THE OLYMPIC MOUNTAINS EXPERIMENT (OLYMPEX) Houze, Robert A.; McMurdie, Lynn A.; Petersen, Walter A. ...
Bulletin of the American Meteorological Society,
10/2017, Volume:
98, Issue:
10
Journal Article
Peer reviewed
Open access
OLYMPEX is a comprehensive field campaign to study how precipitation in Pacific storms is modified by passage over coastal mountains.
•Possible bio- applications of bistable glass-coated microwires are shown.•Biocompatibility was proven experimentally.•Application on temperature sensing in cranium implants is confirmed.•Application ...for osteomalacy monitoring is shown.
In the given contribution, two examples of applications of glass-coated microwires for biomedical sensing are shown. Firstly, application of microwires for contactless sensing of the intracranial temperature below titanium implants confirms the possibility to sense the temperature with sensitivity down to 0.01 °C. Secondly, application of microwires for monitoring the stress applied on bones after injury or for monitoring the osteomalacy effect is shown. Our measurements confirm that high sensitivity of order of 10−10 s/Pa can be obtained.
The ability of ground‐based in situ and remote sensing observations to constrain microphysical properties for dry snow is examined using a Bayesian optimal estimation retrieval method. Power ...functions describing the variation of mass and horizontally projected area with particle size and a parameter related to particle shape are retrieved from near‐Rayleigh radar reflectivity, particle size distribution, snowfall rate, and size‐resolved particle fall speeds. Algorithm performance is explored in the context of instruments deployed during the Canadian CloudSat CALIPSO Validation Project, but the algorithm is adaptable to other similar combinations of sensors. Critical estimates of observational and forward model uncertainties are developed and used to quantify the performance of the method using synthetic cases developed from actual observations of snow events. In addition to illustrating the technique, the results demonstrate that this combination of sensors provides useful constraints on the mass parameters and on the coefficient of the area power function but only weakly constrains the exponent of the area power function and the shape parameter. Information content metrics show that about two independent quantities are measured by the suite of observations and that the method is able to resolve about eight distinct realizations of the state vector containing the mass and area power function parameters. Alternate assumptions about observational and forward model uncertainties reveal that improved modeling of particle fall speeds could contribute substantial improvements to the performance of the method.
Key Points
A retrieval for snow microphysical properties is characterizedGround observations provide information about size‐dependent snow propertiesInformation content metrics suggest improvements for future observing systems
HIGH AND DRY Shupe, Matthew D.; Turner, David D.; Walden, Von P. ...
Bulletin of the American Meteorological Society,
02/2013, Volume:
94, Issue:
2
Journal Article
Peer reviewed
Open access
Cloud and atmospheric properties strongly influence the mass and energy budgets of the Greenland Ice Sheet (GIS). To address critical gaps in the understanding of these systems, a new suite of cloud- ...and atmosphere-observing instruments has been installed on the central GIS as part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit (ICECAPS) project. During the first 20 months in operation, this complementary suite of active and passive ground-based sensors and radiosondes has provided new and unique perspectives on important cloud–atmosphere properties.
High atop the GIS, the atmosphere is extremely dry and cold with strong near-surface static stability predominating throughout the year, particularly in winter. This low-level thermodynamic structure, coupled with frequent moisture inversions, conveys the importance of advection for local cloud and precipitation formation. Cloud liquid water is observed in all months of the year, even the particularly cold and dry winter, while annual cycle observations indicate that the largest atmospheric moisture amounts, cloud water contents, and snowfall occur in summer and under southwesterly flow. Many of the basic structural properties of clouds observed at Summit, Greenland, particularly for low-level stratiform clouds, are similar to their counterparts in other Arctic regions.
The ICECAPS observations and accompanying analyses will be used to improve the understanding of key cloud–atmosphere processes and the manner in which they interact with the GIS. Furthermore, they will facilitate model evaluation and development in this data-sparse but environmentally unique region.
