19-2 Flashcards
what do low and high pressures mean in pressure centers?
Low pressures: clouds/rain
high pressures: clear skies/fair weather
what are cyclones?
Air swirls inward in counterclockwise direction in northern hemisphere called cyclone.
what happens in centers of low pressure? (cyclones)
Warm, less dense air rises, forming low pressure. it expands, reaching the dew point, releasing water vapor, and potentially causing thunderstorms
what are anticyclones?
Air swirls outward in clockwise pattern, air that rose from low at high altitudes move toward highs, dense air sinks at anticyclone
what happens in centers of high pressure? (anticyclones)
cold dense air sinks, as it descends molecules compress and it warms so it can hold more water vapor this decreases relative humidity and causes no precipitation
what is important in weather forecasting?
Tracking high and low pressures is crucial. low pressure brings clouds and rain, while high pressure brings clear skies. In the U.S., cyclones and anticyclones move west to east.
what are global winds?
Global winds blow steadily from specific directions over long distances due to unequal heating of Earth’s surface.
how do global winds affect pressure near the equator and near the poles?
near equator: sunlight hits directly, warming the air, making it rise and creating low pressure. Near the poles, sunlight is weaker, so the air stays colder, denser, and sinks, creating high pressure. This movement drives global winds.
what is the non-rotating earth model?
A model of Earth with no rotation and a smooth surface. It has two large convection cells, one in each hemisphere. surface flow straight to equator, gets warmer, then rises. high altitude flow straight to poles.
what is the rotating earth model?
one hypothetical convection cell would break down into three smaller cells:
what is a doldrum and what are the characteristics?
windless zone at the equator, where direct sunlight heats the air. The hot air rises, cools to the dew point, and causes abundant precipitation. also known as the Low Pressure Zone or Equatorial Low.
what are horse latitudes/subtropical highs? where are they and how do they form?
where air from equator sinks, about 30 N and 30 S latitude, air stops moving toward poles and sinks forming belt of calm air
As air sinks it warms/dries creating a high
what are trade winds? what direction does the southern and northern hemisphere blow?
between equator and 30 N or S, air travels outward from subtropical highs to equator.
Southern hemisphere it blows NW, northern hemisphere it blows SW
what are prevailing westerlies? in the northern and southern hemisphere where do winds blow?
Winds between 30° and 60° N and S of the equator blow out from the subtropical high in opposite directions from trade winds toward polar fronts. In the northern hemisphere, winds blow from southwest to northeast, and in the southern hemisphere, they blow from northwest to southeast, moving toward the poles and turning east.
what are polar easterlies? at the north and south pole what direction does wind blow?
blows cold air away from polar front. result of cold dense air near poles sinking and flowing towards lower latitudes, coriolis effect shifts polar winds to the west.
Blow from northeast to southwest near north pole, blow from southeast to northwest near south pole
what are polar fronts?
near 60 S and 60 N where polar easterlies and prevailing westerlies meet, mixing of warm and cold air has major effect on weather
what are jet streams? where do they occur and what do they resemble? what do they move across the USA?
narrow belts of winds at higher altitudes, top of troposphere flowing from west to east.
Occurs where trade winds and polar easterlies meet prevailing westerlies, resembles fast-moving winding rivers
Moves storms across USA, can bring polar vortex
What is the effect of large landmasses on global pressure patterns?
Landmasses disrupt global pressure patterns. In winter, landmasses become cold, creating high pressure systems. In summer, they heat up, creating low-pressure systems.
How do high and low-pressure systems form over landmasses?
In winter, cold landmasses form high-pressure systems, causing air to flow off land. In summer, heated land creates low-pressure systems, allowing air to flow onto land.
what are monsoons? in warm and winter months what air and monsoon is produced?
seasonal changes in wind direction
Warm months: flow of warm, winter-laden air produces rainy summer monsoon. winter months: dry continental air produces winter monsoon
what are station models used for? how do you find the pressure?
gives information gathered at one of many locations on map.
Pressure over 500: add 9 & decimal, under 500: add 10 & decimal
