From: "Andrew J. Miller" <miller@umbc.edu>

Newsgroups: umbc.course.geog110h

Subject: Third assignment - for Friday, February 21

Date: Wed, 19 Feb 1997 00:30:46 -0500

Geography 110H

Assignment 3 - Due Friday, February 21

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.

I recommend that you look over at least one or two of the following sites. You do not need to write a formal response to everything you see, but some of these sites will greatly enhance your understanding of topics that are touched on only briefly in the textbook.

1. Call up the Web site identified in the homepage list of bookmarks 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.

Next go to the Web site identified in the bookmark list as "SSEC Real Time Data" and click on the menu item entitled "Sea Surface Temperature." Then got to "Latest SST". This is a beautiful color image showing the global distribution of sea-surface temperature. I believe it is updated daily. Also go to the catalogue of archived SST images and call up one from another season. (Unfortunately, they don't seem to have anything outside of the period between November and March, at least not right now. But look in order to see whether you can pick up any significant changes between images taken a few months apart. 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?

For some really impressive animations showing both sea-surface temperatures and the circulation pattern of ocean surface currents, visit the part of the bookmark list labelled "Oceanographic data" and click on "MICOM Movies Year 14-15 Temperature".

Post any interesting comments to the news group. No formal report is required here.

2. 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:

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.

The following instructions are fairly detailed. The main point, however, is to get you to experiment with comparisons of temporal patterns of temperature at different locations, and to relate this to what you are reading about the earth's radiation balance and controls on temperature. You don't need to follow my instructions exactly; if you wish, formulate your own question and look up the data in order to see what kind of answer you come up with.

Visit the Web site entitled "NCDC Climate Visualization" (under "Global climate" in my bookmarks list). Under the heading CLIMVIS Graphics Session, you will see options for both National Weather Service Summary of the Day and Global Summary of the Day. Pick whichever one is appropriate. You have the choice of plotting a time series or a contour map. Start with a time series option. You can plot two parameters at one station, such as maximum and minimum temperature, or you can plot one parameter for a month from two separate stations in the same region or in separate regions. For the two-parameter option, pick your station or stations and select maximum and minimum daily temperature. Plot both together on the same graph for a summer month and a winter month. Comment on any patterns that strike you as interesting or noteworthy. If you know how, you might want to save the plots as graphics files that can be examined in class.

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.

In addition you can make contour plots illustrating spatial patterns of climatic variables across the U.S. for specified time periods. You might want to try experimenting with this.

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. This doesn't have to be an exhaustive discussion or a long report. Just focus on something that you noticed in doing this and post a message about it.

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! If you come up with interesting graphs and are able to print them out, bring them to the next class.