Investigation of a Multi-day PyroCumulonimbus Outbreak on the California-Oregon Border in 2014

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Sunday, 4 January 2015
Britta F. Gjermo, CIMSS/Univ. of Wisconsin, Madison, WI; and S. Bachmeier and B. Baum

When a fire becomes pyroconvective, large quantities of absorbing aerosols are injected into the upper troposphere and often penetrate briefly into the stratosphere producing a PyroCumulonimbus (pyroCb). Once at high altitudes, the dense aerosol plumes can travel thousands of kilometers from the source region in a matter of days. Over the past year, we have captured a number of pyroCb events where the cloud-top temperatures were colder than -40˚ C. Of particular interest to this study is an event that began on July 30, 2014, when a lightning strike started the Oregon Gulch Fire. This quickly became an extremely active fire due to the very dry conditions (extreme drought) in this part of the country. As these fires grew, another thunderstorm system passed through northern California on August 1, 2014 with over 1,000 lightning strikes recorded; this system started a series of fires in that area that quickly spread with the help of even drier conditions in this region (exceptional drought) compared to southern Oregon. These two areas of fires created several pyroCbs from August 1 to August 3, 2014. As it turns out, F-15 Eagles jets from the 173rd Fighter Wing of the Oregon Air National Guard flew in the vicinity of some of the pyroCbs and took spectacular photos. In this presentation, we will summarize the development of this pyroCb outbreak using geostationary satellite imagery and products, as well as data from other satellite sensors.