Term
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Definition
| An immense body of air, some 1600+ km across and 1-3 km thick, with relatively homogeneous physical properties (density, T, & moisture) at a given altitude |
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Term
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Definition
| 2-letter abbreviations are used to indicate Source Region, characteristics, & types of air masses |
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Term
| 1st letter (Classification Scheme) |
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Definition
reference to surface over which it develops and thus the level of humidity (dry vs humid)
*c == continental: forms over a landmass = low water vapor content, dry
* m == maritime: forms over an ocean = high water vapor content, humid |
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Term
| 2nd letter (Classification Scheme) |
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Definition
reference to latitude of origin and thus temperature (cold vs. warm)
* A == arctic; bitterly cold
* P == polar; very cold
* T == tropical; warm
* E == equatorial; very warm |
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Term
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Definition
area in which air mass originates
* it determines initial characteristics of the air mass (cold vs. warm, dry vs. humid) |
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Term
| Criteria for Source Regions |
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Definition
1) large & physically uniform area
2) characterized by a general stagnation of atmospheric circulation |
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Term
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Definition
* Continental Arctic (cA)
* Continental Polar (cP)
* Continental Tropical (cT)
* Maritime Polar (mP)
* Maritime Tropical (mT) |
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Term
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Definition
| bitterly cold and very dry; stable |
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Term
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Definition
| very cold (winter) to cool (summer)& dry; stable |
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Term
| Continental Tropical (cT) |
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Definition
| hot and dry and usually unstable |
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Term
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Definition
*north Pacific = cool & humid; unstable in winter and stable in summer
*NW Atlantic = cold (winter) and unstable to cool *summer) & stable, both are humid |
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Term
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Definition
*Gulf of Mexico, Caribbean & western Atlantic = warm & humid, unstable on the western side of the STH
*Subtropical, eastern Pacific = warm and humid, stable on the eastern side of the STH |
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Term
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Definition
| a boundary separating air masses of different densities; one air mass is usually warmer and more moist |
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Term
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Definition
| frontal zone separating air masses of polar origin from air masses of tropical origin |
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Term
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Definition
* may develop in conjunction with or along the polar front
* low pressure cells and fronts are the primary structure of a mid-latitude wave cyclone |
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Term
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Definition
* Cold
* Warm
* Stationary
* Occluded |
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Term
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Definition
* boundary at the forward edge of an advancing cold air mass that is displacing warmer air
* moves at approximately 25-35 mps
* cumulus and cumulonimbus clouds associated with cold fronts
* symbolized on weather maps as a blue line with triangles |
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Term
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Definition
* boundary at the forward edge of an advancing warm air mass that is displacing cooler air
* moves at approximately 15-20 mph
* usually stratus clouds associated
* symbolized on weather maps as a red line with 1/2 circles |
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Term
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Definition
* when air movement is almost parallel to the boundary (front) and the surface position of the front moves at less than 5 mph
* symbolized on weather maps as a combination of cold/warm front symbolds |
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Term
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Definition
* a front formed when a cold front takes and replaces a warm front at the surface: have cold & warm type occluded fronts
* symbolized on weather maps as a purple line alternating between 1/2 circles & triangles |
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Term
| Mid-Latitude Wave Cyclone |
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Definition
* a low pressure cell that forms & moves along a front
* counter-clockwise circulation (NH) around the cyclone tends to produce the wavelike deformation of the front |
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Term
| Stages of the Wave Cyclone Life Cycle (6) |
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Definition
* usually last a week or less from stage 1-6
1) air masses, a cold and a warm are set-up along a front and move parallel to it
2) a wave forms and warm air starts to move poleward while cold are moves equator-ward
3) cyclonic (counter-clockwise) circulation develops, with general convergence at the surface and uplifting; warm air overrides the cold air (FRONTAL WEDGING)
afterward Cold Front & Warm Front established
4) cold front moving faster than warm front and begin to overtake it; OCCLUSION begins, forming an OCCLUDED FRONT
5) full development of an Occluded front and maximum intensity of the wave cyclone; steep pressure gradient and strong winds
6) pressure gradient weakens, energy exhausted & system dissipates |
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Term
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Definition
* Warm sector: primarily southwesterly to southerly
* Cool sector: southeasterly to easterly and the northeasterly
* Cold sector: northerly to northwesterly to westerly |
