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Articles 61 - 90 of 103
Full-Text Articles in Geological Engineering
The Ozone Monitoring Instrument: Overview Of 14 Years In Space, Pieternel F. Levelt, Joanna Joiner, Johanna Tamminen, J. Pepijn Veefkind, Pawan K. Bhartia, Simon Carn, Et. Al.
The Ozone Monitoring Instrument: Overview Of 14 Years In Space, Pieternel F. Levelt, Joanna Joiner, Johanna Tamminen, J. Pepijn Veefkind, Pawan K. Bhartia, Simon Carn, Et. Al.
Michigan Tech Publications, Part 1
This overview paper highlights the successes of the Ozone Monitoring Instrument (OMI) on board the Aura satellite spanning a period of nearly 14 years. Data from OMI has been used in a wide range of applications and research resulting in many new findings. Due to its unprecedented spatial resolution, in combination with daily global coverage, OMI plays a unique role in measuring trace gases important for the ozone layer, air quality, and climate change. With the operational very fast delivery (VFD; direct readout) and near real-time (NRT) availability of the data, OMI also plays an important role in the development …
Early Warning System For Shallow Landslides Using Rainfall Threshold And Slope Stability Analysis, Shruti Naidu, K. S. Sajinkumar, Thomas Oommen, V.J. Anuja, Rinu Samuel, C. Muraleedharan
Early Warning System For Shallow Landslides Using Rainfall Threshold And Slope Stability Analysis, Shruti Naidu, K. S. Sajinkumar, Thomas Oommen, V.J. Anuja, Rinu Samuel, C. Muraleedharan
Michigan Tech Publications, Part 1
A combined cluster and regression analysis were performed for the first time to identify rainfall threshold that triggers landslide events in Amboori, Kerala, India. Amboori is a tropical area that is highly vulnerable to landslides. The 2, 3, and 5-day antecedent rainfall data versus daily rainfall was clustered to identify a cluster of critical events that could potentially trigger landslides. Further, the cluster of critical events was utilized for regression analysis to develop the threshold equations. The 5-day antecedent (x-variable) vs. daily rainfall (y-variable) provided the best fit to the data with a threshold equation of …
Atmospheric Processes Affecting The Separation Of Volcanic Ash And So < Inf> 2 In Volcanic Eruptions: Inferences From The May 2011 Grímsvötn Eruption, Fred Prata, Mark Woodhouse, Herbert E. Huppert, Andrew Prata, Thor Thordarson, S. Carn
Atmospheric Processes Affecting The Separation Of Volcanic Ash And So < Inf> 2 In Volcanic Eruptions: Inferences From The May 2011 Grímsvötn Eruption, Fred Prata, Mark Woodhouse, Herbert E. Huppert, Andrew Prata, Thor Thordarson, S. Carn
Michigan Tech Publications, Part 1
The separation of volcanic ash and sulfur dioxide (SO2) gas is sometimes observed during volcanic eruptions. The exact conditions under which separation occurs are not fully understood but the phenomenon is of importance because of the effects volcanic emissions have on aviation, on the environment, and on the earth's radiation balance. The eruption of Grímsvötn, a subglacial volcano under the Vatnajökull glacier in Iceland during 21-28 May 2011 produced one of the most spectacular examples of ash and SO2 separation, which led to errors in the forecasting of ash in the atmosphere over northern Europe. Satellite data from several sources …
A Novel Applications Of Photogrammetry For Retaining Wall Assessment, Renee Oats, Rudiger Escobar-Wolf, Thomas Oommen
A Novel Applications Of Photogrammetry For Retaining Wall Assessment, Renee Oats, Rudiger Escobar-Wolf, Thomas Oommen
Michigan Tech Publications, Part 1
Retaining walls are critical geotechnical assets and their performance needs to be monitored in accordance to transportation asset management principles. Current practices for retaining wall monitoring consist mostly of qualitative approaches that provide limited engineering information or the methods include traditional geodetic surveying, which may provide high accuracy and reliability, but is costly and time-consuming. This study focuses on evaluating failure modes of a 2.43 m × 2.43 m retaining wall model using three-dimensional (3D) photogrammetry as a cost-effective quantitative alternative for retaining wall monitoring. As a remote sensing technique, photogrammetry integrates images collected from a camera and creates a …
Expanding Understanding Of Optical Variability In Lake Superior With A 4-Year Dataset, Colleen B. Mouw, Audrey B. Ciochetto, Brice Grunert, Angela W. Yu
