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Chapter 7 Global Climates and Climate Change

Visualizing Physical Geography by Timothy Strahler & Alan Strahler

Chapter Overview

Keys to Climate

Climate Classification

Low-Latitude Climates

Midlatitude Climates

High-Latitude Climates

Climate Change

Keys to Climate

Climate

The annual cycle of prevailing weather conditions at a given place, based on statistics taken over an extended period (30 years).

Temperature and precipitation are the key measures of climate.

To establish the climate of a region, climatologists begin by answering three basic questions:

What is the mean annual temperature?

What is the mean annual precipitation?

What is the seasonal variation in temperature and precipitation?

Keys to Climate

Global Temperature Patterns

Key factors controlling temperature:

Latitude = controls insolation as energy varies with seasons (solar angle and day length)

Location = your location in relationship to a body of water (maritime or continental)

Elevation = temperatures cool with height

Keys to Climate

Latitude:

In general, average annual temperatures are highest at the equator and progressively cooler toward the poles.

Keys to Climate

Maritime vs. Continental:

In coastal locations, temperatures are more moderate and seasonal variations are minimal.

In continental locations, temperatures are more extreme and seasonal variations are more pronounced.

Keys to Climate

A location between Sitka, Alaska, and Ft. Vermilion, Alberta, if located at a similar elevation, would most likely have a ____.

a. greater mean annual temperature than Sitka

b. greater mean annual temperature than Ft. Vermilion

c. greater annual temperature range than Ft. Vermilion

d. greater annual temperature range than Sitka

Keys to Climate

Global Precipitation Patterns

Key factors controlling precipitation:

Air masses (characteristics and movement)

Atmospheric circulation (prevailing winds) and ocean circulation

Topography

Latitude

Persistent high and low pressure centers (apart of atmospheric circulation)

Courtesy NOAA

Keys to Climate

Global Precipitation Patterns

Latitude

Warm air can contain more moisture than cold air, so warmer, low-latitude regions generally have higher precipitation

Courtesy NASA

Keys to Climate

Global Precipitation Patterns

Atmospheric circulation (prevailing winds) and ocean circulation:

Midlatitude west coast:

Drier summers as a result of the cooler, more stable air off the west coast

Moist winters as a result of the westerlies and the southward shift of the polar jet stream (L)

Midlatitude east coast = wetter summers as a result of the warmer waters of the east coast:

Moist winters as a result of the westerlies and the southward shift of the polar jet stream (L)

Keys to Climate

Global Precipitation Patterns

Persistent pressure centers

Low = ITCZ = wet near equator

Subtropical high = drier

Courtesy NASA

Keys to Climate

Seasonal Precipitation Patterns

Arid climate = subtropical high dominates

Semiarid climates:

Influenced by the seasonal migration of the ITCZ and the subtropical high

Keys to Climate

Seasonal Precipitation Patterns

Mediterranean

Influenced by the seasonal migration of the polar jet stream and the subtropical high

Keys to Climate

Global Precipitation Patterns

Topography and orographic lifting

Windward = rising air (moist)

Leeward = sinking air (drier)

Courtesy NASA

Keys to Climate

Global Precipitation Patterns

Air masses

Courtesy NASA

Climate Classification

Climograph

A graph on which mean monthly temperature and precipitation values are plotted for each month of the year

Climate Classification

The greatest amount of rain occurs when the temperatures are highest.

Temperatures usually decrease when the subtropical high is present.

Temperatures usually increase when equatorial trough is present.

There is little rain during the southern hemisphere summer solstice.

Which of the following statements is true based on the climograph?

Climate Classification

Collecting climate data (30 years of data)

Meteorological sensors:

Automated stations record air temperature, wind speed and direction, solar radiation, relative humidity, barometric pressure, and precipitation

Ocean buoys

Weather balloons

NOAA images

Climate Classification

Climate Classification Systems

Climatology is the science of analyzing climate—weather over the long term—as it varies over time, around the globe.

Empirical system

Köppen climate system is based on monthly precipitation and temperature.

