Solar energy received by the earth is distributed over a large area near the poles than at the equator. Thus, the amount of energy received per unit area is more at the equator, which is consequently much warmer than the poles. In contrast, the outgoing radiation is distributed much more uniformly with latitude. For both of these situations to exist simultaneously, there must be a major transfer of heat energy from the equatorial regions towards the poles. This is accomplished through the motion of atmosphere known as winds. Pollutants in the air move with these winds. So one nation’s pollution can become its neighbors problem.
The surface of the earth with its covering, atmosphere and clouds, presents a very mixed reception to incoming solar radiations. Some of the solar energy is absorbed by air, some by clouds, some by earth, and some is reflected back into space , You may notice that the major part of the radiation is absorbed by the ground rather than by the atmosphere. This means that air is generally warmed from the bottom, i.e. by contact with the ground and not by direct radiation from the sun. So during daylight hours, the air nearest the ground is usually the warmest.
Although the major driving force of the air movements is the temperature difference, the topography of the area also has some effect on air movements and hence on pollution. Here we will discuss two localized phenomena, the land-sea breeze and the mountain-valley wind, which have a significant impact on local air pollution.
Coastal areas develop circulations driven by temperature differences between the land and the ocean. In the morning; the sun warms the land much more rapidly than it does the water. Warmer air over the land tends to rise and is replaced by the cooler air over the ocean creating the sea breeze. The sea breeze has an
impact on air pollution in two ways. First, it can play a major role in carrying pollution generated near the sea to inland areas. Second, if an evening land breeze has carried pollution out to sea, a morning sea breeze can bring the pollution back to the land.