Expanding Understanding Of Optical Variability In Lake Superior With A 4-Year Dataset, Colleen B. Mouw, Audrey B. Ciochetto, Brice Grunert, Angela W. Yu
Michigan Tech Publications, Part 1
Lake Superior is one of the largest freshwater lakes on our planet, but few optical observations have been made to allow for the development and validation of visible spectral satellite remote sensing products. The dataset described here focuses on coincidently observing inherent and apparent optical properties along with biogeochemical parameters. Specifically, we observe remote sensing reflectance, absorption, scattering, backscattering, attenuation, chlorophyll concentration, and suspended particulate matter over the ice-free months of 2013-2016. The dataset substantially increases the optical knowledge of the lake. In addition to visible spectral satellite algorithm development, the dataset is valuable for characterizing the variable light field, …
Spatial Variability Of Co < Inf> 2 Uptake In Polygonal Tundra: Assessing Low-Frequency Disturbances In Eddy Covariance Flux Estimates, Norbert Pirk, Jakob Sievers, Jordan Mertes, Frans Jan W. Parmentier, Mikhail Mastepanov, Torben R. Christensen
Spatial Variability Of Co < Inf> 2 Uptake In Polygonal Tundra: Assessing Low-Frequency Disturbances In Eddy Covariance Flux Estimates, Norbert Pirk, Jakob Sievers, Jordan Mertes, Frans Jan W. Parmentier, Mikhail Mastepanov, Torben R. Christensen
Michigan Tech Publications, Part 1
The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias …
New-Generation Nasa Aura Ozone Monitoring Instrument (Omi) Volcanic So2 Dataset: Algorithm Description, Initial Results, And Continuation With The Suomi-Npp Ozone Mapping And Profiler Suite (Omps), Can Li, Nickolay A. Krotkov, Simon Carn, Yan Zhang, Robert J.D. Spurr, Joanna Joiner
New-Generation Nasa Aura Ozone Monitoring Instrument (Omi) Volcanic So2 Dataset: Algorithm Description, Initial Results, And Continuation With The Suomi-Npp Ozone Mapping And Profiler Suite (Omps), Can Li, Nickolay A. Krotkov, Simon Carn, Yan Zhang, Robert J.D. Spurr, Joanna Joiner
Michigan Tech Publications, Part 1
Since the fall of 2004, the Ozone Monitoring Instrument (OMI) has been providing global monitoring of volcanic SO2 emissions, helping to understand their climate impacts and to mitigate aviation hazards. Here we introduce a new-generation OMI volcanic SO2 dataset based on a principal component analysis (PCA) retrieval technique. To reduce retrieval noise and artifacts as seen in the current operational linear fit (LF) algorithm, the new algorithm, OMSO2VOLCANO, uses characteristic features extracted directly from OMI radiances in the spectral fitting, thereby helping to minimize interferences from various geophysical processes (e.g., O3 absorption) and measurement details (e.g., wavelength shift). To solve …
Arctic Micromonas Uses Protein Pools And Non-Photochemical Quenching To Cope With Temperature Restrictions On Photosystem Ii Protein Turnover, Guangyan Ni, Gabrielle Zimbalatti, Cole D. Murphy, Audrey B. Barnett, Christopher M. Arsenault, Gang Li, Amanda M. Cockshutt, Douglas A. Campbell
Arctic Micromonas Uses Protein Pools And Non-Photochemical Quenching To Cope With Temperature Restrictions On Photosystem Ii Protein Turnover, Guangyan Ni, Gabrielle Zimbalatti, Cole D. Murphy, Audrey B. Barnett, Christopher M. Arsenault, Gang Li, Amanda M. Cockshutt, Douglas A. Campbell
Michigan Tech Publications, Part 1
Micromonas strains of small prasinophyte green algae are found throughout the world’s oceans, exploiting widely different niches. We grew arctic and temperate strains of Micromonas and compared their susceptibilities to photoinactivation of Photosystem II, their counteracting Photosystem II repair capacities, their Photosystem II content, and their induction and relaxation of non-photochemical quenching. In the arctic strain Micromonas NCMA 2099, the cellular content of active Photosystem II represents only about 50 % of total Photosystem II protein, as a slow rate constant for clearance of PsbA protein limits instantaneous repair. In contrast, the temperate strain NCMA 1646 shows a faster clearance …
Surface Ozone And Its Precursors At Summit, Greenland: Comparison Between Observations And Model Simulations, Yaoxian Huang, Shiliang Wu, Louisa J. Kramer, Detlev Helmig, Richard E. Honrath
Surface Ozone And Its Precursors At Summit, Greenland: Comparison Between Observations And Model Simulations, Yaoxian Huang, Shiliang Wu, Louisa J. Kramer, Detlev Helmig, Richard E. Honrath
