Climate and Weather Climate and Weather ISCI 2001

Climate and Weather Climate and Weather

Climate Zones Climate Zones

The Earth’s Atmospheres The Earth’s Atmospheres Mostly nitrogen (78%) and oxygen

(21%)◦Troposphere

Temperature ◦-50 to 40 Celsius

Stratosphere ◦Ozone layer (O3)

◦UV light

Greenhouse Effect Greenhouse Effect Terrestrial radiation ‘trapped’ by

greenhouse gases◦Carbon dioxide

Greenhouse Effect – Greenhouse Effect – Greenhouse Gases Greenhouse Gases • (1). Carbon dioxide

– Fossil fuels; deforestation; organic decay; forest fires

• (2). Ozone– Sunlight chemically reacts with O2 (natural)– Photochemical smog production

• (3). Methane– Wetlands; biomass burning; termites; organic decay

• (4). Chlorofluorocarbons– Refrigerants; aerosol spray propellants; cleaning solvents

• (5). Nitrous Oxide – Fertilizers; burning of fossil fuels; forests; grasslands

Importance of Ozone Importance of Ozone Absorbs UV radiation

Formed in the stratosphere

Chlorofluorocarbons (CFCs)

Ozone Holes

GH Effect Importance GH Effect Importance Naturally warms the surface of

the Earth

Keeps the average temperature of the Earth normal (sustain life)◦-18 C otherwise

Global Warming ◦Increased GH effect, GH gases

Atmospheric PressureAtmospheric PressureDensity of air decreases with altitude

◦‘thinning’ of air

Sea Level ◦1cubic meter

Mass 1.2 kg (at 10 km 0.4 kg)

101.3 kPa or 1 atmosphere of pressure

Barometer

Atmospheric Pressure Atmospheric Pressure

How Winds are produced How Winds are produced Air that flows from high to low pressure

areas◦ Uneven heat of the Earth’s surface

Warm air is lower density and low air pressure Cool air higher density and higher air pressure Isobars

Produces a convection current

Local winds ◦ Small scale changes in convection cells and

pressure gradients ◦ Global wind patterns – prevailing winds

Winds – Convection Cells Winds – Convection Cells

Prevailing Winds – Hadley Prevailing Winds – Hadley Cells Cells

Coriolis Effect Coriolis Effect Earth Rotation effects global wind

patterns ◦Objects deviate from straight-line

path including winds – deflected

Deflects winds to the right in the Northern Hemisphere and to the Left in the Southern Hemisphere

Jet Streams

Cloud Formation and Cloud Formation and PrecipitationPrecipitationAggregates of water droplets

formed by rising air that expands and cools ◦Cumulus, stratus or cirrus

Cloud Classification Cloud Classification

Cirrocumulus

Cirrostratus

Altocumulus

Cumulonimbus

Air Masses and Fronts Air Masses and Fronts Air Mass

◦Arctic, polar, tropical

Weather Fronts ◦Warm vs Cold Fronts ◦Stationary

Animation

Fronts Fronts

Formation of Cyclones Formation of Cyclones Hurricanes

Tornados

Solar Radiation, Tilting of the Solar Radiation, Tilting of the Earth and the Seasons Earth and the Seasons