Wind Strength Research Articles

What Controls the Skill of General Circulation Models to Simulate the Seasonal Cycle in Water Isotopic Composition in the Tibetan Plateau Region?

AbstractThis study evaluates the simulation of the seasonal cycle of water isotopic composition over Tibetan Plateau regions (TP) from six isotope‐enabled general circulation models (GCMs) participating in the second Phase of Stable Water Isotope Intercomparison Group. For both meteorological factors (precipitation rate and wind field) and isotopic composition, GCMs generally agree with reanalysis data and in‐situ observations, but there is a significant spread across models and the isotopic seasonality is systematically underestimated. In the southern TP, the precipitation isotopic composition is more depleted in summer than in winter, and the amplitude of the simulated isotopic seasonal variations is primarily driven by the amplitude of the simulated upstream precipitation. In contrast, in the northern TP, the precipitation isotopic composition is more depleted in winter than in summer, and the amplitude of the simulated seasonal variability of isotopes is mainly driven by the simulated strength of the zonal wind. We conclude that the skill of a GCM to simulate the seasonal cycle in the isotopic composition depends mainly on the skill of the GCM to simulate the Indian summer monsoon precipitation and the westerlies. The same causes contributing to the underestimated seasonality at present‐day may also contribute to the underestimated δ18O change at the mid‐Holocene.

Investigating the Role of Amazonian Mesoscale Wind Patterns and Strength on the Spatial Distribution of Martian Bedrock Exposures.

The Martian highlands contain Noachian-aged areally-extensive (>225km2) bedrock exposures that have been mapped using thermal and visible imaging datasets. Given their age, crater density and impact gardening should have led to the formation of decameter scale layers of regolith that would overlie and bury these outcrops if composed of competent materials like basaltic lavas. However, many of these regions lack thick regolith layers and show clear exposures of bedrock materials with elevated thermal inertia values compared to the global average. Hypothesized reasons for the lack of regolith include: (a) relatively weaker material properties than lavas, where friable materials are comminuted and deflated during wind erosion, (b) long-term protection from regolith development through burial and later exhumation through one or more surface processes, and (c) spatially concentrated aeolian erosion and wind energetics on well-lithified basaltic substrates. To test the third hypothesis, we used the Mars Regional Atmospheric Modeling System to calculate wind erosive strength at 10 regions throughout the Martian highlands and compared it to their thermophysical properties by using thermal infrared data derived from the Thermal Emission Spectrometer to understand the effect that Amazonian mesoscale wind patterns may have on the exposure of bedrock. We also investigated the effect of planet obliquity, Ls of perihelion, and atmospheric mean pressure on wind erosion potential. We found no evidence for increased aeolian activity over bedrock-containing regions relative to surrounding terrains, including at the mafic floor unit at Jezero crater (Máaz formation), supporting the first or second hypotheses for these regions.

Моделирование критических локальных деформаций коры растущего дерева при ветровой нагрузке

The interaction between wind loads and forest plantations has been fairly well understood. A large amount of valuable scientific and practical information has been obtained and published so far in this field. There are some known data on wind load damage to plantations, its effect on their growth, and the ability of forest plantations to reduce wind speed and force. Nevertheless, the issues of wind impact on both individual trees and forested areas remain relevant. Analysis of the literature and Internet resources showed that the research has left out the issue of the wind load impact on the grown wood quality. Multi-year observations and a wind rose created using these observations enable the determination of the prevailing wind strength and direction for each area. Knowing the features of the wind load impact on the quality of timber after logging, it is possible to predict the percentage of the yield of commercial and low-quality wood, and to purposefully influence this parameter in plantation forest growing by setting out the planting material in accordance with these data. The article shows the developed method for theoretical estimation of the probability of occurrence of critical bark deformations in the compressed zone, which appears when bending a growing tree due to wind load. Classical studies of the critical state of compressed rods on an elastic base were used as the theoretical basis of the method. A part of growing tree bark plays the role of a rod, while cambium and other living cells between the bark and the trunk wood play the role of the elastic base. A correlation simple enough for practical application is proposed in order to obtain quantitative estimates. Adequacy of the modeling results is confirmed by their consistency with the experimental data. The application of the developed methodology is shown on the examples.

