[cdn-nucl-l] More pollution from space - this time in China

["Adam McLean" <adam.mclean@utoronto.ca>]

As previous... simply unbelievable.

Adam

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http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=5257

Pollution Over Yellow River Valley, China

Thick aerosols blanket much of China's Huang He, or Yellow River, in this
true-color MODIS image from October 22, 2001. The Yellow River begins at the
upper left of the image and flows briefly east before turning south, a path
it follows nearly the length of the image. This part of the river is
relatively undeveloped, with few large towns or cities. Near the bottom
center of the image, the river makes a second eastward turn and flows out
across the plain where it empties into Bo Hai Bay.

The location of the aerosols reflects the interaction of human geography,
topography, and regional weather. Large cities, sources for aerosol
emissions, are located along river valleys. For example, in the center of
the image, aerosols are packed into the Fen River Valley, which flows
southwest and into the Yellow River. Both the large aerosol cloud along the
coast and the smaller pockets along the river valleys follow the lines of
rising terrain.

What kept the aerosols confined to the lower elevations on this day was a
strong temperature inversion. Normally, air temperature decreases as
altitude increases. On those days, the temperature and pressure gradients
cause warmer surface air to move upward, allowing the aerosol emissions to
escape from the surface and disperse.

On this day, however, a temperature inversion occurred, and cold, dense air
was trapped near the surface, while the air above was warmer. In this
situation, mixing of the atmosphere was suppressed, the cold dense air
didn't rise up, and emissions stayed trapped near their source, confined to
the lower elevations. This situation happens often in winter, because the
surface of the Earth loses heat rapidly at night, and when dawn arrives, the
weaker winter sunlight takes much longer to warm it back up.

Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA
GSFC. [Thanks to Si-Chee Tsay and Allen Chu for providing analysis and
interpretation.]