Seasons, Weather & Climate

SEASONS Earth revolves at 23.5 angle around sun different parts of earth get different amount sun = seasons Solstices – beginning of summer & winter (longest/shortest day of yr.) Equinoxes – beginning of spring & autumn (day & night equal length) Rotation vs. Revolution

WEATHER Factors causing weather solar energy water vapor – determines precipitation cloud cover – clouds hold water vapor landform & bodies of water – water heats & loses slowly, land heats & loses rapidly elevation – higher = less moisture air movement – wind makes weather change quickly precipitation depends on water vapor – warm air rises, cools, loses ability to hold vapor, forms clouds, drops when heavy As air masses warm & cool & move across Earth, weather created can be severe

HURRICANES typhoons (Asia) move heat out of tropics air over ocean with water temp of 80 F+ gets huge amounts heat/ moisture this moves to low-pressure core, tighten, form the eye (10-20mi across), calm around eye winds can be 200mi/ hour

TORNADOES develop quickly counter-clockwise winds 300+ mi/ hour small diameters – 300 ft, travel about 1 mi, last minutes 3 out of 4 hit US, 700/ year Joplin, Missouri “Before” Joplin, Missouri “After”

BLIZZARDS winds 35+ mi/ hour 76” in Silver Lake, CO –1921, 189” in Mt Shasta, CA – 1959 eastern & western shores of Great Lakes are snow belts, Lake Erie/ Ontario – 450”/ yr

DROUGHTS & FLOODS Dust Bowl – dust storms, 150,000 sq-mile region 1930s 10/2010 – 8/2011: Driest 11 months on record in Texas since state began keeping records in 1895 Floods: water spreads over land frequently in areas with a high water table

Weather vs. Climate Weather – condition of the atmosphere at a particular location and time. Climate – weather conditions of a location over a long period of time. Weather today…..

Factors Affecting Climate Elevation Topography (orographic precipitation) Zones of Latitude Low/tropical Middle/temperate High/polar

Factors Affecting Climate

Factors Affecting Climate Wind Currents

Factors Affecting Climate Ocean Currents

Three Types of Precipitation

Coriolis Effect & Rain Shadow Earth’s wind currents are bent because of rotation of earth. Rain Shadow The dry or leeward side of a mountain range. The precipitation is dropped on the wet or windward side. (See previous slide.)

Biome The ecosystem of a region Forest Grassland Desert Tundra

Greenhouse Effect Fossil Fuels burned = trapped solar energy Global Temperature goes up. Works in the same way as a Greenhouse; keeps the heat in.

El Nino & La Nina (in the N. hemisphere) El Nino: warms Pacific waters; results in wetter than normal conditions. La Nina: cools Pacific waters; results in dryer than normal conditions In Southern Hemisphere, effects are the opposite.

El Nino & La Nina Cont’d.

“Spheres” of the Earth

12 Climate Zones Tropical Wet Tropical Wet & Dry Desert Semiarid Mediterranean Humid Subtropical Humid Continental Subarctic Highland Tundra Icecap Marine West Coast

Tropical Wet Almost daily convectional precipitation Think rainforest or jungle Hot and muggy year around. Average annual rainfall varies from about 70 to 100 inches Temperatures are high, and they change little during the year. The coolest month has an average temperature no lower than 64 degrees F The temperature difference between day and night is greater than the temperature difference between summer and winter. Frost and freezing temperatures do not occur. Plants grow all year.

Tropical Wet & Dry Characterized by a wet season and a dry season Think “Serengeti” Next to regions that have tropical wet climates. Temperatures remain high throughout the year. Winters are dry, and summers are wet. Support savannas--grasslands with scattered trees.

Desert & Semiarid Defining characteristic is LACK OF PRECIPITATION. Semiarid and desert climates occur in regions with little precipitation. Desert climates are drier than semiarid climates. Semiarid climates, also called steppe climates, usually border desert climates. Temperature change between day and night is considerable. One reason for the wide swings in temperature is that the skies are clear and the air is dry.

Mediterranean Hot summers and mild, wet winters. Found on western coasts. Good for vineyards Roughly between 30 degrees and 45 degrees latitude. The closer to the coast the area is, the more moderate the temperatures and the less the contrast between summer and winter temperatures. Chapparal is a recurring vegetation type in the Mediterranean. Locations: Mediterranean, also San Diego.

Humid Subtropical This is us! Characterized by warm to hot summers and cool winters. Rainfall is distributed fairly evenly throughout the year. Winter rainfall--sometimes snowfall--associated with large storm systems. Most summer rainfall occurs during thunderstorms Occasional tropical storm or hurricane. Lie on the southeast side of continents, roughly between 25 degrees and 40 degrees latitude

Humid Continental Four distinct seasons Mild to warm summers and cold winters. The temperature difference between the warmest and coldest months of the year in-creases inland. (continentality) Precipitation is distributed fairly evenly throughout the year, though many locations well inland have more precipitation in the summer. Snow is a major element in humid continental climates. Winter temperatures are so low that snowfall can be substantial and snow cover persistent.

Marine West Coast Think…Seattle Found only on the western sides of continents where prevailing winds blow from sea to land. The moderating influence of the ocean reduces the seasonal temperature contrast so that winters are cool to mild and summers are warm. Moderate precipitation occurs throughout the year. Low clouds, fog, and drizzle are common. Thunderstorms, cold waves, heat waves, and droughts are rare.

Highland Found at higher elevations (thus the name). Highland climates occur in mountainous regions. Because air temperature decreases with increasing elevation, each climate area is restricted to a certain range of altitude.

Subarctic Found only in the Northern hemisphere. Taiga – world’s largest forest found here. Spread across Russia and Canada. Subarctic climates have short, cool summers and long, bitterly cold winters. Freezes can occur even in midsummer. Most precipitation falls in the summer. Snow comes early in the fall and lasts on the ground into early summer. Occupies the higher midlatitudes, generally between 50 and 70 degrees North. Boreal means (north). Taiga is a Russian term for the tree found predominately in this climate also found in Canada.

Tundra & Icecap Tundra Icecap Tundra climates are dry, with a brief, chilly summer and a bitterly cold winter. Continuous permafrost (permanently frozen ground) lies under much of the treeless tundra regions. Icecap Icecap climates are the coldest on earth. Summer temperatures rarely rise above the freezing point. Temperatures are extremely low during the long, dark winter. Precipitation is meager and is almost always in the form of snow.