Michigan Tech Publications, Part 1
Recent studies have shown significant challenges for atmospheric models to simulate tropospheric ozone (O3/and its precursors in the Arctic. In this study, ground-based data were combined with a global 3-D chemical transport model (GEOS-Chem) to examine the abundance and seasonal variations of O3 and its precursors at Summit, Greenland (72.34° N, 38.29° W; 3212 ma.s.l.). Model simulations for atmospheric nitrogen oxides (NOx/, peroxyacetyl nitrate (PAN), ethane (C2H6/, propane (C3H8/, carbon monoxide (CO), and O3 for the period July 2008-June 2010 were compared with observations. The model performed well in simulating certain species (such as CO and C3H8/, but some significant …
Quantitating Active Photosystem Ii Reaction Center Content From Fluorescence Induction Transients, Cole D. Murphy, Guangyan Ni, Gang Li, Audrey Barnett, Kui Xu, Jessica Grant-Burt, Justin D. Liefer, David J. Suggett, Douglas A. Campbell
Quantitating Active Photosystem Ii Reaction Center Content From Fluorescence Induction Transients, Cole D. Murphy, Guangyan Ni, Gang Li, Audrey Barnett, Kui Xu, Jessica Grant-Burt, Justin D. Liefer, David J. Suggett, Douglas A. Campbell
Michigan Tech Publications, Part 1
Photosystem II (PSII) is a pigment-protein complex that photochemically extracts electrons from water, generating the reductant that supports biological productivity in all biomes. Estimating the content of active PSII reaction centers in a liquid sample is a key input for estimating aquatic photosynthesis rates, as well as for analyzing phytoplankton stress responses. Established procedures for PSII content quantification based on oxygen evolution are slow, imprecise and require dense cell suspensions, and are thus inapplicable to many laboratory or field studies. A new approach uses baseline chlorophyll fluorescence emission divided by the effective absorbance cross section for PSII photochemistry, with both …
Improving Global Detection Of Volcanic Eruptions Using The Ozone Monitoring Instrument (Omi), Verity Flower, Thomas Oommen, Simon Carn
Improving Global Detection Of Volcanic Eruptions Using The Ozone Monitoring Instrument (Omi), Verity Flower, Thomas Oommen, Simon Carn
Michigan Tech Publications, Part 1
Volcanic eruptions pose an ever-present threat to human populations around the globe, but many active volcanoes remain poorly monitored. In regions where ground-based monitoring is present the effects of volcanic eruptions can be moderated through observational alerts to both local populations and service providers, such as air traffic control. However, in regions where volcano monitoring is limited satellite-based remote sensing provides a global data source that can be utilised to provide near-real-time identification of volcanic activity. This paper details a volcanic plume detection method capable of identifying smaller eruptions than is currently feasible, which could potentially be incorporated into automated …
Utilizing Vegetation Indices As A Proxy To Characterize The Stability Of A Railway Embankment In A Permafrost Region, Priscilla Addison, Pasi T. Lautala, Thomas Oommen
Utilizing Vegetation Indices As A Proxy To Characterize The Stability Of A Railway Embankment In A Permafrost Region, Priscilla Addison, Pasi T. Lautala, Thomas Oommen
Michigan Tech Publications, Part 1
Degrading permafrost conditions around the world are posing stability issues for infrastructure constructed on them. Railway lines have exceptionally low tolerances for differential settlements associated with permafrost degradation due to the potential for train derailments. Railway owners with tracks in permafrost regions therefore make it a priority to identify potential settlement locations so that proper maintenance or embankment stabilization measures can be applied to ensure smooth and safe operations. The extensive discontinuous permafrost zone along the Hudson Bay Railway (HBR) in Northern Manitoba, Canada, has been experiencing accelerated deterioration, resulting in differential settlements that necessitate continuous annual maintenance to avoid …
Global Ocean Particulate Organic Carbon Flux Merged With Satellite Parameters, Colleen B. Mouw, Audrey Barnett, Galen A. Mckinley, Lucas Gloege, Darren Pilcher
Global Ocean Particulate Organic Carbon Flux Merged With Satellite Parameters, Colleen B. Mouw, Audrey Barnett, Galen A. Mckinley, Lucas Gloege, Darren Pilcher
