investigations into the nature, severity, and impact of pyrocumulonimbus
Fromm, Michael David
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Pyrocumulonimbus (pyroCb) storms have been shown to have an eruptive dynamic and capacity similar to volcanic eruptions that penetrate into the stratosphere. Much remains unknown about pyroCb, for instance its storm structure, frequency, impact on satellite cloud imagery, and impact on regional/hemispheric climate. This study pursues in-depth exploration of pyroCb using observational data analysis and modeling. The observational aspect of this research will be founded in satellite data from imagers and profilers, going back to the late 1970s. These data are examined for clues that will eventually allow the characterization of a pyroCb-frequency climatology. The particular data sets include Total Ozone Mapping Spectrometer (TOMS) and Ozone Monitoring Instrument (OMI) aerosol index, nadir imagery in the visible and infrared, and aerosol profiles. In addition, available ground-based data (such as lidar) are also exploited. PyroCb radiative impact is explored by combining aerosol optical depth data with a long-term Microwave Sounding Unit (MSU) and radiosonde temperature archive and a radiative transfer model. This work comprises studies of two pyroCb events, in the southern and northern hemisphere, and an analysis of the radiative impact of stratospheric smoke comprising two seasons with multiple pyroCbs. The major findings include the revelation that pyroCb can generate tornadoes, significantly suppress precipitation due to super-abundance of condensation nuclei, increase by factors of 2 to 5 the zonal average stratospheric aerosol optical depth, pollute air mass regimes from tropics to polar, and perturb zonal average stratospheric temperature.