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Geol 1302 Chapter 6 Climate Change, Talbot, UH Exam 2 (SG)
Terms in this set (88)
Mt. Washington (April 12, 1934)
The greatest surface wind speed ever observed by human instrumentation, other than tropical cyclone was recorded at Mount Washington in New Hampshire. The wind gust was 231 miles per hour.
Continuity and Variability of Wind
is a link between the horizontal and vertical motions of air.
The push or pull on an object, and a vector quantity with both magnitude and direction.
a measure of force acting on a unit area.
Sea Level Average Air Pressure
1031.25 millibars (mb) and at an altitude of 5500m (18,000 ft.), air pressure is half of its average value than at sea level.
varies with both distance and time, shaping the circulation of the atmosphere.
varies inversely with both temperature and humidity; air density increases with falling temperature and decreasing humidity. Cold, dry air masses are denser and usually produce higher surface pressures than warm, humid air masses.
The change in air pressure over a distance. They occur both vertically and horizontally within the atmosphere. the vertical air pressure gradient always decreases with height since air pressure always decreases with increasing altitude at a rate dependent on the decreasing density of the air.
Pressure Gradient Force
always orients perpendicular to isobars and toward lowest pressure. The magnitude of the ? is inversely related to the spacing of isobars. The wind is relatively strong where the pressure gradient is steep (closely spaced isobars), and light where the pressure gradient is weak (widely spaced isobars).
Coriolis Effect (Newton's First Law of Motion)
referred to as the deflection
Coriolis Force (Newton's First Law of Motion)
the apparent force derived to describe its magnitude and direction. The magnitude of the Coriolis force ranges from zero at the equator and maximum at both the North and South poles.
is the resistance that an object or medium encounters as it moves in contact with another object or medium.
one source of fluid friction is the random motion of molecules composing of liquid or gas.
fluid friction that arises from much larger irregular motions, called eddies that develop within fluids. (Example swiftly flowing stream of water)
Visible as swirls of water that tap the stream's kinetic energy causing the stream to slow.
Atmospheric Boundary Layer
where frictional resistance (eddy viscosity) arising from the surface effects essentially confined.
Gravity (Newton's Law of Universal Gravitation)
is the force attraction between Earth and another object, its magnitude directly proportional to the product of the masses of Earth and the object, but inversely proportional to the square of the distance between their centers of mass.
Oblate Spheroid (Earth)
Not a perfect sphere, with equatorial zone that bulges slightly. The bulging is caused by the rotation that ensures surface gravity is marginally less at the equator than at the poles, since the equator is at a greater distance from the center of Earth's mass.
GRACE (Gravity Recovery and Climate Experiment Mission)
This mission acquires high-resolution, global-scale measurements of Earth's gravity field to provide insights into variations of the global distribution of water.
If our Earth did not rotate what would happen with the winds?
The winds would blow directly from high pressure to low pressure.
is an un-accelerated, horizontal movement of air that follows a straight path at altitudes above the atmospheric boundary layer. It is a balance between the horizontal pressure gradient force and the Coriolis force, because the Coriolis force is significant only in larger-scale circulations. It only develops in large-scale weather systems.
is a realistic model for atmospheric air flow. It shares similar characteristics as the geostrophic wind but has curved isobars and is large-scale and frictionless blowing parallel to isobars, path is curved, not straight. Forces are not balanced because a net centripetal force constrains air parcels to a curved trajectory.
How does surface roughness affect horizontal surface winds blowing around an anticyclone or cyclone?
Surface winds in a pressure field where isobars are straight and parallel, friction slows anticyclonic and cyclonic winds and, combined with the Coriolis force, shifts horizontal winds so they blow at an angle less than 90 degrees across isobars and toward the low pressure.
consists of free-swinging horizontal shaft with a vertical plate at one end and a counterweight (arrowhead) at the other end.
is always designated and reported as the direction from which the wind blows.
consists of 3 or 4 open hemispheric or conical-shaped cups mounted to spin horizontally on a vertical shaft. One cup faces the wind at any time. They are calibrated to read in m/s, km/hr, or knots.
is based on the effect of wind on the propagation of sound waves. Replaced anemometers at NWS, ASOS in 2005.
Scatterometers (ISS-RapidScat Mission)
they are mounted on satellites and International Space Station to monitor near-surface ocean wind speeds and directions accurately and continually. They are a radar system, they emit pulses of microwave energy to the instrument as an echo. Stronger the wind results in more backscatter and higher microwaves.
systems are continental or oceanic in scale, such as extratropical cyclones, hurricanes, and air masses. (Space scale, 100-10,000km) (Time Scale, weeks to months).
systems that include thunderstorms, and sea and lake breezes, circulation systems that are so small that they may influence the weather in only a portion of a county or large city. Space scale (1-100km), (Time Scale Hours to a day).
