A revised version of the GLOBE cloud quiz and related materials has been posted. In the new version, only sharp cloud images are used, and foreground (trees, houses, etc) is included to provide a reference for scale. Ambiguous or incorrect cloud identifications were replaced or removed. Further, we removed pictures that showed more than one prominent cloud type. You will see that we have also revised the short descriptions of each cloud type to include more information. Nimbostratus was removed from the quiz because it is difficult to distinguish nimbostratus from darker stratus or stratocumulus without knowing whether it is raining.

We will be adding new cloud images to the collection at this location on the GLOBE Web site in the coming months. We invite you to send images showing typical cloud types. Since GLOBE is global, we particularly welcome images from locations outside the United States. As much as possible, one cloud type should dominate in the image. The images should include foreground (houses, trees, etc.), and we prefer that the cloud images be taken using a standard lens rather than a telephoto. We prefer cloud images taken near solar noon, when GLOBE cloud observations are generally taken. If you do not have an electronic camera, you may send a hard copy, and we will scan it and return the original. We may not use all the images we receive, and we may use some of the more complex images to illustrate how more complex clouds are identified - an advanced cloud quiz.

Please send electronic images to me (lemone@globe.gov). Include the location and time of day, as well as your name and affiliation (usually a school).

Hard copies can be sent to:

Margaret LeMone
Chief Scientist, GLOBE
3450 Mitchell Lane
Boulder, CO 80301 USA

We want to commend those of you who have taken cloud observations for GLOBE. These observations are being used to evaluate cloud types identified from satellites. Comparisons between the MODIS (MODerate resolution Imaging Spectrometer) satellite cloud product and GLOBE student observations show matches or partial matches over 80 percent of the time. The differences reveal some shortcomings of both the satellite cloud product and the cloud observations. For example, cloud heights are not always accurate, even when estimated by an expert observer. Also, there are cirrus clouds that are so thin that you cannot always see them! Finally, the current satellites see the top of the clouds, while people on the ground see the cloud bottoms. In the near future, GLOBE cloud observations will be used to help interpret data from Cloudsat. Matt Rogers and Graeme Stephens of Colorado State University, USA, who conducted this research, summarized the results at the 8th GLOBE Annual Meeting in Boulder, Colorado. View the PowerPoint Presentation.

For those of you curious about the images that we are replacing, I offer some samples and some reasons.

We acknowledge the trainers who pointed out problems with the cloud quiz during this last summer's US Train-the-Trainer workshops.

Peggy LeMone
GLOBE Chief Scientist

Some examples of deleted cloud images and why they were deleted:

Picture 1(below), Altocumulus and contrail. Because there is no foreground for reference, it is hard to tell whether this is a field of cumulus clouds photographed with a wide-angle lens or a field of altocumulus clouds.

Picture 2 (below), identified incorrectly as "altostratus intersecting mountains". The mountains in the picture are about 1 km high, and the clouds are intersecting the mountains. Thus the clouds are low clouds (stratus), and not middle clouds (altostratus). Sometimes it is difficult to distinguish between stratus and altostratus, because there is so little structure. When surface temperatures are warm, a distinct solar disk indicates water clouds and thus stratus, and a fuzzy indistinct solar image indicates altostratus. But, in the winter when temperatures are below freezing, the stratus can contain ice as well.

Picture 3 (below), identified incorrectly as "cirrostratus". This cloud has an aureole around the sun . note the circles of color. This is a phenomenon caused by diffraction of light by tiny water drops. Thus it is probably a middle cloud and not cirrostratus as identified earlier.