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