Research on Intelligent Fault Diagnosis of Wind Power Generation System Based on Data Fusion

With the consume of traditional petrifaction energy origin such as coal, matelote and physical gas and the increasingly serious question of entire warming, the penetration ratio of wind power in the energy economy continues to enhance. Wind farms are generally built-in areas with strong winds, tough working environments and a high probability of equipment failure. Faults on large grid-connected wind turbines will seriously influence the safety and stability of conventional strength grids. In addition, unplanned maintenance after a breakdown of wind turbines needs a lot of manpower and corporeal resources, which greatly decrease the efficiency of wind strength production and enhance production costs. Therefore, the key to solving the above problems is to quickly and efficiently identify fan faults, which in turn enables accurate troubleshooting. In the article, the malfunction diagnosis of intelligent wind power system based on data fusion is discussed, and it is found that the GBoost algorithm has high accuracy in detecting sensor gain error, sensor offset error and sensor standard error when the Gaussian white-to-noise ratio exceeds 45 dB. In addition, DBN has different diagnostic effects for different faults with different Gaussian noises, at 45 dB and 35 dB, each type of error varies slightly, and the dotted line varies; at 25 dB, each type of error has a large difference. The difference is large, indicating that at 25 dB, this type of error is more sensitive; comparing the state estimation effect makes DLSTM have good adaptability to time series, and also shows that DLSTM considers the system to be reliable enough, and can be obtained by data fusion of the parameters of each system. What is the state of its system, and then take corresponding measures.

The impact of environment on the lives of disc galaxies as revealed by SDSS-IV MaNGA

ABSTRACT Environment has long been known to have significant impact on the evolution of galaxies, but here we seek to quantify the subtler differences that might be found in disc galaxies, depending on whether they are isolated, the most massive galaxy in a group (centrals), or a lesser member (satellites). The MaNGA survey allows us to define a large mass-matched sample of 574 galaxies with high-quality integrated spectra in each category. Initial examination of their spectral indices indicates significant differences, particularly in low-mass galaxies. Semi-analytic spectral fitting of a full chemical evolution model to these spectra confirms these differences, with low-mass satellites having a shorter period of star formation and chemical enrichment typical of a closed box, while central galaxies have more extended histories, with evidence of ongoing gas accretion over their lifetimes. The derived parameters for gas infall time-scale and wind strength suggest that low-mass satellite galaxies have their hot haloes of gas effectively removed, while central galaxies retain a larger fraction of gas than isolated galaxies due to the deeper group potential well in which they sit. S0 galaxies form a distinct subset within the sample, particularly at higher masses, but do not bias the inferred lower mass environmental impact significantly. The consistent picture that emerges underlines the wealth of archaeological information that can be extracted from high-quality spectral data using techniques like semi-analytic spectral fitting.

Implications of the loess record for Holocene climate and human settlement in Heye Catchment, Jiuzhaigou, eastern Tibetan Plateau, Sichuan, China

AbstractWe examine the Holocene loess record in the Heye Catchment on the margins of the Tibetan Plateau (TP) and China Loess Plateau (CLP) to determine: the region to which the Heye Catchment climate is more similar; temporal change in wind strength; and modification of the loess record by mass wasting and human activity. Luminescence and radiocarbon dating demonstrate loess deposited in two periods: >11–8.6 ka and <5.1 ka. The 8.6–5.1 ka depositional hiatus, which coincides with the Mid-Holocene Climatic Optimum, is more similar to the loess deposition cessation in the TP than to the loess deposition deceleration in the CLP. Grain-size analysis suggests the Heye loess is a mixture of at least three different grain-size distributions and that it may derive from multiple sources. A greater proportion of coarse sediments in the older loess may indicate stronger winds compared with the more recent depositional period. Gravel incorporated into younger loess most likely comes from bedrock exposed in slump scarps. Human occupation of the catchment, for which the earliest evidence is 3.4 ka, postdates the onset of slumping; thus the slumps may have created a livable environment for humans.