Michigan Tech Publications, Part 1
Particulate organic carbon (POC) flux estimated from POC concentration observations from sediment traps and 234 Th are compiled across the global ocean. The compilation includes six time series locations: CARIACO, K2, OSP, BATS, OFP, and HOT. Efficiency of the biological pump of carbon to the deep ocean depends largely on biologically mediated export of carbon from the surface ocean and its remineralization with depth; thus biologically related parameters able to be estimated from satellite observations were merged at the POC observation sites. Satellite parameters include net primary production, percent microplankton, sea surface temperature, photosynthetically active radiation, diffuse attenuation coefficient at …
A Global Catalogue Of Large So < Inf> 2 Sources And Emissions Derived From The Ozone Monitoring Instrument, Vitali E. Fioletov, Chris A. Mclinden, Nickolay Krotkov, Can Li, Joanna Joiner, Nicolas Theys, S. Carn, Mike D. Moran
A Global Catalogue Of Large So < Inf> 2 Sources And Emissions Derived From The Ozone Monitoring Instrument, Vitali E. Fioletov, Chris A. Mclinden, Nickolay Krotkov, Can Li, Joanna Joiner, Nicolas Theys, S. Carn, Mike D. Moran
Michigan Tech Publications, Part 1
Sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI) satellite sensor processed with the new principal component analysis (PCA) algorithm were used to detect large point emission sources or clusters of sources. The total of 491 continuously emitting point sources releasing from about 30 kt yr-1 to more than 4000 kt yr-1 of SO2 per year have been identified and grouped by country and by primary source origin: volcanoes (76 sources); power plants (297); smelters (53); and sources related to the oil and gas industry (65). The sources were identified using different methods, including through OMI measurements themselves applied …
The Impact Of Satellite Sensor Viewing Geometry On Time-Series Analysis Of Volcanic Emissions, Verity Flower, Simon A. Carn, Robert Wright
The Impact Of Satellite Sensor Viewing Geometry On Time-Series Analysis Of Volcanic Emissions, Verity Flower, Simon A. Carn, Robert Wright
Michigan Tech Publications, Part 1
Time-series analysis techniques are being increasingly used to process satellite observations of volcanic gas emissions and heat flux, with the aim of identifying cyclic behaviour that could inform hazard assessment or elucidate volcanic processes. However, it can be difficult to distinguish cyclic variations due to geophysical processes from those that are artefacts of the observation technique. Here, we conduct a comprehensive investigation into the origin of cyclicity in volcanic observations by analysing daily, global satellite measurements of volcanic SO2 loading by the Ozone Monitoring Instrument (OMI) and thermal infrared anomalies detected by the Moderate Resolution Imaging Spectroradiometer (MODIS). We use …
Adjusting Particle-Size Distributions To Account For Aggregation In Tephra-Deposit Model Forecasts, Larry G. Mastin, Alexa R. Van Eaton, Adam J. Durant
Adjusting Particle-Size Distributions To Account For Aggregation In Tephra-Deposit Model Forecasts, Larry G. Mastin, Alexa R. Van Eaton, Adam J. Durant
Michigan Tech Publications, Part 1
Volcanic ash transport and dispersion (VATD) models are used to forecast tephra deposition during volcanic eruptions. Model accuracy is limited by the fact that fine-ash aggregates (clumps into clusters), thus altering patterns of deposition. In most models this is accounted for by ad hoc changes to model input, representing fine ash as aggregates with density ρagg, and a log-normal size distribution with median μagg and standard deviation σagg. Optimal values may vary between eruptions. To test the variance, we used the Ash3d tephra model to simulate four deposits: 18 May 1980 Mount St. Helens; 16-17 September 1992 Crater Peak (Mount …
Improving Automated Global Detection Of Volcanic So2 Plumes Using The Ozone Monitoring Instrument (Omi), Verity Flower, Thomas Oommen, Simon Carn
Improving Automated Global Detection Of Volcanic So2 Plumes Using The Ozone Monitoring Instrument (Omi), Verity Flower, Thomas Oommen, Simon Carn
Michigan Tech Publications, Part 1
