Cloud features related to sharp sea surface temperature (SST) gradients

February 26th, 2008 |

GOES-12 visible images (Animated GIF)

Some interesting cloud features were seen in the western North Atlantic Ocean on 26 February 2008, about 300 miles southeast of New England (and about 300 miles south of Nova Scotia, Canada): a narrow line of cumulus clouds (oriented approximately north-south), and a patch of stratus cloud (or possibly fog?) that developed just east of the cumulus line. These cloud features were apparently related to very sharp gradients in the Sea Surface Temperature (SST) over that particular area.

GOES-12 10.7µm IR images (Animated GIF)

AWIPS images of the GOES-12 10.7µm IR channel (above) showed that there were large cold eddies (darker green enhancement) located over the western North Atlantic, along the north wall of the Gulf Stream (RTG_SST analysis). These cold water eddies remained stationary as patches of colder clouds (cyan to blue enhancement) drifted eastward across the region.

MODIS sea surface temperature (SST) product

An 8-day composite of the MODIS Sea Surface Temperature product (above) confirmed the presence of a very sharp SST gradient in that area (near 40º N latitude, 65º W longitude), with a patch of water having SST values in the 40s F (cyan to blue enhancement) located just to the east of water having SST values in the 60s F (green enhancements) — black features on the SST image are clouds. Low-level baroclinicity enhanced by the sharp SST gradient was aiding the development and maintenance of the cumulus line; as warm air moving eastward encountered the colder pocket of water, stratus cloud quickly formed as the marine boundary layer air was rapidly cooled to its dew point.