Coating's influence on wind erosion of porous stones used in the Cultural Heritage of Southern Italy: Surface characterisation and resistance

Wind erosion (or aeolian corrosion) is one of the most relevant causes of weathering and degradation which has affected building surfaces in Cultural Heritage. The effect depends on the wind strength, the impact of particles transported and their size and the characteristics of surfaces affected. This aspect is very important for historical buildings constructed by using limestone as Lecce stone (LS). LS has an extraordinary ability to be shaped, but is very sensitive to decay. Exfoliation, wind erosion, absorption of water by capillary from the soil, are its main degradation causes. For such a reason, the application of effective products able to act as “sacrifice film” became necessary in order to minimise the degradation rate by preserving the limestone substrate against serious weathering agents. In this work, the effects of aeolian corrosion, simulated by means the accelerated test with sandblasting method, were studied. In particular, the effectiveness of two specific commercial coatings, such as an innovative free-solvent hybrid organic-inorganic coating (HYBRID) and a solvent-based coating (AS), was assessed relating to their capability to preserve Lecce stone from the aeolian corrosion phenomenon. The protective efficacy was guaranteed by both the commercial coatings even after accelerated wind erosion test, by confirming a high hydrophobicity, low capillary water absorption and an adequate depth of penetration inside the stone able to assure durability.

The Western Pacific North Equatorial Countercurrent Responses to Two Forms of El Niño during the Period 1978 to 2017

This research aims to examine how the Western Pacific North equatorial countercurrent (NECC) flow reacts to two different forms of El Niño (EN) over a 40-year period. To establish the prevailing modes for each season, we implemented Empirical Orthogonal Function (EOF) analysis on the eastward current component of the Ocean Reanalysis System 5 (ORAS5) dataset. In comparison to the Central Pacific (CP) episode, the time series principal component of the first mode (PC1) demonstrated that the strongest NECC’s magnitude often emerged during the development period (spring to fall) of the Eastern Pacific (EP) EN event. However, in episode CP 2002/2003, we witnessed an abnormal behavior in which the stronger NECC manifested. This was due to the emergence of a strong anomalous westerly wind, which differed from other CP events and forced the NECC’s magnitude to be greater. When approaching the peak stage, on the other hand, the magnitude of the NECC during the CP episode was typically greater than that of the EP episode. The NECC’s magnitude fell greatly in the second year of the EP episode, particularly during the spring season, since most EP episodes would transition into an La Niña (LN) event in the succeeding event. During the EP EN, it was found that the strength of the westerly wind had a bigger effect on the NECC than during the CP EN.

Quantification of motion-induced measurement error on floating lidar systems

Abstract. Floating lidar systems (FLSs) are widely used for offshore wind site assessment, and their measurements show good agreement when compared to trusted reference sources. However, some influence of motion on mean wind speed data from FLS has to be assumed but could not have been quantified with experimental methods yet because the involved uncertainties are larger than the expected impact of motion. This study describes the motion-induced bias on horizontal mean wind speed estimates from FLS with the help of simulations of the lidar sampling pattern of a continuous-wave (CW) velocity–azimuth display (VAD) scanning wind lidar. Analytic modeling is used to validate the simulations. It is found that the mean bias depends on amplitude and frequency of motion, the angle between motion and wind direction, and wind speed and strength of wind shear. The simulations are used to quantify the measurement deviation that is caused by motion for the example of the Fugro SEAWATCH Wind LiDAR Buoy (SWLB) carrying a ZX 300M profiling wind lidar. The strongest bias of −0.67 % of the measurement values was estimated for a test case with “strong” waves aligned with the inflow wind direction. Under “normal” wave conditions the bias is smaller. The reason for these low errors lies in a fortunate combination of the frequencies of lidar prism rotation and tilt motion.

