AOSC 200Lesson 22

Past and present climates

• weather - short time fluctuations• climate – long-term behavior

- location- time- average and extremes

• climate controls- latitude- elevation- topography- proximity to large bodies of water- atmospheric circulation

THE CHANGING CLIMATE

• Climate involves more than just the atmosphere.• Climate may be broadly defined as the long-term

behavior of global environmental system • “To understand fully and to predict changes in the

atmospheric component of the climate system. one must first understand the sun, oceans, ice sheets, solid earth, and all forms of life"

• Thus we talk about a climate system consisting of the atmosphere, hydrosphere, solid earth, biosphere and cryosphere.

• Climate system involves the exchange of energy and moisture among these components

Locations close together can have different climates.

Cities at the same latitude can have different climates

Fig. 14-3, p. 414

The three convective cells produce different climates. These cells move with the seasons producing sud-climates

CLIMATE ZONES

• VLADIMAR KOPPEN ZONES • TROPICAL MOIST – A• DRY – B• MOIST WITH MILD WINTERS – C• MOIST WITH SEVERE WINTERS – D• POLAR – E• HIGHLAND – H

Fig. 14-2, p. 413

World map of the Kopper climate classification scheme

Tropical Humid Climates - A

• High mean monthly temperature, at leaest 18.3 C.

• Rage of temperature is small, less than 10 degrees.

• Divided into three sub-types• Tropical wet climates (Af)• Tropical wet and dry climates (Aw)

• Tropical monsoon climates (Am)

Fig. 14.4

Tropical Humid Climates

Iquitos, Peru (Af), Pirenopolis, Brazil, Aw, Rochambeau French Guiana, Am

Tropical rain forest near Iquitos, Peru, (Af)

Baobob and Acacia trees in grassland savanna (Aw)

Dry Climates• Evaporation plus transpiration exceeds precipitation. Descending branch of the Hadley cell.

• Mainly over land, diurnal variation larger than annual variation.

• Two subtypes• Steppe or semi-arid (BS)• Arid or desert (BW)• BSh and BWh are warm dry climates• BSk and BWk are cold dry climates

Fig. 14.5

Dry Subtropical Climates

Dakar, Senegal BSh, Cairo, Egypt BWh

Fig. 14.6

Warm Dry Climates

San Diego, Calif.BSk, Santa Cruz, Argentina, BWk

Rain streamers are common in warm dry climates. Rain evaporates before it

reaches the ground.

Creosote bushes and catcus in the arid southwestern deserts (BWh)

Steppe grasslands of western North America (BS)

Moist Subtropical and Midlatitude Climates

• Characterized by humid and mild winters.

• Lie between the tropics and mid-latitudes

• Three major subgroups• Marine West Coast Cfb and Cfc• Humid Subtropical Cfa and Cwa• Mediterranean Csa or Csb

Fig. 14.7

Marine West Coast Cfb, Cfc

Bergen, Norway Cfb, Reykjavik, Iceland Cfc

Fig. 14.8

Humid Subtropical Cfa, Cwa

New Orleans, Louisiana, Cfa, Hong Kong China, Cwa

Fig. 14.9

Mediterranean , Csa, Csb

Lisbon, Portugal, Csa, Santiago, Chile, Csb

Mediterranean-type climate of North America. Chaparral : foothill pine,

chamise and manzanita.

Severe Midlatitude Climates, D

• Tend to be located in the eastern regions of continents.

• Temperature range is generally greater than seen in the western climates (C)

• To be classified as D the average cold temperature must be less than -3 C, and the average summer temperature must exceed +10 C.

• Two basic types• Humid Continental (Dfa/b and Dwa/b)• Subarctic (Dfc/d and Dwc/d)• a,b,c, - hot summers, d - severe winter and cold

summer

Fig. 14.10

Humid Continental

Vladosvostok, Russia Dwb, Fargo, North Dakota, Dfb

Adirondack Park - humid continental climate (Dfa)

Fig. 14.11

Subarctic

Fairbanks, Alaska, Dfc, Verkhoyansk, Siberia, Dfd

Coniferous forests occur where winter temperatures are low and precipitation is abundant (Dfc)

Polar Climates, E

• Occur poleward of the Arctic and Antarctic circles• Mean temperatures are less than 10 C for all

months.• Annual precipitation is less than 10 inches.• Two polar climate types are identified• Tundra (ET) and Ice Caps (EF)• EF have essentially no vegetation

Fig. 14.12

Polar Climates, E

Barrow, Alaska, ET, Eismitte, Greenland, EF

Tundra vegetation in Alaska – sedges and dwarfed wildflowers

(ET)

Highland climate (H)