A region’s “general” weather conditions as established over a long period of time is known as climate.

Climate is defined by two weather variables: temperature and atmospheric moisture.

Lincoln, NE ~ 40˚N Providence, RI ~ 40˚N

“How is it possible that two locations at the same latitude can experience different climates?”

CLIMATE

Climate Regions

P = Annual Precipitation (moisture)PET = Potential Evapotranspiration (temperature)

ARIDP < PET

HUMIDP > PET

SUB-HUMIDSEMI-ARID

P ≅ PET

Factors Affecting Climate

Latitude

Large Bodies

of Water

Planetary Winds and Pressure

Belts

Vegetation Cloud

Cover

Ocean Currents

Elevation

Mountains

Climate Change due to Latitude The Earth receives maximum intensity and fairly consistent duration of insolation between 23 ½ ˚N and 23 ½ ˚S during its revolution around the

Sun.

Annual temperatures tend to be high and there is a minimal variation in temperature throughout

the year.

Latitudes north of 23 ½ ˚N and latitudes south of 23 ½ ˚S never receive direct

insolation and the duration of insolation fluctuates.

Annual temperatures tend to vary over a wide range seasonally.

Climate Change due to Latitude The location of pressure belts will alter the moisture conditions at

certain latitudes.

Low

Low

Low

High

High

Low pressure belts (convergence) are

known for rising air, cloud development and precipitation.

Humid-like climate

High pressure belts (divergence) are

known for descending air, few clouds and

lack of precipitation.

Arid-like climate

Climate Change due to Large Bodies of Water

Land tends to heat up and cool down more quickly than water (due to specific heat).

The temperature of a location near a large body of water will be moderated by its presence near the water (MARINE CLIMATE)

The temperatures of locations far away from large bodies of water are not affected by the presence of water (CONTINENTAL CLIMATE).

Providence, RI(MARINE CLIMATE)

The Atlantic Ocean helps to moderate the temperature of

the city.

Cooler summers and warmer

winters.

A narrow annual temperature range.

Lincoln, NE(CONTINENTAL

CLIMATE)

There is no large body of water nearby

to moderate the temperature of the

city.

Hot summers and Cold winters.

A wide annual temperature range.

Climate Change due to Prevailing Winds

Prevailing winds are generated by the convergence/divergence of air near pressure

belts and due to the Coriolis Effect.

Southern California is much “more of a marine climate” (more moderate

climate )due to the southwesterly winds blowing off the Pacific Ocean.

Storm track moving westward pick up moisture over the Great Lakes. Cities in northwestern New York

experience “lake effect” snows and rains due to this movement (more humid climate).

Climate Change due to Ocean Currents

Surface ocean temperatures are a

reflection of the amount of insolation

received.

Warm ocean currents tend to move away from the equator.

Warm ocean currents create warm, humid conditions for coastal

locations.

Cool ocean currents tend to move towards

the equator. Cool ocean currents create cool, drier conditions for coastal locations.

RT = Pg. 4

Some parts of Europe (Ireland, Iceland, England) may be more humid and a bit warmer during certain times of the year due to their presence near warm ocean currents.

The location and pathway of

ocean currents will change as the amount of

insolation received by

certain parts of the oceans

changes during Earth’s

revolution.

Climate Change due to Elevation

Elevation

Air

Tem

pera

ture

ElevationCh

ance

of

Prec

ipita

tion

Generally speaking…..

As air rises it expands and cools.

Higher elevations are less likely to be affected by greenhouse gases and the infrared radiation being absorbed by

them.

As air rises its temperature drops as does its capacity to hold water vapor. Dewpoint temperature is

reached, clouds form and precipitation follows.

Climate Change due to Mountains “The Orographic Effect”

WINDWARD LEEWARD

As prevailing winds move up the mountain:

1. Air rises, expands, and cools.2. Dewpoint is reached; clouds form

due to condensation.3. Precipitation occurs.

As prevailing winds move down the mountain:

1. Air descends, compresses, and warms.2. Air temperature is too high for

dewpoint to be reached.3. Little to no precipitation occurs.

Cool and humid Warm and arid

Climate Change due to Vegetation The vegetation of a region is determined by its climate.

Arid Humid

When the vegetation of a region is removed, the climate will change.

The destruction of this forest will cause the climate to change:

1. More insolation reaches the soil2. Temperatures rise3. Increase in greenhouse gases4. Less infiltration of water into the soil

UrbanizationDeforestation

Climate Change due to Cloud Cover

Areas that are prone to cloudy skies often experience

climatic change:

1. Less insolation strikes the earth’s surface.

2. Slight drop in temperature.

3. Clouds absorb and reflect insolation back into space.

“How come the equator is NOT the warmest spot on Earth’s surface? Where is the warmest place?”

Ecuadorian Beach, South America ~ 0˚ latitude (equator)

The equator is NOT the warmest spot on Earth due to the uplift of air from the low

pressure belt. This will lead to cloud formation and

precipitation.

The warmest place on Earth would be at the high pressure belts (30˚ N and S) where air is descending and there is a lack

of clouds.