(This document can be found at: http://funnel.sfsu.edu/courses/erth535/S18/labs/act.08.WthrPttrns.html)
Global Patterns of Temperature, Pressure, Wind, and Clouds
Objectives:
- Become acquainted with global atmospheric patterns of the following:
- temperature in the lower troposphere;
- pressure in the upper troposphere;
- winds in the upper troposphere (including the jet stream);
- sea-level pressure; and
- cloudiness
- Identify connections among the these patterns.
- Become acquainted with some important regional-scale patterns of sea-level
pressure, winds, and temperature associated with midlatitude cyclonic storms
in the midlatitudes.
- Understand what the pattern of winds and temperatures in midlatitude cyclones
implies Earth's annual, zonally-averaged energy budget.
1. Global Temperature Patterns in the Lower Troposphere
The JavaScript animation tool linked to the thumbnail image below shows color-filled
contour maps of temperature at an altitude of around 10,000 ft. (3 km) above sea
level. This altitude is in the lower troposphere but relatively far above the
earth's surface in most places, which means that it tends not to be directly affected
by short term (e.g., a day or less) variations in sensible and latent heat fluxes
or radiative fluxes from the surface. It also does not exhibit the strong variations
in temperature with elevation that characterize surface temperatures. However,
the temperature at 10,000 ft is still low enough to represent the part of the
broad, global temperature pattern near the earth's surface associated with longer
term (e.g., a day to a year) temperature variations associated mainly with (1)
differences in heating due to variation in sun angle with latitude, and (2) transport
of heat by air motions.
- Click on the thumbnail image above to see the JavaScript animation interface.
Select a period of 5 days in mid-September within the last year, with an interval
between images of 6 hours. Click on the "Build Animation" button
and wait until the individual images in the animation load. (Once the animation
starts, you can stop and restart it , speed it up and slow it down, and stop
it and step through the images one at a time, using the appropriate control
buttons.)
- Describe what appear to you to be the three most clearly identifiable features
of the global temperature pattern.
- How does each of these features change (if it changes) over the period
of several days shown?
- Open a new browser window with a second copy of the JavaScript animation
interface (click
here). Select another 5 day period with images at intervals of
6 hours, this time in February within that last year. Click on the "Build
Animation" button again.
What differences do you see between the September and February animations?
Can you account for any of them?
2. Global Pressure Patterns in the Upper Troposphere
The images linked to the thumbnail images below show color-filled
contour maps of pressure at an altitude around 30,000+ ft (9-10 km),
which is in the upper troposphere.
- Describe what appear to you to be the three most clearly identifiable features
of these pressure patterns.
- How do they change over time?
- How do they compare to the main features of the temperature patterns in
the lower troposphere (1) above?
3. Global Wind Patterns in the Upper Troposphere
The JavaScript animation tools linked to the thumbnail images in the second column
below show maps of winds at an altitude around 30,000+ ft (9-10 km), the same
as the
pressure
maps above. The arrows represent both the wind direction and wind speed (longer
arrows represent faster winds). Areas with wind speeds in excess of about 72
mph
(60 knots, or nautical miles per hour) are colored in shades of gray, with areas
of progressively faster winds colored in progressively lighter shades of gray.
The views are from directly above the North Pole (Northern Hemisphere) and directly
above the South Pole (Southern Hemisphere), respectively. In the first column
below are global maps of wind speed only, at the same altitude.
Select animation periods for about the same two times of year as you did for
the global temperature animations in (1) above, and start the
animations.
- In what directions do the winds at this altitude tend to blow?
- How would you characterize the main features of these wind patterns?
- How do these features tend to change over a period of several days?
- How do they compare (in general terms) to the pressure patterns at the
same time and at the same altitude shown in (2) above?
- How do the patterns of wind in your animations vary seasonally (September
to February)?
- How are the patterns in the Southern and Northern Hemispheres similar and
how are they different?