Volcanic eruptions pose an ever-present threat to human populations around the globe, but many active volcanoes remain poorly monitored. In regions where ground-based monitoring is present the effects of volcanic eruptions can be moderated through observational alerts to both local populations and service providers such as air traffic control. However, in regions where volcano monitoring is limited satellite-based remote sensing provides a global data source that can be utilized to provide near real time identification of volcanic activity. This paper details the development of an automated volcanic plume detection method utilizing daily, global observations of sulphur dioxide (SO2) by the …
Developing The Greatest Blue Economy: Water Productivity, Fresh Water Depletion, And Virtual Water Trade In The Great Lakes Basin, A. L. Mayer, Stanley Mubako, Benjamin L. Ruddell
Developing The Greatest Blue Economy: Water Productivity, Fresh Water Depletion, And Virtual Water Trade In The Great Lakes Basin, A. L. Mayer, Stanley Mubako, Benjamin L. Ruddell
Michigan Tech Publications, Part 1
The Great Lakes basin hosts the world's most abundant surface fresh water reserve. Historically an industrial and natural resource powerhouse, the region has suffered economic stagnation in recent decades. Meanwhile, growing water resource scarcity around the world is creating pressure on water-intensive human activities. This situation creates the potential for the Great Lakes region to sustainably utilize its relative water wealth for economic benefit. We combine economic production and trade datasets with water consumption data and models of surface water depletion in the region. We find that, on average, the current economy does not create significant impacts on surface waters, …
Multi-Decadal Satellite Measurements Of Global Volcanic Degassing, S. A. Carn, L. Clarisse, A. J. Prata
Multi-Decadal Satellite Measurements Of Global Volcanic Degassing, S. A. Carn, L. Clarisse, A. J. Prata
Michigan Tech Publications, Part 1
Satellite instruments have been providing measurements of global volcanic emissions of sulfur dioxide (SO2) since 1978, based on observations in the ultraviolet (UV), infrared (IR) and microwave spectral bands. We review recent advances in satellite remote sensing of volcanic gases, focusing on increased instrument sensitivity to tropospheric SO2 emissions and techniques to determine volcanic plume altitude. A synthesis of ~36 years of global UV, IR and microwave satellite measurements yields an updated assessment of the volcanic SO2 flux to the upper troposphere and lower stratosphere (UTLS) between 1978 and 2014 (~1-Tg/yr). The present availability of multiple UV and IR satellite …
Post-Eruption Deformation Processes Measured Using Alos-1 And Uavsar Insar At Pacaya Volcano, Guatemala, Lauren Schaefer, Zhong Lu, Thomas Oommen
Post-Eruption Deformation Processes Measured Using Alos-1 And Uavsar Insar At Pacaya Volcano, Guatemala, Lauren Schaefer, Zhong Lu, Thomas Oommen
Michigan Tech Publications, Part 1
Pacaya volcano is a persistently active basaltic cone complex located in the Central American Volcanic Arc in Guatemala. In May of 2010, violent Volcanic Explosivity Index-3 (VEI-3) eruptions caused significant topographic changes to the edifice, including a linear collapse feature 600 m long originating from the summit, the dispersion of ~20 cm of tephra and ash on the cone, the emplacement of a 5.4 km long lava flow, and ~3 m of co-eruptive movement of the southwest flank. For this study, Interferometric Synthetic Aperture Radar (InSAR) images (interferograms) processed from both spaceborne Advanced Land Observing Satellite-1 (ALOS-1) and aerial Uninhabited …
The Impact Of Mpowir A Decade Of Investing In Mentoring Women In Physical Oceanography, Sarah Clem, Sonya Legg, Susan Lozier, Colleen B. Mouw
The Impact Of Mpowir A Decade Of Investing In Mentoring Women In Physical Oceanography, Sarah Clem, Sonya Legg, Susan Lozier, Colleen B. Mouw
Michigan Tech Publications, Part 1
MPOWIR (Mentoring Physical Oceanography Women to Increase Retention) is a US communityinitiated and community-led mentoring program aimed at improving the retention of women physical oceanographers in academic and/or research positions. This article describes the MPOWIR program elements designed by the US physical oceanography community, quantifies the participation in these programs, describes MPOWIR’s impact to date, and outlines future directions. An examination of surveys to date indicates that MPOWIR, several years after its implementation, is having a positive impact on the retention of junior women in physical oceanography, primarily by giving them a broad professional network and focused mentoring.
