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The Turkana Basin of northern Kenya and southwestern Ethiopia is well–known for its mammalian fauna of Pliocene and Pleistocene age. In addition, many important hominid fossils have been discovered in the three formations of the Turkana Basin exposed east and west of lake Turkana and in the lower Omo Valley. Much of our understanding of the stratigraphic relations between these well known Plio-Pleistocene deposits of the Shungura, Koobi Fora, and Nachukui Formations results from geochemical study of the glass fractions of tephra layers interbedded within these sediments. The gross character of a particular tephra layer may change markedly from one locality to another within a region–a tephra layer may be present as a thin air fall deposit at one locality, but as a thick channel fill at another locality. Therefore one can not use lithologic characters as basis of correlations over large areas.

Over the past thirty years more than 1500 of chemical analyses of tephra layers have been obtained from the Turkana Basin. The correlations achieved thus far between the three formations of the Turkana Basin rest on compositional characteristics of these tephra layers. These analyses have been organized into approximately 130 chemical distinct types and 12 major groups. Few tephra layers are widespread, and not all tephra layers have been found in all formations, and each formation has a number of tephra layers present only locally, which reflects localized deposition or erosion.

Tephrostratigraphic study, the use of volcanic ash and tuff beds (tephra layers) is used to arrange all of the tephra layers into a single ordered sequence, has provided isotopic ages and temporal correlations. Because the number of tuffs is so large, individual tuffs are grouped into subsets with respect to widespread ash layers that serve as markers. All tephra layers mapped up to this study are discussed here from oldest to youngest with their type locality, chemical analysis and areal distribution. Those tephra layers that were not defined previously are defined.

Hosts Alex Guth (alguth@mtu.edu) and Elisabet Head (emhead@mtu.edu)

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The observed warming over the industrial era has resulted from radiative forcing from increases in greenhouse gases and air pollution by humankind. Controlling both of these is at the forefront of public policy to protect our health and our climate system. My talk will elucidate the role of atmospheric aerosols, small particles that scatter and/or absorb solar radiation, influence clouds, ice albedo and the hydrological cycle, on climate. Aerosols have a multitude of sources, are short lived but are transported to remote regions and undergo physical and chemical transformations, complicating their treatments in climate models. For example sulfate aerosols scatter sunlight to cool climate while soot absorbs sunlight to warm climate, and the non-linear interactions determine the effect of mixed sulfate-soot aerosols. I will summarize results of aerosol optical and chemical properties made with modern state-of-the art instrumentation made by us in several field campaigns over a range of environments that include (1) Mexico City in March 2006, (2) Houston in August 2006 (2) The Arctic in April 2008 and (3) Jeju Island, South Korea in September 2008. Our data spans both fresh pollution from megacities and long-range transport of aerosols into pristine remote regions. I plan to convey the message that our understanding of aerosols is maturing, and they should be an important near-term consideration, particularly for developing countries, in the United Nations climate negotiations in Copenhagen in December 2009.

Suggested Reading Material

Smoke and Climate Change, J. Quaas, Perspectives, Science, 325, 153, 10 July 2009 and references cited therein.

Host Claudio Mazzoleni (cmazzoleni@mtu.edu)

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Vulcanian eruptions are impulsive explosions that occur as a result of rapid decompression of a volcanic conduit containing bubbly magma. Upon decompression, a leading shock wave may form and travel away from the vent into the atmosphere and a decompression-induced fragmentation wave travels down the conduit. At the fragmentation front the bubbly magma is disrupted into a gas-solid mixture, propelled upward, and ejected from the vent at velocities up to 400 m s^-1. Typically only a portion of the magma in the conduit is fragmented and evacuated such that Vulcanian eruptions characteristically last only seconds to minutes.