Local and remote forcing on the interannual variations of the sedimentary δ15N in Santa Barbara Basin during the past 80 years

Sedimentary nitrogen isotope (δ15Nsed) in Santa Barbara Basin (SBB) has been mostly interpreted as the record of the eastern tropical North Pacific (ETNP) intermediate water denitrification process. Nevertheless, debate remains regarding sources and control mechanisms of δ15Nsed signal in SBB. Multi-proxy analyses including δ15Nsed, total organic carbon (TOC), total nitrogen (TN), C/N ratio, and marine biomarkers were performed on a 46-cm sediment core (SBB-190629) collected from SBB in 2019. The core was dated with varve counting and 210Pb dating method, showing a depositional history of 1938–2019 CE with a sedimentation rate of 0.564 cm/year. The findings show that the δ15Nsed record (at ~0.25-year resolution) ranges from 6.24‰ to 7.43‰, which was affected by both local and remote forcing. The long-term variations of the SBB δ15Nsed signature show a general decreasing trend from 1940 to the late 1980s, low values during 1980~2000, and an increase afterward, which is thought to reflect changes in ETNP denitrification induced by the strength of tropical trade winds. Our results also reveal a series of abrupt annual to multiannual changes, superimposed on the long-term variation mentioned above. The SBB local δ15N signal (Δδ15NSBB) is accessed by using the deviation from the mean δ15N (Δδ15N) of SBB-190629 to subtract the Δδ15N of the ETNP. The Δδ15NSBB record compares well with redox-sensitive proxies (Re/Mo ratio and C29 stanol/stenol ratio) from the SBB bottom water and with the OCmarine content calculated based on the C/N ratio mixing model, indicating that the Δδ15NSBB is mainly controlled by bottom water denitrification, which was induced by the change of upwelling intensity and marine productivity. Since various climatic factors (e.g., El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Pacific Gyre Oscillation (NPGO)) have different impacts on the upwelling intensity (hence the marine productivity and denitrification) in SBB on different timescales, the influence of combined climatic factors on SBB denitrification is time dependent.

The IACOB project

Context. Stellar rotation is of key importance in the formation process, the evolution, and the final fate of massive stars. Aims. We perform a reassessment of the empirical rotational properties of Galactic massive O-type stars using the results from a detailed analysis of ground-based multi-epoch optical spectra obtained in the framework of the IACOB & OWN surveys. Methods. Using high-quality optical spectroscopy, we established the velocity distribution for a sample of 285 apparently single and single-line spectroscopic binary (SB1) Galactic O-type stars. We also made use of the rest of the parameters from the quantitative spectroscopic analysis presented in prior IACOB papers (mainly Teff, log g, and multiplicity) to study the v sin i behavior and evolution from the comparison of subsamples in different regions of the spectroscopic Hertzsprung–Rusell diagram (sHRD). Our results are compared to the main predictions – regarding current and initial rotational velocities – of two sets of well-established evolutionary models for single stars, as well as from population synthesis simulations of massive stars that include binary interaction. Results. We reassess the known bimodal nature of the v sin i distribution, and find a non-negligible difference between the v sin i distribution of single and SB1 stars. We provide empirical evidence supporting the proposed scenario that the tail of fast rotators is mainly produced by binary interactions. Stars with extreme rotation (>300 km s−1) appear as single stars that are located in the lower zone of the sHRD. We notice little rotational braking during the main sequence, a braking effect independent of mass (and wind strength). The rotation rates of the youngest observed stars lean to an empirical initial velocity distribution with ⪅20% of critical velocity. Lastly, a limit in v sin i detection below 40–50 km s−1 seems to persist, especially in the upper part of the sHRD, possibly associated with the effect of microturbulence in the measurement methodology used.

