GY 101 Exam 2

Polar Jet Stream

A fast stream of air that exists in the upper troposphere, winds are twice as strong in winter as summer

Pacific Decadal Oscillation

A large, long-lived oscillation pattern that exists across the pacific ocean

Subtropical Jet Stream

A mechanism to transport moisture and energy from the tropics towards the poles

Southern Oscillation

A periodic fluctuation in sea-level atmospheric pressures, linked to the oceanic variations that most El Nino events are dubbed ENSO events

Intertropical Convergence Zone (ITCZ)

A zone of low pressure at the equator due to intense heating. Also referred to as the Equatorial Low

Categories of Vorticity

Absolute Vorticity Relative Vorticity Earth Vorticity Positive Vorticity Negative Vorticity

Continental Arctic (cA)

Air masses that contain extremely cold and dry conditions

Continental Tropical (cT)

Air masses that form during the summer over hot, low latitude areas, unstable due to low availability of water vapor, do not usually produce precipitation

Continental Polar (cP)

Air masses that form over large, high latitude land masses, such as N Canada and Liberia, typically stable

Maritime Polar (mP)

Air masses that form over the N Pacific and are more moderate than cP, migrate east

Maritime Tropical (mT)

Air masses that form over warm tropical waters, influence the southeastern US primarily in the summer, high moisture content and instability create oppurtunites for precipiation

Polar Easterlies

Air moving towards the equator that is deflected by the Coriolis

Polar Highs

Areas of high pressure

Semipermanent Pressure Cells

Areas of high/low pressure that undergo seasonal changes in position and strength

Subpolar Lows

Areas of low pressure

Source Regions

Areas of the globe where air masses form. Air masses will reflect the temperature and humidity characteristics of the source region.

Global Scale

Atmospheric features that cover large portions of earth and maintained over and extensive time period

Sea Breezes

Blow from sea to land

Land Breezes

Blow out to sea from land

Fronts

Boundaries between different air masses, usually linked to midlatitude cyclones

Drylines

Boundaries between humid air and denser dry air, favored location for Tstorm development

Northeasters

Bringing cold winds and heavy snowfall to the US northeast, result from mP air masses

Westerlies

Caused by air moving from the subtropical highs towards the subpolar lows by the Coriolis Effect

El Nino

Characterized by unusually warm waters in the eastern equatorial Pacific Ocean

Polar Cell

Circulates air at the poles

Hadley Cell

Circulates air between the tropics and subtropics

Ferrel Cell

Circulates air in the middle latitudes

Air Masses

Contain uniform temperature and humidity characteristics

Mesoscale

Cover just a few square km to hundreds of square km

Tornado Outbreaks

Describe and event in which a single weather system produces at least 6 tornados

Polar Front Theory

Describes interactions between unlike air masses and the related aspects of the mid latitude cyclones

Cyclogenesis

Describes the formation of a midlatitude cyclone, occurs along the boundary separating cold from warmer westerlies

Single-cell Model

Describes the general movement of the atmosphere, proposed by George Hadley

Microbursts

Downbursts with diameters of less than 4km

Gust Front

Downdrafts that reach the ground and surge forward as a wedge of cold dense air

Gulf Stream

Formed when the N Equatorial current reaching the S American coast turns northward

Outflow Boundary

Formed when the downdraft spreads outward and converges with the warmer surrounding air

Equatorial Countercurrent

Formed when the water from the N and S Equatorial Currents converges and piles up in the western equatorial Atlantic

Downburst

Gusts of wind that can reach speeds in excess of 270km/hr

Severe Thunderstorms

Have wind speeds that excees 93km/hr, hail larger than 2.4cm, or spawn tornados

Conveyor Belt Model

Helps describe conditions associated with midlatitude cyclones through 3D model

Synoptic Scale

High and low pressure patterns over large parts of continents

Monsoon

Indicated a seasonal reversal in sureface winds. Occur due to seasonal thermal differences between landmasses and large water bodies

