Lecture 1: Composition & Structure of the Atmosphere (Ch1)

• Weather vs. Climate ( + web resources related to)

• Alberta – some useful facts re- weather & climate

• Composition of the atmosphere**

**

Weather: short-term, local phenomena

Climate: long term patterns (statistics: averages, extremes, frequencies of events…)

“Climate is what you expect but weather is what you get”

• weatheroffice.ec.gc.ca/charts/index_e.html

• weatheroffice.ec.gc.ca/city/pages/ab-50_metric_e.html

Rain shadow aridFarthest south, driest hot

Our weather discussions will usually focus on Central Alberta weather… here, the basic geography…

60 oN

49 oN

For estimating distances on the map its useful to know that this length is:

11o latitude

( each degree 111 km )

TIME

12 Zulu= 12 GMT= 12 UTC= 06 MDT

MSL: p 1000 mb, z 0 m

700 mb , z 3 km = 300 dam

500 mb , z 5.5 km = 550 dam

250 mb , z 10.5 km = 1050 dam (34,000 feet)

density 1 kg / m3

““Mandatory” (Conventional) Reporting/Analysis LevelsMandatory” (Conventional) Reporting/Analysis Levels

Edmonton Int’l, z = 723 m

Increasing height, decreasing pressureIncreasing height, decreasing pressure

1 millibar (mb) = 1 hectoPascal (hPa) = 100 Pascals (Pa)

850 mb , z 1.5 km = 150 dam

Fig. 1-2

Permanent Gases

• N2 78 % (of dry air, by volume)• O2 21 %• Ar 1 %

Variable Gases

• H2O < 4 % (¼ % globally)

• CO2 0.038% (380 ppm)• ozone• methane•

uniformly-mixed in the “homosphere” (lowest 80 km)and “inactive”

not uniformly-mixed,these gases “active”

Atmos. CompositionAtmos. Composition

1skg

kg

Q

MT res

N2 – example of a gas that is unimportant (inactive) with respect to weather

• crucial to plant nutrition• added to atmos by decay of organic material• removed by soil bacteria

“slowly” (small Q)

huge

small

= tens of millions of years

1skg

kg

Q

MT res

H2O – a variable gas that is not uniformly mixed and is “active”

• interacts with longwave radiation (“radiatively active” or “greenhouse” gas)

• affects atmospheric motion by means of buoyancy (moist air is lighter)

• every 1 kg of vapour stores 2.5 million Joules of latent heat (ie. energy)

small

large(evaporation, precipitation)

= about 10 days

GOES water vapour image (6.5-7 m):

Calculation: how long ( “t ” ) must you run a 100 W light bulb to use 2.5 million Joules of energy?

Given, energy E: 610x5.2E [ J ]

tPE x(where P = Power [W], t = time [s] )

Formula:

Unknown, time t :

CO2

Note annual cycle; there is a summertime daily cycle over crops, too

• radiatively active (greenhouse gas)• added to atmos by volcanoes, respiration and decay of vegetation,

breathing, burning fuels• removed by photosynthesis, oceanic uptake

Fig. 1-4

now 380 ppmv

Barnola, J.-M., D. Raynaud, C. Lorius, and N.I. Barkov. 2003. Historical CO2 record from the Vostok ice core. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

(now 380 ppmv)

Dr Eric Wolff, British Antarctic Survey: “Ice cores reveal the Earth's natural climate rhythm over the last 800,000 years. When carbon dioxide changed there was always an accompanying climate change…”

(now 380 ppmv)

CH4 (methane)

• another greenhouse gas; extremely effective because interacts at a wavelength where atmos. otherwise is transparent**

• rice cultivation, biomass burning, cattle, fossil fuel extraction, vents on ocean floor (thawing of permafrost?)

Stabilized?

**Analogy: all your loonies and quarters have been robbed. The next loonie robber doesn’t bother you, but a dime-robber does

See Fig. 1-6

47,000 cattle

Laser gas detectors downwind of feedlot

Measured methane emission rate from Texas feedlot… UA team

(see Appendix C)

Celcius on Canadian maps

Wind code in metres/sec:

10 m/s (NW)

7.5 m/s (ENE)

17.5 m/s (SW)