Results of two relevant experimental studies are presented here. The first examines the initial burst phase and leading shock waves via 1-D shock-tube experiments in which mixtures of air and spherical particles are rapidly decompressed into a low-pressure environment via diaphragm rupture. Maximum gas-particle mixture velocities decrease with increasing particle diameter for a given initial pressure ratio across the diaphragm. Experiments with particles produce weaker and more slowly propagating shock waves relative to experiments with air alone. Comparison of experimental data to theoretical and computational solutions produced two key conclusions: 1) the effective interphase drag coefficient during high-acceleration stages of an eruption is less than values previously used in multiphase models of explosive eruptions; therefore a new formulation is prescribed; and 2) leading shock waves are formed by the gas phase alone, not the solid-gas mixture, with shock wave characteristics reflecting losses due to drag between gas and particles; shock wave calculations should consider these losses rather than treat the system as a perfectly-coupled pseudogas.

The second set of experiments examines the subsequent propagation of the pyroclastic jet or plume by injecting discrete pulses of (negatively or positively) buoyant fluids into fresh water. Dimensional analysis, based on two source parameters, total injected momentum and total injected buoyancy, identifies a universal scaling relationship for the initial propagation of short-duration impulsive flows; the non-dimensional, time-varying velocity varies as the square root of the time-varying, non-dimensional ratio of source parameters. The relationship successfully describes experiments and several well-documented Vulcanian eruptions over a wide-range of conditions. Vertical flow front velocity (u) decays with time (t) and the decay trend depends on vent conditions: u in experiments with momentum only (neutrally buoyant fluids) decays as t^-3/4, while u in experiments with both momentum and buoyancy decays as t^-1. Note that these trends are distinct from the classic case of a buoyant thermal (u~t^-1/2). These formulations expand the range of theoretical relationships appropriate for Vulcanian explosions, which have typically been treated as steady plumes or discrete thermals.

The utility of both sets of experiments is demonstrated by estimating pre-eruption pressures, time-varying vent mass flux and total mass erupted for several well-documented eruptions, with results comparing favorably to independent estimates.

Suggested Reading Material

A. B. CLARKE, J. C. PHILLIPS & K. N. CHOJNICKI
An investigation of Vulcanian eruption dynamics using laboratory analogue experiments and scaling analysis

K. Chojnicki, A. B. Clarke, and J. C. Phillips
A shock-tube investigation of the dynamics of gas-particle mixtures: Implications for explosive volcanic eruptions

Hosts John Lyons (jlyons@mtu.edu) and Stephanie Tubman (sctubman@mtu.edu)

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The dramatic decay of Earth's dipole magnetic field observed over the last 150 years has led to speculation that we are heading toward a geomagnetic field reversal. The unusual nature of the decay is highlighted by its rapid time-scale, as compared to ohmic resistance, and models predicting constant field intensities between 1590 and onset of the decay near 1840. These and some models which call for only minor fluctuations of field strength for Southern Hemisphere (SH) sites extending to more than a thousand years before present are limited by the lack of SH archeomagnetic values. I will discuss new archeomagnetic results from ceramics of southern Africa resulting from collaborations between the Paleomagnetic Research Group at the University of Rochester and colleagues at KwaZulu-Natal University and Witwatersrand University in South Africa. These yield field strength values that match model predictions for the 1700-1800 interval but also reveal centennial scale variations for older times that are not captured in prior models. I will discuss the implications of these results for the geodynamo and future of the field, as well as efforts to better define the past variations using multiple types of archeomagnetic objects (e.g. ceramics and burnt structures) and different paleointensity techniques.

Host Aleksey Smirnov (asmirnov@mtu.edu)

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Wildfire is becoming the focus of increasing attention with heightened concerns related to climate change, global warming, and safety in the urban-wildland interface. One aspect of wildfire blowup has been totally overlooked until recently—the role of pyrocumulonimbus (pyroCb for short) in both firestorm dynamics and atmospheric impact. PyroCb are fire-started or -augmented thunderstorms that in their most extreme manifestation inject huge abundances of smoke and other biomass burning emissions into the lower stratosphere. The observed hemispheric spread of smoke and other biomass burning emissions could have important climate consequences. Such an extreme injection by thunderstorms was previously judged to be impossible because the extratopical tropopause is considered to be an effective lid on convection.

