Factors affecting the ratio of erythemal UV (UVER) to broadband (G) irradiance were investigated in this study. Data from four solar monitoring sites in Thailand, namely Chiang Mai, Ubon Ratchathani, Nakhon Pathom and Songkhla were used to investigate the UVER/G ratio in response to geometric and atmospheric parameters. These comprised solar zenith angle, aerosol load, total ozone column, precipitable water and clearness index. A modeling scheme was developed to isolate and examine the effect of each individual environmental parameter on the ratio. Results showed that all parameters with the exception of solar zenith angle and clearness index influenced the ratios in a linear manner. These results were also used to develop a semi-empirical model for estimating hourly erythemal UV irradiance. Data from 2009 to 2010 were used to construct the ratio model while validation was performed using erythemal UV irradiance at the above four sites in 2011. The validation results showed reasonable agreement with a root mean square difference of 13.5% and mean bias difference of − 0.5%, under all sky conditions and 10.9% and − 0.3%, respectively, under cloudless conditions.

Item Type:	Refereed Article
Keywords:	UV radiation, erythemal solar ultraviolet, broadband radiation, empirical model, sensitivity
Research Division:	Earth Sciences
Research Group:	Atmospheric Sciences
Research Field:	Atmospheric Radiation
Objective Division:	Environment
Objective Group:	Atmosphere and Weather
Objective Field:	Atmosphere and Weather not elsewhere classified
Author:	Nunez, M (Dr Manuel Nunez)
ID Code:	98452
Year Published:	2014
Web of Science® Times Cited:	1
Deposited By:	Geography and Environmental Studies
Deposited On:	2015-02-17
Last Modified:	2017-10-30
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