chapter 8 Flashcards
Weather
the short-term condition of the atmosphere, as compared to climate, which reflects long-term atmospheric conditions and extremes. Temperature, air pressure, relative humidity, wind speed and direction, day-length, and Sun angle are important measurable elements that contribute to the weather.
Meteorology
the scientific study of the atmosphere, including its physical characteristics and motions; related chemical, physical and geological processes; the complex linkages of atmospheric systems; and weather forecasting
Air mass
a distinctive, homogeneous body of air that has taken on the moisture and temperature characteristics of its source region
Principal air masses that affect North America
continental polar (cP), maritime polar (mP), Maritime tropical (mT)
Continental polar (cP)
form only in the Northern Hemisphere, most developed in winter and cold-weather conditions, major places in middle - and high - latitude weather, cold, dense air
Maritime polar (mP)
masses in the Northern Hemisphere sit over the northern oceans, cool, moist, unstable conditions
Maritime tropical (mT)
mT Gulf/Atlantic (unstable, humide) and mT Pacific (stable, and less moist), influence North America
why is that the longer an air mass remains stationary over a region, the more definite its physical attributes become
Their temperature and moisture characteristics slowly change to the characteristics of the land over which they pass
Lake effect
when air masses absorbs heat energy and moisture from the lake surface
Convergent lifting
air flows toward an area of low pressure, displacing air upward
Convectional lifting
air is stimulated by local surface heating, lifting
Orographic lifting
the uplift of a migration air mass as it is forced over a barrier such as a mountain range, the lifted air cools adiabatically as it moves upslope, oro means mountain
Rain shadow
the area on the leeward slope of a mountain rage where precipitation receipt is greatly reduced compared to the windward slope on the other side
chinook wind
north American term for a warm, dry, downslope airflow; characteristic of the rain-shadow region on the leeward side of mountains
Frontal lifting
air is displaced upward along the leading edges of contrasting air masses of different densities
- the leading edge of an advancing air mass is its front
- Density differences are most often caused by temperature differences
- Separate air masses with contrasting temperatures
Cold front
the leading edge of an advancing cold air mass
- caused by its greater density and more uniform characteristics
- before; shifting winds, dropping temperature, and lowering barometric pressure
- after; winds
- represented as a line with triangular spikes that point in the direction of the frontal movement
squall line
a zone slightly ahead of a fast-advancing cold front, where wind patterns are rapidly changing and blustery and precipitation is strong
Warm front
the leading edge of an advancing warm air mass, which is unable to push cooler, passive air out of the way, carried by jet stream, warm air moves up and slow the cold air
Midlatitude cyclone, or wave cyclone, or extratropical cyclone
an organized area of low pressure, with converging and ascending airflow producing an interaction of air masses, dominate weather patterns in the middle and higher latitudes of both the Northern and the Southern Hemisphere
Storm track
seasonally shifting path followed by a migrating low-pressure system
State of a midlatitude cyclone
- Cyclogenesis: atmospheric process in which low-pressure wave cyclones develop and strengthen
- Open stage; warm air begins to move northward along an advancing front, while cold air advances southward to the west of the centre
- Occluded Stage; can create Occluded front: the overrunning of a surface warm front by a cold front and the subsequent lifting of the warm air wedge off the ground; initial precipitation is moderate to heavy. Because the cooler, more unified air mass, act like a bulldozer blade, moves faster than the warm front. Can also create stationary front: a frontal area of contact between contrasting air masses that shows little horizontal movements; winds in opposite directions on either side of the front parallel along the front
- Dissolving Stage; the lifting mechanism is completely cut off the warm air mass, which was its source of energy and moisture, then dissipate in the atmosphere
Synoptic analysis
is the evaluation of weather data collected at a specific time
Satellite - Key tools in forecasting
massive computers handle volumes of data from surface, aircraft, and orbital platforms for accurate forecasting of near-term weather
Doppler radar - Key tools in forecasting
backscatter from two radar pulses, it detect the direction of moisture droplets toward or away from the radar source indicating wind direction and speed
what pourcentage did the Weather-related destruction has risen and why
500% over the past three decades as population has increased
Freezing precipitation
freezing rain, ice glaze, or ice pellets
Ice storm
at least 6.4 mm of ice accumulates on exposed surfaces. Occur when a layer of warm air is between two layers of cold air, it may form a variety of freezing precipitation including freezing rain, ice glaze, and ice pellets
Blizzards
frequent gusts greater than 40 km/h for longer than 4 jours and blowing snow that reduces visibility to 400 m or less
