Download dry adiabatic lapse rate

A little diet advice:
A) The Japanese eat very little fat and suffer fewer heart attacks than the
British or Americans.
(B) On the other hand, the French eat a lot of fat and also suffer fewer
heart attacks than the British or Americans.
(C) The Japanese drink very little red wine and suffer fewer heart attacks
than the British or Americans.
(D) The Italians drink excessive amounts of red wine and also suffer fewer heart attacks
than the British or Americans
(E) Conclusion: Eat & drink what you like. It's speaking English that kills
you.
Air Quality
Atmospheric Composition
Nitrogen
Oxygen
Argon
Carbon Dioxide
Neon
Helium
78.0%
20.1%
0.9%
0.03%
0.002%
0.0005%
This is pure air. It does not exist. All air contains what we call pollutants.
We will define a pollutant as any material (gas, solid, or liquid) that, when
added to air at sufficiently high concentrations, will cause adverse effects.
Meteorology and Air Movement
Troposphere: 5 km thick
at poles, 18 km at
equator. Temperature
decreases with altitude.
More than 80% of the
mass of the atmosphere
Stratosphere: little
mixing. Temperature
profile inverted. High
ozone concentration.
Only 0.1% mass of air in
layers above stratosphere
Pollutants are generally only a problem in the troposphere. The
exception is ozone depletion problem in the stratosphere.
Pollutants may be either naturally produced or manmade and are
moved through the atmosphere by air currents we call wind.
Wind may be caused by many different phenomena ranging
from global wind patterns caused by the differential warming
and cooling of the earth as it rotates under the sun, to local
winds caused by differential temperatures between land and
water masses.
Wind not only moves pollutants horizontally, but also causes
the pollutants to disperse, reducing the pollutant
concentration as it moves away from the source.
The amount of dispersion is directly related to the stability of
the atmosphere, or how much vertical movement is taking place
As an imaginary parcel of air rises through the atmosphere it
experiences lower and lower pressure so it expands.
The expansion causes the temperature to drop (thermodynamics)
Ideally a parcel of air will cool at about 1oC/100 m or 5.4of/1000 ft
This is called the dry adiabatic lapse rate (adiabatic means no
heat transfer between the air parcel and the surrounding air). It is
independent of the atmospheric conditions and always holds for
dry air.
When there is moisture in the air the rate is different (called the
wet adiabatic lapse rate) because of the evaporation and
condensation of moisture in the atmosphere
The actual temperature versus elevation measurement is called the
prevailing lapse rate (solid lines below)
Superadiabatic lapse rate (or strong lapse rate) is when the actual atmospheric
temperature drops more than 1oC/100 m
Subadiabatic lapse rate (weak lapse rate) is when the actual temperature drops
less than 1oC/100 m
A special case of the weak lapse rate is called an inversion. This is where
warm air is above cool air
If superadiabatic conditions apply, this atmosphere is called unstable.
If Subadiabatic conditions exist, especially inversions conditions the
atmosphere is called stable
Example
A stack 100 m tall emits a plume at 20oC. The prevailing lapse rates are shown
in the figure below. How high will the plume rise (if we assume dry adiabatic
conditions)?
The prevailing lapse rate is
subadiabatic to 200 m and there
is an inversion above 200 m.
The smoke at 20oC finds itself
surrounded by colder air
(18.6oC) so it will rise. As it
rises it cool, so that at 200 m it
is 19oC. At about 220 m, the
surrounding air is at the same
temperature (about 18.7oC) and
so the smoke will stop rising.
Inversions
Subsidence inversion occurs when a large warm air mass moves over a cooler air mass
A radiation inversion occurs when air close to the ground loses heat at night as the
earth cools, causing the air close to the ground to be cooler than the air above it.
Often
accompanied by
fog
Major Air pollutants
Particulates
Dust: solid particle that:
a)
Entrained by process gases
directly from material handling
or processing
b)
Direct offspring of parent
material undergoing a
mechanical operation
c)
Entrained materials used in a
mechanical operation
Fume: solid particle, often a metal oxide, formed by the condensation of vapors
by sublimation, distillation, calcination, or chemical reaction processes
Mist: entrained solid particles formed by the condensation of a vapor
Smoke: entrained solid particles formaedas the result of incomplete
combustion of carbonaceous materials.
Spray: liquid particle formed by the atomization of a parent liquid
Measurement of Particles
High-Volume Sampler (Hi-vol)
Total Suspended particulates (TSP)
PM10
Respirable particulates
Gaseous Pollutants
Measurement of Gases