EARTH SYSTEM SCIENCE

WRITING ASSIGNMENT #5 - ANALYSIS OF GLOBAL WINDS

This week we are going to attempt to examine patterns of global atmospheric circulation by tracking the direction and speed of winds observed across Earth's ocean. To do this, we will locate, download, synthesize, and analyze graphic images depicting global surface wind speed and direction obtained using a radar scatterometer onboard the QuickScat satellite. To learn more about QuickScat and radar scatterometry, explore the global winds website maintained by NASA's Jet Propulsion Laboratory in Pasadena, California. This website contains extensive documentation regarding the nature of scatterometry and how radar measures wind over the oceans. As such it is an invaluable resource for completing this assingment.

Satellite sensors of all kinds are actively monitoring Earth's environment so that we may gain insight into the complex interactions among Earth's systems which make our planet habitable. Because satellite sensors are able to obtain data from around the world on relatively short time intervals (many satellites complete an orbit of Earth in approximately 90 minutes), these data are continuously transmitted to various receiving stations 24 hours each day, 7 days a week, 52 weeks each year. As such, there is an enormous quantity of information available about our planet. With the advent of the Internet and World Wide Web, many government and university research facilities have chosen to make these data available to all interested parties by distributing them in cyberspace.

Today we will investigate the data holdings of one such distributed data archive, the Physical Oceanography Distributed Active Archive Center (PO DAAC). The PO DAAC maintains archived data from a number of orbital platforms. Among the data in this archive are records of global surface winds over the ocean obtained from a radar scatterometer onboard the QuickScat satellite.

YOUR ASSIGNMENT FOR THIS WEEK:

Your assignment this week will be to construct a movie showing global surface winds over the ocean for an entire year. This will require that you obtain a graphic image depicting global surface winds for each of the 365 days in the year (i.e. your movie will have 365 frames). This seems like it would take a very long time to compile, but the purpose of this exercise is to show how simple it is using advanced technologies and to use those technologies to help us better understand the complex phenomenon of atmospheric circulation. Follow the directions below EXACTLY to compile your movie, then use your observations of your movie to answer the questions at the end of the assignment.

Here's what to do:

1. Go to the Physical Oceanography Distributed Active Archive Center.

2. Once at the site, locate "Ocean Vector Winds" in the center of the page. Click on this title. On the Ocean Vector Winds Overview page, you will see a list of products on the left-hand frame. Move your cursor over the words "Sea Winds on QuickSCAT" and click on this link..

3. This link takes you to the Sea winds on QuickSCAT web page. The first product listed on the page (QuikSCAT Level 3 Daily, Gridded Ocean Wind Vectors (JPL SeaWinds Project) (#109)
) is the one we will use for this week's exercise. From here, there are several ways to access the data you will need to compile your movie. Selecting the "Browse" link from the Tools & Services cell of the table will take you to an interactive interface where you could download each image separately. This device is very helpful when you are just beginning, but downloading 365 images is quite time consuming and tedious. There is a faster way.

4. On the Tools & Services cell, there is a link labeled "FTP". Follow this link to go directly to the directory on the web server where the archived data are stored. Once on the FTP site, you will see a number of folders displayed across the page. Double click on the folder labeled "browse". Double click on the 2005 folder.

5. Notice that there are many files stored in this folder. Each is labeled as "QS_XWGRD3_YYYYxxx.gif" where YYYY is the year the xxx represent the day of the year (i.e. 01 January is day 001, etc.). To download each day to your computer, click once on the first file (QS_XWGRD3_YYYY001.gif) to select it. Hold down the shift key and scroll to the last file in the list (QS_XWGRD3_YYYY365.gif). While holding down the shift key, click on the last file. You should see that all files are selected. Now simply drag and drop your images into a folder on your desktop Wait until all images are downloaded to this folder. Note: this step may take a few minutes to complete.

6. Now you should have an image for each day of 2005 in the folder. Since the days are numbered sequentially, you could select them all from the folder and drop them into Windows Movie Maker. Additionally, they would load sequentially into the film if you select all files, then drag and drop all images into the first frame of the movie. However, since these images are relatively large, it would take a long time to compile them into an animation using Movie Maker. Since we want to have some freedom to explore our data, including scrolling forward and backward through the data set, we will use a different method of animation this week.

7. Locate the folder containing your images and double click to open the folder. In Windows XP, you will see a menu on the left-hand frame that indicates you can display the contents of the folder as a slide show. Move the cursor to this option and click on it. Your images should load as a full screen slide show. To make the slides advance more quickly, type using either the down arrow or right arrow key on the keyboard. To scroll backward through the images, type on the up arrow or left arrow key. You can pause the slide show at any time by clicking on the pause button at the top of the screen or by right clicking on your mouse.

8. Spend some time scrolling forward and backward through your images. Once you feel that you are familiar with the operation of your slide show, use the images to answer the questions below.

QUESTIONS TO CONSIDER:

9. Why are these data represented by vectors? How do you interpret these images?

10. Why aren't there wind vectors over the continents?

11. How were these data determined (i.e. how does QuickSCAT measure wind over the ocean?).

12. Select a representative image from your data set. When you think you have found one that you like, right click on your mouse and print a copy of the image. Using the hardcopy of your image, mark the approximate boundaries of the Northeast and Southeast Trade Winds, and the Westerlies in the northern and southern hemispheres.

13. Identify a specific series of images that shows the development and life cycle of a tropical cyclone (also known as hurricane, typhoon, cyclone, and willy-willy). What characteristics identify tropical cyclones? Can you recognize a general pattern to the movement of tropical cyclones? If so, what is it? During which months of the year were tropical cyclones most abundant in 2005? What area produced the largest number of tropical cyclones during 2005?

14. What area of Earth seems to have the most energetic circulation patterns (i.e. what area has the strongest winds throughout the year?).

16. Observe the general direction of winds in the Arabian Sea (between India and Africa) for the year. What happens to the wind field in the Arabian Sea? Can you explain your observations?

Please note that this assignment is due Monday, 27 Feb 2006.