scholarly journals ‘Georods’: the development of a four-element geophone for improved seismic imaging of glaciers and ice sheets

2013 ◽  
Vol 54 (64) ◽  
pp. 142-148 ◽  
Author(s):  
Donald E. Voigt ◽  
Leo E. Peters ◽  
Sridhar Anandakrishnan
Keyword(s):  
Seismic Data ◽  
Climate Models ◽  
Seismic Imaging ◽  
Ice Sheets ◽  
Weather Conditions ◽  
Single Element ◽  
Blowing Snow ◽  
High Quality ◽  
Field Campaigns ◽  
Excellent Source

Abstract Active seismic imaging of glaciers and ice sheets is important for constraining inputs to climate models, such as englacial ice fabric and the nature of the basal interface. However, acquiring high-quality seismic data is time-consuming and resource-intensive. Using traditional single-element geophones requires ideal weather conditions (e.g. light winds) and excellent source coupling. In addition, deploying and retrieving these geophones is slow and cumbersome. We have developed a four-element ‘georod’ that enhances signal levels by 20–30dB in a variety of conditions, including blowing snow and poorly coupled source detonations. The long, slender design of these georods makes them easy to deploy and retrieve, allowing researchers to acquire greater line-kilometers of seismic data during field campaigns that are commonly time-constrained.

scholarly journals An exemplary case of a bromine explosion event linked to cyclone development in the Arctic

2016 ◽  
Vol 16 (3) ◽  
pp. 1773-1788 ◽  
Author(s):  
A.-M. Blechschmidt ◽  
A. Richter ◽  
J. P. Burrows ◽  
L. Kaleschke ◽  
K. Strong ◽  
...  
Keyword(s):  
Numerical Models ◽  
Weather Conditions ◽  
Conveyor Belt ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Blowing Snow ◽  
Air Stream ◽  
Combined Use ◽  
Arctic Sea ◽  
Development Duration

Abstract. Intense, cyclone-like shaped plumes of tropospheric bromine monoxide (BrO) are regularly observed by GOME-2 on board the MetOp-A satellite over Arctic sea ice in polar spring. These plumes are often transported by high-latitude cyclones, sometimes over several days despite the short atmospheric lifetime of BrO. However, only few studies have focused on the role of polar weather systems in the development, duration and transport of tropospheric BrO plumes during bromine explosion events. The latter are caused by an autocatalytic chemical chain reaction associated with tropospheric ozone depletion and initiated by the release of bromine from cold brine-covered ice or snow to the atmosphere. In this manuscript, a case study investigating a comma-shaped BrO plume which developed over the Beaufort Sea and was observed by GOME-2 for several days is presented. By making combined use of satellite data and numerical models, it is shown that the occurrence of the plume was closely linked to frontal lifting in a polar cyclone and that it most likely resided in the lowest 3 km of the troposphere. In contrast to previous case studies, we demonstrate that the dry conveyor belt, a potentially bromine-rich stratospheric air stream which can complicate interpretation of satellite retrieved tropospheric BrO, is spatially separated from the observed BrO plume. It is concluded that weather conditions associated with the polar cyclone favoured the bromine activation cycle and blowing snow production, which may have acted as a bromine source during the bromine explosion event.

Analog Models for Empirical-Statistical Downscaling

2021 ◽  
Author(s):  
María Laura Bettolli
Keyword(s):  
Statistical Downscaling ◽  
Climate Models ◽  
Global Climate ◽  
Regional Climate ◽  
Weather Conditions ◽  
Climate Information ◽  
Analog Method ◽  
Weather Typing ◽  
Regional Climates ◽  
Local Weather

Global climate models (GCM) are fundamental tools for weather forecasting and climate predictions at different time scales, from intraseasonal prediction to climate change projections. Their design allows GCMs to simulate the global climate adequately, but they are not able to skillfully simulate local/regional climates. Consequently, downscaling and bias correction methods are increasingly needed and applied for generating useful local and regional climate information from the coarse GCM resolution. Empirical-statistical downscaling (ESD) methods generate climate information at the local scale or with a greater resolution than that achieved by GCM by means of empirical or statistical relationships between large-scale atmospheric variables and the local observed climate. As a counterpart approach, dynamical downscaling is based on regional climate models that simulate regional climate processes with a greater spatial resolution, using GCM fields as initial or boundary conditions. Various ESD methods can be classified according to different criteria, depending on their approach, implementation, and application. In general terms, ESD methods can be categorized into subgroups that include transfer functions or regression models (either linear or nonlinear), weather generators, and weather typing methods and analogs. Although these methods can be grouped into different categories, they can also be combined to generate more sophisticated downscaling methods. In the last group, weather typing and analogs, the methods relate the occurrence of particular weather classes to local and regional weather conditions. In particular, the analog method is based on finding atmospheric states in the historical record that are similar to the atmospheric state on a given target day. Then, the corresponding historical local weather conditions are used to estimate local weather conditions on the target day. The analog method is a relatively simple technique that has been extensively used as a benchmark method in statistical downscaling applications. Of easy construction and applicability to any predictand variable, it has shown to perform as well as other more sophisticated methods. These attributes have inspired its application in diverse studies around the world that explore its ability to simulate different characteristics of regional climates.

