Atmospheric Structure

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# Atmospheric Structure - PowerPoint PPT Presentation

Atmospheric Structure . Theodore S. Dibble Chemistry Department SUNY-Environmental Science and Forestry Syracuse, NY. Temperature defines regions of the atmosphere. Pressure (mbar). Altitude (km). Pressure and the Barometric Law.

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## Atmospheric Structure

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Presentation Transcript

Atmospheric Structure

Theodore S. Dibble

Chemistry Department

SUNY-Environmental Science and Forestry Syracuse, NY

Pressure and the Barometric Law

P = Poe-Mgh/RTapplies to individual compounds at equilibrium

Atmosphere not at equilbrium!

Below 130 km, long lived gases have constant mole fraction

Pressure behaves as if M =28.8 g/mole (78:21:1 N2:O2:Ar)

Exercise: Calculate the partial pressure of

O2 at 6 km if PTotal is 0.5 bar.

Atmospheric Composition

How can chemistry (reactions) occur?

Units

Part per million, etc. by volume = mole fraction

1 ppmv = mole fraction 1 x 10-6

1 ppbv = mole fraction 1 x 10-9

1 pptv = mole fraction 1 x 10-12

Molecules/cm3 (use ideal gas law)

1 atm = 2.5 x 1019 molecules cm-3 at 298 K

if PTotal = 1 atm, 1 ppmv = 2.5 x 1013 molecules cm-3

PTotal = 1 Torr  3.2 x 1016 molecules cm-3

At 220 K, 1 Torr = 4.3 x 1016 molecules cm-3

3 months

2 weeks

2 years

Mixing Times in Troposphere

Mixing in Troposphere

Vertical

ground to tropopause in 1 week

Horizontal

Around a latitude line in weeks

Mid-latitude to equator in months

Cross equator in 1 year

[CO] = 120 ppbv in N.H. and 60 ppbv in S.H.

Question: CO has a lifetime of ~2 months

Will it be evenly distributed over oceans and remote continental regions within the N.H.?

Key Points
• Temperature structure
• Most of mass in troposphere
• Chemistry competes with transport