be highly correlated with those obtained using a normal incidence pyrheliometer to measure direct irradiance, I , at two sites in the very dissimilar radiation climates of Israel and Ireland. The statistical relationships are presented for a variety of time‐scales, ranging from annual to hourly totals. For individual mean monthly values the common linear relationship was I =2.209 n −0.955 MJ m −2 day −1 , with a standard error of estimate of ±1.368 MJ m −2 day −1 and a coefficient of determination of r 2 =0.969. Analysis of long‐term series of sunshine hour measurements indicate that reductions in direct irradiance have occurred at both measurement sites. © 1998 Royal Meteorological Society