scholarly journals Atmosphere similarity patterns in boreal summer show an increase of persistent weather conditions connected to hydro-climatic risks

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Peter Hoffmann ◽  
Jascha Lehmann ◽  
Bijan H. Fallah ◽  
Fred F. Hattermann
Keyword(s):  
Northern Hemisphere ◽  
Climate Models ◽  
Weather Conditions ◽  
Boreal Summer ◽  
Climatic Extremes ◽  
Weather Patterns ◽  
Dry Conditions ◽  
Climatic Risks ◽  
Long Term Trend

AbstractRecent studies have shown that hydro-climatic extremes have increased significantly in number and intensity in the last decades. In the Northern Hemisphere such events were often associated with long lasting persistent weather patterns. In 2018, hot and dry conditions prevailed for several months over Central Europe leading to record-breaking temperatures and severe harvest losses. The underlying circulation processes are still not fully understood and there is a need for improved methodologies to detect and quantify persistent weather conditions. Here, we propose a new method to detect, compare and quantify persistence through atmosphere similarity patterns by applying established image recognition methods to day to day atmospheric fields. We find that persistent weather patterns have increased in number and intensity over the last decades in Northern Hemisphere mid-latitude summer, link this to hydro-climatic risks and evaluate the extreme summers of 2010 (Russian heat wave) and of 2018 (European drought). We further evaluate the ability of climate models to reproduce long-term trend patterns of weather persistence and the result is a notable discrepancy to observed developments.

scholarly journals Identification of blowing snow particles in images from a multi-angle snowflake camera

2018 ◽  
Author(s):  
Mathieu Schaer ◽  
Christophe Praz ◽  
Alexis Berne
Keyword(s):  
Austral Summer ◽  
Gaussian Mixture ◽  
Second Step ◽  
Blowing Snow ◽  
Kappa Score ◽  
Probabilistic Information ◽  
Complex Interactions ◽  
Field Campaigns ◽  
Number Of Particles ◽  
Image Frequency

Abstract. A new method to automatically discriminate between hydrometeors and blowing snow particles on Multi-Angle Snowflake Camera (MASC) images is introduced. The method uses four selected descriptors related to the image frequency, the number of particles detected per image as well as their size and geometry to classify each individual image. The classification task is achieved with a two components Gaussian Mixture Model fitted on a subset of representative images of each class from field campaigns in Antarctica and Davos, Switzerland. The performance is evaluated by labelling the subset of images on which the model was fitted. An overall accuracy and Cohen's Kappa score of 99.4 and 98.8 %, respectively, is achieved. In a second step, the probabilistic information is used to flag images composed of a mix of blowing snow particles and hydrometeors, which turns out to occur frequently. The percentage of images belonging to each class from an entire austral summer in Antartica and during a winter in Davos, respectively, are presented. The capability to distinguish precipitation, blowing snow and a mix of those in MASC images is highly relevant to disentangle the complex interactions between wind, snowflakes and snowpack close to the surface.

Microseepage through Evaporite Sequences – a Gulf of Suez Example

2021 ◽  
pp. 1-30
Author(s):  
Alan H. Silliman ◽  
Rick Schrynemeeckers
Keyword(s):  
Grain Boundaries ◽  
Seismic Data ◽  
Oil And Gas ◽  
Seismic Imaging ◽  
Passive Samplers ◽  
Ductile Material ◽  
Gulf Of Suez ◽  
Calibration Data ◽  
Geochemical Survey ◽  
Molecular Movement

Salt is one of the most effective agents for trapping oil and gas. As a ductile material it can move and deform surrounding sediments and create traps. However, effective sealing of reservoirs for movement of hydrocarbons along breaching faults or fracture swarms (i.e. macroseepage) is a completely different mechanism than the molecular movement of hydrocarbons through grain boundaries and microfractures as found in microseepage. Forum Exploration chose to evaluate the applicability of passive surface geochemistry for mapping hydrocarbons in their onshore West Gebel El Zeit lease due to difficulties in seismic imaging through salt and anhydrites sequences. Two economic producing wells had been drilled in the lease, but due to compartmentalization and complexity in the area, three dry wells had also been drilled. Target formations included the Kareem Formation at ∼2,700 m and the Rudeis Formation at ∼3,000 m.The geochemical survey encompassed 100 passive geochemical modules. Passive samplers were also deployed around two producing wells and one dry well. Calibration data generated positive thermogenic signatures around the two producing wells in contrast to the background or baseline signature developed around the dry well. The Rudeis Formation calibration signature ranged from ∼nC5 - ∼nC9 while the Kareem Formation calibration signature ranged from ∼nC6 – nC12. This suggested the Rudeis calibration signature was lighter than the Kareem. This correlated with independent API gravity testing on produced oil samples (41o API gravity oil for the Rudeis, 35o API gravity oil for the Kareem).A post-survey well, Fh85-8, was drilled based on combined geochemical and seismic data results. The well was an oil discovery, with initial production of 800 BOPD. The evidence presented in this Gulf of Suez example shows that microseepage can occur through salt sequences. As such, ultrasensitive passive surface geochemical surveys provide a powerful tool for derisking salt plays.

