Lifting potential of solar‐heated aerosol layers

Boers, R.; Laat, A. T. de; Zweers, Deborah Claire Stein; Dirksen, R.

doi:10.1029/2010gl045171

Cited by 35 publications

(58 citation statements)

References 14 publications

(14 reference statements)

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“…Strong bushfires, very high temperatures, low winds, and thunderstorm evolution on 7 February, 2009, ("Black Saturday") triggered the lifting of enormous amounts of smoke towards the upper troposphere from where the smoke layers ascended by the self-lifting mechanism to a height of 15-20 km (Boers et al, 2010;de Laat et al, 2012). Similar maximum 532 nm AEC and AOT values as measured over central Europe on 21-22 August 2017, were observed with the CALIPSO lidar in the lower stratosphere over the South Pacific east of Australia at heights above the tropopause and below 20 km a few days after 7 February, 2009, (de Laat et al, 2012.…”

Section: Discussionmentioning

confidence: 99%

“…Khaykin et al (2018) found that the smoke plumes ascended rapidly over the first few days following their injection into the upper troposphere with a rate of 2-3 km per day. This cross isentropic ascent was caused by radiative heating of smoke aerosols (Boers et al, 2010). The second aspect is that the wind velocity decreases with height from the tropopause to an altitude of 16 km (GDAS, 2018) as well as from the tropopause to the middle troposphere (5 km height).…”

Section: Satellite-derived Products: Modis and Omi Retrievalsmentioning

confidence: 99%

“…Fromm et al (2000Fromm et al ( , 2003 and Rosenfeld et al (2007) showed that large amounts of fire smoke can be lifted up to the tropopause within a short time period (less than 1 h) and can partly reach the lower stratosphere via the formation of pyrocumulonimbus clouds that are associated with strong updrafts with vertical wind velocities of 10-30 m s −1 (Fromm et al, 2010;Peterson et al, 2017). Self-lifting effects (Boers et al, 2010;Siddaway and Petelina, 2011;de Laat et al, 2012) and gravito-photophoresis forces (Rohatschek, 1996;Pueschel et al, 2000;Cheremisin et al, 2005;Renard et al, 2008) lead to a further ascent of the soot-containing layers.…”

Section: Introductionmentioning

confidence: 99%

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Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

et al. 2018

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Abstract. Light extinction coefficients of 500 Mm −1 , about 20 times higher than after the Pinatubo volcanic eruptions in 1991, were observed by European Aerosol Research Lidar Network (EARLINET) lidars in the stratosphere over central Europe on 21-22 August 2017. Pronounced smoke layers with a 1-2 km vertical extent were found 2-5 km above the local tropopause. Optically dense layers of Canadian wildfire smoke reached central Europe 10 days after their injection into the upper troposphere and lower stratosphere which was caused by rather strong pyrocumulonimbus activity over western Canada. The smoke-related aerosol optical thickness (AOT) identified by lidar was close to 1.0 at 532 nm over Leipzig during the noon hours on 22 August 2017. Smoke particles were found throughout the free troposphere (AOT of 0.3) and in the pronounced 2 km thick stratospheric smoke layer at an altitude of 14-16 km (AOT of 0.6). The lidar observations indicated peak mass concentrations of 70-100 µg m −3 in the stratosphere. In addition to the lidar profiles, we analyzed Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) over Canada, and the distribution of MODIS AOT and Ozone Monitoring Instrument (OMI) aerosol index across the North Atlantic. These instruments showed a similar pattern and a clear link between the western Canadian fires and the aerosol load over Europe. In this paper, we also present Aerosol Robotic Network (AERONET) sun photometer observations, compare photometer and lidar-derived AOT, and discuss an obvious bias (the smoke AOT is too low) in the photometer observations. Finally, we compare the strength of this recordbreaking smoke event (in terms of the particle extinction coefficient and AOT) with major and moderate volcanic events observed over the northern midlatitudes.

