Comment on "Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport"

Fromm, M.; Nedoluha, Gerald E.; Charvát, Zdeněk

doi:10.1126/science.1228605

Cited by 49 publications

(50 citation statements)

References 4 publications

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“…(2014) and references therein). While there is some debate regarding the altitude of the plume injection heights (Vernier et al, 2013;Fromm et al, 2013Fromm et al, , 2014, Clarisse et al (2014) suggest that the main injection occurred over altitudes of 15-17 km consistent, with observed plume trajectories, as shown in Bourassa et al (2013). The stratospheric aerosol layer occurred at somewhat higher altitudes (above 18 km; Bourassa et al, 2012;Fairlie et al, 2014), consistent with slow upward transport in the monsoon circulation.…”

Section: Discussion and Summarysupporting

confidence: 60%

Transport pathways from the Asian monsoon anticyclone to the stratosphere

2016

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Abstract. Transport pathways of air originating in the uppertropospheric Asian monsoon anticyclone are investigated based on three-dimensional trajectories. The Asian monsoon anticyclone emerges in response to persistent deep convection over India and southeast Asia in northern summer, and this convection is associated with rapid transport from the surface to the upper troposphere and possibly into the stratosphere. Here, we investigate the fate of air that originates within the upper-tropospheric anticyclone from the outflow of deep convection, using trajectories driven by ERA-interim reanalysis data. Calculations include isentropic estimates, plus fully three-dimensional results based on kinematic and diabatic transport calculations. Isentropic calculations show that air parcels are typically confined within the anticyclone for 10-20 days and spread over the tropical belt within a month of their initialization. However, only few parcels (3 % at 360 K, 8 % at 380 K) reach the extratropical stratosphere by isentropic transport. When considering vertical transport we find that 31 % or 48 % of the trajectories reach the stratosphere within 60 days when using vertical velocities or diabatic heating rates to calculate vertical transport, respectively. In both cases, most parcels that reach the stratosphere are transported upward within the anticyclone and enter the stratosphere in the tropics, typically 10-20 days after their initialization at 360 K. This suggests that trace gases, including pollutants, that are transported into the stratosphere via the Asian monsoon system are in a position to enter the tropical pipe and thus be transported into the deep stratosphere. Sensitivity calculations with respect to the initial altitude of the trajectories showed that air needs to be transported to levels of 360 K or above by deep convection to likely ( 50 %) reach the stratosphere through transport by the large-scale circulation.

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Section: Discussion and Summarysupporting

confidence: 60%

Transport pathways from the Asian monsoon anticyclone to the stratosphere

2016

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“…Bourassa et al (2012) have suggested deep convection associated with the Asian monsoon circulation to explain the strong impact of the eruption on the stratospheric aerosol loading. However, this mechanism is controversial after Vernier et al (2013) and Fromm et al (2013) provided satellite evidence for direct injection of the initial Nabro plume into the lower stratosphere.…”

Section: Nabromentioning

confidence: 99%

“…For the present study, we have applied a correction for SO 2 loss using a τ value different for each emission layer. From the decay observed in the total SO 2 mass after the end of the first major injection episode (not shown), we derive an e-folding lifetime of 5 days for the high altitude plumes at 15-18 km (Vernier et al, 2013;Fromm et al, 2013). The e-folding time parameterization as a function of altitude was estimated by interpolation between the values at surface level, taken as 2 days, and the one at 15-18 km (5 days).…”

Section: Inversion Settingsmentioning

confidence: 99%

“…As a test, we have run a FLEXPART simulation starting on 14 June 2011 (i.e., more than 30 h after the start of the eruption) using the IASI SO 2 observations as emission cells, the source strengths being modulated by the corresponding measured SO 2 masses. Only the data with latitudes above 20 • N have been kept and the simulations assumed a uniform SO 2 profile between 15 and 18 km (Vernier et al, 2013;Fromm et al, 2013). The results are shown in Fig.…”

