Wind-induced seismic noise at the Princess Elisabeth Antarctica Station

Abstract. Icequakes are the result of processes occurring within the ice mass or between the ice and its environment. Studying icequakes provides a unique view on ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental or climate changes are reflected in icequakes. Counting and characterizing icequakes is thus essential to monitor them. Most of the icequakes recorded by the seismic station at the Belgian Princess Elisabeth Antarctica Station (PE) have small amplitudes corresponding to maximal displacements of a few nanometres. Their detection threshold is highly variable because of the rapid and strong changes in the local seismic noise level. Therefore, we evaluated the influence of katabatic winds on the noise measured by the well-protected PE surface seismometer. Our purpose is to identify whether the lack of icequake detection during some periods could be associated with variations in the processes generating them or simply with a stronger seismic noise linked to stronger wind conditions. We observed that the wind mainly influences seismic noise at frequencies greater than 1 Hz. The seismic noise power exhibits a bilinear correlation with the wind velocity, with two different slopes at a wind velocity lower and greater than 6 m s−1 and with, for example at a period of 0.26 s, a respective variation of 0.4 dB (m −1 s) and 1.4 dB (m −1 s). These results allowed a synthetic frequency and wind-speed-dependent noise model to be presented that explains the behaviour of the wind-induced seismic noise at PE, which shows that seismic noise amplitude increases exponentially with increasing wind speed. This model enables us to study the influence of the wind on the original seismic dataset, which improves the observation of cryoseismic activity near the PE station.

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Wind-induced seismic noise at the Princess Elisabeth Antarctica Station

10.5194/tc-2020-267 ◽

2020 ◽

Author(s):

Baptiste Frankinet ◽

Thomas Lecocq ◽

Thierry Camelbeeck

Keyword(s):

Wind Velocity ◽

Noise Level ◽

Seismic Noise ◽

Climate Changes ◽

Seismic Station ◽

Detection Threshold ◽

Ice Dynamics ◽

Katabatic Winds

Abstract. Icequakes are the result of processes occurring within the ice mass, or between the ice and its environment. Studying icequakes provide a unique view on the ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental, or climate, changes, are reflected in icequakes. Counting and characterizing icequakes is thus essential to monitor them. Most of the icequakes recorded by the seismic station at the Belgian Princess Elisabeth Antarctica Station (PE) have small amplitudes corresponding to maximal displacements of a few nanometres. Their detection threshold is highly variable because of the rapid and strong changes in the local seismic noise level. In this study, we evaluated the influence of katabatic winds on the noise measured by the well-protected PE surface seismometer. Our purpose is to identify whether the lack of icequakes detection during some periods could be associated with variations in the processes generating them or simply to a stronger seismic noise linked to stronger wind conditions. We observed that the wind mainly influences seismic noise at frequencies greater than 1 Hz. The seismic noise level well correlates linearly with the wind velocity, but this correlation follows different linear laws at wind velocity lower and greater than 6 m/s, with a respective variation of 0.4 dB/(m/s) and 1.4 dB/(m/s). These results allowed presenting a model and synthetic spectrogram that explain the behaviour of the wind-induced seismic noise at PE. This model enables us partially removing the influence of wind impact from the original seismic dataset, which improves the observation of cryoseismic activity near the PE station.

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Approach to study the seismicity in the Perunica Glacier, Livingston Island, Antarctica

10.5194/egusphere-egu21-7830 ◽

2021 ◽

Author(s):

Gergana Georgieva ◽

Liliya Dimitrova ◽

Dragomir Dragomirov

Keyword(s):