Two recurring themes have developed as pyroCb research unfolds. First, some “mystery layer” events—puzzling stratospheric aerosol layer observations—and volcanic aerosol layers can now be explained in terms of pyroconvection as the “smoking gun.” Secondly, pyroCb events occur with surprising frequency, and they are likely a relevant aspect of several historic wildfires. Here we will show that pyroCbs offer an alternative explanation for previously assumed volcanic aerosols in 1989-1991. In addition we will explore more recent pyroCb and volcano events to illustrate the challenge we have understanding stratospheric pollution from these eruptions. Finally we take one fire season, 2002, and go deeply into how frequently pyroCb storms occur.

Suggested Reading Material

NEUBER, ET AL.
Latitudinal distribution of stratospheric aerosols during the EASOE winter 1991/92

SASSEN AND HOREL
Polarization Lidar and Synoptic Analyses of an Unusual Volcanic Aerosol Cloud

YUE, VEIGA AND WANG
SAGE II Observations of a Previously Unreported Stratospheric Volcanic Aerosol Cloud in the Northern Polar Summer of 1990

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TEPHRA2 is a parallel code written in C and MPI and is used to forecast tephra accumulation following explosive volcanic eruptions. The code uses a closed-form solution of the advection-diffusion equation, particle fall velocities that depend on local Reynold's number, and stratified wind field to forecast tephra accumulation, usually expressed as kilogram per cubic meter, particle size distribution at specific locations from the vent, and maximum clast size expected as a function of distance from the vent. In practice, deposits of specific eruptions can be modeled if sufficient field data are available using TEPHRA2 and a nonlinear inversion method, the downhill simplex algorithm, to estimate best fit eruption parameters. I demonstrate wide applicability of TEPHRA2 with examples from Cerro Negro, Nicaragua (small volume basaltic eruption), Colima, Mexio (short-lived basaltic-andesite vulcanian eruption), and Chaiten, Chile (comparatively small volume Plinian eruption of rhyolite composition). In each case models of the eruption based on inversion of the deposit thickness and/or granulometry compares well with independent observations. An advantage of this inversion procedure is that it is possible to assign numerical uncertainty to estimates of deposit volume, eruption column height, eruption duration, and similar eruption input parameters.

Suggested Reading Material

Connor, C.B., B.E. Hill, B. Winfrey, N.M. Franklin, and P.C. LaFemina
Estimation of volcanic hazards from tephra fallout

Bonadonna, C., C.B. Connor, B.F. Houghton, L. Connor, M. Byrne, A. Laing, and T. Hincks
Probabilistic modeling of tephra dispersal: Hazard assessment of a multiphase rhyolitic eruption at Tarawera, New Zealand

Hosts Erika Vye (ecvye@mtu.edu) and Jarod Maggio (jcmaggio@mtu.edu)

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Organic carbon in the troposphere consists of a wide range of compounds in both the gas and particle phase. These compounds can make up a dominant fraction of fine aerosol, with implications for climate, health, and visibility. The oxidation of gas-phase organics is a key element of ozone formation. Despite the importance of these compounds, the global budget of organic carbon in the atmosphere is very poorly understood. In this talk I will use examples of my own work on the organic carbon budget, the emissions of isoprene, the primary source of biological aerosol particles and the changing composition of organic aerosol to discuss some of the challenges and mysteries of organic carbon in the atmosphere.

Suggested Reading Material

GOLDSTEIN AND GALBALLY
Known and Unexplored Organic Constituents in the Earth's Atmosphere

KANAKIDOU ET AL.
Organic Aerosol and Global Climate Modelling: A Review

Host Shiliang Wu (slwu@mtu.edu

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The National Hydrologic Data (NHD) is a comprehensive set of digital spatial data representing the surface water of the United States using common features such as lakes, ponds, streams, rivers, canals, and oceans. These data are designed to be used in general mapping and in the analysis of surface-water systems using geographic information systems (GIS). The data is key source of information in delineating riparian zones.

