Page 294 - Fundamentals of Air Pollution

250 17. The Physics of the Atmosphere

Fig. 17-3. Annual mean radiation by latitude. Note that the latitude scale simulates the
amount of the earth's surface area between the latitude bands. Incoming radiation is that
absorbed by earth and atmosphere. Outgoing radiation is that leaving the atmosphere. Source:
2
2
1
After Byers (2) (1 cal cm~ min" = 697.58 W m~ ).
solar radiation and the radiation escaping to space. This balance is depicted
in Fig. 17-4.

II. STABILITY AND INSTABILITY

Vertical air motions affect both weather and the mixing processes of
importance to air pollution. Upward vertical motions can be caused by
lifting over terrain, lifting over weather fronts, and convergence toward
low-pressure centers. Downward vertical morions can be caused by sinking
to make up for divergence near high-pressure centers. One must know
whether the atmosphere enhances or suppresses these vertical motions to

TABLE 17-3
Poleward Flux of Heat across Latitudes
19
(10 kcal per year)"
Latitude Flux Latitude Flux
10 1.21 50 3.40
20 2.54 60 2.40
30 3.56 70 1.25
40 3.91 80 0.35
" Adapted from Table 12 of Sellers (3).