4. Global Sea-Level Pressure Patterns
The images linked to the thumbnail images below show global maps of
sea-level pressure.
- How would you characterize the main features of these pressure patterns?
- How do these features tend to change over a period of several days?
- Do they seem to have any relation to the patterns of lower-troposphere
temperature, upper-troposphere pressure, or upper-troposphere winds?
5. Global Patterns of Clouds
The JavaScript animation tool linked to the thumbnail image below shows global,
composite infrared satellite images.
Select animation periods for about the same two times of year
as you did for the global temperature animations in (1) above,
and start the animations.
- What main cloud features or patterns do you see on your animations?
- Do the main features on these satellite images (both high, cold cloud-top
patterns and areas lacking such features) seem to have any relation to any
of the patterns of temperature, pressure, and winds that you've already looked
at?
6. Regional Sea-Level Pressure, Wind, and Cloud Patterns
The images linked to the thumbnail images below show:
- First column: temperature patterns at around 10,000 ft. (in the lower
troposphere);
- Second column: the
jet
stream
patterns
aloft, at
around 30,000 ft. (in the upper troposphere);
- Third column: sea-level pressure patterns; and
- Fourth column: infrared satellite
images (fourth column)
The first row of images shows a single time for the Northern Hemisphere;
the second row shows a four-day animation for the Northern Hemisphere; the
third
row shows images at a single time for the North Pacific and western North America;
and the fourth (last) row shows four-day animations for the North
Pacific Ocean and western North America.
(Click on any of the thumbnail images below to get a larger image.)
- On the two Northern Hemisphere maps (top row), what associations do you
see between the temperature pattern at 10,000 ft. and the jet stream pattern
at 30,000
ft.?
- Do these associations hold in particular on the pair of North Pacific/Western
U.S. maps of the same quantities (second row, first two columns)?
- What associations to you see between the sea-level pressure pattern on
one hand, and the temperature pattern at 10,000 ft. and jet stream pattern
aloft on the other hand (second row)?
- What associations do you see between the surface wind patterns and
the sea-level pressure patterns?
- What associations do you see between the patterns of high, cold cloud tops
and sea-level pressure patterns?
- How do the patterns of sea-level pressure, surface wind, and high, cold
cloud tops change over a period of several days (bottom row)?
7. Heat Transport in Midlatitude Cyclones
Linked to the thumbnail images below are (1) a color-filled contour map showing
the
pattern of sea-level pressure and surface winds;
(2)
a
color-filled contour
map showing
the pattern of temperature and winds at about 3,000 meters (about 10,000 ft.).
above
sea
level; and (3) an infrared satellite image for the same region (North Pacific
Ocean)
at
the
same
time (Tuesday
Oct
9,
2007
at 5 p.m. PDT). Notice in particular the large midlatitude cyclone on the West
Coast of North America—the
low pressure center, the counterclockwise surface wind pattern, the relatively
large temperature contrasts across the storm, and the
band of high, cold cloud tops (which assumes the common
comma shape), are all signatures of midlatitude cyclones in the Northern Hemisphere.
- Consider a line of latitude through the center, or a little ways south
of the center, of the circulation pattern associated with the midlatitude
cyclone. Based on
the
pattern of
winds and
temperature at various points on this line of latitude in the storm, what
can you say about the net
transport of heat by the winds across this line in the vicinity of the storm?
That is, is there net poleward or net equatorward transport of heat?
[Hint: Consider the region immediately poleward of the latitude line in the
vicinity of the storm, and consider the temperature of the air moving into
that region
across the
latitude
line
compared
to the temperature of the air leaving the region, and estimate whether the
region will experience a net heat gain or loss as a result. To check your
result, repeat for the region immediately equatorward of the latitude line—the
results should be consistent.]
- What implication does your answer have for the unbalanced
annual- and zonal-averaged radiative energy budgets that we analyzed using My World?
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