•Hydration of rhyolitic glass at 175–375 °C yields 3–5 wt.% H2O solubiliy.•H2O profiles have a “snowplow” form that resembles silicate melt DH2O experiments.•Molecular H2O diffusion is the primary ...mechanism for O isotope exchange in glass.•The δ18O of water-in-glass (wig) rapidly reaches local equilibrium within the glass.•The 103lnαglass-wig spans from ∼+14‰ at 100°C to ∼+10‰ at 375 °C.
In many volcanic settings, eruptive deposits experience prolonged cooling in the presence of water, such as in subglacial or submarine eruptions. Under these conditions, volcanic glass will rehydrate and record the isotopic composition of the water. This isotope exchange is moderated by H2O solubility and diffusivity in the glass. In this study, we report results from glass hydration experiments conducted at 175–375 °C to constrain H2O solubility and diffusivity under these hydrothermal conditions over timescales lasting hours to months. We use anhydrous high and low silica rhyolites as well as hydrous high silica rhyolite (perlites) with isotopically labeled water as starting materials. Measurements of bulk H2O by TC/EA of experimental glasses provide minimum H2O solubility estimates. High-Si rhyolitic glass has an H2O solubility between 2.75 wt.% (175 °C, 0.89 MPa) and 4.1 wt.% (375 °C, 21 MPa) while low-Si rhyolite H2O solubility is uniformly ∼0.5 wt.% higher at each temperature. We find a roughly linear relationship of solubility vs 1/T that is ∼1–2 wt.% greater than extrapolations from magmatic temperature solubility relationships. Furthermore, three independent methods of diffusion modeling – one in situ and two mass balance approaches – all produce H2O diffusivity (DH2O) values that up to 5.5 times greater than predicted by extrapolation of the 1/T – DH2O relationships above 400 °C to the experimental P-T-XH2O conditions. In situ H2O profiles in rhyolite particles measured by NanoSIMS have the characteristic “snowplow ” functional form that arises from the H2O concentration dependence of DH2O. We cannot detect diffusively driven kinetic fractionation of D relative to H with the NanoSIMS data. Diffusion and mass balance calculations that fit TC/EA time series of bulk H2O in particles of a single size distribution, and calculations that reconcile two sets of different sized particles at a single experimental duration, return similar DH2O constraints. We also present time series δ18O of bulk glass (δ18Obulk) and the δ18O of water-in-glass (δ18Owig) measurements, which indicate that molecular water (H2Om) dissolved in the glass is the primary driver of subsequent oxygen isotope exchange between glass and an external fluid. Local equilibrium between the δ18Owig and the δ18Obulk is rapidly established and ranges from approximately −14‰ at 175 °C to −10‰ at 375 °C. Both the δ18Obulk and δ18Owig then increase with time moving slowly towards estimated bulk glass δ18O equilibrium with the external experimental water. Oxygen isotope exchange between glass and a fluid is therefore strongly linked to – and is limited by – H2O diffusivity, which is slower at lower P-T conditions and lower H2O solubilities as H2Om diffusion is the main exchange mechanism.
The annual cycle of snowfall at Summit, Greenland Castellani, Benjamin B.; Shupe, Matthew D.; Hudak, David R. ...