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Term
| Warm Sector (moisture, sky, & weather conditions) |
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Definition
| humid to very humid, warm temperatures, clear skies to scattered cumulus clouds |
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Term
| Cool Sector (moisture, sky, & weather conditions) |
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Definition
| humid, cool temperatures, large area of stratus clouds with light to moderate precipitation ahead of the warm front |
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Term
| Cold Sector (moisture, sky, & weather conditions) |
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Definition
| dry clear air back front the cold front, intense precipitation (T-storms) alonf the cold front, cold temperatures |
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Term
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Definition
| process that creates or develops a new wave cyclone, OR strengthens an existing wave cyclone |
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Term
| Criteria for a wave cyclone to form (3) |
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Definition
* Cyclonic flow must be established
* Vorticity
* Happens in the area of a jet stream or low pressure trough & is strengthened downwind of the trough |
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Term
| Vorticity/Absolute Vorticity Components |
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Definition
* Relative vorticity: the vorticity (spin) relative to Earth's surface
* Earth vorticity: which is due to Earth's daily rotation about its' axis
* If the flows are both in the same direction (counterclockwise in NH) then they complement each other increasing absolute vorticity |
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Term
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Definition
| Where air moves faster in one area of the jet stream wave than another |
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Term
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Definition
| Horizontal spreading of the airstream |
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Term
| Low pressure cells in the NH basically show _______ ________, while High pressure cells in the NH basically show _______ _________. |
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Definition
positive vorticity
negative vorticity |
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Term
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Definition
| the vorticity changes as you move along a wave and which is caused by convergence of air in one portion and divergence in another |
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Term
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Definition
| on the downslope of a trough, there is more convergence and thus increase vorticity or spin, while on the upslope there is divergence and decreased vorticity (ex: snowboarding in a 1/2 pipe) |
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Term
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Definition
| helps draw air upward from the surface and acting as a lifting mechanism above the surface low pressure cell |
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Term
| Speed divergence/convergence & cyclone development |
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Definition
| occur along the Rossby Wave with speed divergence occurring basically on the downslope of a trough and speed convergence |
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Term
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Definition
* this is the change in the horizontal component of moving air.
* Diffluence - air being spread apart (on the rough upslope)
* Confluence - air being forced closer together (on the trough downslope) |
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Term
| All the factors to produce POSITIVE VORTICITY (convergence, speed divergence, & confluence) are on the ___________ of the ________. |
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Definition
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Term
| All the factors to produce NEGATIVE VORTICITY (divergence, speed convergence, diffluence) are on the _________ of the _________. |
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Definition
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Term
| The primary mover of cyclones is the ____ ______. |
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Definition
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Term
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Definition
* narrow ribbons of high speed geostrophic winds & are part of the general Westerlies flow
* they occur in the mid-latitudes & can attain high wind speeds
* they're not stationary & show a Zonal/Meridional pattern |
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Term
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Definition
* affect daily weather in mid-latitudes
* in conjuntion with the movement of cP and mT air masses
* its undulations are the Rossby waves (determines where a cyclone will develop & the path it will move in) |
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Term
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Definition
| * influences the initial flow of mT air northward & a stirring mechanism for tropical cyclone development |
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Term
| The Jet Stream shifts ______ & ______ with the seasons, & is usually further ______ in the summer months & towards the _______ in the winter. (directions) |
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Definition
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Term
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Definition
a storm characterized by a cumulonimbus (Cn) cloud & accompanied by lightning & thunder
* of relatively short duration, a few hours
* accompanied by strong wind gusts, heavy rain, sometimes hail, & tornadoes
* great instability & vertical development |
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Term
| Requirements for formation of a thunderstorm |
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Definition
* warm, moist air -- which released latent energy when lifted & needs a continuous supply to overcome dry air and evaporation
* high surface T's -- enhances instability, air parcel warming & uplift |
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Term
| Stages of Formation of Thunderstorms |
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Definition
* Cumulus stage
* Mature stage
* Dissipating stage |
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Term
