Influences of the clearness index for the whole spectrum and of the relative optical air mass on UV solar irradiance for two locations in the Mediterranean area, Valencia and Cordoba

Abstract

Abstract. Ultraviolet solar irradiance (290-385 nm) was analyzed in Valencia and IntroductionUltraviolet solar radiation has a significant influence on the Earth's atmosphere. In the stratosphere the absorption of ultraviolet radiation causes an increase of the air temperature in the upper atmospheric layers and is the origin of the existence and variability of stratospheric ozone. On the surface, UV solar radiation represents a small part of the spectrum, although it is an important part because of its biological and photochemical effects. Thus a clear awareness of its availability and its variation, both temporal and spatial, is of great importance in many research areas: (1) Several studies have been conducted to quantify the attenuation of UV radiation by clouds. Factors such as cloud location, percent cover, cloud optical thickness, liquid water content, and particle distribution make it difficult to develop a quantitative relationship relating cloud properties to the attenuation of UV radiation. Some authors [Zavodska and Reichrt, 1985] classify the daily total and UV radiation measurements using the cloud amount as a parameter. Cloud cover is not a very objective measurement because it may be related to very different sky conditions, depending on the relative Sun-cloud position. In this sense, Estupi•an et al. [1996] showed that for the same cloud cover, reductions of up to 99% or increases of up to 27% of UV radiation may be produced with respect to the same measurement on clear days in terms of whether or 4759

Total ozone and solar erythemal irradiance in southwestern Spain: Day‐to‐day variability and extreme episodes

“…The decrease in the clearness of the atmosphere is mainly associated to the cloudiness as first factor of attenuation [Alados-Arboledas et al, 2003]. The aerosols may be considered as secondary factor since its influence over the clearness variability is lower than the clouds influence [Cañada et al, 2000]. In order to guarantee the simultaneity of UVER and clearness index measurements, global solar irradiance (310-2800 nm) was measured by a CM-6B pyranometer (Kipp&Zonen) co-located besides the UV-S-E-T erythemal radiometer and recording simultaneously.…”

The erythemal clearness index for Valencia, Spain

“…htm). This index has been used subsequently by other authors (Foyo-Moreno et al, 1999Cañada et al, 2000;Ogunjobi and Kim, 2004;Kudish et al, 2005;Retalis et al, 2005).…”

Selection of cloudless sky conditions by applying solar global ultraviolet irradiance measurements

“…For the UV band it was called k tUV , and it was correlated with broadband k t , UV, and broadband irradiance measurements (Foyo Moreno et al 1999, Martínez Lozano et al 1994, Martínez Lozano et al 1999, Cañada et al 2000, Cañada et al 2003, Ogunjobi and Kim 2004, Bo et al 2010). But it is important to remark that the extraterrestrial solar constant between the wavelengths 290295 to 385 nm, obtained from the spectrum of Gueymard (2004), reaches a value of 83.80280.985 W/m 2 .…”

“…The SRGV carried out periodic calibrations of the above instruments using procedures recommended by the manufacturers, as can be seen in Cañada et al (2000 andCañada et al 2003). The broadband pyranometers were compared yearly against a reference Eppley PSP especially kept for calibrations, and the calibration constant had remained practically constant.…”