Journal of geophysical research. Atmospheres,
16 July 2015, Volume:
120, Issue:
13
Journal Article
Peer reviewed
Open access
While snow accumulation over central Greenland has been extensively studied, interannual variability of snowfall in the region is not well understood due to a dearth of observations. The Integrated ...Characterization of Energy, Clouds, Atmospheric state and Precipitation at Summit (ICECAPS) project at Summit, Greenland, offers a unique, ground‐based opportunity to study precipitation in central Greenland where the surface mass balance is positive. Combining data from a Precipitation Occurrence Sensor System (POSS), Millimeter‐wavelength Cloud Radar (MMCR), and snow stake field, the annual cycle of precipitation at Summit is examined. Average daily snowfall is higher by a factor of 3 from June to October compared to November to May, while surface height change is only higher by 15% during the same timeframes. This reduced variability in surface height is explained by the seasonally varying nature of latent heat flux, compaction, and wind contributions. The ICECAPS remote sensors and stake field measurements do not agree as far as total annual water equivalent. This discrepancy is likely due to a low bias in the POSS and MMCR snowfall retrievals for Summit. To further examine the seasonal cycle, snowfall measurements by the POSS were linked to local meteorological parameters, including wind direction, liquid water path (LWP), 2 m temperature, and precipitable water vapor. An observed wind direction and moisture dependence are consistent with snowfall being linked to pulses of moist air that originate over nearby, ice‐free ocean, a resource that becomes more readily available in summertime as the winter sea ice retreats. LWP is shown to have little relationship to snowfall, indicating that ice‐phase precipitation processes are quite important for snowfall at Summit.
Key Points
Snowfall amounts at Summit are a factor of 3 larger in summer relative to winter
Precipitation is dominated by conditions with moist, southerly winds
Ice‐phase precipitation processes are quite important at Summit
Obsessive-compulsive disorder (OCD) is a disabling condition, often associated with a chronic course. Given its role in attentional control, decision-making, and emotional regulation, the anterior ...cingulate cortex is considered to have a key role in the pathophysiology of the disorder. Notably, the cingulum bundle, being the major white matter tract connecting to this region, has been historically a target for the surgical treatment of intractable OCD. In this study, we aimed to identify the extent to which focal-more than diffuse-abnormalities in fiber collinearity of the cingulum bundle could distinguish 48 adults with OCD (mean age SD = 23.3 4.5 years; F/M = 30/18) from 45 age- and sex-matched healthy control adults (CONT; mean age SD = 23.2 3.8 years; F/M = 28/17) and further examine if these abnormalities correlated with symptom severity. Use of tract-profiles rather than a conventional diffusion imaging approach allowed us to characterize white matter microstructural properties along (100 segments), as opposed to averaging these measures across, the entire tract. To account for these 100 different segments of the cingulum bundle, a repeated measures analysis of variance revealed a main effect of group (OCD < CONT; F
= 5.3; P = 0.024) upon fractional anisotropy (FA, a measure of fiber collinearity and/or white matter integrity), in the cingulum bundle, bilaterally. Further analyses revealed that these abnormalities were focal (middle portion) within the left and right cingulum bundle, although did not correlate with symptom severity in OCD. Findings indicate that focal abnormalities in connectivity between the anterior cingulate cortex and other prefrontal cortical regions may represent neural mechanisms of OCD.
Magma‐water interaction can dramatically influence the explosivity of volcanic eruptions. However, syn‐ and post‐eruptive diffusion of external (non‐magmatic) water into volcanic glass remains poorly ...constrained and may bias interpretation of water in juvenile products. Hydrogen isotopes in ash from the 2009 eruption of Redoubt Volcano, Alaska, record syn‐eruptive hydration by vaporized glacial meltwater. Both ash aggregation and hydration occurred in the wettest regions of the plume, which resulted in the removal and deposition of the most hydrated ash in proximal areas <50 km from the vent. Diffusion models show that the high temperatures of pyroclast‐water interactions (>400°C) are more important than the cooling rate in facilitating hydration. These observations suggest that syn‐eruptive glass hydration occurred where meltwater was entrained at high temperature, in the plume margins near the vent. Ash in the drier plume interior remained insulated from entrained meltwater until it cooled sufficiently to avoid significant hydration.