A weather system that covers a very small area, such as several city blocks or a small town, represents the smallest spatial subdivision of atmospheric motion. Space Scale (0.001-1), (Time Scale Seconds to Hours).
Atmosphere's Planetary-Scale Circulation
plays an important role in the transport of heat poleward from energy surplus regions to energy deficit regions and the atmospheric transport of water is also a part of the global water cycle.
Non-rotating Sphere (Model of Non-rotating Earth)
huge convection currents develop on the sunlit portion of the planet's Northern and Southern Hemispheres so that air circulates between the hot equator and cold poles.
Rotating Earth (Northern Hemisphere)
surface winds blow from the Northeast in the Northern Hemisphere owing Coriolis Effect.
Rotating Earth (Southern Hemisphere)
surface winds blow from the Southeast owing the Coriolis Effect.
divide into 3 belts in each Hemisphere of a rotating planet.
Converging and Diverging Zones
winds give rise to East-West belts of low pressure and high pressure. By adding the continents and ocean basins produces the realistic model for time-averaged planetary-scale circulation.
Semi-Permanent Pressure Systems
They undergo important seasonal changes in both location and strength. They include subtropical anticyclones, the intertropical convergence zone (ITCZ), subpolar lows and polar highs and are linked by planetary-scale wind belts.
Subtropical Highs (Subtropical Anticyclones)
are imposing features of the planetary-scale circulation centered over subtropical latitudes, on average, near 30 degrees N and S of the North and South Atlantic, the North and South Pacific, and the Indian Ocean. Extending from the ocean surface up to the tropopause, and they are a major influence on climate over vast areas of the ocean and continents.
Name given to all latitudes between about 30 and 35 degrees N and S under subtropical highs.
Surface winds north of the horse latitudes that are highly variable at mid-latitudes.
Surface winds blowing from the northeast out of the southern flanks of the anticyclones.
Intertropical Convergence Zone (ITCZ)
has the most active weather and is the location where a you will find a discontinous low-pressure belt with thunderstorms paralleling the equator.
In the Southern Hemisphere, the midlatitude northwesterlies and the polar southeasterlies converge along a nearly continuous belt of low pressure around the Antarctic continent, producing and upper-air eastward flowing jet stream encircling the Antarctic.
is a narrow zone of transition between air masses that differ in temperature, humidity or both.
is not continuous around the globe, instead, it is well-defined in some areas and not in others, depending on the temperature contrast across the front. It is well defined temperature gradient in the winter and is a potential site for development of extratropical cyclones.
are situated on either side of the (ITCZ) and extend poleward to the subtropical highs.
Trade Wind Inversion
a persistent and climatically significant feature of the planetary-scale circulation over the eastern portions of tropical ocean basins. The formation of the trade wind inversion is the descending branch of the Hadley cell.
Intertropical Convergence Zone (ITCZ)
follows the sun's path in the sky, reaching its most northerly latitudes in July and its most southerly latitudes in January.
Rossby Waves (Carl-Gustav Rossby Swedish-American meteorologist)
Discovered in late 1930's characterize the westerlies above the 500-mb level, where the atmospheric pressure is 500mb. At lower levels, waves are distorted somewhat by friction and topographic irregularities of Earth's surface.
Meridional Component (Weaving Westerlies)
The north-south airflow located at midlatitude westerlies with significant north-south component.
Zonal Component (Weaving Westerlies)
the west-to-east airflow with only a small meridional component.
a cutoff low or a cutoff high that prevents the usual west-to-east movement of weather systems. Blocking tends to exist for extended periods of time, often several weeks or longer, weather extremes, such as drought, flooding, or excessive heat or cold.
the implication is anthropogenic global warming could heighten the chances that some regions in the mid-latitudes could experience both exceptionally warm and cold patterns in some seasons.
Norwegian Cyclone Model (Bergen School of Meteorology WW1, 1920's)
Led by Bjerknes, Swedish Meteorologist, experimented the variance in air mass types, fronts and cyclones by taking surface weather data samples from observations and recording them in journals.
The birth of a cyclone, usually occurs along the polar front, directly under an area of strong horizontal divergence in the upper troposphere.
narrow corridors of very strong winds.
Polar Front Jet Stream
is located above the polar front in the upper troposphere between the midlatitude tropopause and the polar tropopause. This jet follows the meandering path of the planetary westerly waves and attains wind speeds that frequently top 160 km/hr (100mph). Also, helps steer the cyclones in a given direction.
tend to originate and develop where key atmospheric conditions and topographic features coalesce and form where atmospheric stability is weak, favoring ascending motion of air, with a nearby source of warm, humid air, which favors condensation of water vapor at low levels, release of latent heat and increased bouyancy.
Extratropical Cyclone Path (Coterminous U.S.)
