Weather Flashcards
Weather
Gives the conditions of the atmosphere at a certain time and place on the planet.
Factors reported with weather
temperature, pressure, humidity, wind direction and speed, and the presence and types of clouds
Climate
the average weather that occurs at a location over a period of time
Pressure-gradient flow
Air flows from zones of higher pressure to lower to fill areas where air rose due to buoyancy. As air is heated in the equator it expands and decreases in density, making it rise.
Wind is controlled by
pressure gradients
Isobars
lines of constant pressure
Wind theoretically flows ____ to isobars
perpendicular
If isobars are far apart, there is a ____ pressure gradient and a ____ wind speed
low low
If isobars are close together, there is a ____ pressure gradient and a ____ wind speed
steep, higher
Geostrophic flow
when flow becomes parallel to isobars, the pressure is exactly balanced by the Coriolis effect and pressure gradient
On earth, the flow turns into ___ due to the effect of the Coriolis effect
loops
Flow is broken down into cells due to
Coriolis effect, global air circulation, and pressure-gradient flow
Hadley cells
driven by pressure gradient flow, they are located at the equator
Ferrel cells
poorly defined with circulation driven by the movement of adjacent cells
Polar cells
driven by pressure gradient flow, they re located near the poles
Air circulation cells (3)
Hadley, Ferrel, and Polar
The intersection of polar and Ferrel cells
rising air that is warm and moist
the intersection of Ferrel and Hadley cells
descending air that is cool and dry
the intersection of two Hadley cells
rising air that is warm and moist
The intersection of polar cells
descending air that is cold and dry
At high altitudes wind is
geostrophic
Near the surface of the earth, flow is not geostrophic because
friction reduces the Coriolis effect on pressure gradient flow
In the northern hemisphere, wind is deflected ___ relative to isobars
counterclockwise
Ekman spiral - high-pressure spiral moves ___ in the northern hemisphere
CW outward spiraling winds (CW and downward)
Ekman spiral - low-pressure spiral ___ in the northern hemisphere
CCW inward spirling wind (CCW and up)
Ekman spirals are caused by
modification of pressure-gradient flow by the Coriolis force
Intertropical convergence zone
is a zone of low pressure near the equator
between the Hadley and Ferrel cells are subtropical ___ pressure zones caused by ____
high pressure caused by descending air
Between Ferrel and Polar cells are subpolar ___ pressure zones caused by ____
low pressure caused by rising air converging tropical and polar air masses meeting at the polar front
Easterly winds
coming from the east, dominate the equatorial zone
Westerlies winds
dominate the subtropical high-pressure zones
Trade winds
wind patterns (westerlies and easterlies) that were critical for exploration by ships
Jet stream
The strong geostrophic flow resulting from the steep pressure gradient from mid-latitude changes in the altitude of the troposphere.
The jet stream is located above the
polar front
The jet stream can reach speeds up to:
460 km/hr
Rossby waves are caused by
Large undulations in the position of the polar front (where polar cells and Ferrel cells meet).
Rossby waves affect the ___ and ___ of the jet stream
position, velocity
Rossby waves can cause cold air to move towards the __ and warm air to move towards the ___
equator, poles
Weather is controlled by
air masses
air masses
large volumes of air that have internally consistent properties, including pressure, humidity, and temperature
Air masses are characterized by the following factors
- do they form over a continent (c)?
- do they form over maritime regions (m)?
- do they form in the tropics (T)?
- do they form in polar regions (P)?
Sea breeze results from
local pressure gradient winds - during the day the land heats faster causing air to rise over land and create a region of low pressure and the sea breeze blows toward the land
Land breeze results from
local pressure gradient winds - at night land cools faster than sea which creates a zone of low pressure and the land breeze blows towards the sea
Chinooks result from
regional atmospheric flow forces air over the mountains. Descending air warms adiabatically as it is compressed
Thunderstorms
form in warm moist air masses, during daytime heating, especially along cold fronts where mT (maritime-tropical) contacts cP (continent-Polar) air resulting in density lifting.
Lightning is caused by
strong air currents cause the ionization of air molecules, such that the top of the cloud becomes positively charged and the base becomes negatively charged. Electrical discharges result in lightning.
Tornadoes are caused by
initiated in spiral uplifts and have tightly rotating centers that rotate in the direction of the larger air mass.
Tropical cyclones form by:
- warm moist air over the sea
- condensation to supply latent heat for continued density lifting
- Coriolis effect to drive rotation