Riparian zones are unique, diverse networks of vegetation and soils in close proximity to freshwater streams, rivers and lakes. These zones are linked to the watercourse network via flooding and intercepting upland runoff. Vegetation communities along stream banks often delineate riparian boundaries. However, geology, soil chemistry, and hydrologic changes need to be considered as well. Previous approaches to riparian boundary delineation utilized fixed width buffers, but this methodology has proven to be inadequate as there are two factors that all riparian zones are dependent on: the watercourse and its associated floodplain. Using a fixed width riparian buffer only takes the watercourse into consideration. Past research has determined the 50-year floodplain is the optimal hydrologic descriptor of a riparian zone. By hydrologically defining a riparian zone to occur at the 50-year flood height and incorporating digital elevation data, the spatial modeling capabilities of GIS are utilized to map riparian zones accurately and efficiently.

A GIS based model using the NHD has been developed to delineate a variable-width riparian boundary that characterizes a stream’s ecotone. This approach offers advantages over other previously used methods of riparian zone mapping by better characterizing the watercourse and its associated floodplain. The riparian zones delineated using 10 and 30 meter DEMs, along with stream course information from the National Hydrological Data, which is derived from remotely sensed imagery were found to be statistically significant (p < 0.001).

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Abstract Coming Soon

Hosts Miriam Rios-Sanchez (mriossan@mtu.edu) and Rüdiger Escobar Wolf (rpescoba@mtu.edu)

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The first successful meteorological experiment conducted from a satellite was launched on Explorer VII on 13 October 1959, fifty years ago last month. Explorer VII carried an instrument that measured Earth’s heat balance. Today, we take for granted the bird’s-eye view of developing weather systems that satellites provide. Forecasters use these orbiters to monitor shifting weather systems including thunderstorms, hurricanes, and extratropical cyclones. And, thanks to the web, anyone can access quality satellite images with just a few mouse clicks. Today, more than 120 U.S. space-based instruments observe our planet. We have come a long way in 50 years.

This presentation will focus on the observations of the atmosphere. We’ll begin by exploring how current satellite observations are used to derive meteorological information for weather applications, including atmospheric temperature and moisture, winds and cloud properties. We’ll discuss some of the historic applications as well as current methods for deriving these properties. We’ll discuss issues surrounding the validating of these satellite derived products. While we’ve come a long way, we are still not observing some critical components of the hydrological cycle. As an example, we’ll explore in detail new measurements being developed for future satellite measurements that will provide new information on cloud properties.

While the US geostationary satellite instruments have not changed in 20 years, new applications of those observations are continually being developed. Examples of new applications that are being developed to support aviation forecasting will be presented, including turbulence and convective initiation. We’ll end by reviewing the US plans for its next generation weather satellite, and show some simulations of those measurements.

References

T. J. Schmit, M. M. Gunshor, W. Paul Menzel, Jun Li, Scott Bachmeier, James J. Gurka, 2005: Introducing the Next-generation Advanced Baseline Imager (ABI) on GOES-R, Bull. Amer. Meteor. Soc., Vol 8, pp. 1079-1096.

Liu, C-Y, J. Li, E. Weisz,. T. J. Schmit, S. A. Ackerman, and H-L Huang, 2008:Synergistic use of AIRS and MODIS radiance measurements for atmospheric profiling.GRL, 35, L21802, doi:10.1029/2008GL035859., 1057-1072

Ackerman, S. A., R. E. Holz, R. Frey, E. W. Eloranta, B. Maddux, and M. McGill, 2008: Cloud Detection with MODIS: Part II Validation. JTECH.25, 1073-1086

Uhlenbrock, N. L., K. M. Bedka, W. F. Feltz, and S. A. Ackerman, 2007: Mountain Waves Signatures in MODIS 6.7 micron Imagery and Their Relation to Pilot Reports of Turbulence. Wea. Forecasting. 22, 662-670.