| Cumulus stage (thunderstorms) |
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Definition
initial build-up of cumulus clouds fueled by updrafts of warm, moist air cooling adiabatically
* updrafts are dominant in this stage |
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Term
| Mature stage (thunderstorms) |
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Definition
raindrops start to fall initiating downdrafts; process of entrainment (the influx of cool, dry surrounding air helping to fuel the downdrafts
* heavy rains, lightning, thunder, and hail in this stage |
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Term
| Dissipating stage (thunderstorms) |
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Definition
| downdrafts dominate; rain lessens; cooling with loss of warm air source & energy; storm breaks up and clouds evaporate |
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Term
| Locations of thunderstorm occurrence |
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Definition
* along the ITCZ, US (primarily east of the Rockies
* Florida is the state with the highest incidence of T-storms (# of days/year)
* Great Plains is the region with the greatest # per year |
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Term
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Definition
strong linear or "straight line" winds produced by thunderstorms
* winds in excess of 58 mps
* the result of downbursts (downdrafts)
* most occur between May & August in the Upper Midwest |
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Term
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Definition
| small (less than 2mi in diameter), severe downbursts of strong winds |
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Term
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Definition
| flash of light generated by the flow of electrons between oppositely charged parts of a cloud or between the cloud & the ground |
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Term
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Definition
* charges are separated within the clouds as the T-storm develops
* positive charges near the top, negative charges at the base
* it's the clouds' way of trying to equalize the charge difference or imbalance
* to discharged the negative base of the cloud |
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Term
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Definition
* within cloud lightning
* cloud-to-cloud lightning
* cloud-to-ground lightning |
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Term
| The lightning stroke (cloud-to-ground lightning) |
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Definition
* first an invisible step leader of electrons is formed from the cloud base to the ground
* then this path is illuminated as the electrons move back cloud-ward in the return stroke
* the first stroke is often followed by 3 or 4 more strokes, which makes up the single flash we see |
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Term
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Definition
* ball lightning: appears as a round, glowing mass of electrified air, usually of basketball size or smaller and lasting around 15 seconds
* St. Elmo's fire: result of ionization in the air causing tall objects such as steeples or ship's masts to glow as they emit sparks
* Sprites: large (up to 57 miles above the cloud top) but short-lived electrical bursts that rise from cloud tops as lightning occurs below (looks like a giant red jellyfish)
* Blue jets: an upward moving electrical ejection from the tops of the most active thunderstorms. They move at about 60 mph, attaining heights of 30 miles above the surface |
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Term
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Definition
the sound emitted by rapidly expanding gases along a channel of lightning discharge
* air heated quickly, expands explosively and you hear the sound waves = thunder |
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Term
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Definition
| violently rotating column of air or vortex attended by a funnel-shaped or tubular cloud extending downward from a cumulonimbus cloud |
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Term
| Characteristics of Tornadoes |
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Definition
* pressure at the center of vortex often 90-100 mb below the surrounding air = strong pressure gradient (estimated)
* high winds are measured on the Enhanced Fujita Scale EF0-EF5
* travels horizontally
* form in association with thunderstorms & likely to occur in the area of the T-storm adjacent to (behind) the area of large hail, usually the SW section of the T-storm |
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Term
| Requirements of Formation of Tornadoes (4) |
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Definition
* T-storm, usually associated with a cold front or squall line
* 2 air masses with strong T gradient across the frontal boundary
* moist air with high degree of instability
* upper level support, jet stream, which helps pull away rising air promoting greater surface uplift |
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Term
| Formation of tornadoes (2) |
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Definition
* Weak tornadoes: (EF0 & EF1) form as winds drawn into the T-storm converge and form a vertical vortex, and is pulled upward into the cloud base
* Stronger tornadoes: (EF2-EF5) start out in a horizontal position. As wind is drawn into the T-storm from miles away, air closest to the ground moves slower than the air above it, causing the air to tumble like a barrel rolling on the ground. This mesocyclone is then drawn upward by the updrafts and becomes a vertical tornado |
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Term
| Locations of tornado occurrence |
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Definition
* dominate in N. America & esp. the US
* avg. 750-800/yr in the US
* highest concentration in "Tornado Alley" (central Texas to Nebraska)
* associated with hurricanes
* seasonal with the SE US Tornado season in March/April |
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Term
| Watch vs. Warning: Tornado or Thunderstorm |
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Definition
* Watch: means conditions are favorable for the occurrence of this type of weather in your area, within the time period stated in the watch announcement
* Warning: this type of weather has been spotted by a trained observer, or has been indicted by Doppler radar in your area |
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Term