Characterising Volcanic Cycles At Soufriere Hills Volcano, Montserrat: Time Series Analysis Of Multi-Parameter Satellite Data, Verity Flower, Simon Carn
Characterising Volcanic Cycles At Soufriere Hills Volcano, Montserrat: Time Series Analysis Of Multi-Parameter Satellite Data, Verity Flower, Simon Carn
Michigan Tech Publications, Part 1
The identification of cyclic volcanic activity can elucidate underlying eruption dynamics and aid volcanic hazard mitigation. Whilst satellite datasets are often analysed individually, here we exploit the multi-platform NASA A-Train satellite constellation to cross-correlate cyclical signals identified using complementary measurement techniques at Soufriere Hills Volcano (SHV), Montserrat. In this paper we present a Multi-taper (MTM) Fast Fourier Transform (FFT) analysis of coincident SO2 and thermal infrared (TIR) satellite measurements at SHV facilitating the identification of cyclical volcanic behaviour. These measurements were collected by the Ozone Monitoring Instrument (OMI) and Moderate Resolution Imaging Spectroradiometer (MODIS) (respectively) in the A-Train. We identify …
Capturing Optically Important Constituents And Properties In A Marine Biogeochemical And Ecosystem Model, S. Dutkiewicz, A. E. Hickman, O. Jahn, W. W. Gregg, C. B. Mouw, M. J. Follows, C. Mouw
Capturing Optically Important Constituents And Properties In A Marine Biogeochemical And Ecosystem Model, S. Dutkiewicz, A. E. Hickman, O. Jahn, W. W. Gregg, C. B. Mouw, M. J. Follows, C. Mouw
Michigan Tech Publications, Part 1
We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; detrital particles; and coloured dissolved organic matter, CDOM). The model is evaluated against in situ-observed and satellite-derived products. In particular we compare to concurrently measured biogeochemical, ecosystem, and optical data along a meridional transect of the Atlantic Ocean. The …
Seasonal Variability Of Atmospheric Nitrogen Oxides And Non-Methane Hydrocarbons At The Geosummit Station, Greenland, L. J. Kramer, D. Helmig, J. F. Burkhart, A. Stohl, S. Oltmans, R. E. Honrath
Seasonal Variability Of Atmospheric Nitrogen Oxides And Non-Methane Hydrocarbons At The Geosummit Station, Greenland, L. J. Kramer, D. Helmig, J. F. Burkhart, A. Stohl, S. Oltmans, R. E. Honrath
Michigan Tech Publications, Part 1
Measurements of atmospheric nitrogen oxides NOx (NOx = NO + NO2), peroxyacetyl nitrate (PAN), NOy, and non-methane hydrocarbons (NMHC) were taken at the Greenland Environmental Observatory at Summit (GEOSummit) station, Greenland (72.34° N, 38.29° W; 3212 m a.s.l.), from July 2008 to July 2010. The data set represents the first year-round concurrent record of these compounds sampled at a high latitude Arctic site. Here, the study focused on the seasonal variability of these important ozone (O3) precursors in the Arctic troposphere and the impact from transported anthropogenic and biomass burning emissions. Our analysis shows that PAN is the dominant NOy …
Spatial Analysis Of Mount St. Helens Tephra Leachate Compositions: Implications For Future Sampling Strategies, P. M. Ayris, P. Delmelle, B. Pereira, E. C. Maters, D. E. Damby, A. J. Durant, D. B. Dingwell
Spatial Analysis Of Mount St. Helens Tephra Leachate Compositions: Implications For Future Sampling Strategies, P. M. Ayris, P. Delmelle, B. Pereira, E. C. Maters, D. E. Damby, A. J. Durant, D. B. Dingwell
Michigan Tech Publications, Part 1
Tephra particles in physically and chemically evolving volcanic plumes and clouds carry soluble sulphate and halide salts to the Earth’s surface, ultimately depositing volcanogenic compounds into terrestrial or aquatic environments. Upon leaching of tephra in water, these salts dissolve rapidly. Previous studies have investigated the spatial and temporal variability of tephra leachate compositions during an eruption in order to gain insight into the mechanisms of gas-tephra interaction which emplace those salts. However, the leachate datasets analysed are typically small and may poorly represent the natural variability and complexity of tephra deposits. Here, we have conducted a retrospective analysis of published …
