 Rudimentary Aspects of Geology (before we proceed):

EARTH'S SHALLOW SPHERES

(Ref: Chapter 3 Schlesinger, Chapter 3 Turekian)

ATMOSPHERE AND OCEANS (COMPOSITION/STRUCTURE)

Why Study?

Basis for understanding El Nino, Ozone, Green House Warming, Pollution Transport and Residence Time

FUNDAMENTALS:

Basic Structure of the atmosphere:

THERMOSPHERE (185 to hot)

Mesopause @ 86 km

MESOSPHERE (270 to 185 degK or -5 to -90 degC)

Stratopause @ 50 km

STRATOSPHERE (ozone, responsible for T-reversal from troposphere)

210 to 270 degK (-65 to -5 degC)

Tropopause @ 15 km (vary seasonally and with latitude)

TROPOSPHERE (air we breath, weather, 80 % of the total atm mass) 290 to 210 degK (15 to -65 deg-C)

Imagine installing a thermometer in a balloon. Each "pause" reflects a T change and the atmosphere partitioned by these "pauses" are named troposphere, stratosphere, mesosphere, thermosphere.

TROPOSPHERE:

How tropospheric thermal structure controls weather patterns?

Hadley cells à two direct ones are the tropical and polar circulation patterns that also drive the indirect circulation between 30 and 50 deg latitude. This "indirect circulation" controls prevailing winds and weather patterns in North America.

Coriolis effect/force (sketch Earth's rotation)à in the northern hemisphere, everything that moves down or up in latitude swings to the RIGHT (at the southern hemisphere, they swing to the left). So the northward swing of the indirect Hadley from 30 to 50 deg causes this to swing to the right, resulting in a dominant westerly air movement (from west to east).

For the southern hemisphere, surface tropical circulation veers to the left as the equator is approached. This causes a dominant easterly near the equator, which reinforces the easterly from the northern hemisphere (hence the easterly equatorial currents).

Modified by land-sea distribution, vegetation, albedo, topography, local

COMPOSITION (of the dry troposphere à 99.9 % N₂ (78.1), O₂ (20.9), Ar (0.9). Balance is:

N₂ (78.1)

O₂ (20.9)

Ar (0.9)

CO2 (350 ppm or 0.035 %)

Neon (18.1 ppm)

Helium (5.2 ppm)

Methane (1.4 ppm)

Hydrogen (0.5 ppm)

NO_x (0.3 ppm)

H₂O (don't forget) (0.33 % by volume)

CFCs

Ozone (comparable to NO_x)

aerosols

STRATOSPHERE (20 km):

20 km (12.5 miles) is not that far away:

I live in Clifton Park, exactly 20 km away from here.

High planes (39,000 feet à 12 km). Others just around 15 km. Supersonic jets >20 km.

It is obviously not far enough away - we sent CFCs up there. Volcanoes can eject dust to it directly.

Key issue is OZONE, produced from photolytic reactions involving O₂.

FIGURE (O2, N2, H2O etc. decreasing, but O₃ and O showing maxima at 30 and 90 km, respectively)

WHAT DETERMINES TRACE CHEMISTRY OF ATMOSPHERE?

Sources, sinks, reservoir, mass, mass fluxes, residence times.

Explain the relationships between all these!

Residence time? IF I asked you to estimate the average RESIDENCE TIME of undergraduates or graduate students at RPI, how would you suggest we do it?

Total number of undergraduate/graduates per year or

Residence Time (t)= Reservoir Content/Flux

This is the way of the atmosphere, oceans and any reservoir (FIGURE 3.4 Schlesinger).

Formally: MRT = Mass/flux

(Total Mass of ATMOSPHERE: 5.136x1021 grams)

MRT (1/fractional turnover. 1/9.3 days = 0.11 or 11 percent turnover)

Water 9-13 days variable 11% turnover

O₂ 10,000 years homogenous

CO₂ 50-200 years(?) homogenous

O₃ days variable

CH₄ 10 years

Hydrocarbons 1-100 days

SO₂ 14 days

NO_x 1 day very variable 100% turnover

NH₃ 14 days

CFC 130

CFC12 150

WHAT ARE THE IMPLICATIONS OF THIS to CLEAN UP? If we bring greenhouse gas production to 1990 level now, how long more do we have to feel the effect of increased emission from 1990-1991? The answer depends on the residence times!

l What processes are we talking about in terms of sources and sinks:

Sources - (1) emission and (2) chemical production (internal)

(emission - combustion, biochemical, industrial, volcanoes)

Sinks - (3) "deposition" (incl. dissolution, uptake by weathering as in CO₂), (4) chemical loss.

NON STEADY STATE:

M (kg) mass of X in atmosphere

P (kg/yr) total production rate (all sources, (1) + (2))

L (kg/yr) total loss rate (all sinks, (3) + (4))

dM/dt (kg/yr) non-steady-state change in mass of X in atmosphere/yr

dM/dt = P - L

l in steady state: t (residence time) is M/P or M/L, dM/dt = 0

l in non-steady-state: dM/dt ¹ 0, but t can be defined as M/L

l Physical Redistribution/Mixing (Dispersion from point sources, interhemispheric exchange). (1) HORIZONTAL (tropospheric), (2) VERTICAL (intra-tropospheric - 1 month; trop to strat -10 yrs; strat to trop - 2 years). Handout FIGURE.

This explains vertical and horizontal variations, depending on residence time of species (Jacob Figures).