Section 1:

• A Cycle consisting of water A Cycle consisting of water entering the atmosphere through entering the atmosphere through evaporation and returning evaporation and returning through condensationthrough condensation and and precipitationprecipitation

Terms for the “Hydrologic cycle”

• Transpiration -

• Evaporation -

• Evapotranspiration -

• Condensation -

• Ground Water -

Transpiration . . . . .

• The loss of water into the atmosphere through the leaves of plants (sometimes referred to as “plant sweat”)

Evaporation . . . .

• The change of liquid water to gaseous water vapor

Evapotranspiration . . . .

• The combined effects of transpiration and evaporation.

Condensation

• The change of gaseous water vapor back into the liquid phase

Ground Water . . .

• Water which is stored and moves through the ground

Part 2: PrecipitationPart 2: Precipitation

Precipitation requires…..Precipitation requires…..

• Relatively warm moist air…

• Some agent to cause the warm moist air to rise …..

• Expansion of the air due to lower air pressure above it…..

• Causing the air to cool down below the “dew point”

Precipitation terms...Precipitation terms...• Capacity Capacity - The amount of water vapor the - The amount of water vapor the

air can hold at a given temperatureair can hold at a given temperature

• (Warm air can hold more moisture than (Warm air can hold more moisture than cold air)cold air)

• Absolute humidityAbsolute humidity - The amount of water - The amount of water vapor actually in the air at a given timevapor actually in the air at a given time

• Relative humidity -Relative humidity - A comparison of the A comparison of the absolute humidity to the capacityabsolute humidity to the capacity

Water will evaporate into dry air leading to a saturated condition such as is seen in the last flask.

As the temperature falls, the capacity of the air in the flask decreases and the water condenses

In order for clouds to form,3 basic ingredients must exist.

There must be warm moist airThere must be cooling temperaturesThere must be dust particles around

which the water vapor can condense to form cloud droplets.

As air rises, it expands As air rises, it expands and cools. This and cools. This lowers the capacity of lowers the capacity of the air and causes the air and causes condensation (cloud condensation (cloud formation) to occur.formation) to occur.

As Cloud droplets

strike one another,

they coalesce

(stick together) until they are heavy enough to

fall through the rising column of

air.

Mountains can block moving parcels of air and

force them upwards, cooling them by expansion.

Such cooling by expansion is called “Adiabatic Cooling”

III. Factors which affect III. Factors which affect climateclimate

A. Latitude

• 1. Areas of low latitude (near the equator) receive high angles of insolation (AOI) and are therefore warmer.

2. Areas of high latitude (near the poles) receive low angles of insolation and are therefore cooler.

3. The average AOI is equal to the compliment of the latitude. AOI = 90 - latitude

II. Altitude

• 1. As Altitude increases, the average daily temperature decreases.– a. The thinner blanket of air at higher altitudes

holds in less heat radiating from the earth back into the atmosphere than does a thicker layer at lower altitudes.

– b. Due to cooler temperatures, snow is often found at the highest altitudes, making temperatures even colder since white reflects rather than absorbs heat.

C Orographic Effects

• Mountains barriers force warm moist air to rise, making the windward sides of mountain ranges cool and wet and the leeward sides warmer and drier (deserts).

D. Proximity to large bodies of water

• 1. Since large bodies of water heat up and radiate heat more slowly than land, they “temper” the climate. Regions close to large bodies of water tend to have cooler summers and warmer winters.

• 2. Inland areas tend to have more severe temperature ranges with frigid winters and hot summers.

The “Badlands” of interior U.S. The “Badlands” of interior U.S. show evidence of extremesshow evidence of extremes

The Pacific Northwest is close to the ocean & is more temperate

E. Ocean Currents

• 1. Eastern coasts of continents tend to be warmed by currents coming up from the equator (driven by the Coriolis Effect)

• 2. Western coasts of continents tend to be cooler due to the ocean currents flowing down from the polar regions.

F. Planetary Wind Belts