Strahler’s climate classification system is based on air mass movement and frontal zones.

Climate Classification

Climate Classification Systems

Three broad groups of climate: low, middle, and high latitude

Highland

Climate Classification

Climate Classification Systems

Highland’s impact temperature and precipitation

Climate Classification

Climate Classification Systems

Highland’s impact temperature and precipitation

Climate Classification

Highland climates: Temperature and precipitation

Low-Latitude Climates

Four low-latitude climates:

Wet equatorial 2. Monsoon and trade-wind coastal

3. Wet-dry tropical 4. Dry tropical

Low-Latitude Climates

Wet Equatorial Climate

Moist climate of the equatorial zone with a large annual water surplus and uniformly warm temperatures through the year

Low-Latitude Climates

Wet Equatorial Climate

Controlled by ITCZ

Warm, moist mE and mT air masses

Heavy convectional rainfall

Uniform temperatures through the year

Low-latitude rainforests

Low-Latitude Climates

The Monsoon and Trade-Wind Coastal Climate

Moist climate of low latitudes showing a strong rainfall peak in summer (ITCZ) and short period of reduced rainfall in low-sun season (subtropical high)

Strong seasonal pattern

Trade winds bring moist air to east coasts

Low-latitude rainforests

Low-Latitude Climates

The Monsoon and Trade-Wind Coastal Climate

Rainfall impacted by seasonal shift of ITCZ.

Monsoon winds bring moist air from the coast in summer and dry air from land in winter.

Low-Latitude Climates

Climate of the tropical zone characterized by a very wet season alternating with a very dry season.

The Wet-Dry Tropical Climate

Low-Latitude Climates

Very dry season at low sun

ITCZ is far away

Very wet season at high sun

ITCZ is nearby

Savanna vegetation

The Wet-Dry Tropical Climate

Low-Latitude Climates

Climate of the tropical zone with high temperatures (except along some west coasts) and low rainfall.

The Dry Tropical Climate

Low-Latitude Climates

Center and east sides of subtropical high pressure cells

Extreme heat, large daily temperature range

Generally between 15º and 25º N and S

Arid deserts and semiarid steppes

The Dry Tropical Climate

Low-Latitude Climates

Desertification in the Sahel

Vegetation Index Map

The Dry Tropical Climate

Low-Latitude Climates

Western Coastal desert

Cool current and upwelling along the west coasts

The Dry Tropical Climate

Midlatitude Climates

8. Marine West-coast

9. Dry midlatitude

10. Moist Continental

Six midlatitude climates:

5. Dry Subtropical

6. Moist Subtropical

7. Mediterranean

Midlatitude Climates

Dry climate of the subtropical zone, transitional between the dry tropical climate and the dry midlatitude climate

Poleward extension of dry tropical climate

High annual temperature range

Arid and semiarid subtypes

The Dry Subtropical Climate

Midlatitude Climates

Climate: moist climate of the subtropical zone, characterized by a moderate to large annual water surplus and a strong seasonal temperature cycle

The Dry Subtropical Climate

Midlatitude Climates

Eastern sides of continents, between 20º and 35º N and S

mT air from western side of subtropical high pressure cells

Warm humid summers, abundant rainfall

Mild winters, ample rainfall

Forest vegetation

The Moist Subtropical Climate

Midlatitude Climates

Climate type of the subtropical zone, characterized by the alternation of a very dry summer and a mild, rainy winter.

The Mediterranean Climate

Midlatitude Climates

Wet winter, dry summer

West coast of continents

Located between 30º and 45º N and S

Vegetation: shrubs and trees with hard leaves to resist water loss (sclerophylls)

The Mediterranean Climate

Midlatitude Climates

Cool, moist climate of west coasts in the midlatitude zone, usually with abundant precipitation and a distinct winter precipitation maximum

Abundant precipitation, winter maximum

Frequent cyclonic storms

Mild winters, low annual temperature range

West coasts, between 35º and 60º N and S

The Marine West-Coast Climate

Midlatitude Climates

Dry climate of the midlatitude zone with a strong annual temperature cycle and cold winters

Interior of North America and Eurasia

Within the rainshadow of mountain ranges

Large annual temperature range

Arid and semiarid, desert and steppe

The Dry Midlatitude Climate

Midlatitude Climates

Moist climate of midlatitude zone with strongly defined winter and summer seasons and adequate precipitation throughout the year.

