Stratospheric impact of the Chisholm pyrocumulonimbus eruption: 2. Vertical profile perspective

Abstract

[1] Extreme pyrocumulonimbus (pyroCb) blowups that pollute the stratosphere have been documented on at least five occasions. However, the frequency of these events is still uncertain. One published pyroCb case study, the Chisholm Fire in May 2001, was restricted to the convective phase and its immediate aftermath. Here and in a companion paper we describe the stratospheric impact of the Chisholm pyroCb. The companion paper focuses on nadir satellite views of the plume. This paper synthesizes a broad array of space-, balloon-, and ground-based profile measurements. The Chisholm pyroCb, which we identify as the singular cause of stratospheric aerosol increase in northern spring/ summer of 2001, created a doubling of the zonal average aerosol optical depth in the lowermost stratosphere. The meridional spread of the plume was from the tropics (20°N) to the high Arctic (79°N) within the first month. The stratospheric Chisholm smoke became a hemispheric phenomenon in midlatitudes and northern tropics and persisted for at least 3 months. A size-resolved particle concentration profile over Laramie, Wyoming, indicated a lower stratospheric aerosol with a twofold to threefold increase in volume of particles with radii between 0.3 and 0.6 mm. We also find evidence of localized warming in the air masses of four of the lidar-measured smoke layers. This work contains the first reported stratospheric smoke layers measured by lidar at Ny Å lesund, Esrange, Kühlungsborn, Garmisch-Partenkirchen, Boulder, and Mauna Loa. In addition, the first detection of smoke-enhanced aerosol extinction at near IR wavelengths by the Halogen Occultation Experiment (HALOE) is introduced.

35 yr of stratospheric aerosol measurements at Garmisch-Partenkirchen: from Fuego to Eyjafjallajökull, and beyond

“…The Chisholm particles gradually filled the lowermost stratosphere in the entire Northern Hemisphere, as determined from observations with satellites and with NDACC lidar systems (Fromm et al, 2008b). The integrated backscatter coefficient in Fig.…”

“…Two pyroCb events that yielded also plume observations at GarmischPartenkirchen were recently studied in an international co-operation (Fromm et al, 2008b(Fromm et al, , 2010; see marks in Fig. 1).…”

“…The lidar system at IMK-IFU is an instrument of both NDACC and EARLINET. This system was originally built in 1973 (Impulsphysik GmbH), based on a ruby laser, and, in addition to a large number of routine and campaign-type tropospheric measurements (e.g., Reiter and Carnuth, 1975 Jäger et al, 1988Jäger et al, , 2006Forster et al, 2001;Trickl et al, 2003Trickl et al, , 2011, has been almost continually used for measurements of stratospheric aerosol since autumn 1976 (e.g., Jäger, 2005;Deshler et al, 2006;Fromm et al, 2008bFromm et al, , 2010. The lidar was converted to a spatially scanning system with a Nd:YAG laser (Quanta Ray, GCR 4, 10 Hz repetition rate, about 700 mJ per pulse at 532 nm) in the early 1990s for additional investigation of contrails (Freudenthaler, 2000;Freudenthaler et al, 1994Freudenthaler et al, , 1995.…”

An investigation of methods for injecting emissions from boreal wildfires using WRF-Chem during ARCTAS

“…Plumes can escape the boundary layer (Val Martin et al, 2010;Kahn et al, 2008) and have been observed to accumulate in layers of relative stability (e.g., Kahn et al, 2007). The wildfire smoke can even reach the lower stratosphere during cases of strong pyroconvection (e.g., Fromm, 2008;Trentmann et al, 2006). Releasing simulated emissions at appropriate altitudes has been a crucial and difficult problem to successfully modeling plume transport (e.g., Colarco et al, 2004;Westphal and Toon, 1991).…”

Composition and evolution of volcanic aerosol from eruptions of Kasatochi, Sarychev and Eyjafjallajökull in 2008–2010 based on CARIBIC observations

“…Additional sources contributing to the aerosol load in the UT/LMS, include air traffic (Ferry et al, 1999;Kjellström et al, 1999), meteorites (Cziczo et al, 2001) and boundary layer aerosol and precursor gases transported across the tropopause (Papaspiropoulos et al, 2002;Köppe et al, 2009). Especially aerosol from forest fires can be brought to high altitudes by extreme convection, however, the frequency and global contribution of such events is poorly understood (Fromm et al, 2004(Fromm et al, , 2008. Guan et al (2010) estimated that on average about six such events per year lead to injection of particles to altitudes above 8 km.…”