Seismic Activity ◽

Seismic Noise ◽

Seismic Station ◽

Velocity Model ◽

Noise Power ◽

Noise Sources ◽

Seismic Stations ◽

Glacial Origin ◽

Livingston Island ◽

The Antarctic

The seismicity caused by the movement of glaciers was discovered only 30-40 years ago, and it was initially assumed that only glaciers in Greenland create this type of seismicity. Today, a significant part of the earthquakes registered by the Antarctic seismic stations are of glacial origin. In recent years, scientists' interest in studying the seismic activity of glaciers and its relationship to various environmental factors has increased due to the response of the ice mass to climate change.The interest of studying seismicity of Antarctica has increased in the last decade with installation of a growing number of seismic stations in the region.In 2015, with the first installation of the LIVV seismic station, Bulgarian seismologists began studying the seismicity of the Perunika Glacier, located on Livingston Island, Antarctica. Between 2015 and 2018, seismic recordings were made only in the astral summer, and from January 2020 the seismic station was installed for year-round operation. The seismic station is located near the glacier.In this study, an approach to analyze the ice generated events recorded during all working period of the LIVV station is presented. Depending on the source mechanism and therefore the different waveform shapes, several types of icequakes and earthquakes are distinguished.Registered icequakes are more than 16000. Its duration varies between less than a second and more than a minute. A few events are several minutes long. We have noticed that from 2015 to 2020, the number of glacier events is increasing while its duration is decreasing. Localization of the ice generated events with duration below 1 s is calculated. In the localization procedure, a velocity model developed for the area of the seismic station is applied. The produced icequake epicenters are grouped in several clusters within the Perunika glacier. The nature of these glacier events are still studying.Another approach to study the seismic activity of the glacier is carried out by estimating the ambient seismic noise. Frequent and spectral distribution of the power of seismic noise is made over the seismic data recorded during all working periods. It is concluded that the noise sources in the periods around 0.5 s are linked to the dynamic processes in the Perunika Glacier. Some relationship between the change in the noise power in the 0.2-0.6s period band and tidal cycles has been found.Acknowledgment: The presented study is supported by project: No 70.25-171/22.11.2019 &#8220;Study the activity of the Perunika glacier during year-round deployment&#8221; funded by the National Center for Polar Studies, Bulgaria.

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Analysis of Noise and Velocity in GNSS EPN-Repro 2 Time Series

Remote Sensing ◽

10.3390/rs13142783 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2783

Author(s):

Sorin Nistor ◽

Norbert-Szabolcs Suba ◽

Kamil Maciuk ◽

Jacek Kudrys ◽

Eduard Ilie Nastase ◽

...

Keyword(s):

Time Series ◽

Visual Inspection ◽

Flicker Noise ◽

Vertical Component ◽

Likelihood Estimation ◽

Noise Model ◽

Noise Amplitude ◽

Allan Deviation ◽

Power Spectral ◽

Position Time Series

This study evaluates the EUREF Permanent Network (EPN) station position time series of approximately 200 GNSS stations subject to the Repro 2 reprocessing campaign in order to characterize the dominant types of noise and amplitude and their impact on estimated velocity values and associated uncertainties. The visual inspection on how different noise model represents the analysed data was done using the power spectral density of the residuals and the estimated noise model and it is coherent with the calculated Allan deviation (ADEV)-white and flicker noise. The velocities resulted from the dominant noise model are compared to the velocity obtained by using the Median Interannual Difference Adjusted for Skewness (MIDAS). The results show that only 3 stations present a dominant random walk noise model compared to flicker and powerlaw noise model for the horizontal and vertical components. We concluded that the velocities for the horizontal and vertical component show similar values in the case of MIDAS and maximum likelihood estimation (MLE), but we also found that the associated uncertainties from MIDAS are higher compared to the uncertainties from MLE. Additionally, we concluded that there is a spatial correlation in noise amplitude, and also regarding the differences in velocity uncertainties for the Up component.

