Intensity, solar radiation, equation

The energy source for the entire system is solar radiation EA(t,p, X,z), the intensity of which depends on time t, latitude p, longitude A, and depth z. The equation that describes the biomass dynamics of living elements is... 

Different variables affect the intensity of solar radiation. As the emission of solar radiation is considered constant, the summer sun is stronger than the winter sun, the sun on the equator stronger than the sun in Lapland, and the midday sun burns more than the afternoon sun. Eog does not slow down UV penetration, but urban pollution is, on the contrary, a powerful sunblock because of the presence of aromatic hydrocarbons, which make excellent UV blocks. Altitude in itself has less influence than the angle of incidence, but snow, on the other hand, reflects 85% of UV rays, whereas dry sand only reflects 17%, water 5% and grass 2%. Therefore, places lying between snow-covered mountains on a very sunny day are particularly dangerous. 

Steele (1956) (6) found that the steady-state assumption did not apply to the seasonal variation of the phytoplankton population. Instead, he used two volume segments to represent the upper and lower water levels and kept the time derivatives in the equations. Thus, both temporal and spatial variations were considered. In addition, the differential equations for phytoplankton and zooplankton concentration were coupled so that the interactions of the populations could be studied, as well as the nutrient-phytoplankton dependence. The coefficients of the equations were not functions of time, however, so that the effects of time-varying solar radiation intensity and temperature were not included. The equations were numerically integrated and the results compared with the observed distribution. Steele applied similar equations to the vertical distribution of chlorophyll in the Gulf of Mexico (7). 

Diurnal and seasonal variations in solar intensity are, of course, of utmost importance to ecosystems. In the extreme polar regions there is no direct solar radiation at all for more than four months of the year, whereas near the equator the overall intensity of sunlight fluctuates less than 10% annually. The spectral energy distribution also varies with the season. For example, in July in the middle latitudes (ca. 40 ), the fraction of shorter-wave UV (290-315 nm) in the total solar radiation is more than three times higher than it is in December, due to the shorter path these easily scattered wavelengths have to traverse through the atmosphere. For similar reasons, shortwave UV is more intense at high elevations, particularly in the tropics where stratospheric ozone is less concentrated (Caldwell et al., 1980). 

Due to the interaction of solar radiation with molecules and particles of the atmosphere, the radiant flux decreases with the path x through the atmosphere (Fig. 2.12). Johann Heinrich Lambert showed in 1760 that the reduction of light intensity is proportional to the length of path x (or layer thickness) and the light (radiant flux) itself, A = x E, from which we derive the equation fIF... 

CIE publication No. 85 [197] provides data on the spectrum of sunlight under atmospheric conditions. A shorter version in the form of a table is included in ISO 4892 describing maximum global radiation at the equator [198]. Reference values for spectral solar radiation intensity on the ground are contained in ISO 9845 [199]. DIN EN 61725 [200] provides an analytic presentation for solar daytime radiation profiles [94]. 

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