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)