Section: Transport Of the Early Plumementioning

confidence: 99%

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Volcanic SO<sub>2</sub> fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS

et al. 2013

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Abstract. Sulphur dioxide (SO2) fluxes of active degassing volcanoes are routinely measured with ground-based equipment to characterize and monitor volcanic activity. SO2 of unmonitored volcanoes or from explosive volcanic eruptions, can be measured with satellites. However, remote-sensing methods based on absorption spectroscopy generally provide integrated amounts of already dispersed plumes of SO2 and satellite derived flux estimates are rarely reported. Here we review a number of different techniques to derive volcanic SO2 fluxes using satellite measurements of plumes of SO2 and investigate the temporal evolution of the total emissions of SO2 for three very different volcanic events in 2011: Puyehue-Cordón Caulle (Chile), Nyamulagira (DR Congo) and Nabro (Eritrea). High spectral resolution satellite instruments operating both in the ultraviolet-visible (OMI/Aura and GOME-2/MetOp-A) and thermal infrared (IASI/MetOp-A) spectral ranges, and multispectral satellite instruments operating in the thermal infrared (MODIS/Terra-Aqua) are used. We show that satellite data can provide fluxes with a sampling of a day or less (few hours in the best case). Generally the flux results from the different methods are consistent, and we discuss the advantages and weaknesses of each technique. Although the primary objective of this study is the calculation of SO2 fluxes, it also enables us to assess the consistency of the SO2 products from the different sensors used.

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“…Furthering the understanding of the transport of aerosol near and across the tropopause would also benefit from higher spatial and temporal resolution observations. This is evident in the case of volcanic plumes, such as that from Nabro in 2011, the transport and origin of which has been studied extensively and the conclusions are somewhat controversial (Bourassa et al, 2012c(Bourassa et al, , 2013Vernier et al, 2013;Fromm et al, 2013Fromm et al, , 2014Fairlie et al, 2014;Clarisse et al, 2014). However, this is also the case for the formation of background-level aerosol, particularly in the region of the Asian and North American monsoons, which have been identified as a source of substantial, seasonal, and highly structured aerosol formation from precursor tropospheric source gases (Vernier et al, 2011a;Neely et al, 2014;Thomason and Vernier, 2013).…”

Section: Introductionmentioning

confidence: 99%

The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

et al. 2016

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Abstract. The Aerosol Limb Imager (ALI) is an optical remote sensing instrument designed to image scattered sunlight from the atmospheric limb. These measurements are used to retrieve spatially resolved information of the stratospheric aerosol distribution, including spectral extinction coefficient and particle size. Here we present the design, development and test results of an ALI prototype instrument. The longterm goal of this work is the eventual realization of ALI on a satellite platform in low earth orbit, where it can provide high spatial resolution observations, both in the vertical and cross-track. The instrument design uses a large-aperture acousto-optic tunable filter (AOTF) to image the sunlit stratospheric limb in a selectable narrow wavelength band ranging from the visible to the near infrared. The ALI prototype was tested on a stratospheric balloon flight from the Canadian Space Agency (CSA) launch facility in Timmins, Canada, in September 2014. Preliminary analysis of the hyperspectral images indicates that the radiance measurements are of high quality, and we have used these to retrieve vertical profiles of stratospheric aerosol extinction coefficient from 650 to 1000 nm, along with one moment of the particle size distribution. Those preliminary results are promising and development of a satellite prototype of ALI within the Canadian Space Agency is ongoing.

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Comment on "Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport"

Cited by 49 publications

References 4 publications

Transport pathways from the Asian monsoon anticyclone to the stratosphere

Transport pathways from the Asian monsoon anticyclone to the stratosphere

Volcanic SO<sub>2</sub> fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS

The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

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Comment on "Large Volcanic Aerosol Load in the Stratosphere Linked to Asian Monsoon Transport"

Cited by 49 publications

References 4 publications

Transport pathways from the Asian monsoon anticyclone to the stratosphere

Transport pathways from the Asian monsoon anticyclone to the stratosphere

Volcanic SO&lt;sub&gt;2&lt;/sub&gt; fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS

The Aerosol Limb Imager: acousto-optic imaging of limb-scattered sunlight for stratospheric aerosol profiling

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Product

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Volcanic SO<sub>2</sub> fluxes derived from satellite data: a survey using OMI, GOME-2, IASI and MODIS