Solar zenith angles Winter

FIGURE 3.22 Effect of latitude on solar zenith angle. On the scale of true solar time, also called apparent solar time and apparent local solar time, the sun crosses the meridian at noon. The latitudes and seasons represented are as follows I, 20°N latitude, summer solstice II, 35°N latitude, summer solstice III, 50°N latitude, summer solstice IV, 20°N latitude, winter solstice V, 35°N latitude, winter solstice VI, 50°N latitude, winter solstice (from Leighton, 1961). 

Calculated for typical winter conditions of a solar zenith angle of 70° and a surface reflectivity of 80% for a collimated incident light beam. 

The smaller the solar zenith angle is, the less atmosphere (particularly ozone) the total solar flux passes through before reaching the troposphere, and therefore the greater the incident flux. The solar zenith angle has its minimum in the summer and maximum in the winter. The variation of solar zenith angle with latitude for a given season is less important than the seasonal variation. 

The winter noontime values of n(0H), n(HC>2), and n(CH202) decrease by a factor 3.5 from those calculated for the summer. The primary cause is an increase in the solar zenith angle, which decreases the intensity of ultraviolet radiation required to produce 0(1D). Because of lower winter temperatures, n(H20) also decreases but... 

The monitored site lies between 47 20" northern latitude and 27 bO" eastern longitude (Figure 1). At this latitude incident solar zenith angles between the solar radiation and the Earth s surface of about 19 23 during the winter and 66°17 during the summer, at midday, are reached with a variation of about 47°. 

The photodissociation frequencies for several important trace species are shown in Figure 4.52 for specific conditions (winter at 40° latitude, solar maximum). The determination of these photolysis rates J at altitude z for solar zenith angle x is accomplished by the numerical methods described below. 

Tulsa during winter months, 0 Angle of incidence (Solar zenith angle)... 

FIGURE 3.13 Heating rate from absorption of solar radiation by ozone for solar zenith angles 00 = 0°, 60°, 80°. The solid curve is for an ozone distribution representative of equatorial conditions the dashed curve is representative of polar winter conditions. This calculation accounts for the change in ozone mixing ratio with altitude, whereas the analytical formula (3.52) assumes mixing ratio is constant with altitude. 

Figure IX-A-2c. Plot of the solar zenith angle as a function of latitude and local time for December 22, Winter solstice in the Northern Hemisphere. Note that the Sun is below the horizon for the entire 24 h period for locations at high latitudes (from Calvert et al., 2008).

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