Geography 210H
Assignment 3
Due Friday, February 23
In order to understand the behavior of the atmosphere and oceans
and the global pattern of climates, we need first to have some
basic understanding of the earth's radiation balance. The nature
of the electromagnetic spectrum and the range of wavelengths
characteristic of incoming (shortwave) solar radiation and
terrestrial (longwave) radiation are discussed in chapter 4 of the
textbook. Also discussed are the various processes that may
transport energy from one part of the system to another. The
global energy balance not only controls the spatial pattern and
annual cycle of temperatures; it also drives the motions of the
atmosphere and ocean currents and plays a critical role in the
distribution of moisture and precipitation and of storm activity.
This week we will take a closer look at aspects of the radiation
balance and at patterns of global temperature.
You will be looking at images throughout this assignment. If you
can you should save .gif images from plots or maps or images that
strike you as interesting enough to be worth sharing or that would
be useful as accompaniment to your comments. Put these on a floppy
disk so that I can retrieve them and either view them myself or
post them on the Web page for everyone to see. This is particularly
important for the graphs under item 3 below; I would like to save a
set of temperature plots for comparison.
Your assignment includes the following:
1. Call up the Web site identified in the bookmark file as
Wxwise ERBE. This is a site at the University of Wisconsin at
Madison that contains an article discussing the earth's
radiation balance. Read the article and look at some of the
images showing mapped distributions of albedo, outgoing
longwave radiation, and net radiation balance. View the
animated loop showing the annual cycle of changes in the net
radiation balance. How is the pattern you see related to the
exercise you did last week on length of daylight at different
locations? Pick one or two locations on the globe and focus
on those as you watch the loop several times. Is what you see
consistent with the general discussion of radiation balance
in the textbook? If anything jumps out at you as particularly
worth commenting on, please take the opportunity to do so in
a posting to the newsgroup.
2. Next go to the Web site identified in the bookmark list as
"SSEC Real Time Data" and call up the image entitled "Latest
SST". This is a beautiful color image showing the global
distribution of sea-surface temperature. I believe it is
updated about once a week. The latest image as of this
writing is from Feb. 11, 1996. Also go to the catalogue of
archived SST images and call up one from several months ago.
(Right now the oldest one listed is from Nov. 5, 1995). What
significant differences can you see between the two patterns?
How do they relate to the patterns you observed in the annual
cycle of the net radiation balance? Note in particular that
although temperature varies mostly with latitude, there are
significant anomalies that clearly are affected by factors
other than latitude. Identify one or two such anomalies. What
do you think might explain them?
You can also access a more complete archive of monthly
average SST; these will not be based on data from a single
date but will be long-term averages for each month. They
provide the opportunity to view patterns for every month of
the year. Go into the bookmark file and locate the item
entitled "Live Access to Climate Data". Keep the default
options of a global view, a longitude-latitude plot, and sea-
surface temperature. Request to have the information
transmitted in the form of a plot. (They aren't as beautiful
as the one you just looked at, but they are still quite
informative. The plot for March is shown on the Web page for
this course.) Examine the plots for several months spread
over the course of the annual cycle and consider the
questions asked above.
If you are so inclined you may wish to play with some of the
other plotting options. This Web page allows you to display
information in some interesting ways and is well worth
revisiting in the future.
3. Next we are going to focus on changing patterns of
temperature over time and space by looking at records from
individual stations. Before visiting the next Web site, do
the following:
a. pick a latitude for comparative study. Using a world map
or atlas, locate at least one continental and one maritime
location at or close to the same latitude. If you're
ambitious you might choose one west-coast location and one
east-coast location as well as a continental interior
location. This does not have to be limited to sites in the
U.S.; there are both U.S. and global data sets available.
You may also choose a pair of stations at different latitudes
but comparable maritime or continental interior locations, if
you so desire.
b. Next post a message to the newsgroup, indicating the
latitude and the names of the locations you have selected.
Check other students' messages to make sure you haven't
duplicated their choices.
c. Visit the Web site entitled "NCDC Climate Visualization".
Under the heading CLIMVIS Graphics Session, you will see
options for both U.S. Summary of the Day and Global Summary
of the Day. Pick whichever one is appropriate. The next
screen asks you what kind of plot you want to make. You can
start by picking "display two parameters for one station".
(You will come back afterward and try a couple of other
options also.) Next you will be asked to select your location
from a map or from a list. You will get a list of states or
countries; when you pick one, you will get a list of
meteorological stations and a list of parameters to choose
from. Pick your station and select both maximum and minimum
daily temperature. Plot both together on the same graph for a
summer month and a winter month and request output in GIF
format. Comment on any patterns that strike you as
interesting or noteworthy.
You can try this again for another site you have selected.
Afterwards, go back and try a different graph type: "display
the period of record for one parameter at one station" (only
works for U.S. stations) or "display one parameter for a
specified time frame" (up to one year; works for U.S. and
global data sets). You can use this to plot temporal
variations in maximum, mean, or minimum temperatures to show
seasonal cycles. In the case of the U.S. data set you can also
see multiple years laid out in sequence and get a real feel
for year-to-year variation in temperature patterns. Do this
for at least two stations, preferably the ones you have
already been looking at.
Finally, back up again and select "display one parameter for
two stations." Select your stations, your parameter (maximum,
mean, or minimum temperature) and the one-month period you
wish to plot. Do this for both summer and winter months, or
perhaps a spring or fall month if you wish. Note how the two
stations compare in each season, including both the
differences and the extent to which they do or don't track
each other in their ups and downs. If you want to compare
three stations, you can try them in different pairwise
arrangements.
For all of these observations, comment on how the observed
patterns do or don't conform to what you would expect based
on the book's discussion of factors affecting both seasonal
patterns and spatial patterns of global temperature.
Next week we will have exercises involving analysis of global
patterns of atmospheric pressure, winds, and the general
circulation of the atmosphere and ocean currents. Remember to post
comments to the newsgroup!