On statistical irregularity of stratospheric warming occurrence during northern winters

NASA Astrophysics Data System (ADS)

Savenkova, Elena N.; Gavrilov, Nikolai M.; Pogoreltsev, Alexander I.

2017-10-01

Statistical analysis of dates of warming events observed during the years 1981-2016 at different stratospheric altitudes reveals their non-uniform distributions during northern winter months with maxima at the beginning of January, at the end of January - beginning of February and at the end of February. Climatology of zonal-mean zonal wind, deviations of temperature from its winter-averaged values, and planetary wave (PW) characteristics at high and middle northern latitudes in the altitude range from the ground up to 60 km is studied using the database of meteorological reanalysis MERRA. Climatological temperature deviations averaged over the 60-90°N latitudinal bands reveal cooler and warmer layers descending due to seasonal changes during the polar night. PW amplitudes and upward Eliassen-Palm fluxes averaged over 36 years have periodical maxima with the main maximum at the beginning of January at altitudes 40-50 km. During the above-mentioned intervals of more frequent occurrence of stratospheric warming events, maxima of PW amplitudes and Eliassen-Palm fluxes, also minima of eastward winds in the high-latitude northern stratosphere have been found. Climatological intra-seasonal irregularities of stratospheric warming dates could indicate reiterating phases of stratospheric vacillations in different years.

Cogging Torque Reduction in a Permanent Magnet Wind Turbine Generator: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, E.; Green, J.

2002-01-01

In this paper, we investigate three design options to minimize cogging torque: uniformity of air gap, pole width, and skewing. Although the design improvement is intended for small wind turbines, it is also applicable to larger wind turbines.

30 WS North Base Wind Study

NASA Technical Reports Server (NTRS)

Wheeler, Mark

2011-01-01

The 30 Weather Squadron (30 WS) is concerned about strong winds observed at their northern towers without advance warning. They state that terrain influences along the extreme northern fringes of Vandenberg Air Force Base (VAFB) make it difficult for forecasters to issue timely and accurate high wind warnings for northeasterly wind events. These events tend to occur during the winter or early spring when they are under the influence of the Great Basin high pressure weather regime. The Launch Weather Officers (LWOs) have seen these rapid wind increases in the current northern Towers 60, 70 and 71 in excess of their 35 kt operational warning threshold. For this task, the 30 WS requested the Applied Meteorology Unit (AMU) analyze data from days when these towers reported winds in excess of 35 kt and determine if there were any precursors in the observations that would allow the LWOs to better forecast and warn their operational customers for these wind events. The 30 WS provided wind tower data for the cool season (October - March) from the period January 2004-March 20 IO. The AMU decoded and evaluated the wind tower data for 66 days identified by the 30 WS as having high-wind events. Out of the 66 event days, only 30 had wind speed observations of > or =35 kt from at least one of the three northern towers. The AMU analyzed surface and upper air charts to determine the synoptic conditions for each event day along with tower peak wind speed and direction time series and wind rose charts for all 30 event days. The analysis revealed a trend on all event days in which the tower winds shifted to the northeast for a period of time before the first recorded > or =35 kt wind speed. The time periods for the 30 event days ranged from 20 minutes to several hours, with a median value of 110 minutes. This trend, if monitored, could give the 30 WS forecasters a precursor to assist in issuing an operational warning before a high wind event occurs. The AMU recommends developing a high-wind alert capability for VAFB using a local mesoscale model to forecast these wind events. The model should incorporate all of the VAFB local data sets and have a forecast capability of between 2 to 24 hours. Such a model would allow the meteorologists at VAFB to alert the operational customers of high wind events in a timely manner so protective action could be taken.

