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This satellite image shows pockets of open cells (POCS) in stratocumulus clouds over the Southeast Pacific Ocean.
Click on image for full size
Image Courtesy of the MODIS Science Team at NASA GSFC

Pockets of Open Cells in Stratocumulus Clouds

The Southeast Pacific region typically has extensive stratocumulus cloud cover over the ocean. These offshore clouds can contain clear areas in the clouds that scientists call "pockets of open cells," or POCs. Scientists think that drizzle is responsible for the formation of POCs. They have also found a connection between drizzle and aerosols in the atmosphere.

Aerosols are tiny particles in the air that water droplets condense on within clouds during cloud formation. The concentration of aerosols in the atmosphere may impact the structure of the clouds (this is what you would see if you looked down on stratocumulus clouds from an airplane or a satellite). When there are fewer aerosols in the atmosphere, the cloud droplets that form on these aerosols are larger and produce more drizzle. This is when POCs form in the clouds. When there is a higher concentration of aerosols in the atmosphere, the cloud droplets that form are smaller and don't produce drizzle. These clouds contain closed cells.

Understanding the reasons for this difference in cloud structure is one of the objectives of the VOCALS project. Scientists studying the climate in the Southeast Pacific are trying to learn more about the amounts of aerosols and how they affect the presence of POCs in the clouds, as well as how they impact the amount of drizzle these clouds produce.

Last modified September 19, 2008 by Becca Hatheway.

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