Estimation of daily average values of the Ångström turbidity coefficient β using a Corrected Yang Hybrid Model

This paper aims to test a method for estimating daily values of atmospheric turbidity from non-specialized data, such as those obtained from agro-meteorological stations. This method allows estimating the spatial and temporal evolution of aerosols concentration in more places than just those in which direct measurements are available. The method is based on the Corrected Yang Hybrid Model (CYHM). The data used in the determination of errors between measured and estimated values of the daily Ångström turbidity coefficient β were recorded in Valencia, Spain, during 2009 and 2011. These data were global solar irradiance, direct solar irradiance, temperature, relative humidity and Aerosol Optical Depth (AOD) measured at an AERONET station. The errors are shown as a function of daily clearness index Kt, observing that as Kt decreased, the error of estimate β increased. Taking into account that the nominal error of the apparatus used to measure AOD has the same order of magnitude as the calculated errors and that most of the terms involved in the measurement of atmospheric transmittance phenomena have been estimated, the method produces results that are acceptable for general purposes. The method was applied to historical meteorological data recorded in Bogotá, Colombia. The daily values of atmospheric turbidity were estimated for 1983 and 1997, showing little changes in atmospheric turbidity between those years.