The Moist Continental Climate

Midlatitude Climates

Cold winters, warm summers

Located in the polar-front zone

Ample precipitation

Forests and tall grasslands

The Moist Continental Climate

High-Latitude Climates

Three high-latitude climates: 11. Boreal Forest 12. Tundra 13. Ice Sheet

High-Latitude Climates

The Boreal Forest Climate

Cold climate of the subarctic zone in the northern hemisphere with long, extremely severe winters and several consecutive months of frozen ground

High-Latitude Climates

The Boreal Forest Climate

Low, irregular topography

Total annual precipitation is low but higher in the summer

High-Latitude Climates

The Boreal Forest Climate

Long cold winters, short, cool summers

Source region for cP air masses

Greatest range of temperature

Boreal forests—needleleaf

High-Latitude Climates

The Tundra Climate

Cold climate of the arctic zone with eight or more months of frozen ground

High-Latitude Climates

Polar and arctic air masses

Permafrost below surface

Saturated soil in summer

Tundra vegetation—low herbs and shrubs

The Tundra Climate

High-Latitude Climates

The Tundra Climate

Tundra describes both an environmental region and a major class of vegetation and is dominated by permafrost.

Permafrost = permanently frozen ground.

Temperature increases in the Arctic in some regions have thawed the upper permafrost layer:

Unstable soils impacting infrastructure

Oil exploration and Arctic National Wildlife Refuge

High-Latitude Climates

The Ice Sheet Climate

Severely cold climate found on the Greenland and Antarctic ice sheets

Arctic and Antarctic air masses

Mean temperature below freezing all months

Low precipitation, high winds

Climate Change

Shifting Climate Characteristics

Glacial periods

Interglacial (warmer) periods

Evidence from carbon dioxide stored in ice cores

Carbon dioxide and temperature relationship

Change today related to increasing levels of greenhouse gases

Climate Change

Courtesy Scripps

Courtesy EPA

Climate Change

Shifting Climate Characteristics

Temperature increase, especially in the Arctic.

Arctic Sea ice has decreased in spatial coverage during late summer.

Climate Change

If the Arctic continues to warm, which of the following transformations is most likely?

a. The tundra climate region will expand in all directions.

b. The boreal forest climate will expand in all directions.

c. The boreal forest climate will move into areas once considered tundra climate.

d. The tundra climate will move into areas once considered boreal forest climate.

Climate Change

Shifting Precipitation Characteristics

Subtropical high-pressure may strengthen and move poleward, reducing precipitation in subtropics

Rainfall may increase at higher latitudes and in some topical areas

Uncertainty

Monitoring Global change

http://iridl.ldeo.columbia.edu/maproom/Global/

Climate Change

Weather Variability

Frequency of extreme weather is predicted to change

Variation in storm paths and intensity of storms

ENSO

Costly

What role do population growth and infrastructure development play in the damages caused by natural disasters?

Climate Change

Future Challenges and Adaptations

Global climate modeling

Climate Change

Future Challenges and Adaptations

Global climate models

IPCC (Intergovernmental Panel on Climate Change)

Accuracy and mitigating negative environmental impacts

Climate Change

Future Challenges and Adaptations

Global climate models

IPCC (Intergovernmental Panel on Climate Change)

Accuracy and mitigating negative environmental impacts

Climate Change

Heat from this house, near Fairbanks, Alaska, and blocking the access of cold air to the land surface, has caused the permafrost underneath the house to thaw.

1. Relate the trends in climate change to the impacts felt by polar societies.

2. What kinds of adaptations would you recommend for communities perched

on permafrost?