Physical Geography Unit 2 notes

Circulation systems

everything is a system

what is wind?

The horizontal movement of air 

what produces wind?

Differences in air pressure between two places 

what is atmospheric pressure?

the force per unit area exerted against a surface by the weight of air above that surface, decreases with increasing altitude

what do the four forces in the atmosphere do?

determine both speed and direction 

gravitational force

the Earth’s pull on the gas particles that make up the air, directed toward the center of the Earth 

pressure gradient force

when air flows from high to low pressure, responsible for triggering the initial movement of air 

Coriolis force

an effect on Earth's rotation that deflects moving objects (deflects to the right in the northern hemisphere, and left in the southern hemisphere) (strongest near poles, none on equator) (force increases as object speed increases) 

friction force

drags on wind as it moves across Earth’s surface, decreasing with height above the surface (friction force counters Coriolis Force so winds cross isobars at an angle 

general atmospheric circulation

Hadley cell → ferrel cell → polar cell → subtropical jet stream → polar jet stream

Jet streams and characteristics

a jet stream is a high altitude river of high speed air, weak during summer and strong during winter (7600-10,700 m altitude)

El Niño

(warm phase) weakened/ revered trade winds, warmer SST’s, reduces upswelling (droughts in Africa, Australia, and India) (strong pacific hurricanes and heavy rain in Peru and U.S. southwest)

La Niña

(cool phase) stronger trade winds, cooler SST’s, enhanced upswelling 

Phase change

when water changes its state

1. Freezing and melting

2. Condensating, and evaporating 

3. Depositing and sublimating 

heat exchange 

during phase change provides >30% of energy powering atmospheric circulation 

humidity

water vapor in air  

maximum specific humidity

 maximum water vapor possible per unit mass of air

relative humidity

comparison of how much vapor exists vs how much the air can hold for given temperature 

dew point

 temperature at which air becomes saturated, and condensation begins to form water droplets

environmental lapse rate

decrease in temp. With increase altitude (rate for non-rising stable air)

DAR

rate at which dry air cools be expansion (if exceeding) or heat by compression (if descending) 

MAR

rate at which ascending air parcel that is moist and saturated cools by expansion 

atmospheric conditions 

relationship of DAR, MAR, and ELR determine atmospheric stability

unstable atmospheric conditions

when ELR>DAR (parcel stays warmer/less dense than environment, forming clouds and often precipitation)

conditionally unstable atmospheric conditions

when DAR<ELR<MAR (unsaturated parcels resist lifting, but once saturated at the lifting condensation level they become unstable and rise, forming clouds and often precipitation)

stable atmospheric conditions

ELR<DAR, and MAR (rising parcels is cooler/denser than its environment, skies are generally clear with limited vertical cloud coverage 

warm cloud precipitation 

warm clouds produce rain by collision-coalescence, tiny droplets condense on nuclei, collide, and merge into larger drops

cold cloud precipitation

 in cold clouds precipitation often forms by the bergeron process

weather

short-term day-to-day conditions of the atmosphere

climate

long term average (over decades) of weather conditions and extremes in a region 

what are air masses?

a body of air with uniform temperature, humidity, and stability characteristics

Classification of air masses

1. Moisture (M)

2. Temperature (A)

3. mT

4. cP 

Moisture (M)

for maritime (wet) and “c’ for continental (dry)

Temperature (A)

for arctic “P” for polar, “T” for tropical,

mT

maritime tropical

cP

continental polar 

converging lifting

low pressure center- air converging, and ascending, cooling and condensation occurring

convection lifting

the air above the warmer surfaces is heated and rises

Orographic lifting

air is forced to ascend upslope as it is pushed against a mountain 

frontal lifting

cold front and warm front

warm front

warm air moved up and over cold air, precipitation ahead of the warm front

cold front

cold air forces warm air upwards, precipitation behind and at cold front

how do tornadoes form?

A violently rotating column of air, a vortex, that extends downward from a cumulonimbus cloud

different names for hurricanes

hurricanes, cyclones, typhoons 

scale used for tornadoes

the enhanced Fujita (EF) scale, measures wind speed and damage (0-5)

scale used for hurricanes

the Saffir-Simpson hurricane wind scale, estimates possible damage from winds, (0-5)

Evapotranspiration

actual moisture demand (evaporation + transpiration)

what are the different surface water features?

resservions, lakes, wetlands

what are reservoirs fed by?

fed by rivers, streams, snowfall, rainfall

what are lakes fed by?

fed by rain, snow, streams, rivers, runoff, seepage from underground aquifers 

what are wetlands fed by? 

precipitation, groundwater, rivers, surface runoff

snow and ice

largest amount of freshwater is stored in glaciers, permafrost, and polar ice

rivers

flowing bodies of water that moves across land, originating from sources such as rainfall, or snowmelt 

lakes

large standing bodies of water, surrounded by land, often fed by rivers

Aquifers (confined)

bounded above and below by impermeable layers 

Aquifers (unconfined)

has a permeable layer above and in impermeable layer beneath

what happens to dry aquifers

without water for support, the aquifers begin to compact and collapse 

porosity

the void/empty space in a material

permeability 

deciding which liquids will be able to pass through 

point source pollution

pollution that originates from a single, identifiable source, such as a pipe or outlet.

non-point source pollution

pollution that comes from multiple, diffuse sources, making it difficult to pinpoint its origin, such as runoff from agricultural fields.