The Atmosphere: Climate and Weather John Todd 6 lecture mini-series

Teaching Goals Stimulate your interest in this subject Basic understanding of main processes: energy flow, air movement, water cycle, air pressure Present some of the terminology Demonstrate where climate/meteorology is useful across many disciplines

Your Lecturer PhD in atmospheric physics Interest in atmospheric transmission as an astronomer Air pollution control (Dept of Env) Lecturing Environmental Studies –Interdisciplinary First time with this class

Jobs Core Business –Meteorologist –Architect –Engineer –Pollution control –Farmer –Fisher –Renewable energy Competitive advantage –Sailor –Commodity trading –Insurance –Outdoor sports Assists understanding –Sociologists –Psychiatrists –Medical science –Fashion design –Novelist

Mini-Series on Weather and Climate 1.Atmosphere: composition, temperature 2.Radiant energy flows, seasons 3.Global circulation 4.Water cycle 5.Weather 6.Human changes to atmosphere

The Atmosphere: composition, structure and temperature Chapter 3 of Christopherson Need to know –Magnitude –Changes with height –Main gases

The Atmosphere How thick? –10km, 480km, 32,000+km How much? –5x10 15 tonnes –1 million t each! What is it? –Nitrogen and oxygen –H 2 O, CO 2 12,700km

Pressure Air behaves like any gas – it is compressible, hence it becomes denser near the Earth’s surface. –At sea level pressure of about 1kg/cm 2 –Measured as hectopascal (1013 hPa) [1hPa=1mb] –Drops about 1hPa per 10m near sea level –By 16km down to 100hPa, by 32km down to 10hPa –This means most air (75%) is below 16km –Mt Everest (8850m) ~ 300hPa (i.e. 1/3 the oxygen)

Temperature In troposphere (up to about 16km) temperature decreases with height by about 1 o C every 150m. Gas laws: reduce pressure  lower temp. –Important from pollution perspective Higher up more heating by sun

Upper layers Exosphere (above 480km) –Outer reaches, Earth’s influence detectable, essentially ‘outer space’, satellites Thermosphere (about 80 to 480km) –Extremely thin atmosphere, aurora, meteors, temperature not as we would sense it Mesosphere (about 50 to 80km) –Cooling because not much air to heat Noctilucent clouds

Below 50km Stratosphere (about 18 to 50km) –Temperature rise due to absorption of solar UV –Ozone layer –Little mixing from below Troposphere (below about 16km equator and 8km at poles) –Well mixed –Most clouds, water vapour, dust, pollutants –Weather

Composition in Troposphere GasPer centVariableRad. Active Nitrogen78 Oxygen21Yes (UV) Water vapourup to 3.5veryyes Argon0.9 Carbon dioxide0.035yes Neon0.002 Helium Ozone yes Hydrogen Nitrogen dioxideTraceyes KryptonTrace

Pollutants Waste from human activities Combustion –CO, NO x, SO2, ‘air toxics’, ….. Evaporation –Volatile organic compounds, petrol, ….. Direct discharge –CFCs, odour, CH 4, ……

Inversions Prevent Dispersion Inversion Prevents the air mixing upwards TEMPERATURE

Summary Atmospheric composition –Mainly N 2 and O 2, some variable, some radiatively active, pollutants Pressure –Air follows gas laws Temperature –Decrease ~6.5 o C per km in troposphere Terminology –Troposphere, etc., lapse rate, see handout

Next Week RADIATION BALANCE Incoming solar radiation Outgoing long-wave radiation How this interacts with the atmosphere The seasons CHAPTERS 2 & 4 of CHRISTOPHERSON