39 Detection and Inventory of Intense Pyroconvection in Western North America using GOES-15 Daytime Infrared Data

Monday, 15 August 2016
Grand Terrace (Monona Terrace Community and Convention Center)
David A. Peterson, NRL, Monterey, CA; and J. Solbrig, E. Hyer, M. Fromm, M. Surratt, and J. R. Campbell

Under certain meteorological conditions, it is possible for a wildfire to generate a fire-triggered storm known as pyrocumulonimbus (pyroCb). An intense pyroCb is capable of injecting a significant quantity of aerosol mass into the upper troposphere and lower stratosphere (UTLS). This study develops a unique near-real-time pyroCb detection algorithm using the infrared (IR) channels available from GOES-West (GOES-15). The algorithm first identifies deep convection near observations of active fires via the longwave IR brightness temperature, distinguishing between mid-tropospheric and UTLS pyroCb injection scenarios. The primary component is identification of unique pyroCb microphysical properties, characterized by a shortwave brightness temperature that is significantly larger than in the longwave. Dependence on shortwave reflectivity focuses pyroCb detection on daytime scenes. A cloud opacity test is also included to reduce potential false detections. Analysis is focused on pyroCb detections for 88 intense wildfires observed during the 2013 fire season in western North America. Results show that cloud microphysics tests are useful for separating pyroCb from traditional convection. The algorithm successfully captures individual intense pyroCb events, pyroCb embedded within traditional convection, and multiple, short-lived pulses of activity. Small anvil size is the primary limitation, especially in in regions with large viewing angles. The algorithm is also sensitive to traditional convection with extreme updraft velocities and convection that ingests smoke from nearby fires. A total of 26 pyroCb events are inventoried, including 31 individual pulses, all of which are capable of injecting smoke within the UTLS. Six previously undocumented intense pyroCb are also identified. This algorithm can be extended to next-generation geostationary sensors such as GOES-R and the Advanced Himawari Imager, which offer significant advantages for pyroCb and fire detection. Improved exploitation of satellite observations and their application to meteorological analyses is paramount for understanding the role of pyroCb in the climate system.
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