Long-wave radiation balances of grassy surface and bare soil in Wrocław

The paper goal is to show diurnal, seasonal and year to year variability of long-wave radiation balances of two contrasting types of active surfaces – grassy and bare soil in the context of bioclimatic and ecological role of plant areas in a big city. The analyses was conducted on example of Wroclaw (SW Poland) and the experimental results were obtained from about twelve-year period of measurements. The average annual values of fluxes of the main components of these long-wave balances reached: 368.6 W/m2 for the long-wave radiation of bare soil, 363.6 W/m2 for the long-wave radiation of grassy surface and 322.9 W/m2 for the downward atmospheric radiation. These differences between values of bare soil and grassy surfaces varied during the year from negative values in winter to positive values in spring and the summer. The final conclusion of the study is an important empirical argument for urban planning to extend share of plant areas in cities and urban agglomerations.