Stratospheric Volcanic Ash Emissions From The 13 February 2014 Kelut Eruption, N. I. Kristiansen, A. J. Prata, A. Stohl, S. A. Carn
Stratospheric Volcanic Ash Emissions From The 13 February 2014 Kelut Eruption, N. I. Kristiansen, A. J. Prata, A. Stohl, S. A. Carn
Michigan Tech Publications, Part 1
Mount Kelut (Indonesia) erupted explosively around 15:50 UT on 13 February 2014 sending ash and gases into the stratosphere. Satellite ash retrievals and dispersion transport modeling are combined within an inversion framework to estimate the volcanic ash source term and to study ash transport. The estimated source term suggests that most of the ash was injected to altitudes of 16-17km, in agreement with space-based lidar data. Modeled ash concentrations along the flight track of a commercial aircraft that encountered the ash cloud indicate that it flew under the main ash cloud and encountered maximum ash concentrations of 9±3mgm-3, mean concentrations …
Separation Of Ash And Sulfur Dioxide During The 2011 Grímsvötn Eruption, E. D. Moxnes, N. I. Kristiansen, A. Stohl, L. Clarisse, A. J. Durant, K. Weber, A. Vogel
Separation Of Ash And Sulfur Dioxide During The 2011 Grímsvötn Eruption, E. D. Moxnes, N. I. Kristiansen, A. Stohl, L. Clarisse, A. J. Durant, K. Weber, A. Vogel
Michigan Tech Publications, Part 1
Modeling the transport of volcanic ash and gases released during volcanic eruptions is crucially dependent on knowledge of the source term of the eruption, that is, the source strength as a function of altitude and time. For the first time, an inversion method is used to estimate the source terms of both volcanic sulfur dioxide (SO2) and ash. It was applied to the explosive volcanic eruption of Grímsvötn, Iceland, in May 2011. The method uses input from the particle dispersion model, FLEXPART (flexible particle dispersion model), a priori source estimates, and satellite observations of SO2 or ash total columns from …
Absorption And Fluorescence Properties Of Chromophoric Dissolved Organic Matter Of The Eastern Bering Sea In The Summer With Special Reference To The Influence Of A Cold Pool, E. J. D'Sa, J. I. Goes, H. Gomes, C. Mouw
Absorption And Fluorescence Properties Of Chromophoric Dissolved Organic Matter Of The Eastern Bering Sea In The Summer With Special Reference To The Influence Of A Cold Pool, E. J. D'Sa, J. I. Goes, H. Gomes, C. Mouw
Michigan Tech Publications, Part 1
The absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM) are reported for the inner shelf, slope waters and outer shelf regions of the eastern Bering Sea during the summer of 2008, when a warm, thermally stratified surface mixed layer lay over a cold pool ( < 2 °C) that occupied the entire middle shelf. CDOM absorption at 355 nm (ag355) and its spectral slope (S) in conjunction with excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) revealed large variability in the characteristics of CDOM in different regions of the Bering Sea. PARAFAC analysis aided in the identification of three humic-like (components one, two and five) and two protein-like (a tyrosine-like component three, and a tryptophan-like component four) components. In the extensive shelf region, average absorption coefficients at 355 nm (ag355, mg-1) and DOC concentrations (μM) were highest in the inner shelf (0.342 ± 0.11 mg-1, 92.67 ± 14.60 μM) and lower in the middle (0.226 ± 0.05 mg-1, 78.38 ± 10.64 μM) and outer (0.185 ± 0.05 mg-1, 79.24 ± 18.01 μM) shelves, respectively. DOC concentrations, however were not significantly different, suggesting CDOM sources and sinks to be uncoupled from