Fog in the Gulf of Maine

July 8th, 2008 |

fogloop.gif

Fog that formed in the Gulf of Maine on Tuesday July 8th developed when relatively moist air moved from the continent over the cooler ocean waters and was cooled from beneath by conduction to the dewpoint. In other words, Advection Fog.

An obvious question arises from the loop: Why does the fog persist over the ocean east of Nantucket and along the coast of Maine even as it clears out in the central part of the Gulf of Maine? The answer is shown in the color-shaded image of SST (available from the Applied Physics Lab at Johns Hopkins University) below. Warmer waters over the central Gulf of Maine will promote the faster erosion of ocean fog because of enhanced vertical mixing because of lower stability. Ocean fog that moves over land — as over southwestern Nova Scotia — also dissipates as heating over land promotes vertical mixing. Dryer air aloft mixed towards the surface reduces the boundary layer relative humidity and the fog evaporates. The dryer air just above the surface is readily apparent in Skew-T plots from Yarmouth, Nova Scotia and from Gray, Maine.

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California fires: burn scar detection

July 8th, 2008 |

MODIS false color + true color images (Animated GIF)

Many large wildfires continued to burn in parts of California on 08 July 2008. A comparison of MODIS false color and true color images from the SSEC MODIS Today site (above) demonstrated the use of the false color imagery for determining the areal coverage of burn scars in the Los Padres National Forest south of Monterey, California; the burn scars show up as reddish-brown features, with active fire hot spots having a brighter light pink appearance on the false color imagery. In the true color imagery, it is difficult to discriminate between thick smoke from the fires and stratus clouds right along the coast, but the smoke exhibits a light blue tint on the false color imagery.