Global Analysis of Atmospheric Transmissivity Using Cloud Cover, Aridity and Flux Network Datasets

Atmospheric transmissivity (tau) is a critical factor in climatology, which affects surface energy balance, measured at a limited number of meteorological stations worldwide. With the limited availability of meteorological datasets in remote areas across different climatic regions, estimation of tau is becoming a challenging task for adequate hydrological, climatic, and crop modeling studies. The availability of solar radiation data is comparatively less accessible on a global scale than the temperature and precipitation datasets, which makes it necessary to develop methods to estimate tau. Most of the previous studies provided region specific datasets of tau, which usually provide local assessments. Hence, there is a necessity to give the empirical models for tau estimation on a global scale that can be easily assessed. This study presents the analysis of the tau relationship with varying geographic features and climatic factors like latitude, aridity index, cloud cover, precipitation, temperature, diurnal temperature range, and elevation. In addition to these factors, the applicability of these relationships was evaluated for different climate types. Thus, empirical models have been proposed for each climate type to estimate tau by using the most effective factors such as cloud cover and aridity index. The cloud cover is an important yet often overlooked factor that can be used to determine the global atmospheric transmissivity. The empirical relationship and statistical indicator provided the best performance in equatorial climates as the coefficient of determination (r(2)) was 0.88 relatively higher than the warm temperate (r(2) = 0.74) and arid regions (r(2) = 0.46). According to the results, it is believed that the analysis presented in this work is applicable for estimating the tau in different ecosystems across the globe.