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Definition
an intense, tropical cyclonic storm consisting of a warm-core low pressure cell at its center, inward spiraling rainbands, & having sustained winds in excess of 74 mph
* due to the necessary requirements for formation, they begin life only in tropical waters; can be found in 3 of the Earth's main oceans |
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Term
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Definition
* hurricane: Atlantic ocean & eastern Pacific ocean
* typhoon: western Pacific ocean (usually a little bigger)
* cyclone: Indian ocean |
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Term
| Characteristics of hurricanes (6) |
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Definition
1) cyclonic storm -- with warm-core low pressure at its center
2) average diameter of 360 miles
3) form over warm ocean waters
4) strong pressure gradient to generate strong winds, strongest in the eye wall & decrease outward
* heavy rain, lightning, and sometimes tornadoes
* avg. life span of 7-10 days, but can last over 2 weeks |
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Term
| Requirements for formation of hurricanes (4) |
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Definition
1) warm, moist air: yields greater instability & life
2) ocean water T's > 27*C (81*F)
3) uplift initiated by an easterly wave (trade winds @ ITCZ)
4) must form between 5*-20* latitude for sufficient Coriolis Force to initiate rotation |
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Term
| Life Cycle of a Hurricane (4) |
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Definition
1) Tropical disturbance
2) Tropical depression
3) Tropical storm
4) Hurricane |
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Term
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Definition
* 1st stage in life cycle of hurricane
* the initial mass of thunderstorms with weak, if any, cyclonic circulation
* usually originate in conjunction with easterly wave (a large undulation or ripple in the normal tradewind) |
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Term
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Definition
* 2nd stage in the life cycle of a hurricane
* stronger cyclonic circulation, greater development
* sustained winds near the center of the system between 25-37 mph
* given a # (stage, category) |
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Term
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Definition
* 3rd stage in the life cycle of hurricane
* well developed cyclonic circulation, with the beginnings of an eye wall and rainbands, but usually no distinct eye as yet
* sustained winds in the eye wall 38-74 mph
* given a name |
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Term
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Definition
* 4th stage in the life cycle of hurricanes
* fully developed with strong cyclonic circle, distinct eye, eye wall, & spiral bands
* sustained winds within the eye wall in excess of 74 mph |
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Term
| Hurricane Category wind speeds |
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Definition
* Cat. 1: 74-95
* Cat. 2: 96-110
* Cat. 3: 111-130
* Cat. 4: 131-155
* Cat. 5: >155 |
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Term
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Definition
* Eye
* Eye wall
* Spiral bands |
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Term
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Definition
| center of low pressure, calm winds with weak downdrifts |
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Term
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Definition
area of strongest pressure gradient & thus most intense winds
* greatest vertical development & concentration of T-storms, rain, tornadoes |
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Term
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Definition
primarily stratus & nimbostratus clouds with light rain to moderate
* often find T-storms
* largest part of a storm in terms of areal coverage |
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Term
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Definition
1) strong, fast winds; also tornadoes; even tropical storm strength winds do damage
2) storm surge - abnormal rise of sea level along the coast & high waves as a result of the strong winds & low pressure
3) Flooding - due to heavy rains & the storm surge
* storm surge, flooding, and wind damage are usually most severe on the right side of the system |
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Term
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Definition
* peak time in Sept.
* depends on the area
~ Atlantic Ocean: June 1-Nov 30
~ Eastern Pacific Ocean: June 1-Oct 31
~ Western Pacific Ocean: June 1-Dec 31 (NH); Jan 1-Mar 31 (SH) |
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Term
| Hurricane watch vs. warning |
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Definition
* watch: an approaching storm will make landfall within 24-36 hours
* warning: an approaching storm will make landfall in less than 24 hours
* tropical storm watch & warning: have the same time periods, but are issued for those areas likely to be affected by tropical storm force winds & not the hurricane force winds |
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Term
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Definition
* originally formed within the Earth & brought to surface by out-gassing or de-gassing
* covers 71% of the earth by area |
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Term
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Definition
* 97.22% is in the oceans & salt water bodies; 2.78% is freshwater
*can be delineated into 4 sections: Pacific, Atlantic, Indian, & Arctic oceans (and gulfs)
* variations in salinity, depth, nutrient, & sediment load |
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Term
| Water's effect on climate |
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Definition
1) as a heat source to generate movement within the atmosphere
2) as a source of water for latent heat transfer, clouds, & precipitation |
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Term
| how the _____ & _______ interact basically dictates most weather patterns |
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Definition
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Term
| Wind helps generate the movement of the oceans... |
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Definition
* but the movement of the oceans also plays a role in the movement of the air, both horizontally (advection or wind) & vertically (convection)
