Download Connections between Forces, Horizontal Wind Patterns and Vertical

Metr 200
Forces/Winds Flowchart
Dr. Dave Dempsey
Fall 2004
Connections between Forces, Horizontal Wind Patterns
and Vertical Air Motions, on Large Scales*
Differential heating/cooling
(1)
(2)
(3)
(Coriolis force
insignificant)
(modified by
Coriolis force)
(4)
(7)
Beneath L’s and H’s aloft,
(6)
creates H’s and L’s
at the surface
Air forcefully
lifted out of
surface L’s
beneath
divergence
aloft;
air
(7)
subsides into
surface H’s
beneath
convergence
aloft
(modified by
force of
friction)
(3)
(5)
Creates H’s
L’sL’s
Creates
H’sand
and
at the
surface
at
thesurface
(6)
((not
not necessarily
necessarily
beneath L’s or H’s aloft)
beneath L’s or H’s aloft)
(modified by
Coriolis and
friction forces)
Metr 200
Forces/Winds Flowchart
Dr. Dave Dempsey
Fall 2004
Comments on Flowchart on Large-Scale* Forces/Winds
(1) Examples of differential heating/cooling:
(a) Because the earth is curved, the sun strikes the earth more directly
at low latitudes (that is, near the equator) than it does at high latitudes (that is, near
the poles). On the average, the sun heats low latitude more than low latitudes cool
by emission of infrared radiation--there is net radiative heating. In contrast, high latitudes cool by emission of infrared radiation more than they are heated by the sun-net radiative cooling. [This gives rise to the earth’s general circulation.]
(b) Land surfaces warm and cool more than ocean surfaces do. In winter, continents become cooler than surrounding oceans. In summer, continents
become warmer than surrounding oceans. [This gives rise to monsoon circulations,
which are examples of modified thermal circulations.]
(c) During the day near coastlines, land surfaces become warmer than
nearby ocean or lake surfaces (especially in summer). At night, land surfaces
become cooler than nearby ocean or lake surfaces (especially in winter). [This gives
rise to land and sea breezes, which are examples of thermal circulations.]
(2) Refer to diagrams of imaginary air columns at different temperatures,
divided into equal-weight “bricks” of air, for connections between temperature differences in the lower troposphere and pressure or height differences aloft.
(3) The Coriolis force is significant only on scales of hundreds of kilometers or larger. At scales smaller than that (for example, the sea breeze, or water
draining in a sink), the PG force is much larger than the Coriolis force, which therefore doesn’t have much effect.
(4) Thermal circulations (e.g., land/sea breeze) are good examples of this.
(5) The polar jet stream at midlatitudes is a good example of this behavior.
(6) Convergence and divergence aloft modify surface pressures by modifying the amount of air (and hence the total weight of air) in imaginary air columns.
(7) On small scales, air rises and sinks for different reasons--due to density
differences on small scales.
Metr 200
Forces/Winds Flowchart
Dr. Dave Dempsey
List of Concepts for Concept Map:
“Connections among Forces, Horizontal Wind Patterns
and Vertical Air Motions, on Large Scales”
(Note: Some concepts on this list can be used more than once.)
Winds aloft
Winds at the
surface
Convergence into lows and
divergence out of highs aloft
Pressure-gradient forces
at the surface
Temperature differences
(mostly in lower troposphere)
Convergence into lows,
divergence out of highs
at the surface
Pressure or height differences (H’s and L’s)-and hence pressure gradient (PG) forces-- aloft
Convergence and
divergence aloft
(not necessarily
into L’s or out of H’s)
Fall 2004
Metr 200
Forces/Winds Flowchart
Dr. Dave Dempsey
Backup List of Concepts for Concept Map:
“Connections among Forces, Horizontal Wind Patterns
and Vertical Air Motions, on Large Scales”
(Note: Some concepts on this list can be used more than once.)
Winds aloft
Winds at the
surface
Convergence into lows and
divergence out of highs aloft
Pressure-gradient forces
at the surface
Temperature differences
(mostly in lower troposphere)
Convergence into lows,
divergence out of highs
at the surface
Pressure or height differences (H’s and L’s)-and hence pressure gradient (PG) forces-- aloft
Convergence and
divergence aloft
(not necessarily
into L’s or out of H’s)
Fall 2004