Assignment 4 -  Thursday, September 28

Our subject matter for this week's assignment encompasses two broad topics: (1) atmospheric pressure, winds, and the general circulation of the atmosphere and oceans; and (2) moisture and precipitation, their global patterns and seasonal variations. I have identified a number of sources for investigation. I will list them here, but the guidelines for this assignment will be in some respects a little less specific than for the previous two assignments.

A series of useful Web sites are listed below. Each provides access to information in the form of maps or time series. First look through the online learning modules from the University of Illinois, which can serve as a basic supplement to material covered in class and in the textbook (this does not require any written response):

1. Forces and winds module from the University of Illinois Onlide Guide to Meteorology
When you visit this site you will find other useful modules, including those on clouds and precipitation, air masses and fronts, hurricanes, midlatitude cyclones, severe storms, weather forecasting, and El Nino. All of these topics will be covered in the next few weeks. It is probably worth your while to look through all of them.

2. Another useful page from the same site is the online guide to reading weather maps. Of particular use are the sections on surface observations and upper-air observations. This provides a general introduction to the basics of reading weather maps and satellite images. In particular look at the discussions of surface maps, constant-pressure surfaces,  upper-air troughs and ridges, surface contours, iosbars and wind direction, and upper-air contours.

Next look through the other sites listed below and pick at least two different topics to investigate. Once you select an option, try to look at the information available, use it to formulate at least one significant question about the behavior of the atmosphere or the atmosphere-ocean system, and try to answer (or at least explore; there may not be a definitive answer) the question with reference to the observations you are able to make. Write these up in report form, which may include printed maps or graphs if appropriate, or may include links that are referenced in a message posted to the newsgroup.

Evaluation of your work on this assignment, apart from standard issues of spelling, grammar, sentence structure, etc., will be based on the extent to which you are able to synthesize and explain the patterns you are seeing. Telling me what sites you visited and whether they were interesting is not the same as making use of the information analyzed to draw conclusions or to gain insight about a scientific question!

Some simple ideas, provided only as examples:

• looking at weather maps and other types of graphs that may be accessible online, can you identify the location of the polar front and the jet stream? Do the patterns of temperature, wind velocity, and pressure provide any key information that helps in interpreting what you see? What if you look at observatons from different elevations or different isobar surfaces? What if you track changes over a period of a couple of days? (Some sites archive weather-map data for at least 48 hours.)
• What is the shape of the polar front, how does it move and how does it change shape over a period of a few days? How do regional weather patterns in the midlatitudes reflect the differences between air masses on opposite sides of the polar front?
• Or what about wind direction in the vicinity of a cyclone or anticyclone, either at the surface or aloft? Does it follow the trend described in the textbook?
• What about ocean-current circulation? Can you see any correspondence between current patterns, sea-surface temperatures, and weather patterns over adjacent land masses?
• Do daily satellite photos show cloud patterns that tell you anything interesting about what is going on?

3. Go to the University of Illinois Current Weather Products page: This site offers a menu of options and allows you to generate a current surface weather map of the continental U.S. with pressure readings, isobars, wind barbs, and a variety of other features (my advice is not to clutter it up with too much). Note the relationship between the pressure distribution and the direction and strength of the wind. Can you identify cyclonic or anticyclonic flow? You can also look at multiple slices through the atmosphere at different "elevations" (actually different pressure surfaces), such as 850, 500, and 250 mb. Note how the wind patterns change with increasing height. Do you see any visible evidence of jet streams and associated weather patterns?

4. The Purdue weather processor: provides access to some good surface maps. You can compare sea- level pressure contour maps and surface temperature maps and see whether you can find the location of the subpolar jet stream.

5. You can look at a description of the jet stream, then examine maps showing its location over North America, the eastern Pacific, or the entire northern hemisphere; you can also run animations to see what it has done over a period of several days, or even consult an archive of images that covers the past 30 days. Try relating this to the current weather map or maps showing pressure and wind patterns over the last several days.

6. Look at the global montage of satellite images, which includes both a still image and a two-week animation with cloud motions that illustrate the general circulation of the atmosphere. The same site includes a rotating globe animation that can also show you two weeks' worth of cloud motion. Note the tropical and midlatitude cyclones, as well as the patterns of cloud being generated over the Pacific and in the tropics over the Indian Ocean and Africa.

7. Look at the CDC Map Room Climate Page for information that allows you to see global wind patterns and a variety of other climate features. The Satellite Climate page will give you (among other things) 5-day global rainfall or wind maps based on satelite data. The Global Circulation and Anomalies Page allows you to track sea-level pressure, surface winds, and winds at different pressure levels in the atmosphere for 1-day, 7-day, 30-day, and 90-day periods. Can you (for example) relate the 30-day surface wind and the 30-day sea-level pressure map, and how do the upper-air wind maps compare with the surface map?

8. Look at one or more of the monsoon sites that provide detailed information on the behavior and computer modeling of the Asian monsoon:

Monsoon on line website (or you can also go to the main homepage for the SHIVA study).

9. You can look at global (or more localized) ocean current patterns and see how they relate to the general circulation of the atmosphere. Some possible sites to investigate include:

The global drifter center, which allows you to access plots showing average velocities for the Pacific and Atlantic oceans based on drifter records. You can also access a page (Drifting Buoy Data Assembly Center) that will allow you to display trajectories by month for different parts of the world; see if you can relate the patterns to the discussion of global currents in the textbook.

A site at the Jet Propulsion Laboratory has movies and pictures that also show ocean current patterns. The sea surface temperature animation, projected on a globe, is particularly effective.

You can also visit the site with animations from the Miami Isopycnic Coordinate Ocean Model (MICOM). There are several options that will illustrate the behavior of ocean currents, even though they actually show temperature or sea-surface height, etc. (skip the 3d animation however, it's not very useful).

10. The National Science Foundation maintains two online weather stations that will provide you with a graphical record of changes in temperature, pressure, relative humidity and dew point, wind speed and direction, and rainfall accumulation over the last 24 hours, the last week, or the last month. These stations are in  Arlington, Virginia and near Boulder, Colorado.. I recommend looking at weekly plots showing both sea-level pressure and wind velocity. Do you notice any relationship between these two variables? If so, how might you explain it? You can also look at rainfall with the same questions in mind.

11. You can also visit the cloud boutique, make your own observations of atmospheric conditions and cloud types for a couple of days, and try to relate those observations to the patterns of changing pressure, wind, temperature, and precipitation that are evident either at a station like the one in Arlington or on weather maps showing both the national pattern and local conditions.

12.NOAA's Live Access to Climate Data produces world maps without the continents filled in, but if you can use your imagination over the land areas it has a lot of useful information. You can make maps showing distributions of temperature, pressure, wind speed, and specific humidity (compare January and July pressure patterns, for example).

13. NOAA's Satellite Climate Research page includes links to monthly rainfall images for the world's oceans for the period from June 1992 to December 1999. If you look at several of these you can get an interesting picture of seasonal patterns of rainfall that may or may not conform to the pattern discussed in the textbook, and perhaps you can see some relationship to the global patterns of pressure and winds. (Or perhaps not?) The archive of satellite climate products allows access to several differnt related sets of images. You can also get an animation of the monthly global pattern of precipitation from this NOAA site.

14. If you didn't read it before, http://www.agu.org/mockler.html provides an interesting introduction to the role of water vapor and clouds in the climate system. Well worth reading, but it doesn't provide the same opportunity for doing your own analysis as some of the data sources listed above.