Host Bill Rose (raman@mtu.edu)

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The MARGINS Distinguished Lecturer on Nov 11 will be Prof. Tim Dixon from the University of Miami, an expert in the application of Synthetic Aperture Radar Interferometry (InSAR) and GPS to crustal deformation studies.

MARGINS Distinguished Lectureship Program

Episodic tremor and/or slow slip events are now well described in the subduction zones of Cascadia, Japan, and Mexico, and are providing insights into the frictional properties of the plate interface in these seismogenic zones. Both Cascadia and Japan are well instrumented with seismometers and high precision GPS systems; Cascadia observations have been greatly augmented by NSF’s Plate Boundary Observatory (PBO). Episodic tremor and slow slip likely occurs in most subduction zones, but lack of network instrumentation makes rigorous comparison difficult. The northern Costa Rica plate boundary zone provides an ideal locale for such a network. Convergence rates are up to a factor of two higher compared to the other well studied regions, and the Nicoya Peninsula extends close to the trench, allowing optimum location of instruments. Beginning in 2005, we installed a sparse network of GPS and seismic instrumentation to study slow slip events and seismic tremor in this region. The data from this new network, which has already recorded a slow slip and tremor event, is revising our picture of both the temporal and spatial aspects of the seismic cycle.

Host Bill Rose (raman@mtu.edu)

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The abundant late Cenozoic bimodal volcanism of the Pacific Northwest occupies an enigmatic intracontinental tectonic setting affected by Cascadia subduction, Basin and Range extension, the Yellowstone plume, and lithospheric topography at the edge of the North American craton. The High Lava Plains of Oregon are characterized by thin widespread Miocene-Pleistocene lava flows of primitive basalt and a belt of silicic eruptive centers that are successively younger to the northwest, describing a mirror image to the basalt plateau and rhyolite age progression of the Snake River Plain. The High Lava Plains are associated with a zone of numerous, small northwest-striking faults and lies at the northern limit of major Basin and Range normal faults. The purpose of the talk is to focus on the late Cenozoic lithospheric evolution of this region, through the lens of the High Lava Plains, by considering structural, geophysical, and temporal perspectives with an emphasis on the petrologic evolution.

Suggested Reading Material

High Lava Plains website: http://www.dtm.ciw.edu/research/HLP/

JORDAN, GRUNDER, DUNCAN, DEINO
Geochronology of age-progressive volcanism of the Oregon High Lava Plains: Implications for the plume interpretation of Yellowstone

Host Elisabet Head (emhead@mtu.edu)

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Abstract Coming Soon

Host Elisabet Head (emhead@mtu.edu)

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Stratovolcanoes are prone to failure by their very nature and often fail catastrophically. Mount St. Helens, Washington and Bezymianny volcano, Russia had remarkably similar catastrophic eruptions including edifice failure in 1980 and 1956, respectively. The progression of activity afterward included explosions, discrete dome building and continuous dome building at both volcanoes. While the similarities morphologically and seismically are striking, the differences give clues to the individual processes at work under each volcano. In particular, the analysis of the continuous dome building phases at both volcanoes has led to two conclusions. The first, that the comparatively vigorous seismicity prior to extrusion of the 2004 dome at Mount St. Helens was due directly to the period of quiescence prior to the eruption. The second conclusion is that the vigorous seismicity that accompanied continuous extrusion at Mount St. Helens was caused by a bend in the conduit, which is supported by a compilation of earthquake locations and tilt. Because of the divergence in compositions between the two volcanoes during the latest phases of activity, it does not appear that Bezymianny is a good predictor of future activity at Mount St. Helens. Several volcanoes worldwide have also had edifice failures and are currently in more advance stages of rebuilding than Mount St. Helens and may be used as analogues for the range of expected behavior. Examples include Reventador, Guagua Pichincha, Tungurahua, Pacaya and Santiaguito.

References

Bogoyavlenskaya et. al, 1985, Catastrophic Eruptions of the Directed-Blast Type at Mount St. Helens, Bezymianny and Shiveluch Volcanoes, Journal of Geodynamics, vol. 3, iss 3-4, pp.189-218.