Plain Language Summary
Explosive volcanic eruptions produce plumes of volcanic ash and gas that commonly mix with water from overlying seawater, glaciers, or hydrothermal systems. Within these plumes, volcanic glass (rapidly cooled magma) can lose its dissolved magmatic water or gain additional water from the surrounding environment. This study uses water concentrations in volcanic glass, and the hydrogen isotopes of that water, to identify if water was lost or gained in ash during the 2009 eruption of Redoubt Volcano, Alaska, USA. Results show that most of the magmatic water was lost, and some external water was gained in samples that fell closest to the volcano. Numerical models show that external water is most easily gained in glass at high temperatures even at the fastest cooling rates. These findings suggest external water was incorporated into the margins of the eruption plumes during the eruption. Ash hydration and aggregation occurred in these wet plume margins near the vent and preferentially deposited it closer to the vent. Ash in the hotter plume core that encounters water at cooler temperatures is erupted to higher altitudes and disperses the drier ash to further distances.
Key Points
Water contents and hydrogen isotopes in volcanic ash record syn‐eruptive hydration during the wet 2009 eruption of Redoubt Volcano, Alaska
The temperature of pyroclast‐water interaction, more than the pyroclast cooling rate, dictates the extent of syn‐eruptive glass hydration
More extensive hydration of proximal ashfall suggests wetter plume margins and drier, higher transport of the plume interiors
•Glass Mountain porous pyroclasts had water content of about 0.45 wt% immediately after eruption.•Meteoric water diffused in pyroclasts at a rate of 10−23.5±0.5 m2s−1 after the eruption.•Degassing ...occurs in closed-system until magma porosity reaches 65±5%, and in open-system beyond.
Volcanic eruptions of rhyolitic magma often show shifts from powerful (Vulcanian to Plinian) explosive episodes to a more gentle effusion of viscous lava forming obsidian flows. Another prevailing characteristic of these eruptions is the presence of pyroclastic obsidians intermingled with the explosive tephra. This dense, juvenile product is similar to the tephra and obsidian flow in composition, but is generally less degassed than its flow counterpart. The formation mechanism(s) of pyroclastic obsidians and the information they can provide concerning the extent to which magma degassing modulates the eruptive style of rhyolitic eruptions are currently subject to active research. Porous tephra and pyroclastic and flow obsidians from the 1060CE Glass Mountain rhyolitic eruption at Medicine Lake Volcano (California) were analyzed for their porosity, ϕ, water content, H2O, and hydrogen isotopic composition, δD. H2O in porous pyroclasts is correlated negatively with δD and positively with ϕ, indicating that the samples were affected by post-eruptive rehydration. Numerical modeling suggests that this rehydration occurred at an average rate of 10−23.5±0.5 m2s−1 during the ∼960 years since the eruption, causing some pyroclasts to gain up to 1 wt% of meteoric water. Pyroclastic and flow obsidians were not affected by rehydration due to their very low porosity. Comparison between modeled δD-H2O relationships in degassing magma and values measured in the Glass Mountain samples supports the idea that rhyolitic magma degasses in closed-system until its porosity reaches a value of about 65±5%, beyond which degassing occurs in open-system until quench. During the explosive phase, rapidly ascending magma fragments soon after it becomes permeable, creating porous lapilli and ash that continue to degas in open-system within an expanding gas phase. As suggested by recent studies, some ash may aggregate and sinter on the conduit sides at different depths above the fragmentation level, partly equilibrating with the continuously fluxing heavier magmatic vapor, explaining the wide range of H2O contents and high variability in δD measured in the pyroclastic obsidians. Using only H2O and δD, it is impossible to rule out the possibility that pyroclastic obsidians may also form by permeable foam collapse, either syn-explosively near the conduit sides below the fragmentation level or during more effusive periods interspersed in the explosive phase. During the final effusive phase of the eruption, slowly ascending magma degasses in open-system until it reaches the surface, creating flows with low H2O and δD. This study shows that H2O measured in highly porous pyroclasts of a few hundred years or more cannot be used to infer syn-eruptive magma degassing pathways, unless careful assessment of post-eruptive rehydration is first carried out. If their mechanism of formation can be better understood, detailed analysis of the variations in texture and volatile content of pyroclastic obsidians throughout the explosive phase may help decipher the reasons why rhyolitic eruptions commonly shift from explosive to effusive phases.
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