Introduction to Climate

1. Introduction to Climate Geography 1050

2. Weather and Climate • Weather: daily phenomena • Marked fluctuations • Can be predicted 7-10 days in advance • Highly variable from year to year • Climate: long-term average of weather conditions • 30 – 50 year average

3. Climate Parameters • If you were trying to describe the climate of northeast Avalon to your distant cousin in Melbourne, Australia, what would you say? • Temperature • Precipitation (rain, snow) • Winds • Sunshine • Other things of interest

4. Climate Factors • elevation • latitude • prevailing winds • topographic barriers • ocean currents • proximity to the ocean (or a large lake)

5. Examples from Labrador Torngat Mts Mealy Mts

6. higher altitude = cooler temperatures • 22 active glaciers in the Torngat Mountains active tundra conditions on the Mealy Mountain summits compared to boreal forest along Lake Melville Elevation

7. Latitude • Temperatures decrease northward • linked to solar insolation (length of day, Solar angle) Hebron 58° 12’ N Near Hopedale, 55° N

8. Interior Labrador has: • lighter winds • colder winters, but less wind chill • warmer summers Molson Lake, Lab. West Prevailing Winds and Topography • Westerly winds (from west) • Effect of Labrador Current limited • Winds funnelled along fjords

9. Labrador Current & Proximity to the Ocean • Reduces summer temperatures • Increases winter temp, but sea ice cover limits influence • topographic influences Hutton Beach, Iron Strand

10. Insolation • Incoming solar radiation • ultimate source of energy for Earth • reaches upper limit of atmosphere as visible light, near infrared and ultraviolet radiation • amount of insolation supplied by Sun varies systematically • e.g. sunspot cycles from 11 - 1000s of years

11. Seasonal Variation distance of Earth from Sun varies 146,000,000 km (perihelion, January 3) 152,000,000 km (aphelion, July 4)

13. Earth’s Atmosphere The atmosphere is vital for maintaining life on Earth because it: • shields the Earth from harmful radiation • helps redistribute energy on Earth • reduces heat losses from Earth • provides a water transfer and storage facility

14. Modal Atmospheric Chemistry Gas Proportional Volume (dry air) Nitrogen (N2) 78.08 % Oxygen (O2) 20.95 % Argon (Ar) 0.93 % Carbon dioxide (CO2) 375 ppm Neon (Ne) 18.2 ppm Helium (He) 5.2 ppm Methane (CH4) 1.7 ppm Krypton (Kr) 1.1 ppm Hydrogen (H2) 0.5 ppm Nitrous oxide (N2O) ≤ 0.1 ppm Sulphur dioxide (SO2)& S-aerosols ≤ 0.1 ppm Ozone (O3) ≤ 0.001 ppm - Dry air, lowest troposphere

15. Present situation Insolation • 47% of Insolation does not reach Earth surface • less than 47% of the total insolation is available for conversion into long-wave (infrared) radiation 14 % 25% Earth 53%: Direct 31%, Diffused 22 % Albedo Radiated Absorbed

16. When insolation reaches surface … • Insolation absorbed by Earth • Albedo- % of incoming radiation that is reflected • Changes in albedo causes further change (positive feedback)

17. After Adsorption… • subsequently reradiated as long-wave thermal infrared radiation • slightly <50% of total provided by Sun • Thermal infrared radiation responsible for warming • Must be retained in atmosphere

18. Trapping Thermal IR • Thermal IR responsible for warming Earth • depends upon successful trapping by greenhouse gases (GHG): • CO2 (carbon dioxide) • CH4 (methane) • NO2 (nitrous oxide) • and water vapour

19. Mars: low greenhouse gas concentrations Mean temp -63°C Venus: high greenhouse gas concentrations Mean temp 464°C Contrasting Neighbours Mars: astrogeology.usgs.gov; Venus: www.bnsc.gov.uk

20. Current Earth Situation • CO2 – 375 ppm • CH4 (methane) – 1.8 ppm • water vapour (0-4 %) • Together, trap about half the thermal IR emitted from Earth’s surface • < 25% of original insolation Mean Surface Temp 16°C

21. “Greenhouse Effect” • naturally occurring phenomenon • necessary for life on Earth • maintains temp. at 16°C, • but … Changes in the concentrations of GHGs will impact climate