Heat, Humidity and HAZE!

The high heat of the past few days has been accompanied by a considerable amount of haze. Satellite imagery below has picked up on this quite well. The enhanced satellite pictures and notes that follow are courtesy of StormCenter Communications, Inc.

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The images were captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA’s Aqua satellite on August 4 and August 7, 2007. They show smoke and haze over US.

Haze over eastern US on August 4, 2007

The Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA’s Aqua satellite captured this image of the smoke and fires on the afternoon of August 4. It is a mosaic of four separate flyovers (separated by faint diagonal lines).

High pressure over the southeastern United States is resulting in light winds, high temperatures and stagnant vertical airflow, leading to the accumulation of haze, smoke, and other air pollutants. The swirls of smoke/haze in the picture are the result of this air moving around an area of high pressure in an anti-cyclonic (clockwise) way. High pressure also inhibits the growth of storms that could provide relief to these conditions.

Haze Over US Southeast Coast on August 7, 2007

This image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite shows haze over US southeast coast on Tuesday afternoon, August 7.

Environmental Impacts:

Strong winds on August 4 created uncontrollable firestorms that forced the evacuation of at least two communities in Montana.

Fires in Montana and Idaho are marked with red dots in the upper-left part of the image of the whole US. In addition to fueling the flames, the winds blew dense plumes of smoke northeast. The thickest plumes rise from the fires in northwestern Montana. By the time the smoke reached eastern Montana, the plumes were no longer distinct. The air was clouded with a soupy, gray haze that curves north into Canada. High-level winds pushed the smoke south over the western Great Lakes, and into the Central and Southern United States. From the bank of clouds over Illinois to the Gulf of Mexico, the air was white-gray with haze.

By this point, smoke from the western wildfires is probably only one component of the haze. High temperatures and stagnant air also amplified the impact of urban pollution, creating Code Orange air quality conditions, which are unhealthy for sensitive groups such as active children or adults or individuals with respiratory ailments. The jet stream—the fast-moving, high-level winds that steer weather systems—is defined by the stark boundary between the hazy air over the Mid-Atlantic and the clear air over New England. Jet stream winds are clearly blocking the smoke from traveling north.

From the Central United States, the plume of pollution snaked over the Mid-Atlantic States and the Chesapeake Bay to the Atlantic Ocean, where it turned north and flowed along the coast. Some additional haze may line the coast south of Cape Hatteras, but reflected sunlight has turned the ocean’s surface into a mirror, effectively masking the presence of any haze.

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The hazy, hot, humid airmass will gradually be pushed south and it should be a little more comfortable in the Baltimore area by the weekend.

John Collins

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