Can climate models capture the high amplitudes circumglobal waves and their surface imprints?  

2021 ◽  
Author(s):  
Fei Luo ◽  
Kai Kornhuber ◽  
Frank Selten ◽  
Dim Coumou
Keyword(s):  
Soil Moisture ◽  
Climate Models ◽  
Phase Locking ◽  
Weather Conditions ◽  
Reanalysis Data ◽  
Circulation Types ◽  
Temperature And Precipitation ◽  
Wave Patterns ◽  
Precipitation Anomalies ◽  
June July

<p>Pronounced circumglobal waves can trigger and maintain persistent summer weather conditions by remaining in their preferred phase-locked positions for several weeks in a row. This phenomenon, especially important for wave numbers 5 and 7, has been observed in recent years, but it is unclear whether climate models can reproduce circulation types and their surface imprints.</p><p>Here we assess three climate models (EC-Earth3, CESM1.2, and MIROC5)  for their representation of amplified circumglobal waves and associated surface imprints in summer (June, July and August) over 1979-2016. ERA5 reanalysis data is used as reference to assess the models’ performance. We run a series of modeling experiments to understand the source of biases in the climate models: free interactive atmosphere and soil moisture runs (AISI), atmospheric nudged runs (AFSI), soil moisture prescribed runs (AISF), and both atmosphere and soil moisture nudged experiments (AFSF).</p><p>We show that all models reasonably well reproduce the climatological wave spectra. Further, both wave 5 and wave 7 are found to exhibit phase-locking behaviors across all models, resulting in similar wave patterns across the hemisphere as compared to reanalysis. The surface imprints are observed in the models as well, but depending on the model, the results vary in strength. We also found the biases in surface temperature and precipitation anomalies mainly come from the atmospheric circulation in the models as these biases reduced considerably from AISI runs to AFSI and AFSF runs where upper atmosphere levels were nudged. Nudging soil moisture also minimizes some biases in the models but not as obvious as nudging the atmosphere. </p><div> <div> <div> </div> </div> </div>

Different ice sheets – different AMOC? Revisiting the ice-sheet effect on the LGM AMOC

2021 ◽  
Author(s):  
Marlene Klockmann ◽  
Marie-Luise Kapsch ◽  
Uwe Mikolajewicz
Keyword(s):  
Southern Ocean ◽  
Climate Models ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Salt Transport ◽  
Max Planck ◽  
Good Opportunity ◽  
Transient Simulations ◽  
Opposing Effects

<p><span>Coupled climate models have produced very different states of the Atlantic Meridional Overturning Circulation (AMOC) in simulations of the Last Glacial Maximum (LGM). In particular, many of them failed to capture the shoaling of the upper AMOC cell, which was indicated by reconstructions. In sensitivity simulations with the Max-Planck-Institute Earth System Model (MPI-ESM) we found that the glacial AMOC response is the sum of two large opposing effects: a strengthening and deepening of the upper cell in response to the glacial ice sheets and a weakening and shoaling of the upper cell in response to the low glacial greenhouse gas concentrations. The magnitude of the respective effects likely depends on the background climate, the ice sheet reconstruction used, and model specifics such as the representation of brine release in the Southern Ocean. </span></p><p><span>Transient simulations of the deglaciation with two differently tuned versions of MPI-ESM and two different ice-sheet reconstructions differ strongly in their respective AMOC states during the LGM. These simulations, together with selected PMIP3 and PMIP4 LGM simulations, provide a good opportunity to compare the effect of different ice sheet reconstructions on the glacial AMOC. We compare key variables such as water mass properties, salt transport and Southern Ocean sea-ice formation across this ensemble of opportunity with the aim of increasing our understanding of the role of ice sheets in the glacial AMOC response.</span></p>

scholarly journals Success of Montreal Protocol Demonstrated by Comparing High-Quality UV Measurements with “World Avoided” Calculations from Two Chemistry-Climate Models

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Richard McKenzie ◽  
Germar Bernhard ◽  
Ben Liley ◽  
Patrick Disterhoft ◽  
Steve Rhodes ◽  
...  
Keyword(s):  
Climate Models ◽  
Montreal Protocol ◽  
High Quality
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