Homework Assignment #6 Due Thursday, March 15,201s se the following atmospheric
ID: 288814 • Letter: H
Question
Homework Assignment #6 Due Thursday, March 15,201s se the following atmospheric aititude versus temperature data have been collected Altitude (m) 1 0 100 200 | 300 | 400 | 500 | 600 l Temperature 239223 700 8000 . For dry conditions, how high would air parcels rise trom the ground (elev. O km) t thair tialmperatures were 25 and 297 What does this behavior imply about air pollution concentrations for pollutants released at the ground, starting at various temperatures? h How high would you expect a plume to rise in the atmosphere with the above sounding it it is emitted at 25 C from a 150-m tall stack and the plume temperature changes at the dry adiabatic lapse rate? Would you expect the plume to be looping, coning, fanning, or fumigating, and why? [The plume shape occurs at the altitude that the plume first achieves neutral buoyancy with the surrounding airExplanation / Answer
a. Assuming dry adiabatic lapse rate of 10C/ km. Then the air parcel of initial temperatures of 25 C and 29 C would decrease its temperature with altitude as:
0 100 200 300 400 500 600 700 800 900 1000
25 25 24 23 22 21 20 19 18 17 16 15
29 29 28 27 26 25 24 23 22 21 20 19
Since the environment attains more temperature than the 25 C parcel above 400m, the parcel will rise up to 400m from the ground. Similarly, the environment attains more temperature than the 29 C parcel above 500m, the parcel will rise up to 500m from the ground. Note that equal temperatures of dry air and environment will cause neutral stability and such a case won't cause the parcel to rise. These scenarios imply that colder the initial temperature, the parcel will be trapped below the inversion layer, i.e 400 m, and more will be the concentration of air pollutants. Warmer the initial temperature more will be the height of the parcel, less will be the concentration of pollutants.
The sounding profile resembles option C, as the plume originates at a height of 150m causing the continuous lifting of plume until it reaches the same temperature (point of neutral buoyancy) as the environment, i.e at a height of about 550m. Since the atmosphere is unstable and traps the plume above stack height due to inversion above 400m, the plume shape should be fumigating.
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