Environmental Engineering FOURTH EDITION

356 ENVIRONMENTALENGINEERING

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eteomlogical data station

Figure 18-7. Pollution roses for SO2 concentrations greater than 250 pg/m3. The
four chemical plants are the suspected sources, but the roses clearly point to Plant 3,
identifying it as the primary culprit.

• Temperature ("C)

Figure 18-8. Ambient lapse rates and the dry adiabatic lapse rate.

When the ambient lapse rate is exactly the same as the dry adiabatic lapse rate,
the atmosphere has neutral stability. Superadiubutic conditions prevail when the air
temperature drops more than 9.8OCh (l0C/100m). Subadiubutic conditions pre-
vail when the air temperature drops at a rate less than 9.8OCllan. A special case of
subadiabatic conditions is the temperature inversion, when the air temperature actu-
ally increases with altitude and a layer of warm air exists over a layer of cold air.
Superadiabatic atmospheric conditions are unstable and favor dispersion; subadiabatic