3. Current weather conditions Mainly cloudy Temp.: -18°C Pressure: 103.5 kPa ↓ Visibility: 64km Humidity: 58% DewPoint: -23.8°C Wind: S 13 km/h 17h00 1/11/11

6. Hurricane Katrina (August 29, 2005)

8. Lethbridge, Alberta

14. WeatherClimate Current state ofStatistical analysis the atmosphereor characterization of what is normal or expected air temperature atmospheric pressure Long term normals humidity clouds *Means* precipitation *Extremes* visibility*Variability* wind

15. 78% N 2 21% O 2 H 2 O CO 2 CH 4 CFCs N 2 O O 3 Aerosols NO 2 CO SO 2 Hydrocarbons

19. Gravity pulls gases toward earth's surface Mean sea level pressure is 101.325 kPa

22. UNSTABLESTABLE