All storms tend to converge toward the northeast
Where do Extratropical Cyclone's form?
they form over the Pacific Ocean, near the Aleutians or the Gulf of Alaska.
develops to the leeward side of the Canadian Rockies in Alberta and travels rapidly east across southern Canada or northern tier United States.
they track toward the northeast along the East Coast, seen typically as "Texas" and "East Gulf of Mexico.
Chapter 6, Climate Change Talbot, UH Lecture
Powerpoint terms and concepts
Friction Influence (Surface Winds, Cyclones, Anticyclones)
diminishes with altitude
strengthen with altitude through the atmospheric boundary layer
Angle between wind direction and isobars is
greatest near Earth's surface and decreases with altitude until essentially zero at the top of the atmospheric boundary layer.
Anticyclone surface winds (Northern Hemisphere)
blow clockwise and spiral outward.
Cyclone surface winds (Northern Hemisphere)
blow counter-clockwise and spiral inward.
Ridge (Isobars High Pressure)
anticyclone curves. Winds parallel isobars above the atmospheric boundary layer.
Trough (Isobars Low Pressure)
cyclonic curves. Winds cross isobars toward low pressure near Earth's surface.
Characteristics of Anticyclone
-Descending air causes temperature and saturation vapor pressure to increase.
-Lowers relative humidity.
-Clear skies, fair weather
-Favors intense nocturnal radiational cooling
Horizontal air pressure gradient is very weak over broad area around center of system
ground may be chilled to saturation at night resulting in dew, frost or fog
Air masses develop under large high pressure systems.
Characteristics of Cyclone
-Ascending air ascends causes temperature and saturation vapor pressure decrease.
-increases the relative humidity of unsaturated air.
-Clouds and precipitaiton might develop.
-Typically stormy weather
Air flows into a low pressure system from all directions, at middle and high latitudes.
Brings together different air masses, seperated by front.
Airport Wind Sock
Cone shaped cloth sleeve open at both ends.
Wind Belt ( Northern Hemisphere Order)
1. Low Pressure (North Pole, Polar Latitudes)
2. High Pressure (Mid latitudes, sub tropical, Bermuda High)
3. Low Pressure (Equator, ITCZ)
Wind Belt ( Southern Hemisphere Order)
1. Low Pressure (Equator, ITCZ)
2. High Pressure (Mid Latitudes, South America and other continent areas in the Southern Hemisphere region).
3. Low Pressure (South Pole, Polar latitudes)
Convergence Zone (Low Pressure)
leads to ascending air, cooling by expansion, cloud development and precipitation.
Divergence Zone (High Pressure)
Where winds diverge, air descends, is compressed and warms, and the weather is generally fair.
in middle latitudes, winds blow from west to east in a wavelike pattern of ridges and troughs. Responsible for the development and movement of synoptic-scale weather systems, cyclones and anticyclones. North and South components contribute to poleward heat transport.
Ocean Surface (Trade Wind Inversion)
Exhibits smaller temperature variations over the course of a year than does land. Causes seasonal reversal in surface air pressure.
Continents (Trade Wind Inversion)
at middle and high latitudes dominated by high pressure in winter and low pressure in summer.
Anticyclone, Winter (Trade Wind Inversion)
due to extreme radiational cooling, cold anticyclones develop over northwestern North America and interior part of Asia.
Southern Hemisphere, Summer (Trade Wind Inversion)
In summer, in response to intense solar heating, a belt of low pressure forms across North Africa and stretches from the Arabian Peninsula eastward into Southeast Asia.
Planetary-Scale Wind Belt (Trade Wind Inversion)
Seasonal shifts in wind belts, pressure systems and ITCZ, mark regional climate characteristics of systems.
Migration ITCZ North (Trade Wind Inversion)
The migration northward movement of the ITCZ triggers summer monsoon rain season in Central America, North Africa, and Southeastern Asia.
Location of Subtropical Anticyclones, Two Cities (Trade Wind Inversion)
1. San Diego, under influence of Hawaiian High, Summer.
2. Charleston, receiving end of the humid airflow on the western flank of the Bermuda-Azores high.
Autumn, highs shift toward equator causing both cities to receive widespread preciptation with west to east moving extratropical cyclones, resulting both place becoming wet.
Blocking Pattern (Summer 1993)
1. Record flooding in the Midwest and drought over Southeast.
2. Some areas of Midwest received more than twice the long-term average seasonal rainfall.
3. Some areas Southeast received less than half of their long term average seasonal rainfall.
The Arctic warming nearly twice as rapidly as the entire Northern Hemisphere.
-Encourages more meridonal flow regimes, increasing blocking patterns
-Anthropogenic global warming is heightening the chances that some regions in mid-latitudes could experience exceptionally warm and cold patterns in some seasons.
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