Meteorology Chapter 6
geostrophic wind
A wind that moves parallel to the isobars as a result of the balance between the pressure gradient force and the Coriolis effect.
Explain the formation of geostrophic wind and describe how they blow relative to isobars.
Aloft wind that blows parallel to isobars
Describe the atmospheric pressure associated with a cyclone compared to an anticyclone.
An anticyclone is a system of winds that rotates around a center of high atmospheric pressure.
List and describe the three forces that act on the atmosphere to either create or alter winds.
Pressure gradient force Coriolis force Friction
hydrostatic balance
The balance between the upward push of air toward space and the downward force of gravity
Explain how horizontal convergence and divergence affect surface
The convergence of horizontal winds causes air to rise, whereas the divergence of horizontal winds causes downward motion of the air (subsidence).
anticyclonic flow
The flow of air around a region of high pressure clockwise in the Northern Hemisphere.
cyclonic flow
The flow of air around a region of low pressure counterclockwise in the Northern Hemisphere.
gradient wind
a wind that blows at a constant speed parallel to curved isobars above the level of frictional influence
What causes convergence over land?
ascending air from smooth oceans to rough land, encounters more surface friction
convergence
causing air to squeeze into a smaller space
Write a generalization relating the spacing of isobars to wind speed.
closer isobars have strong wind speeds wide isobars have light wind speeds
A warm fog can be dispersed by what
cloud seeding
Describe the instruments used to measure wind speed.
cup anemometer or aerovane
US standard atmosphere
depicts the idealized vertical distribution of atmospheric pressure at various altitudes.
What causes divergence over oceans?
descending air from rough land to smooth oceans, encounters less surface friction
two basic wind measurements
direction and speed
For surface low pressure to exist for an extended period, what condition must exist aloft?
divergence of air
troughs
elongated areas of low pressure that sweep equatorward and are associated with cool air moving toward the equator.
ridge
elongated high-pressure areas that extend toward the poles and are associated with warm air moving poleward.
What general weather conditions can we expect when surface pressure is rising/falling?
falling a cyclone(low) rising an anticyclone(high)
Briefly describe how the Coriolis force and friction modify air movement.
friction affects wind and as a result alters its direction/pressure gradient force and the Coriolis effect at the surface causes air to move across the isobars
What is wind, and what causes the air to move?
horizontal air flow due to pressure differences
aerovanes and satellites
measure both wind and speed
Anemometers
measure wind speed
wind vanes
measures wind direction
When the wind direction is 315°, from what compass direction is it blowing?
northwest blowing towards the southeast
Define atmospheric pressure and explain how it is displayed on a weather map.
or simply air pressure, as the force per unit area on a surface exerted by the weight of the air above.
Describe how winds blow in relation to areas of high pressure and low pressure.
shorter the distance between the high and low pressure areas, the faster the wind will blow.
A southwest wind blows from the_________ (direction) toward the _______ (direction).
southwest to northeast
divergence
surface pressure drops
