Environmental Engineering FOURTH EDITION

Meteorology and Air Pollution 37 1

15% was removed by precipitation, and 25% blew away from Great Britain, heading

northwest toward Norway and Sweden.

CONCLUSION

Polluted air results from both emissions into the air and meteorological conditions

that control the dispersion of those emissions. Pollutants are moved predominantly by

wind, so that very light wind results in poor dispersion. Other conditions conducive to

poor dispersion are:

0 little lateral wind movement across the prevailing wind direction,

0 stable meteorological conditions, resulting in limited vertical air movement,

0 large differences between day and night air temperatures, and the trapping of cold

0 fog, which promotes the formation of secondary pollutants and hinders the sun

0 high-pressure areas resulting in downward vertical air movement and absence of

air in valleys, resulting in stable conditions,

from warming the ground and breaking inversions, and

rain for washing the atmosphere.

Air pollution episodes can now be predicted, to some extent, on the basis of meteo-
rological data. The EPA and many state and local air pollution control agencies are
implementing early warning systems, and acting to curtail emissions and provide
emergency services in the event of a predicted episode.

PROBLEMS

18.1 Consider the following temperature soundings: ground level, 21°C; 500m,

20°C; 600 m, 19°C; 1000 m, 20°C. If we release a parcel of air at 600 m, will it rise or

sink or remain at 600 m? If a 70-m stack releases a plume with a temperature of 30"C,

what type of plume results? How high does the plume rise?

18.2 A weather station located at an elevation of 10 m above ground measures

wind speed at 1.5 ds. Plot the wind speed vs elevation for the meteorologic conditions

given in Table 18-2.

18.3 Plot the ambient lapse rate given the following temperature sounding:

Elevation (m) Temperature ("C)

0

50

100

150

200

250

300

20

15

10

15

20

15

20