Geographia Polonica (2026) vol. 99, iss. 3
Statistical model of diffuse solar radiation for temperate climate of Central Europe
Geographia Polonica (2026) vol. 99, iss. 3, pp. 393-404 | 
Full text
doi: https://doi.org/10.7163/GPol.0333
Abstract
The studies of solar radiation, its intensity, and its structure are among the key issues addressed by meteorologists and climatologists. The inflow of solar radiation is crucial to the functioning of the Earth’s climate system. Currently, the most commonly observed characteristic of solar radiation is its global value (Kglob). However, for numerous application studies e.g. in human bioclimatology, agroclimatology, solar energy or urban climate, there are required information on the seasonal pattern and spatial distribution of individual radiation fluxes: direct (Kdir), diffuse (Kdif), and reflected from the ground surface (Kref). Thus the aim of the current research is to propose a statistical model for determining the Kdif values for the climate zone of Central Europe based on available observations of global solar radiation. The model uses the Ångströmclearness index (ACI) which illustrates the attenuation of global solar radiation reaching the Earth’s surface relative to its intensity at the upper boundary of the atmosphere. The development of a statistical model consisted of two stages: model development and model verification with the use of the set independent observational data representing lowland area of Poland (Dfb climate zone) as well as Beskid Sądecki Mts. (Dfc climate zone). The applicability of the model was also tested for other climate zones (southern Vietnam and central Mongolia). The results indicate that the proposed ACI-based model accurately approximates the amount of diffuse radiation for the lowland region of Central Europe. The method provides the satisfactory Kdif approximation in mountainous regions. The study results suggest also that the proposed ACI-based Kdif estimation model can be applied to other climate zones as tested for Aw zone of southern Vietnam, and Csa zone of central Mongolia.
Keywords: diffuse radiation fraction, Central Europe, statistical modelling
[k.blaz@twarda.pan.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences Twarda 51/55, 00-818 Warsaw: Poland