* differing sea surface T helps create differing pressure patterns which in turn helps create differing wind patterns
* the various movement patterns of the oceans help dictate the above patterns |
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Term
| 2 Primary ocean movements |
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Definition
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Term
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Definition
the horizontal movement of ocean water, primarily at the surface
* instrumental in the transfer of heat energy from the tropics towards the poles & visa vera
* they're driven by surface winds, which drag the water along |
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Term
| Ocean current characteristics (7) |
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Definition
* the speed is greatest at the surface & decrease with depth
* the direction is governed by surface winds
* N & S Equatorial currents are move by Trade Winds
* Gulf Stream & Kuroshio currents by the Westerlies
* they flow at a 45* angle & are deflected by the Coriolis Force
* warm currents usually result in higher amounts of precipitation & cold currents usually result in lower amounts
* warm current will keep the land area a little warmer in the winter & a cold current will often keep the land area a little cooler in summer |
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Term
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Definition
| the curvature of the ocean current due to the Coriolis force |
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Term
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Definition
the vertical movement of water within the ocean, between the surface & great depth
* the result of warmer surface water often being pushed seaward (away from land) & replaced by colder water from depth
* often causes cooler T* on adjacent land surface
* doesn't increase nutrient supply at the surface |
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Term
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Definition
| (El Nino/Southern Oscillation) a combination of two events which sometimes happen in the same year |
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Term
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Definition
a southerly flowing warm ocean water current that generally develops off the coast of Ecuador & Peru around Christmastime & may last for several months
* named "the boy child" b/c it's around Christmas |
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Term
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Definition
an oscillation pattern of pressure change over the waters of the eastern Pacific (Peru side) & western Pacific (Indonesia-Australia side)
* normally there is persistent high pressure over the eastern pacific and low over western Pacific, which generated wind patterns from E to W, which is known as the Walker Circulation
* sometimes the pressure patterns reverse |
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Term
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Definition
* causes a "piling-up" of warm ocean water off the NW coast of South America
* sea surface T*'s may warm as much as 8*c (14*F)
* the Peru current brings cold, nutrient-rich water up from lower depths (upwelling)
* the cold water yields a relatively drier climate along the coast (Atacama desert)
* warm water flows south, depressing the nutrient-rich waters & thus the fish population
* the warmer waters change weather patterns primarily by increasing precipitation |
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Term
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Definition
may impact on a more global scale, effecting weather patterns across the Pacific into the Northern Hemisphere
* drier, warmer conditions in Indonesia & Australia, perhaps even reaching to India
* wetter conditions in parts of South America
* wetter winter conditions in SW & Southern US
* warmer than avg. winters in northern US, into Canada
* strong westerly winds in the uppoer troposhere which depress the development of hurricanes in the Atlantic |
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Term
| Examples from the '83 ENSO |
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Definition
* sea-level & T's increase in the eastern Pacific
* 100" of rain over 6-months in Peru & Ecuador
* monsoon rains in western pacific moved eastward leaving drought conditions in Indonesia, Australia, & India
* one of the warmest winters & wettest springs for the US |
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Term
| History & Occurrence of ENSO Events |
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Definition
* Sir Gilbert Walker - coined the term
* recurrence avgs. every 3-5 years, but may range 2-12 years |
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Term
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Definition
a condition when sea surface T's are cooler than normal in the eastern Pacific & this cool water extends farther westward than usual
* sometimes referred to as the anti-El Nino or "cold phase"
* don't always follow and ENSO or El Nino
* cycles aren't as distinct as El Nino |
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Term
| La Nina's impact on global climate |
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Definition
* typically opposite of El Nino impacts
* warmer, drier winters in SE US
* cooler winters in western US & Great Plains than normal |
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Term
| Pacific Decadal Oscillation (PDO) |
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Definition
shifting of SSTs between the northern & western Pacific & the easter tropical Pacific ocean
* has a warm phase (high SST's in the eastern tropical Pacific) & a cold phase (low SST's in the eastern tropical Pacific)
* may also affect El Nino events, at times enhancing these impacts |
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Term
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Definition
variation in pressure, wind, * SST's between northern polar regions & lower latitudes
* in a warm phase event, there is relatively low pressure over polar locations & higher-than-normal pressure at lower latitudes, thus creating warmer winters
* in a cold phase event, the opposite conditions prevail |
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Term
| North Atlantic Oscillation (NAO) |
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Definition
| an oscillation similar to the PDO, but more closely linked to changes in the AO cycle |
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