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Section: Discussionmentioning

confidence: 99%

Section: Satellite-derived Products: Modis and Omi Retrievalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

et al. 2018

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“…Or in other words, rather than being advected passively with the prevailing winds, absorbing aerosols may actually have a direct impact on their own vertical transport. The framework for this idea dates back to the work of Malone et al [1986] and Radke et al [1990] and was revived by Boers et al [2010]. According to calculations by Boers et al [2010], optically thick layers of absorbing aerosols can be lifted from the lower troposphere to the (extratropical) tropopause due to diabatic heating within 3–4 days, the so‐called “self‐lofting” mechanism of Radke et al [1990].…”

Section: Introductionmentioning

confidence: 99%

A solar escalator: Observational evidence of the self‐lifting of smoke and aerosols by absorption of solar radiation in the February 2009 Australian Black Saturday plume

et al. 2012

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We present an analysis of the evolution of the smoke plume caused by the Black Saturday bushfires, which started on 7 February 2009 in the Australian state of Victoria. Within 3 days this smoke plume was located at altitudes between 15 and 20 km thousands of kilometers away from its source region. Standard explanations for high tropospheric and lower stratospheric absorbing aerosols are either volcanic eruptions or pyroconvection. We performed a detailed analysis of various satellite observations, forward trajectory calculations, and meteorological conditions during the fire episode, yet we could not find evidence of either of these standard mechanisms explaining the observed plume evolution. Pyroconvection observed within the initial smoke plumes remained predominantly below 10 km altitude. Furthermore, there are not active volcanoes in the region. We postulate that the subsequent rise beyond approximately 10 km altitude during the first 3 days after the fires started was caused by absorption of short‐wave solar radiation in the plume. Observations indicate that the plume was highly absorptive and optically very thick. One‐dimensional plume height radiative transfer calculations with realistic assumptions about the optical properties of the smoke show that the plume could rise to 16–18 km after 5 days and up to 20 km after 10 days. The plume rise exhibits a characteristic step‐like time evolution that tracks the variation in diurnal insolation and resembles an escalator. We argue that this is the first time that this mechanism, known as “self‐lifting,” has been observed on a large scale. The key features of this mechanism and its implications are briefly discussed.

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“…Plumes containing soot particles also change the local atmospheric stability due to the ability to heat the ambient air by absorbing the solar radiation. Hence, elevated biomass burning layers have the potential of additional lifting, increasing persistence and thus longer lifetimes in the free troposphere (Boers et al, 2010). At the top of the atmosphere semi-direct radiative effects can differ in sign depending on the location of the biomass burning plumes and their underlying surface, that is, if they are located above land (positive semi direct radiative effect) or ocean (negative semi direct radiative effect) (Sakaeda et al, 2011).…”

Section: Transport Of Smoke Plumes Downwind From the Source Regionmentioning

confidence: 99%

Long-term in situ observations of biomass burning aerosol at a high altitude station in Venezuela – sources, impacts and interannual variability

et al. 2013

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Abstract. First long-term observations of South American biomass burning aerosol within the tropical lower free troposphere are presented. The observations were conducted between 2007 and 2009 at a high altitude station (4765 m a.s.l.) on the Pico Espejo, Venezuela. Sub-micron particle volume, number concentrations of primary particles and particle absorption were observed. Orographic lifting and shallow convection leads to a distinct diurnal cycle at the station. It enables measurements within the lower free troposphere during night-time and observations of boundary layer air masses during daytime and at their transitional regions. The seasonal cycle is defined by a wet rainy season and a dry biomass burning season. The particle load of biomass burning aerosol is dominated by fires in the Venezuelan savannah. Increases of aerosol concentrations could not be linked to long-range transport of biomass burning plumes from the Amazon basin or Africa due to effective wet scavenging of particles. Highest particle concentrations were observed within boundary layer air masses during the dry season. Ambient sub-micron particle volume reached 1.4 ± 1.3 µm 3 cm −3 , refractory particle number concentrations (at 300 • C) 510 ± 420 cm −3 and the absorption coefficient 0.91 ± 1.2 Mm −1 . The respective concentrations were lowest within the lower free troposphere during the wet season and averaged at 0.19±0.25 µm 3 cm −3 , 150±94 cm −3 and 0.15±0.26 Mm −1 . A decrease of particle concentrations during the dry seasons from 2007-2009 could be connected to a decrease in fire activity in the wider region of Venezuela using MODIS satellite observations. The variability of biomass burning is most likely linked to the El Niño-Southern Oscillation (ENSO). Low biomass burning activity in the Venezuelan savannah was observed to follow La Niña conditions, high biomass burning activity followed El Niño conditions.

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Lifting potential of solar‐heated aerosol layers

Cited by 35 publications

References 14 publications

Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

Extreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21–22 August 2017

A solar escalator: Observational evidence of the self‐lifting of smoke and aerosols by absorption of solar radiation in the February 2009 Australian Black Saturday plume

Long-term in situ observations of biomass burning aerosol at a high altitude station in Venezuela – sources, impacts and interannual variability

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