Changes in solar radiation energy and its relation to monthly average temperature

Abstract

In the analysis of problems of surface evapotranspiration, the conclusion is that the potential and actual values of water surface evaporation and those of transpiration of plants are different in different months of the year, depending on monthly temperature averages. In the spring and early summer evapotranspiration has higher values than in the autumn months.The analysis of the changes of monthly values of solar radiation energy including global radiation, radiation energy reaching flat surfaces and specific energy that can be utilized by solar cells give the result that the energy values estimated for late summer and autumn on the basis of spring and early summer changes in radiation energy show a deficit. As an annual average, actual values “fall behind” potential values by 9 – 17% and if the deficit is projected to autumn months involved, the extent of the “shortage” is 23 – 30%. Besides this energy deficit, the decreased evapotranspiration also results from the vegetation cycle of plants and from the fact that in summer months there can be a shortage of groundwater, too.

Keywords

• solar radiation
• evapotranspiration
• temperature averages