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Estimating long‐wave radiation at the Earth's surface from measurements of specific humidity
Author(s) -
Rosa Rafael,
Stanhill Gerald
Publication year - 2014
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/joc.3793
Subject(s) - environmental science , humidity , satellite , atmospheric sciences , climatology , calibration , radiation , residual , root mean square , meteorology , geography , geology , mathematics , statistics , physics , algorithm , quantum mechanics , astronomy
The relationship between specific humidity ( q ) and down‐welling long‐wave radiation (E l↓ ) was investigated on a daily, monthly and annual basis for 39 widely distributed sites of the Baseline Surface Radiation Network ( BSRN ) and validated using two additional BSRN sites. A power relationship between E l↓ and q was fitted to the data for each site; the constant did not change significantly with time and geographic location. Neither the mean value of q nor the residual value of E l↓ changed significantly between 1998 and 2011, suggesting the applicability of the relationship over periods without large changes in the Earth's temperature and/or concentration of H 2 O . The root mean square error for both the calibration and validation sites was comparable to that reported for both direct measurements and satellite‐derived estimates for daily, monthly and annual periods. The power relationships were weaker for three tropical sites located in the Pacific Ocean, where the seasonal variation in q was smaller than at the other sites. For the remaining stations, a common power relationship, E l↓ = 212.64 q 0.22 , enabled monthly values of E l↓ to be accurately estimated from widely available measurements of air temperature, humidity and pressure at the Earth's surface.