To begin classifying, select an image in the Cloud Gallery. Using the menu below the enlarged image, choose the cloud types you see and click "submit."

If you're unsure about which cloud types you see, click on the "key" tab on the lower left corner of the screen. This tab opens a set of thumbnail images for each of the 10 most common cloud types. By clicking on the thumbnails, you can see enlargements of these images and read about some of the most important characteristics of each type of cloud.

The points you earn for each cloud you classify correctly will be added to your Lab report, which is at the top right of the NOVA Labs home page. (You won't be able to save your points if you haven't signed in as a registered user.)

Once each image is classified, it moves automatically to your "My Classifications" folder, with all the correct cloud types clearly identified. You can also “favorite” the images you like the most to add them to your "My Favorites" gallery.

Finally, if you want to share your own cloud images, you can do so at the NOVA Cloud Spotting Tumblr or on the NOVA Labs Facebook page.