Chapter 12 Weather and Climate

Climate

the average of day to day weather over a long duration

Microclimate

Climate very near the ground in a small zone(eg: park, airport, tarmac)

Mesoclimate

Climate of a small area of Earth’s surface(eg: forest, beach, valley, town )

Often created by human activity. For example, slash and burn agriculture where forests are burned to create fields for grazing cattle, will change the mesoclimate.

Macroclimate

Climate of a bigger area (eg: state, small nation )

Global climate

planet-scale climate

Factors that produce day to day weather

• sunshine intensity and its variation with latitude 

• distribution of land and water and the built environment 

• ocean currents

• prevailing winds

• positions of high and low pressure areas

• mountain barriers

• altitude

Global temperatures

• west coast climates are milder due to the upwelling of cool water and equatorward transport

• interior land mass temperatures are higher than coastal areas at the same latitude

Fact

continental land mass temperatures tend to be higher than coastal areas at the same latitude.

Continental climates exist where cold air masses infiltrate during the winter and warm air masses form in the summer under conditions of high sun and long days.

Global Precipitation

• equatorial regions are typically wet

• subtropics and polar regions are dry

• precipitation patters are tied to wind patterns 

• precipitation is prevalent in areas where air rises 

• mountains disrupt patterns

• windward side is wet leeward side is dry 

Windward slopes of the mountains 

As weather systems move from the Pacific coast and toward the interior of the continent and they traverse of mountain ranges, precipitation will occur in the windward slopes of the mountains 

The Koppen System 

• Based on annual/monthly averaged temperatures and precipitations 

• tropical moist 

• dry

• moist mid latitude with mild winters

• moist mid latitude with severe winters

• polar

• highland climates

The global pattern of climate

• the climate regions specified today are based largely on the work of Koppen

• tropical moist climates- Group A

• dry climates: Group B

• Moist subtropical mid-latitude climates- Group C

• Moist continental climates- Group D

• Polar climates: Group E

• Highland climates; Group H

Tropical moist climates (Group A)

• General characteristics: Year- round warm temperatures abundant rainfall 

• Extent: Northward and southward from the equator to about 15 to 25

• Major types: Tropical wet(Af), tropical monsoon (Am), and tropical wet and dry (Aw),

Dry Climates (Group B)

• general characteristics: most of the year has insufficient precipitation; potential evaporation and transpiration may be more than precipitation

• extent: Large continental areas between the latitudes of 20 and 30 are home to subtropical deserts, which are frequently encircled by mountains

• Major types: Arid (BW) and semi-arid(BS).

Moist Subtropical Mid Latitude Climates (Group C)

• General characteristics: Humid with mild winters

• Extent: Eastern and western regions of most continents, from about 25 to 40 latitude.

• Major types: Humid subtropical(cfA), marine (Cfb), dry-summer subtropical, and Mediterranean (Cs).

Moist Continental Climates (Group D)

• General characteristics: warm to cool summers and cold winters; winters are severe with snowstorms blustery winds, bitter cold; climate controlled by large continent. 

• extent: north of moist subtropical mid-latitude climates

• major types: humid continental with hot summers, humid continental with cool summers and subpolar. 

Polar climates (Group E)

• General characteristics: year- round low temps

• Extent: northern coastal areas, of north American and Eurasia; Greenland and Antarctica. 

• polar tundra and polar ice caps

Highland climates (group H)

• temperature decreases with altitude 

• great deal of variation in temperature, precipitation, and vegetation over a relatively short vertical change in elevation

Alexander von Humboldt (1769-1859)

• plant geography 

• holistic approach to landscapes

• ecology and interacting entities (systems )

Permafrost

An area of the Earth’s surface that is permanently frozen is known as permafrost. It is typically composed of ice holding soil, gravel, and sand together. For at least two years, permafost often persists at or below 0.