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Analysis for the Effect of Wind Barrier on Reducing Wind Velocity across a Bridge

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.256-259.2739 ◽

2012 ◽

Vol 256-259 ◽

pp. 2739-2742

Author(s):

Ji Hong Bi ◽

Peng Lu ◽

Jian Wang ◽

Chun Bao

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Wind Speed ◽

Wind Velocity ◽

Efficient Design ◽

Wind Barrier ◽

Strong Winds

A bridge, which is located in the route of typhoon, is considered how to assure normal traffic use against strong winds. As one of the measures, wind barrier is proposed to be set on both sides of the bridge section for reducing wind velocity across it. In this study, an analysis by using CFX, a computational fluid dynamics program, is carried out to investigate the effects of wind barrier. The speed of wind is assumed as 60m/s. To find out an efficient design of the boards, different porosity ratios(r) of the boards is assumed for comparison. The result shows that wind barrier could reduce the wind speed across the bridge effectively.

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Experimental Study of Vertical Axis Wind Turbine with Wind Speed Self-Adapting

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.215-216.1323 ◽

2012 ◽

Vol 215-216 ◽

pp. 1323-1326

Author(s):

Ming Wei Xu ◽

Jian Jun Qu ◽

Han Zhang

Keyword(s):

Wind Speed ◽

Wind Turbine ◽

Wind Velocity ◽

Vertical Axis ◽

Maximum Power ◽

The Self ◽

Power Coefficient ◽

Speed Ratio ◽

Vertical Axis Wind Turbine ◽

Opening And Closing

A small vertical axis wind turbine with wind speed self-adapting was designed. The diameter and height of the turbine were both 0.7m. It featured that the blades were composed of movable and fixed blades, and the opening and closing of the movable blades realized the wind speed self-adapting. Aerodynamic performance of this new kind turbine was tested in a simple wind tunnel. Then the self-starting and power coefficient of the turbine were studied. The turbine with load could reliably self-start and operate stably even when the wind velocity was only 3.6 m/s. When the wind velocity was 8 m/s and the load torque was 0.1Nm, the movable blades no longer opened and the wind turbine realized the conversion from drag mode to lift mode. With the increase of wind speed, the maximum power coefficient of the turbine also improves gradually. Under 8 m/s wind speed, the maximum power coefficient of the turbine reaches to 12.26%. The experimental results showed that the new turbine not only improved the self-starting ability of the lift-style turbine, but also had a higher power coefficient in low tip speed ratio.

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Dominant climatic factors driving annual runoff changes at the catchment scale across China

Hydrology and Earth System Sciences ◽

10.5194/hess-20-2573-2016 ◽

2016 ◽

Vol 20 (7) ◽

pp. 2573-2587 ◽

Cited By ~ 10

Author(s):

Zhongwei Huang ◽

Hanbo Yang ◽

Dawen Yang

Keyword(s):

Wind Speed ◽

Air Temperature ◽

Climate Changes ◽

Climatic Factors ◽

Southern China ◽

Resource Planning ◽

Annual Runoff ◽

Net Radiation ◽

Catchment Scale ◽

The Impact

Abstract. With global climate changes intensifying, the hydrological response to climate changes has attracted more attention. It is beneficial not only for hydrology and ecology but also for water resource planning and management to understand the impact of climate change on runoff. In addition, there are large spatial variations in climate type and geographic characteristics across China. To gain a better understanding of the spatial variation of the response of runoff to changes in climatic factors and to detect the dominant climatic factors driving changes in annual runoff, we chose the climate elasticity method proposed by Yang and Yang (2011). It is shown that, in most catchments of China, increasing air temperature and relative humidity have negative impacts on runoff, while declining net radiation and wind speed have positive impacts on runoff, which slow the overall decline in runoff. The dominant climatic factors driving annual runoff are precipitation in most parts of China, net radiation mainly in some catchments of southern China, air temperature and wind speed mainly in some catchments in northern China.

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Climate changes modulated the history of Arctic iodine during the Last Glacial Cycle

Nature Communications ◽

10.1038/s41467-021-27642-5 ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

Juan Pablo Corella ◽

Niccolo Maffezzoli ◽

Andrea Spolaor ◽

Paul Vallelonga ◽

Carlos A. Cuevas ◽

...

