The influence of cloudiness and atmospheric circulation on radiation balance and its components

Abstract

The article contains an analysis of the influence of cloudiness and atmospheric circulation on the components of radiation balance (Q*) using the example of measurements taken in an extra-urban area of Koniczynka near Toruń (Central Poland) in the years 2011–2018. The average annual value of Q* was 1,818.5 MJ·m−2 with a maximum of 352.3 MJ·m−2 in June, and negative values from November to January (December: −27.4 MJ·m−2). The shortwave radiation balance (S*) amounted to 3,129.2 MJ·m−2 and the longwave radiation balance (L*) was ˗1,310.7 MJ·m−2. In June the average solar irradiance (S↓) at midday was 600 W·m−2. The natural annual and diurnal course of Q* components, determined by astronomical factors, is disturbed by changes in cloudiness and inflow of various air masses. It has been found that an increase in cloudiness causes the amount of incoming solar radiation (S↓) to fall, thus decreasing the S* balance. Moreover, clouds restrict longwave radiation balance (L*), in particular, downward atmospheric radiation (L↓) increases. The opposite relationships of S* and L* affect Q* in individual months. The components of Q* are influenced by atmospheric circulation; it has been observed that anticyclonic types, characterised by smaller cloud amounts, favour a greater influx of (S↓) and—at the same time—greater emittance (L↑); however, Q* is then greater than in the case of cyclonic circulation. A statistically significant trend of Q* and its components has not been ascertained. A notable great year-on-year variability of Q*, ranging from 1,640.4 MJ·m−2 (in 2011) to 2,081.6 MJ·m−2 (in 2018), affects the environment. The changes are related to the cloudiness and the frequency of occurrence of different atmospheric circulation types. The role of snow cover is also important as snow reflects solar radiation which leads to the decrease of S* and—as a result—to a negative value of Q* in winter.