DOC. Mean spectral slopes S were elevated in the middle shelf (24.38 ± 2.25 μmg-1) especially in the surface waters (26.87 ± 2.39 μmg-1) indicating high rates of photodegradation in the highly stratified surface mixed layer, which intensified northwards in the northern middle shelf likely contributing to greater light penetration and to phytoplankton blooms at deeper depths. The fluorescent humic-like components one, two, and five were most elevated in the inner shelf most likely from riverine inputs. Along the productive "green belt" in the outer shelf/slope region, absorption and fluorescence properties indicated the presence of fresh and degraded autochthonous DOM. Near the Unimak Pass region of the Aleutian Islands, low DOC and ag355 (mean 66.99 ± 7.94 μM; 0.182 ± 0.05 mg-1) and a high S (mean 25.95 ± 1.58 μmg-1) suggested substantial photobleaching of the Alaska Coastal Water, but high intensities of humic-like and protein-like fluorescence suggested sources of fluorescent DOM from coastal runoff and glacier meltwaters during the summer. The spectral slope S vs. ag355 relationship revealed terrestrial and oceanic end members along with intermediate water masses that were modeled using nonlinear regression equations that could allow water mass differentiation based on CDOM optical properties. Spectral slope S was negatively correlated (r2 = 0.79) with apparent oxygen utilization (AOU) for waters extending from the middle shelf into the deep Bering Sea indicating increasing microbial alteration of CDOM with depth. Although our data show that the CDOM photochemical environment of the Bering Sea is complex, our current information on its optical properties will aid in better understanding of the biogeochemical role of CDOM in carbon budgets in relation to the annual sea ice and phytoplankton dynamics, and to improved algorithms of ocean color remote sensing for this region.
Seasonal Variability And Long-Term Evolution Of Tropospheric Composition In The Tropics And Southern Hemisphere, K. M. Wai, S. Wu, A. Kumar, H. Liao
Seasonal Variability And Long-Term Evolution Of Tropospheric Composition In The Tropics And Southern Hemisphere, K. M. Wai, S. Wu, A. Kumar, H. Liao
Michigan Tech Publications, Part 1
Impacts on tropospheric composition in the tropics and the Southern Hemisphere from biomass burning and other emission sources are studied using a global chemical transport model, surface measurements and satellite retrievals. Seasonal variations in observed CO at remote island sites are examined. Easter Island (eastern Pacific Ocean) is impacted indirectly by the hemispheric zonal transport of CO due to the burning in southern Africa/South America, via the westerlies. An increasing trend in CO by 0.33 ppb yr-1 in the past decade at Ascension Island is attributed to the combined effects of South American/southern Africa burnings and the increases in CH4 …
Effects Of Stratospheric Ozone Recovery On Photochemistry And Ozone Air Quality In The Troposphere, H. Zhang, Shiliang Wu, Y. Huang, Y. Wang
Effects Of Stratospheric Ozone Recovery On Photochemistry And Ozone Air Quality In The Troposphere, H. Zhang, Shiliang Wu, Y. Huang, Y. Wang
Michigan Tech Publications, Part 1
There has been significant stratospheric ozone depletion since the late 1970s due to ozone-depleting substances (ODSs). With the implementation of the Montreal Protocol and its amendments and adjustments, stratospheric ozone is expected to recover towards its pre-1980 level in the coming decades. In this study, we examine the implications of stratospheric ozone recovery for the tropospheric chemistry and ozone air quality with a global chemical transport model (GEOS-Chem). With a full recovery of the stratospheric ozone, the projected increases in ozone column range from 1% over the low latitudes to more than 10% over the polar regions. The sensitivity factor …