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Radiative Forcing ◽

Climate Changes ◽

Ice Cores ◽

The Arctic ◽

Glacial Cycle ◽

Ice Dynamics ◽

Sea Ice Dynamics ◽

Ultrafine Aerosol

AbstractIodine has a significant impact on promoting the formation of new ultrafine aerosol particles and accelerating tropospheric ozone loss, thereby affecting radiative forcing and climate. Therefore, understanding the long-term natural evolution of iodine, and its coupling with climate variability, is key to adequately assess its effect on climate on centennial to millennial timescales. Here, using two Greenland ice cores (NEEM and RECAP), we report the Arctic iodine variability during the last 127,000 years. We find the highest and lowest iodine levels recorded during interglacial and glacial periods, respectively, modulated by ocean bioproductivity and sea ice dynamics. Our sub-decadal resolution measurements reveal that high frequency iodine emission variability occurred in pace with Dansgaard/Oeschger events, highlighting the rapid Arctic ocean-ice-atmosphere iodine exchange response to abrupt climate changes. Finally, we discuss if iodine levels during past warmer-than-present climate phases can serve as analogues of future scenarios under an expected ice-free Arctic Ocean. We argue that the combination of natural biogenic ocean iodine release (boosted by ongoing Arctic warming and sea ice retreat) and anthropogenic ozone-induced iodine emissions may lead to a near future scenario with the highest iodine levels of the last 127,000 years.

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Wind Profiling by Passive Optical Method

EPJ Web of Conferences ◽

10.1051/epjconf/202023706021 ◽

2020 ◽

Vol 237 ◽

pp. 06021

Author(s):

Vadim Dudorov ◽

Anna Eremina

Keyword(s):

Wind Speed ◽

Wind Velocity ◽

Optical Method ◽

Video Sequence ◽

Distant Object ◽

Observation Path

Possibilities of the wind speed profiling along an observation path of a distant object from the analysis of a video sequence of images of the object are studied in this work. The method is based on the analysis of two neighbor frames of a video sequence of incoherent images. The wind velocity retrieved is compared with data of acoustic anemometers.

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Seismic Noise Model for Romania Revisited

10.3997/2214-4609.202149bgs77 ◽

2021 ◽

Author(s):

A. Tolea ◽

B. Grecu ◽

C. Neagoe

Keyword(s):

Seismic Noise ◽

Noise Model

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Prediction and suppression of long-period nonpropagating seismic noise

Bulletin of the Seismological Society of America ◽

10.1785/bssa0630030937 ◽

1973 ◽

Vol 63 (3) ◽

pp. 937-958

Author(s):

Anton Ziolkowski

Keyword(s):

Transfer Function ◽

Pressure Distribution ◽

Noise Level ◽

Seismic Noise ◽

Wave Number ◽

Earth Model ◽

Noise Power ◽

Long Period ◽

Band Limited ◽

Time Invariant

abstract Approximately half the noise observed by long-period seismometers at LASA is nonpropagating; that is, it is incoherent over distances greater than a few kilometers. However, because it is often strongly coherent with microbarograph data recorded at the same site, a large proportion of it can be predicted by convolving the microbarogram with some transfer function. The reduction in noise level using this technique can be as high as 5 db on the vertical seismometer and higher still on the horizontals. If the source of this noise on the vertical seismogram were predominantly buoyancy, the transfer function would be time-invariant. It is not. Buoyancy on the LASA long-period instruments is quite negligible. The noise is caused by atmospheric deformation of the ground and, since so much of it can be predicted from the output of a single nearby microbarograph, it must be of very local origin. The loading process may be adequately described by the static deformation of a flat-earth model; however, for the expectation of the noise to be finite, it is shown that the wave number spectrum of the pressure distribution must be band-limited. An expression for the expected noise power is derived which agrees very well with observations and predicts the correct attenuation with depth. It is apparent from the form of this expression why it is impossible to obtain a stable transfer function to predict the noise without an array of microbarographs and excessive data processing. The most effective way to suppress this kind of noise is to bury the seismometer: at 150 m the reduction in noise level would be about 10 db.

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