Evidence for Fluctuating Wind in Shaping an Ancient Martian Dune Field: The Stimson Formation at the Greenheugh Pediment, Gale Crater

AbstractTemporal fluctuations of wind strength and direction can influence aeolian bedform morphology and orientation, which can be encoded into the architecture of aeolian deposits. These strata represent a direct record of atmospheric processes and can be used to understand ancient Martian atmospheric processes as well as those on Earth. The strata can: give insight to ancient atmospheric circulation, how the atmosphere evolved in response to global changes in habitability, and how ancient processes differ from modern processes. The Stimson formation at the Greenheugh pediment (Gale crater) records evidence of fluctuating wind across multiple temporal scales. The strata can be subdivided into three intervals–Gleann Beag, Ladder, and Edinburgh intervals. Internally, the intervals record changes of dune morphology and orientation, correlatable to wind fluctuations at multiple temporal scales. The basal Gleann Beag interval comprises compound cross‐strata, deposited by oblique compound dunes. These dunes record a bimodal wind regime, resulting in net sediment transport toward the north. The Ladder interval records a reversal of sediment transport to the south, where straight‐crested simple‐dunes shaped by a seasonally variable winds formed. Finally, the Edinburgh interval records sediment transport to the west, where a unimodal wind formed sinuous‐crested simple dunes. These observations demonstrate active and variable atmospheric circulation in Gale crater during the accumulation of the Stimson dune field, at multiple temporal scales from seasonally driven winds to much longer time‐frames, during the Hesperian. These observations can be used to further understand ancient atmospheric conditions and processes, at a high temporal resolution on Mars.

에어로졸 입자의 이동, 성장, 소광을 모의하는 3차원 수치모델 개발 II: 흡습성장 및 소광 효과 모의

The model reported in the companion paper was improved further and validated against field experiments. An interpolation subroutine was added to determine the flow field at any input wind speed and temperature conditions from the database prepared using the OpenFOAM simulations. The polydispersity of the aerosol emission is taken into account in the improved model. To account for the growth by condensation without moving the grown particles to larger sections, which causes numerical diffusion, additional variables representing the aerosol water content in each section were added. The coagulation subroutine was accordingly revised to take into account the particle size change due to condensation. The effects of particle hygroscopicity were added in the condensation subroutine. Hygroscopic growth was assumed to be completed instantly after emission because extensive simulations showed that hygroscopic growth reached 90 % of its destination within one time step in most cases. A method to determine the model parameter representing particle hygroscopicity experimentally is suggested. A set of simple field experiments was performed with three different levels of wind strength when wind speed and direction were maintained steady. The observed spatial distribution of aerosol plumes and resulting light extinction showed qualitatively good agreement with model predictions.

Greenhouse Natural Ventilation Models: How Do We Develop with Chinese Greenhouses?

Greenhouse technology has advanced over the past few decades in terms of environmental control (e.g., indoor temperature, relative humidity, and CO2 concentration). Ventilation is an effective way to adjust the indoor climate. Natural ventilation has gained significant research attention recently because of its low energy requirement. To evaluate the ventilation effectiveness, the ventilation rate is often used. This review summarizes the published review papers related to greenhouse ventilation. Ventilation models are reported under different conditions, including wind-induced, buoyancy-induced, and combined effects-induced ventilation in greenhouses. The influencing factors are described, such as the wind and buoyancy strength and distribution, greenhouse geometry, and vent arrangement. Various methods assessing natural ventilation in greenhouses are introduced, consisting of tracer gas techniques, the pressure difference method, the energy balance method, the emptying fluid-filling box method, and numerical simulation. The values of the key coefficients deduced and used in the literature are listed. This paper reports what has been done in the world and where we can start to develop dynamic ventilation models for solar and tunnel-type greenhouses in China. Further valuable investigations are discussed. The pressure distribution function in greenhouses with horizontal openings, a model for cross-ventilation induced by combined wind and buoyancy force, and an analytical plant-considered ventilation model with higher applicability are described. To ensure the accuracy of the ventilation models, other environmental variables, especially geography-dependent ones, can be added. More criteria are suggested to evaluate the ventilation performance rather than the ventilation rate to provide a comprehensive assessment.

