Introduction to Climate

Introduction to ClimateIntroduction to Climate

Geography 1050Geography 1050

Weather and Weather and ClimateClimate

Weather: daily phenomenaoMarked fluctuationsoCan be predicted 7-10 days in advanceoHighly variable from year to year

Climate: long-term average of weather conditions

o30 – 50 year average

Climate ParametersClimate Parameters

If you were trying to describe the climate of If you were trying to describe the climate of northeast Avalon to your distant cousin in northeast Avalon to your distant cousin in Melbourne, Australia, what would you say?Melbourne, Australia, what would you say?

TemperatureTemperature Precipitation (rain, snow)Precipitation (rain, snow) WindsWinds SunshineSunshine Other things of interestOther things of interest

Climate FactorsClimate Factors

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

Torngat Mts

Mealy Mts

Examples from Labrador

• 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

ElevationElevation

LatitudeLatitude• Temperatures decrease northward

• linked to solar insolation (length of day, Solar angle)

Hebron 58° 12’ N

Near Hopedale, 55° N

Prevailing Winds and TopographyPrevailing Winds and Topography

Westerly winds (from west)Westerly winds (from west) Effect of Labrador Current limitedEffect of Labrador Current limited Winds funnelled along fjordsWinds funnelled along fjords

Interior Labrador has:

• lighter winds

• colder winters, but less wind chill

• warmer summers

Molson Lake, Lab. West

Labrador Current Labrador Current & Proximity to the Ocean& Proximity to the Ocean

Reduces summer temperatures

Increases winter temp, but sea ice cover limits influence

topographic influencesHutton Beach, Iron Strand

InsolationInsolation

Incoming solar radiationIncoming solar radiation ultimate source of energy for Earth ultimate source of energy for Earth reaches upper limit of atmosphere as reaches upper limit of atmosphere as

visible light, near infrared and visible light, near infrared and ultraviolet radiationultraviolet radiation

amount of insolation supplied by amount of insolation supplied by Sun varies systematicallySun varies systematically

e.g. sunspot cycles from 11 - 1000s e.g. sunspot cycles from 11 - 1000s of yearsof years

Seasonal VariationSeasonal Variation

distance of Earth from Sun varies

146,000,000 km (perihelion, January 3)

152,000,000 km (aphelion, July 4)

Earth’s AtmosphereEarth’s Atmosphere

The atmosphere is vital for maintaining life on The atmosphere is vital for maintaining life on Earth because it:Earth because it:

shields the Earth from harmful radiationshields the Earth from harmful radiation helps redistribute energy on Earthhelps redistribute energy on Earth reduces heat losses from Earthreduces heat losses from Earth provides a water transfer and storage facilityprovides a water transfer and storage facility

Modal Atmospheric ChemistryModal Atmospheric ChemistryGas Proportional

Volume (dry air)Nitrogen (N2) 78.08 %Oxygen (O2) 20.95 %Argon (Ar) 0.93 %Carbon dioxide (CO2) 375 ppmNeon (Ne) 18.2 ppmHelium (He) 5.2 ppmMethane (CH4) 1.7 ppmKrypton (Kr) 1.1 ppmHydrogen (H2) 0.5 ppmNitrous oxide (N2O) ≤ 0.1 ppm

Sulphur dioxide (SO2)& S-aerosols ≤ 0.1 ppmOzone (O3) ≤ 0.001 ppm- Dry air, lowest troposphere

Present Present situationsituation

14 %

25%

Earth 53%:

Direct 31%,

Diffused 22 %

Albedo

Radiated

Absorbed

• 47% of Insolation does not reach Earth surface

• less than 47% of the total insolation is available for conversion into long-wave (infrared) radiation

Insolation

When insolation reaches surface …When insolation reaches surface …

Insolation absorbed by Insolation absorbed by EarthEarth

Albedo- % of incoming Albedo- % of incoming radiation that is radiation that is reflected reflected

Changes in albedo Changes in albedo causes further change causes further change (positive feedback)(positive feedback)

After Adsorption…After Adsorption…

subsequently reradiated as long-wave subsequently reradiated as long-wave thermal infrared radiationthermal infrared radiation

slightly <50% of total provided by Sunslightly <50% of total provided by Sun Thermal infrared radiation responsible for Thermal infrared radiation responsible for

warming warming Must be retained in atmosphereMust be retained in atmosphere

Trapping Thermal IRTrapping Thermal IR

Thermal IR responsible for warming EarthThermal IR responsible for warming Earth depends upon successful trapping by depends upon successful trapping by

greenhouse gases (GHG):greenhouse gases (GHG): COCO22 (carbon dioxide) (carbon dioxide)

CHCH44 (methane) (methane)

NONO22 (nitrous oxide) (nitrous oxide) and water vapour and water vapour

Contrasting NeighboursContrasting Neighbours Mars: low greenhouse Mars: low greenhouse

gas concentrationsgas concentrations Mean temp -63Mean temp -63°C°C

Venus: high greenhouse Venus: high greenhouse gas concentrationsgas concentrations

Mean temp 464Mean temp 464°C°C

Mars: astrogeology.usgs.gov; Venus: www.bnsc.gov.uk

Current Earth SituationCurrent Earth Situation

COCO22 – 375 ppm – 375 ppm

CHCH44 (methane) – 1.8 ppm (methane) – 1.8 ppm water vapour (0-4 %)water vapour (0-4 %) Together, trap about half Together, trap about half

the thermal IR emitted the thermal IR emitted from Earth’s surfacefrom Earth’s surface

< 25% of original < 25% of original insolationinsolation

Mean Surface Temp 16°C

““Greenhouse Effect”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