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Using DOAS traverses and atmospheric modelling to determine plumeheight and eruption rate of the 2015 Holuhraun eruption
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Centre for Natural Disaster Science.ORCID iD: 0000-0001-7909-0640
Department of Earth and Space Sciences, Chalmers University of Technology, Gothenburg, Sweden..
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Department of Earth and Space Sciences, Chalmers University of Technology, Gothenburg, Sweden..
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The fissure eruption in Holuhraun — part of the Barðarbunga volcanic system — in 2014–2015 was amajor emitter of SO 2 . We present estimates of the SO 2 release rate of the eruption based on inverseatmospheric modelling and mobile-DOAS measurements made 80–240 km downwind of the main fissurevent. The FLEXPART-WRF and FLEXPART models are used to simulate the dispersion, using differentmeteorological data sets as input. Different inversion schemes were used to determine emission rates basedon modelled and measured column densities. The results were compared with OMI satellite observationsfor validation. This is, to our knowledge, the first case where a ground-based mobile-DOAS measurementshave been used in an atmospheric dispersion model for inverse modelling.

Comparisons were made between dispersion simulations based on meteorological data from different con-figurations of the WRF-model (at a resolution of 1.5 km); comparisons were also made using analysis andforecast data from ECMWF (at 0.2 degree resolution). Dispersion simulations based on data from ECMWFshowed better agreement with OMI satellite data than any of the simulations based on data from WRF.The inversion technique produced less variable emission rates compared to previous estimates, except duringperiods with low directional wind shear. Plume heights determined by the inverse modelling were below4 km for all periods.

We estimate the emission rate of the eruption to 500 kg/s in September 2014 and to 150 kg/s in thebeginning of February 2015, with a steady decrease over time.

Keyword [en]
Dispersion modelling, FLEXPART, Volcanic eruption, Sulfur dioxide, Holuhraun
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:uu:diva-303950OAI: oai:DiVA.org:uu-303950DiVA: diva2:974722
Available from: 2016-09-27 Created: 2016-09-27 Last updated: 2016-09-27Bibliographically approved
In thesis
1. Dispersion modelling of volcanic emissions
Open this publication in new window or tab >>Dispersion modelling of volcanic emissions
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Spridningsmodellering av utsläpp från vulkaner
Abstract [en]

Gases and particles released by volcanoes pose a serious hazard to humans and society. Emissions can be transported over long distances before being reduced to harmless concentrations. Knowing which areas are, or will be, exposed to volcanic emissions is an important part inreducing the impact on human health and society. In this thesis, the dispersion of volcanic emissions is studied using a set of atmospheric models.

The work includes contribution to the development of the Lagrangian Particle Dispersion Model FLEXPART-WRF. Three case studies have been performed, one studying potential ash emissions from potential future eruptions on Iceland, a second covering SO2 emissions from Mt. Nyiragongo in D.R. Congo, and a third studying the SO2 emission rate of the Holuhraun eruption (Iceland) in 2014–2015.

The first study covers volcanic ash hazard for air traffic over Europe. Three years of meteorological data are used to repeatedly simulate dispersion from different eruption scenarios. The simulations are used to study the probability of hazardous concentrations in ash in European airspace. The ash hazard shows a seasonal variation with a higher probability of efficient eastward transport in winter, while summer eruptions pose a more persistent hazard.

In the second study, regional gas exposure around Mt. Nyiragongo is modelled using flux measurements to improve the description of the emission source. Gases are generally transported to the north-west in June–August and to the south-west in December–January. A diurnal variation due to land breeze around lake Kivu contributes to high concentrations of SO2 along the northern shore during the night. Potentially hazardous concentrations are occasionally reached in populated areas in the region, but mainly during the nights.

The third study uses inverse dispersion modelling to determine the height and emission rates based on traverse measurements of the plume at 80–240 km from the source. The calculated source term yields better agreement with satellite observations compared to commonly used column sources.

The work in this thesis presents improvements in dispersion modelling of volcanic emissions through improved models, more accurate representation of the source terms, and through incorporating new types of measurements into the modelling systems.

Abstract [sv]

Gas- och partikelutsläpp från vulkaner utgör en fara för människor och för vårt samhälle. Utsläppen kan transporteras över långa avstånd innan de reduceras till oskadliga halter. Att känna till vilka områden som utsätts för, eller kommer utsättas för, utsläppen är ett viktigt verktyg föratt minska påverkan på folkhälsa och samhälle. I avhandlingen studeras spridningen av utsläpp från vulkanutbrott med hjälp av en uppsättning numeriska atmosfärsmodeller.

Den Lagrangiska Partikelspridningsmodellen FLEXPART-WRF har förbättrats och applicerats för spridningsmodellering av vulkanutbrott. Tre studier har utförts, en fokuserar på vulkanaska från potentiella framtida utbrott på Island, den andra studerar SO2-ustläpp från vulkanen Nyiragongo i Demokratiska Republiken Kongo, och den tredje studerar SO2-ustläpp från utbrottet i Holuhraun (Island) 2014–2015.

Den första studien uppskattar sannolikheten för att vulkanaska från framtida vulkanutbrott på Island ska överskrida de gränsvärden som tillämpas för flygtrafik. Tre år av meteorologisk data används för att simulera spridningen från olika utbrottsscenarier. Sannolikheten för skadliga halter aska varierar med årstid, med en högre sannolikhet för effektiv transport österut under vintermånaderna, sommarutbrott är istället mer benägna att orsaka långvariga problem överspecifika områden.

In den andra studien undersöks spridningen av SO2 från Nyiragongo över en ettårsperiod. Flödesmätningar av plymen används för att förbättra källtermen i modellen. Gaserna transporteras i regel mot nordväst i juni–augusti och mot sydväst i december–februari En dygnsvariation, kopplad till mesoskaliga processer runt Kivusjön, bidrar till förhöjda halter av SO2 nattetid längs Kivusjöns norra kust. Potentiellt skadliga halter av SO2 uppnås av och till i befolkade områden men huvudsakligen nattetid.

Den tredje studien utnyttjar inversmodellering för att avgöra plymhöjd och gasutsläpp baserat på traversmätningar av plymen runt 80–240 km från utsläppskällan. Den beräknade källtermen resulterar i bättre överensstämmelse mellan modell- och satellitdata jämfört med enklare källtermer.

Arbetet i den här avhandlingen presenterar flertalet förbättringar för spridningsmodellering av vulkanutbrott genom bättre modeller, nogrannare beskrivning av källtermer, och genom nya metoder för tillämpning av olika typer av mätdata.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1433
Keyword
dispersion modelling, atmospheric, volcano, gas emissions, volcanic ash, FLEXPART, FLEXPART-WRF, Spridningsmodellering, atmosfär, vulkan, gasutsläpp, vulkanaska, FLEXPART, FLEXPART-WRF
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:uu:diva-303959 (URN)978-91-554-9704-0 (ISBN)
Public defence
2016-11-17, Axel Hambergssalen, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2016-10-27 Created: 2016-09-27 Last updated: 2016-11-02

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