The figure above shows the environmental temperature profile with wet and dry ad

Question

The figure above shows the environmental temperature profile with wet and dry adiabatic lapse rate profiles superimposed. To approximately what altitude will a parcel of pollution rise adiabatically from the surface in unsaturated air if the parcel's initial temperature is 25 degree C? What if its initial temperature is 30 degree C? In the figure above, determine the following quantities: inversion base height, inversion top height, inversion base temperature, inversion top temperature, mixing depth. Why do ozone mixing ratios peak in the afternoon, even though mixing depths are usually maximum in the afternoon? Summarize the meteorological conditions that tend to enhance photochemical smog buildup in an area. If emissions did not change with season, why might CO and aerosol particle concentrations be higher in winter than in summer?

Explanation / Answer

1)From the graph,dry adiabtic lapse rate is determined to be

20-10/0.75= 13.33°C per Km.

As long as the parcel of pollutant is warmer than the ambient temperature,it will continue to rise.

At a height of 0.7501Km ,the temperature of parcel of pollutant and the ambient air is about 15°C ,at any higher distance ,the temperature of ambient air will be more than the parcel of pollutant,so the parcel of pollutant will rise till a height of 0.7501Km .

For a parcel of pollutant at 30°C initially ,it can be seen that the temperature of the parcel of pollutant at 0.9Km =18.003°C,which is almost the same as the ambient temperature of layer 2 at that altitude. Hence,this pollutant parcel rises till the height of 0.9Km.

2) Inversion base height= 0.5Km

Inversion top height = 1Km

Inversion base temperature= 17°C

Inversion top temperature= 19°C

Mixing depth= 0.5Km

3)

Ozone formation is driven by two major classes of directly emitted precursors: nitrogen oxides (NOx) and volatile organic compounds (VOC). The relation between O3, NOx and VOC is driven by complex nonlinear photochemistry.

The relation between O3, NOx and VOC can be illustrated by isopleth plots , which shows peak O3 during the afternoon as a function of NOx and VOC mixing ratios or emission rates.This could be the reason why ozone mixing ratios peak in the afternoon.

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