METC 331 Exam 2

Control of Climate

Large-scale factors that affect regional climates

Surface Winds: Hadley Cell

Air flows northeasterly Trade winds: easterly

Thermally Driven Air

Air that moves purely due to temperature differences

Palmer Drought Severity Index(PDSI)

Assessment of long-term moisture conditions on a weekly basis by climate division across the U.S.

Subtropical Jet Stream

Associated with Hadley Cell Conservation of angular momentum Brought up from the south

Soil-Moisture Recharge

Bringing the soil moisture storage to field capacity

Ocean Circulation

Circular flows called gyres

Potential Evapotranspiration (PE)

Climatic demand for water from the land Driven by the amount of insolation at the surface Peaks in the high-sun season

Atmospheric Lifting Mechanisms

Convergent, convectional, orographic, frontal

Ocean Currents Control

Cool currents found on west coasts Warm currents found on east coasts Cool currents moderate temperatures Warm currents can lead to rising air--showers and storms

Latitude Control

Differing amounts of solar radiation Varying amount of day lengths Annual temperature range

Role of Coriolis: Ocean Currents

Direction of motion

Ferrel Cell

Dynamically driven: due to rotation of earth & interaction with other cells Rising in colder air regions

Seawater Properties

Freezes at a lower temperature App. 3% heavier than freshwater

Trade Wind Inversion

From warm, sinking air-- air warms as it subsides Can trap relatively cooler air closer to the surface --cooler air at the surface is denser Column of trapped air gets larger as one approaches equator Feature of stable air Found most commonly in Hadley Cell

Seawater Salts

From weathering/runoff Chlorine (55%), sodium (30%), sulfur (8%)

Long Term Drought

Greater than 6 months Affects hydrology (rivers, groundwater, lake levels)

Wind and Pressure Belt Control

High pressure locations Low pressure locations Westerlies/easterlies

Thermohaline Circulation

Horizontal and vertical dimensions Responsible for distributing heat and water Density differences --temperature and salinity 0.1m/s Residence time: 1,000years in deep ocean Could be the reason why Britian/Ireland are temperate

Wind Belts: Midlatitude Westerlies

Interplay between subtropical highs and sub polar lows Westerlies

Short Term Drought

Less than 6 months Affects grasses, agricultural crops that don't extend too deeply in the soil

Palmer Hydrological Drought Index(PDHI)

Longer term analysis than PDSI Reflects conditions relating to ground water availability and reservoir supplies

Flows in Ferrel Circulation

Low-level flow: westerly Upper-level flow: easterly Product of interaction with other cells Influenced by polar front

Shutting Down Thermohaline Circulation

May have shut down before Freshwater input--hard for heat energy to be aquired Turns climate much cooler

Location on Continent Control

More drastic temperature ranges inland compared to coastal locations Delayed onset of seasons near the coast

Topography Control

Mountainous locations have various climates across a small area Mass and density decrease with height...Water evaporates more quickly

Surface Winds: Polar Cell

Polar Easterlies Deflection very strong

Surplus

Precipitation beyond that needed for ET or soil-moisture recharge

Local Features Control

Presence of lakes, wetlands, forests, agricultural areas, urban areas Impact local or microclimates

Polar Front Jet Stream

Product of strong temperature gradient Strong pressure gradient Set into motion by temp gradient

Halocline

Rapid decrease in salinity

Pycnocline

Rapid increase in density warmer waters=less dense

General Circulation of the Atmosphere

Redistributes heat that arrives at the earth in greater quantities near the equator than near the poles --second law of thermodynamics

Thermocline

Region of rapid temperature decrease

Evapotranspiration (ET)

Represents the actual amount of water transpired by plants or evaporation that does occur Always less than or equal to PE Peaks at different times of the year

Role of Subtropical Highs: Ocean Currents

Set surface currents into motion Sinking air spreads out on surface Clockwise in NH

Ekman Spiral

Spiral flow of water that occurs in ocean's top 100m Also found in atmosphere Factor in upwelling Most water transported 90* from wind direction

Soil Moisture Utilization

Taking water out of soil to meet climate's demand (PE)

Soil Moisture Storage

The amount of water stored in the soil that is accessible to plants

Forcings of Thermohaline Circulation

Thermal forcing: warm water rises, cold sinks Haline forcing: saltier water sinks

Hadley Cell

Thermally driven Equatorial low Adiabatic cooling is why it does not reach the poles Air diverges at the surface near 30* --subtropical highs

Polar Cells

Thermally driven Net energy deficits at the poles cause the air to increase in density Air diverges at the surface Converging air near 60* is forced to rise--Subpolar lows

Circulation on a non-rotating earth

Tropical air should warm, become less dense, rise, go towards the poles Reaches the poles, cools, sinks, diverge at surface, head back to equator

Deficit (D)

When water supply is not enough to meet demand

Orographic Effect

enhanced precipitation over uplands that results from lifting and cooling of air masses as they are forced over mountains Rain shadow on other side of the mountain

Eddy

swirling current of water or air

Atmospheric Circulation is ______, whereas Ocean Circulation is ____.

uninhibited (not constrained); inhibited (constrained by presence of continents)