thunderstorms
- Buildup of giant cumulonimbus clouds that can be associated with squall lines of heavy raine, including freezing precipitation, blustery winds, hail, and tornados
- May develop within an air mass, in a line along a front (particularly a cold front), or where mountain slopes cause orographic lifting
- More at the ITCZ
- The energy is from the condensation of a large amount of water vapour in clouds
Turbulence and Wind Shear
created by the mixing of air of different densities or by air layes moving at different speeds and directions in the atmosphere
- Wind shear; the variation of the wind speed and direction with altitude
- Downbursts; which are strong downdrafts that cause exceptionally strong winds near the ground
Mesocyclone
a spinning, cyclonic, rising column of air associated with a convective storm and produce heavy rain, large hail, blustery winds, and lightning
lightning
flashes of light caused by enormous electrical discharges
Thunder
the violent expansion of suddenly heated air, created by lightning discharges, which send out shock waves as an audible sonic bang
Hail
- raindrops circulate repeatedly above and below the freezing level in the cloud, adding layers of ice until circulation in the cloud can no longer support their weight
- Can also grow from the addition of moisture on a snow pellet
- For larger hail to form, the frozen pellets must stay aloft for longer periods
Damaging Winds
Straight-line winds associated with fast-moving, severe thunderstorms can cause significant damage to urban areas
Straight-line winds
linear winds associated ties thunderstorms and bands of showers that cause significant damage and crop losses
Downbursts
a powerful downdraft associated with thunderstorms and bands of showers
Microbursts
severe turbulence from a thunderstorm, smaller in size and speed than a downburst
Plough winds
linear winds associated with thunderstorms and bands of showers that cause significant damage and crop losses
Derecho
strong linear winds in excess of 26m/sec, associated with thunderstorms and bands of showers crossing a region
Tornadoes
an intense, destructive cyclonic rotation, developed in response to extremely low pressure; generally associated with mesocyclone formation
Tornado Measurement
Fujita Scale, classifies tornadoes according to wind speed as indicated by related property damage
Tornado Frequency
most of them in North America, b/c latitudinal position and topography are conductive to the meeting of contrasting air masses and the formation of frontal precipitation and thunderstorms, peak month are May and June
Increases in tornado is related to what
to rising sea-surface temperature, warmer oceans increase evaporation rates, which increase the availability of moisture in the mT aire masses, thus producing more intense thunderstorm activity
Tropical Cyclones
a cyclonic circulation originating in the tropics, with winds between 30 and 64 knots; characterized by closed isobars, circular organization, and heavy rains
Most powerful; hurricanes, typhoons, or cyclones
- convert heat energy from the ocean into mechanical energy in the wind — the warmer the ocean and atmosphere, the more intense the conversion and powerful the storm
Hurricanes, Typhoon, Cyclones
a tropical cyclone that is fully organized and intensified in inward-spiralling trainbands; ranges from 160 to 960 km in diameter, with wind speeds in excess of 119km x h-1 (65 knots); a name used specifically
- hurricanes; in the Atlantic and eastern Pacific
- typhoon; in the western pacific
- cyclones; in indonesia, bangladesh, and india
What triggers the start of a tropical cyclone
slow-moving easterly waves of low pressure in the trade-wind belt of the tropics
eyeball - physical structure of tropical cyclones
this is the zone of most intense precipitation, warmest area, As winds rush toward the center of a tropical cyclone, they turn upward, forming a wall of dense rain bands
Landfall - physical structure of tropical cyclones
the location along a coast where a storm moves onshore, where the eye moves ashore, there might be a couple tornadoes
eye - physical structure of tropical cyclones
The central area of a hurricane, which is quiet and warm
Saffir — Simpson Hurricane Winds Scale
stimate possible damage from hurricane-force winds, from smaller category 1 storms to extremely dangerous category 5 storms
Damage from storms depends on what
the degree of property development at a storm’s landfall site, how prepared citizens are for the blow, and the local building codes in effect
Storm surge
seawater that is pushed inland during a hurricane and can combine with the normal tide to create a storm tide of 4.5 m or more in height
basins
Primary formation areas of storm
Catarina
one of the only hurricane in the southern hemisphere
Vince
one of the only
Atlantic tropical cyclone that hit Europe
katrina
In New Orleans, 2005, resulted more from human engineering and construction errors, 1800 people died, one of the five deadliest hurricanes in the history of the United States
juan
Septembre 29, 2003, Nova Scotia and then Prince Edward Island, most powerful and damaging hurricanes ever to affect Canada, lots of flooding
how to avoid damaged from storms
Requiring tougher building standards to qualify for coverage — or, in some cases, refusing to insure property along vulnerable coastal lowlands