Stable Southern Hemisphere westerly winds throughout the Holocene until intensification in the last two millennia

The Southern Hemisphere westerly winds sustain the Southern Ocean’s role as one of Earth’s main carbon sinks, and have helped sequester nearly half the anthropogenic CO2 stored in the ocean. Observations show shifts in the vigor of this climate regulator, but models disagree how future change impacts carbon storage due to scarce baseline data. Here, we use the hydrogen isotope ratios of sedimentary lipids to resolve Holocene changes in Southern Hemisphere westerly wind strength. Our reconstruction reveals stable values until ~2150 years ago when aquatic compounds became more 2H-enriched. We attribute this isotope excursion to wind-driven lake water evaporation, and regional paleoclimate evidence shows it marks a trend towards a negative Southern Annular Mode – the Southern Ocean’s main mode of atmospheric variability. Because this shift is unmatched in the past 7000 years, our findings suggest that previously published millennium-long Southern Annular Mode indices used to benchmark future change may not capture the full range of natural variability.

Observations of the Turkana Jet and the East African Dry Tropics: The RIFTJet Field Campaign

Abstract The Turkana low-level jet (LLJ) is an intrinsic part of the African climate system. It is the principle conduit for water vapor transport to the African interior from the Indian Ocean, and droughts in East Africa tend to occur when the jet is strong. The only direct observations of the Turkana jet come from manual tracking of pilot balloons in the 1980s. Now, modern reanalysis datasets disagree with one another over the strength of jet winds and underestimate the strength of the jet by 25%–75% compared to the pilot balloon data. This article gives an overview of a field campaign based in northwest Kenya—the Radiosonde Investigation for the Turkana Jet (RIFTJet)—which measured the Turkana jet for the first time in 40 years using modern technologies. Radiosonde data reveal a persistent low-level jet, which formed on every night of the campaign, with an average low-level maximum wind speed of 16.8 m s−1 at 0300 LT. One of the latest reanalysis datasets (ERA5) underestimates low-level wind speeds by an average of 24% (4.1 m s−1) at 0300 LT and by 33% (3.6 m s−1) at 1500 LT. The measurements confirm the role of the Turkana LLJ in water vapor transport: mean water vapor transport at Marsabit is 172 kg m s−1. The dataset provides new opportunities to understand regional dynamics, and to evaluate models in one of the most data-sparse regions in the world.

Verifying the efficiency of the Biogents Sentinel trap in the field and investigating microclimatic influences on responding Aedes aegypti behavior.

Successful surveillance and control of mosquito arbovirus vectors requires effective and sensitive trapping methods for adult insects. The Biogents Sentinel (BGS) trap is widely used for mosquito trapping but has low capture efficiency for both female and male Aedes aegypti under semi-field conditions. Efficiency refers to the proportion of mosquitoes that are trapped of those encountering the trap. We verified the efficiency of the BGS under field conditions in suburban Riverside, California, U.S.A., following our previous work determining the efficiency under semi-field conditions in Cairns, Northern Australia. The efficiency of the BGS with CO2 and a human skin odor mimic (BG-Lure) for both Ae. aegypti sexes in the field was 9%. This closely aligns with the results of our previous study, the efficiency for females being 5% and males being 9%. In the present study microclimatic conditions were monitored and capture occurred during periods of significantly lower mean temperature. There were no discernible changes in wind directionality or strength in the 60 s leading up to mosquito capture by the BGS. Our results support our previous findings that capture efficiency of the BGS for Ae. aegypti is low.