Moran et al., Seismicity associated with renewed dome building at Mount St. Helens, 2008, from: A Volcano Rekindled: The Renewed Eruption of Mount St. Helens 2004-2006, USGS Professional Paper, Chap. 2.

Host Greg Waite (gpwaite@mtu.edu)

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The Ozone Monitoring Instrument (OMI) on NASA Aura satellite makes global daily measurements of the total column of sulfur dioxide (SO₂), a short-lived trace gas produced by fossil fuel combustion, smelting, and volcanoes. This talk highlights most recent science results enabled by using OMI SO₂ data. OMI daily contiguous volcanic SO₂ data continue 25+ climatic record by its predecessors (Total Ozone mapping Spectrometers 1978-2005), but higher SO₂ sensitivity allows measuring volcanic plumes for a longer time as well as measuring passive volcanic degassing from space. New algorithm development first allows direct estimating of SO₂ plume heights to refine SO₂ tonnages in largest volcanic plumes important for climate applications. Interplay between volcanic and anthropogenic SO2 emissions resulted in highly variable SO₂ pollution levels in Peru and Mexico City. OMI first enabled daily detection of SO₂ burdens from individual smelters as well as observed SO₂ pollution lofting from boundary layer and long-range transport in free troposphere. We have updated our copper smelter analysis, which showed interesting new trends. Combining OMI data with trajectory models and aerosol/cloud measurements by A-train sensors (MODIS, CALIPSO) allowed tracking long-range transport of volcanic and anthropogenic aerosol/SO₂ plumes. These studies placed new constraints on conversion rates of SO₂ to sulfate at different heights from free troposphere to the lower stratosphere. New results on inverse trajectory modeling of the OMI SO₂ data allow deriving information on the altitude distribution of SO₂ and the emission time-series. Quantitatively, anthropogenic SO₂ is more difficult to measure from space, since ozone absorption and Rayleigh scattering reduce sensitivity to pollutants in the lower troposphere. We describe new techniques for spatial and time averaging that have been used to determine the global distribution of anthropogenic SO₂ burdens, and the efficacy of abatement strategies. OMI seasonal to multi-year average images clearly show the world-highest consistent SO₂ pollution in eastern China. China is the world’s largest SO₂ emitter, mostly due to the burning of high-sulfur coal in its many coal-fired power plants, which lack the technology used in many other countries to remove sulfur from smoke stack emissions. Recently, China’s government has instituted nationwide measures to control SO₂ emissions through the adoption of flue-gas desulfurization technology on new power plants; and even greater measures were adopted in the Beijing area in anticipation of the Olympic Games. To study the environmental effects of the emission controls we compared OMI SO₂ time series over eastern China for 2005 through 2009. By mid-March 2008 OMI first observed substantial periods of lower SO₂ values compared to 2007, and by mid June the 2008 values were consistently lower than 2007 and prior years. The decline is widespread with highest SO2 typically located to the south and southwest of Beijing in regions with large clusters of power plants and also around Shanghai. The decline also lasted beyond the Olympic season through summer 2009. Combining model provided SO₂ and aerosol vertical profile shapes allows refining satellite columns as well as estimating surface SO₂ concentrations for air-quality applications. Finally we present our plans to use the OMI SO₂ columns to provide a top-down constraint on SO₂ regional emissions.

Host Simon Carn (scarn@mtu.edu)

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The last two decades have seen significant advances in the measurement and characterization of air-sea fluxes. Thanks to developments in theoretical understanding, models/parameterizations of air-sea fluxes have also been expanded to include trace gases and particles. The role of waves and breaking waves is still an unsolved problem and, to date, most of the work has been done at wind speeds less than 20 m/s. This means that fluxes in hurricanes represent a major unanswered but important question. In this talk I will attempt to give a broad outline of flux measurement technology and recent expansion of capabilities to make measurements (almost) routinely from ships. I will then discuss efforts to measure fluxes and wave properties in hurricanes using remote sensing.

Host Judith Perlinger (jperl@mtu.edu).