Subtropical Highs

Large band of high pressure

Derechos

Large scale horizontal winds produces by strong dowdrafts associated with MCCs

Rossby Waves

Largest of the atmospheric waves, circle the globe at any one time and each have its own wavelength and amplitude

Cold Conveyor Belt

Lies north of the warm front

Sheet Lightning

Lightning that is obscured by clouds

Upper air divergence must be present for a __________ to form

Midlatitude Cyclone

Three-cell Model

Model that divides each hemisphere into 3 cells: The Hadley, Ferrel and Polar cells

Zonal Winds

Move in an east/west or west/east direction

Meridional Winds

Move in north/south or south/north direction

Occluded Fronts

Occur when two fronts meet, the warm air mass between them is displaced aloft

Walker Circulation

Occurs in the tropical Pacific where air normally rises over the western ocean decends over the eastern pacific

Cloud-to-Cloud Lightning

Occurs when clouds discharge electricity within clouds, happens when voltage gradient overcomes the electrical resistance of the air, 80% of all lightning is this

Cloud-to-Ground Lightning

Occurs when electrical discharge travels between the base of the cliud and the surface, 20% of lightning is this

St. Elmo's Fire

Occurs when ionization in the air causes tall objects to glow as they emit sparks

Upwelling

Occurs when strong offshore winds along a coastal region drag warmer surface waters seaward

Occlusion

Occurs when the cold front joins the warm front, closing off the warm sector

Warm-Type Occlusion

Occurs where the cold front associated with mP air, migrates to an area that is occupied by cP

Supercell

One powerful cell, as opposed to a cluster of smaller cells, most severe and intense storms

Mesoscale Convective Systems (MCSs)

Organized groups of Tstorms

Dry Conveyor Belt

Originates in the upper troposphere as a part of the westerly flow

Warm Conveyor Belt

Originates near the surface in the warm sector and flows toward the warm front

Ekman Spiral

Refers to a structure of currents or winds near a horizontal boundary in which the flow direction rotates as one moves away from the boundary

Ball Lightning

Refers to a type of lightning that appears a round glowing mass of electrified air

Runaway Breakdown

Refers to the energy released when a large number of runaway electrons accumulate in a a small volume

Air Mass Thunderstorms

Relatively small, localized, short-lived Tstorms that do not produce strong winds, large hail or tornados, most common and least destructive Tstorms

Suction Vortices

Several small zones of intense rotations in tornados

Polar Fronts

Strong boundaries that occur between warm and cold air

Arctic Front

The boundary between cA and cP

Stepped Ladder

The rapid and staggered advance of a shaft of negatively charged air

Vorticity

The rotation of air (think vortex)

Waterspouts

Tornados that occur over warm bodies, instead of over land

Multicell Thunderstorms

Tstorms that develop into clusters

Mesoscale Convective Complexes (MCCs)

Type of MCS, circular clusters

Squall Lines

Type of MCS, linear bands of Tstorms

Blue Jets

Upward-moving electrical ejections from the tops of the most active regions of thunderstorms

Cold-Type Occlusion

Usually occurs where a cold front associated with cP air meets a warm front with mP air ahead

Sprites

Very large electrical bursts that rise from cloud tops as lightning occurs below

Microscale

Very small scale, like ripples that form on snow or a sandy beach

Katabatic Winds

Warm by compression but originate when air is locally chilled over high elevations, air becomes dense and flows downslope

Mature Cyclone

Well-developed fronts circulating about a deep low pressure center

NE Trade Winds

Winds in the N Hemishere deflected to the right

SE Trade Winds

Winds in the S Hemisphere deflected to the left

Chinook Winds

Winds on the eastern side of the Rocky Mountains and form when low pressure systems occur east of the mountains

Foehn Winds

Winds that flow down the side of mountain slopes, air undergoes compressional warming

Santa Ana Winds

Winds that occur in California during the transitional seasons, contribute to the spread of wildfires

Tornados

Zones of extremely rapid, rotating winds beneath the base of a cumulonimbus cloud