Bio 126 Climate and Weather

Earth from the moon

Meteorology Climate- over all combination of temperature and precipitation that a region experiences – Mediterranean= winter precipitation followed by long hot, dry summers Weather- daily, weekly variations in these phenomena

Solar radiation

Climate zones Warm at equator, cooler towards poles. – Caused by intensity of sunlight at equator. – Poles receive less on a per area basis.

Solar radiation around the Globe

Seasons Caused by tilting of earth on its rotational axis. – Intensity of sunlight varies. – Most extreme at poles – Little change at equator.

Causes of Seasons

Precipitation Varies by latitude. Wet at equator 0 0, and 60 0 N / S Dry at 30 0, and 90 0 poles – Poles are frozen deserts Caused by formation of Hadley Cells

Hadley Cells Air currents in Hadley Cells caused by air density not just temperature. Uneven heating in different regions on the earth cause winds.

Hadley Cells Air rises (0, 60) due to warming of surface. – Adiabatic Cooling as air rises as rises the air becomes less dense and cooler this cause water to condense and fall as rain, snow Air falls (30, poles) – Adiabatic warming as air falls air becomes compressed, and heats. air absorbs moisture, falls as dry air and absorbs moisture from the environment.

Global air circulation, precipitation, and winds: Hadley cells

Global Air Circulation

West Coast Latitudes San Diego=32.5; LA= 34; Sta. Barbara= 34.5 ; Sta. Cruz=37, SF 37.75; Eureka= Approx. Portland= 45.5; Seattle= 47.5 ; Juneau= 58; Anchorage = 61 CA large enough to span climate zones between Hadley cells. – South dry – North wet

Seasons- tilting of earth moves solar equator. Effectively moves 30 0 dry zone north in summer – descending dry air belt is pushed farther north in our summer, the wet belt moves farther south giving us wet winters

Causes of Seasons

Prevailing winds These Hadley cell wind currents move North or South The spinning of the earth makes it seem like they come at an angle. – In CA our winds, storms usually come from the south west. – Rains often bring warmer weather

Ocean currents Prevailing winds cause ocean waters to move in the prevailing direction. huge gyres form due to earth’s spinning known as the Coriolus effect – In Northern Pacific clockwise general direction of flow from our coast. – Ca. Current, with its cold, nutrient rich water flows from Alaska southwards along our coast – At Sta. Barbara coastline moves east, current flows due south, allowing Southern Ca. water to warm

Hadley cells

Barometer measures air pressure Low pressure (rising air) associated with storms. High pressure (descending air) blocks storms. – High pressure off California in summer blocks most storms

Global Trade Wind Patterns

Ocean Currents

Biomes Major vegetation types that also determine the animal community present. Determined mostly by climate – Soil also important factor

Figure 50.3 A climograph for some major kinds of ecosystems (biomes) in North America

Biomes

Patterns of distribution in the biosphere

Major Biomes

Coniferous forest, Lady Bird Grove (top left), Sequoias (right), rain forest (bottom left)

Temperate deciduous forest, Great Smokey Mountains National Park

Tropical forests

Savanna

Desert. Organ Pipe State Park (top), Joshua Tree National Park (bottom left), Death Valley (bottom right)

Temperate grassland- Prairie

Tundra. Denali National Park (left), reindeer (right)

Rain shadow Precipitation increases as storms are pushed up over mountians. – accordingly rain becomes snow – As air moves up slope in the Sierras it cools 3-5 degrees per 1,000 ft. This is the same effect as moving 300 miles farther north ! Causes deserts in Nevada Most islands with mountains have wet and dry sides

Rainshadow

Rainshadow

Summer Fog – Inland air warms quickly. This rising air, pulls in coastal air. – Cold water off CA. cools incoming warm, moist ocean – Coast causes summer fog. Essential for southern ranges of Coast Redwoods, and relic pines, cypress species

Temperature Inversion layers dense air flows downhill and collects in low spots, valleys. Great Central valley is an example. – This dense air may be blocked by hills etc. from warmer winds which blow over the top of dense air, leaving it alone. – Dense tule fog may form for days. Inversion layer (cold air higher up) also traps pollutants. Mexico City problems Reno, Tahoe now ban fireplaces. Often “burn off” in summer but leave the haze of phytochemical smog behind.