climate

CLIMATE

An Abrupt Climate Change Scenario and Its Implications for United States National Security (Pentagon Report, 2003). Global warming “should be elevated beyond a scientific debate to a US national security concern... future wars will be fought over the issue of survival rather than religion, ideology or national honour.”

Understanding climate matters...

CLIMATE

I. Large Scale Determinants

A. Solar Radiation1. Average Radiation Budget

- Solar Constant = 2 calories/cm2/min

- 50% is reflected, absorbed, reradiated (Most ultraviolet light is reflected/absorbed) by the atmosphere

- on average, 1 cal/cm2/min strikes earth. (but this varies dramatically, as we will see…)

- 50% is reflected, absorbed, reradiated (Most ultraviolet light is reflected/absorbed)

Greenhouse effect

AB

SO

RB

AN

CE

CO2 fills ‘window’ in H2O absorbance

YAY OZONE!

A. Solar Radiation1. Average Radiation Budget 2. Local Radiation Budget – Angle of incidence (latitude and season)

3) More is reflected off surface; a lower percentage of what strikes/unit area is absorbed

1) Goes through more atmosphere2) Less energystrikes/unit area

(since it is spread over more area)

A. Solar Radiation1. Average Radiation Budget 2. Local Radiation Budget – Angle of incidence (latitude and season)

HIG

H E

NER

GY

LOW

EN

ERG

Y

LOW ENERGYB. Effects on Atmospheric Circulation

HIG

H E

NER

GY

LOW

EN

ERG

Y

LOW ENERGY

As air rises: - decrease pressure - increase volume - decrease energy/unit volume - decrease temperature

As air rises: - decrease pressure - increase volume - decrease energy/unit volume - decrease temperature

Decrease temp, increase tendancy of water vapor to condense

“Adiabatic cooling”

PV = nRT

As air rises: - decrease pressure - increase volume - decrease energy/unit volume - decrease temperature

Decrease temp, increase tendancy of water vapor to condense

“Adiabatic cooling”

As dry cold air falls: - increase pressure - decrease volume - increase energy/unit volume - increase temperature

“Adiabatic warming”

Increase temp of this dry air, evaporate water off surface

As dry cold air falls: - increase pressure - decrease volume - increase energy/unit volume - increase temperature

“Adiabatic warming”

30oN

30oS

30oN

30oS

TROPICAL RAINS at solar equator

HOT, DRY, DESERTS

HOT, DRY, DESERTS

30 N

30 S

Latitude of solar equator drive seasonal rainy seasons in tropics

Latitude of solar equator

Three cycles in each hemisphere:

Hadley

temperate (Ferrel),

polar

Transfer of energy from equator to poles

(“Why are global warming’s greatest effects at the poles, not in raising the temperature of the tropics?)

- Pattern of air movement along the surface of the earth…

C. The Coriolis Effect

-Pattern of air movement along the surface of the earth… - conservation of momentum east - speed relative to Earth changes (treadmill analogy)

C. The Coriolis Effect

C. The Coriolis Effect

D. Effects on Ocean Circulation

E. Long-Term Effects1. ENSO (El Nino Southern Oscillation)

E. Long-Term Effects1. ENSO (El Nino Southern Oscillation)

E. Long-Term Effects1. ENSO (El Nino Southern Oscillation)

2. Younger Dryas - Dramatic cooling of northern Europe 11,000-13,000 years ago, correlating with the melting of the Laurentian Ice Sheet in North America.- Fresh water formed a lens on surface; deflecting Gulf Stream to the east at a much lower latitude, starving Europe of the heat transferred by the Gulf Stream.

E. Long-Term Effects

F. Difficulties in Modeling Global Climate 1. Positive Feedback Loops

F. Difficulties in Modeling Global Climate F. Difficulties in Modeling Global Climate 1. Positive Feedback Loops

F. Difficulties in Modeling Global Climate F. Difficulties in Modeling Global Climate 1. Negative Feedback Loops

II. Determinants of Local Climate A. Topography

1. mountains

Merriam’s Life Zones in the southwestern U.S.

Valleys - Day

II. Determinants of Local Climate A. Topography

1. mountains2. valleys

Valleys - Night

II. Determinants of Local Climate A. Topography

1. mountains2. valleys

II. Determinants of Local Climate A. Topography

1. mountains2. valleys3. slope face

B. Water Bodies - act as heat sink/source as temp changes more slowly than air

SPRING to SUMMER

Land warms more rapidly than water body; heat transfers to cold water...increase in temp is buffered

B. Water Bodies - act as heat sink/source as temp changes more slowly than air

FALL to WINTER

Land cools more rapidly than water body; heat transfers to cold land...decrease in temp is buffered

B. Water Bodies - act as heat sink/source as temp changes more slowly than air

Continental climate Maritime climate

focus on temp (red) and NOTE scales differ!!

CONTINENTAL CLIMATE MARITIME CLIMATE

B. Water Bodies

- also a source of moisture

B. Water Bodies

- also a source of moisture

Maritime climate

B. Water Bodies

also a source of moisture

Continental climate (max 100) Maritime climate (max 160)

focus on precip (blue)

B. Water Bodies

-also a source of moisture

- depends on onshore vs. offshore winds/currents

Vancouver, 49N Boston, 42 N

Note differences in scale

C. Additive Effects - Atacama Desert

D. Seasonality in Temperate Lakes