Connecting radio emission to AGN wind properties with broad absorption line quasars

ABSTRACT Broad absorption line quasars (BALQSOs) show strong signatures of powerful outflows, with the potential to alter the cosmic history of their host galaxies. These signatures are only seen in ∼10 per cent of optically selected quasars, although the fraction significantly increases in IR and radio selected samples. A proven physical explanation for this observed fraction has yet to be found, along with a determination of why this fraction increases at radio wavelengths. We present the largest sample of radio matched BALQSOs using the LOFAR Two-metre Sky Survey Data Release 2 and employ it to investigate radio properties of BALQSOs. Within the DR2 footprint, there are 3537 BALQSOs from Sloan Digital Sky Survey DR12 with continuum signal-to-noise ≥5. We find radio-detections for 1108 BALQSOs, with an important subpopulation of 120 LoBALs, an unprecedented sample size for radio matched BALQSOs given the sky coverage to date. BALQSOs are a radio-quiet population that show an increase of ×1.50 radio-detection fraction compared to non-BALQSOs. LoBALs show an increase of ×2.22 that of non-BALQSO quasars. We show that this detection fraction correlates with wind-strength, reddening, and C iv emission properties of BALQSOs and that these features may be connected, although no single property can fully explain the enhanced radio detection fraction. We create composite spectra for subclasses of BALQSOs based on wind strength and colour, finding differences in the absorption profiles of radio-detected and radio-undetected sources, particularly for LoBALs. Overall, we favour a wind-ISM interaction explanation for the increased radio-detection fraction of BALQSOs.

Regional validation of the use of diatoms in ice cores from the Antarctic Peninsula as a Southern Hemisphere westerly wind proxy

Abstract. The Southern Hemisphere westerly winds are among the most important drivers of recently observed environmental changes in West Antarctica. However, the lack of long-term wind records in this region hinders our ability to assess the long-term context of these variations. Ice core proxy records yield valuable information about past environmental changes, although current proxies present limitations when aiming to reconstruct past winds. Here we present the first regional wind study based on the novel use of diatoms preserved in Antarctic ice cores. We assess the temporal variability in diatom abundance and its relation to regional environmental parameters spanning a 20-year period across three sites in the southern Antarctic Peninsula and Ellsworth Land, Antarctica. Correlation analyses reveal that the temporal variability of diatom abundance from high-elevation ice core sites is driven by changes in wind strength over the core of the Southern Hemisphere westerly wind belt, validating the use of diatoms preserved in ice cores from high-elevation inland sites in the southern Antarctic Peninsula and Ellsworth Land as a proxy for reconstructing past variations in wind strength over the Pacific sector of the Southern Hemisphere westerly wind belt.

Modeling Acoustic Channel Variability in Underwater Network Simulators from Real Field Experiment Data

The underwater acoustic channel is remarkably dependent on the considered scenario and the environmental conditions. In fact, channel impairments differ significantly in shallow water with respect to deep water, and the presence of external factors such as snapping shrimps, bubbles, rain, or ships passing nearby, changes of temperature, and wind strength can change drastically the link quality in different seasons and even during the same day. Legacy mathematical models that consider these factors exist, but are either not very accurate, like the Urick model, or very computationally demanding, like the Bellhop ray tracer. Deterministic models based on lookup tables (LUTs) of sea trial measurements are widely used by the research community to simulate the acoustic channel in order to verify the functionalities of a network in certain water conditions before the actual deployment. These LUTs can characterize the link quality by observing, for instance, the average packet error rate or even a time varying packet error rate computed within a certain time window. While this procedure characterizes well the acoustic channel, the obtained simulation results are limited to a single channel realization, making it hard to fully evaluate the acoustic network in different conditions. In this paper, we discuss the development of a statistical channel model based on the analysis of real field experiment data, and compare its performance with the other channel models available in the DESERT Underwater network simulator.