Short-term effects of aerosol on the layer near the ground in a cloudless atmosphere

The short-term effect of dense atmospheric haze upon the temperature regime of the lower atmosphere is predicted. This is accomplished by solving numerically approximate expressions of the equations of radiative transfer, heat conduction, eddy diffusion and wind motion. In the absence of advection, the influence of haze upon the vertical wind distribution is determined also. In order to visualize the effect of haze more clearly, it is assumed that clouds are completely absent during the prediction period. Four model cases are considered which differ only in roughness height and the geostrophic wind speed.

A mid-latitude winter-time situation is studied at which haze problems are particularly severe. The effect of haze is estimated by predicting the behavior of the air layer near the ground for a haze-free and severely turbid environment. The two situations are then compared to evaluate the effects produced by the presence of haze. Some calculations are carried out using the particular atmospheric model with ground haze concentration of 400 μg/m3, roughness height of 1 cm and geostrophic wind of 5 m/sec. For a winter-time prediction period, starting at the time of sundown, it is found that at sunrise of the first day, the surface temperature of the earth is about 2 degrees higher than one would find in the absence of any haze, other conditions remaining the same. If the haze continues to persist, the nocturnal temperature environment is reversed. It is found that the surface temperature is about 2°C and 4°C lower than the respective temperatures in haze-free air at sunrise of the second and third day of the prediction period.

Mid-day temperatures at the earth's surface are substantially lower in the hazy than in the haze-free atmosphere. After a prediction period of three days, a temperature difference of about 19 degrees is observed. Furthermore, the presence of haze has a pronounced effect on the daytime wind spirals.