Pink Sky

January 08, 2006

Claysky6

Provided by: Oklahoma Mesonet
Summary authors & editors: Deke Arndt

The pinkish skies shown above were caused by the reddish soils from New Mexico, Texas and Oklahoma. Strong winds, prolonged dryness, and unprotected soils combine to lift many fine particles into the air, where they can be transported for hundreds, even thousands, of miles. The clayey soils of the southwest tend to provide even finer particulates than sandy or loamy soils. This provides even more fodder for the season's relentless winds.

Right now, Oklahoma, parts of Texas and New Mexico are in desperate need of precipitation -- to mitigate the drought and to put an end to the dreadful wildfires. One of the "invisible" enhancements to fire danger comes from drying of the subsurface. As the top few inches of soil become almost completely dry, the organic material becomes additional fuel for wildfire. The roots, dead bugs, dead worms, and such in the subsurface literally burn along with the combustible material above the surface. This makes for more energetic, hotter fires. Moreover, they become much more difficult to extinguish.

This process begins to impact fire conditions when the Keetch-Byram Drought Index (KBDI) exceeds about 200. When the KBDI passes 400, the process becomes even more significant. Above 600, this process is profound. In early January, KBDI values are over 400 across more than half of Oklahoma.

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