Geog. 321 -- Climatology
Exercise 2 -- Satellite Imagery

Satellite imagery shows the patterns of clouds and moisture in the atmosphere, and consequently reveals the distribution of storm systems and precipitation.  The images examined here can be found through links on the Current Weather & Climate web page, in the "Satellite Images" section.

Some of the images used here are relatively large, and so you may wish to work on this exercise on a machine that has a fast Internet connection, like those on campus.

Note:  The exercise makes use of "live" images (except for the first one), which might not be available at the time you work on the exercise.  Before starting the exercise, scroll down the page to make sure all images are being displayed.  There should be three single images (Questions 2-1, 2-2, 2-3) and one pair of images (Question 2-4).  If some of the images are missing you could try doing the exercise later, or without losing any points, just type "image not available" and the time, into the answer form.

When you finish entering the answers, click on the "Submit" button at the bottom of the page.  If your name has not been entered or an answer is blank, an error message will appear.  Otherwise, you should get a message indicating that your answers have been submitted.

Please enter your Name before beginning (Last Name, First Name):

And your email address:

Satellite images are not actual photographs, but instead are measurements of the energy being emitted at different wavelengths at thousands of points or pixels.  The amount of energy an object emits at a specific wavelength depends on temperature (Planck's Law), and so the resulting data can be converted into an image by a computer.  Because clouds are colder than the land or ocean surface in most cases (and hence they emit less energy), these emitted-energy measurements can be made to look like a photographic image by displaying cold pixels (clouds) in the image as white or light gray, and warm pixels (land or ocean surface) as black or dark gray.  

Question 2-1:  Note the time of day that appears in the upper left-hand corner of the image.  The four digits in front of the "Z" indicate UTC time in the 24hr format.  Pacific Standard Time is 8 hours earlier, and Pacific Daylight time is 7 hours earlier, so a time of 2300Z as above is equivalent to 3:00pm PST, or late afternoon.  Look at Oregon and California.  Describe the differences in gray tone between the land and ocean surface, and on land between the Sierra Nevada and Central Valley of California and the Cascade Range and Willamette Valley in Oregon.  Which areas are warmer and which are colder?

This following image is produced by the Space Science and Engineering Center at the University of Wisconsin--Madison, and consists of images from several geostationary satellites merged together. 

Note:  If an image does not appear below, enter "image not available" and the time in the answer form.

Question 2-2:  Describe the global pattern of clouds.  Where are clouds more abundant, and where are they less abundant?  Describe the relative size of the cloud patches in different regions (i.e. at the equator as opposed to the mid-latitudes)

The following image is the GOES 10 Visible image, centered on the eastern Pacific Ocean.

Note:  If an image does not appear below, enter "image not available" and the time in the answer form.

Question 2-3:  Note the time of day the image was taken (the four numbers in front of the Z on the bottom of the image--subtract 7 hours to get Pacific Daylight Time, 8 hours to get Pacific Standard Time).  What you will see will depend on the time of day.  Describe the planetary scale pattern of light and dark.  Describe the shape of the border between the illuminated region and dark region.

 

The two images below are from the Weather Channel.

Note:  If images do not appear below, enter "images not available" and the time in the answer form.

Satellite Image
Weather Channel Satellite Image

Surface Weather Map Weather Channel Surface Map

Question 2-4:  Describe, in general terms, the relationship between cloud patterns on the satellite image and surface weather features.  What is the relationship between precipitation (shown in green on the Current Surface map) and clouds?  What features appear on the Current Surface map where there are no clouds?

When you are finished, and all answers have been completed, click on the "Submit" below to send us the exercise.  If you receive an error message, check to make sure that you've answered each question, and that your name has been filled in, and then click on "Submit" again.

Click on this button to turn in your completed exercise: