Last time…• Key questions

1. Why does air move? 2. Are movements of winds random

across Earth’s surface, or do they follow regular patterns?

3. Implications of circulatory systems for global climate?

4. Other factors governing spatial distribution & seasonal patterns of temperature & precipitation?

Gas Laws

• Same “amount” of air

• But volume greater

• Density?

Relationships between Pressure, Temperature, and Volume

Pi * Vi = Pf * Vf Boyles Law

Vi / Ti = Vf / Tf Charles Law

General Gas Law(Pi * Vi) / Ti = (Pf * Vf)/ Tf

Global Energy Redistribution

North-South Circulation in the Troposphere

•Implications of circulatory systems for global climate?

Water Vapor

• Warm air can hold move water vapor

• What happens when you cool air?Undersaturated

Supersaturated

Global Precipitation Distribution

Global Precipitation Distribution

Water Balance

• Water in = rain• Water out = evaporation

Deserts of the World

• 30˚ N and S• H pressure side of Hadley Cells

Hydrologic Cycle

• What are the major reservoirs of water on the Earth?

• What are the components of the hydrologic cycle?

• Why does precipitation occur in some areas and not in others?

• What controls the seasonal cycle of precipitation?

• The hydrologic cycle describes how water moves from one reservoir to another

Often this movement is accompanied by a change of phase and the addition or release of stored energy

Water Cycle

• Atm. -Ocean - Land

• Evap. - PPT - Runoff

Distribution of Water ReservoirsOceans

97%

Atmosphere 0.01%

Rivers, Lakes, and Inland Seas

0.141%Soil Moisture 0.0012%

Ground Water 0.4 – 1.7%

Ice Caps and Glaciers 1.725%

Water Cycle

• Atm. -Ocean - Land

• Evap. - PPT - Runoff

Change of Phase

• Evaporation/Melting/Sublimation – Addition of energy, change of phase

• Condensation/Freezing/Deposition – Release of energy, change of phase

• Water is the ONLY naturally occurring substance that exists in all 3 phases (solid, liquid, gas) at temperatures found on the Earth’s surface

• Water, in all its phases, is the primary

mechanism by which energy and matter are circulated among the Earth system components

Phase Changes of Water

Water Forms and Energy• Converting water absorbs

or releases energy

• If this happens in different places then energy is transferred

Global Water Balance

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Anthes, p. 47 (modified)

Earth’s annual water balance, (original) units are 105 km3 of water per year. Huge quantities of water are cycled through the atmosphere each year. On the continents, precipitation exceeds evaporation and the reverse is true for oceans. Runoff from the continents balances the deficit of the oceans.

Land Ocean

PrecipitationPrecipitation

Runoff

Total Water

Evaporation Evaporation

Transportation

• Precipitation • Runoff • Infiltration / Subsurface Flow • Transport in air • Transport in ocean currents

Why does it rain or snow?

Precipitation is caused by the uplift of moist air

• Air rising along the ITCZ or weather fronts (convergence)

• Convection caused by intense surface heating (not always accompanied by rain)

• Orographic uplift (rain deposited on windward side of mountains)

Relative Scales of Cloud-Forming Processes

Orographic Uplift

Water Vapor

• Warm air can hold move water vapor

• What happens when you cool air?Undersaturated

Supersaturated

Global Circulation

• Where will rain fall??• High Pressure or Low Pressure

Northern Hemisphere Summer Precipitation

• ITCZ Shifts north

• SE Asia wet

• 30˚ N and S - Dry

Northern Hemisphere Winter Precipitation

• ITCZ Shifts south

• SE Asia dry

• 30˚ N and S - Dry