Session: Development and application of guidelines for siting, constructing, operating and monitoring wind turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manville, Albert; Hueckel, Greg

2004-09-01

This session at the Wind Energy and Birds/Bats workshop consisted of two presentations followed by a discussion/question and answer period. The two papers were: 'Development and Application of USFWS Guidance for Site Evaluation, Siting, Construction, Operation and Monitoring of Wind Turbines' by Albert Manville and 'Wind Power in Washington State' by Greg Hueckel. The session provided a comparison of wind project guidelines developed by the U.S. Fish and Wildlife Service (USFWS) in May 2003 and the Washington State Department of Fish and Wildlife in August 2003. Questions addressed included: is there a need or desire for uniform national or statemore » criteria; can other states learn from Washington State's example, or from the USFWS voluntary guidelines; should there be uniform requirements/guidelines/check-lists for the siting, operation, monitoring, and mitigation to prevent or minimize avian, bat, and other wildlife impacts.« less

Response of the coupled M-I-T system to the March 17, 2015 solar wind dynamic pressure enhancement event

NASA Astrophysics Data System (ADS)

Ozturk, D. S.; Zou, S.; Slavin, J. A.; Ridley, A. J.

2017-12-01

When the solar wind dynamic pressure is enhanced, it could perturb the global magnetosphere-ionosphere-thermosphere (M-I-T) system. The most notable indicators of such disruptions are changes in Field-Aligned Currents (FACs), ionospheric convection patterns and magnetic perturbations observed by ground magnetometers. The link between dynamic pressure enhancements and FACs has been well established, but studies on how these FACs affect the ionosphere-thermosphere system are very limited. In order to understand the large-scale dynamic processes in the M-I-T system due to the solar wind dynamic pressure enhancement, we study the 17 March 2015 event in detail. This is one of the most geoeffective events of the solar cycle 24 with Dst minimum of -222 nT. The Wind spacecraft recorded a two-step increment in the solar wind dynamic pressure, from 2 nPa to 12 nPa within 3 minutes, while the IMF Bz stayed northward. We used the University of Michigan Block Adaptive Tree Solarwind Roe Upwind Scheme (BATS'R'US), global MHD code to study the generation and propagation of perturbations associated with the compression of the magnetosphere. To effectively represent the coupled magnetosphere-ionosphere system, we included the Global Magnetosphere (GM), Inner Magnetosphere (IM) and Ionospheric electrodynamic (IE) modules. 600 uniformly distributed virtual magnetometers are included in the simulation to identify the magnetic perturbations associated with the FAC pairs as well as their temporal and spatial variations. In addition, we used the IE module output to drive the University of Michigan Global Ionosphere Thermosphere Model (GITM) to study how the I-T system responds to dynamic pressure enhancement. We show that as a result of the solar wind dynamic pressure enhancement, two pair of perturbation FACs develop in addition to the NBZ current system. These FACs significantly alter the ionospheric convection profile and create elongated vortices that propagate from dayside to nightside. The ion temperature at the location of these vortices is significantly and immediately enhanced. We analyzed the altitude profiles of plasma temperature, electron density and joule heating to quantitatively understand energy deposition during this process, and compare them with observations from ground-based incoherent scatter radar.

The Seasonal Predictability of Extreme Wind Events in the Southwest United States

NASA Astrophysics Data System (ADS)

Seastrand, Simona Renee

Extreme wind events are a common phenomenon in the Southwest United States. Entities such as the United States Air Force (USAF) find the Southwest appealing for many reasons, primarily for the an expansive, unpopulated, and electronically unpolluted space for large-scale training and testing. However, wind events can cause hazards for the USAF including: surface wind gusts can impact the take-off and landing of all aircraft, can tip the airframes of large wing-surface aircraft during the performance of maneuvers close to the ground, and can even impact weapons systems. This dissertation is comprised of three sections intended to further our knowledge and understanding of wind events in the Southwest. The first section builds a climatology of wind events for seven locations in the Southwest during the twelve 3-month seasons of the year. The first section further examines the wind events in relation to terrain and the large-scale flow of the atmosphere. The second section builds upon the first by taking the wind events and generating mid-level composites for each of the twelve 3-month seasons. In the third section, teleconnections identified as consistent with the large-scale circulation in the second paper were used as predictor variables to build a Poisson regression model for each of the twelve 3-month seasons. The purpose of this research is to increase our understanding of the climatology of extreme wind events, increase our understanding of how the large-scale circulation influences extreme wind events, and create a model to enhance predictability of extreme wind events in the Southwest. Knowledge from this paper will help protect personnel and property associated with not only the USAF, but all those in the Southwest.

North Atlantic storm driving of extreme wave heights in the North Sea

NASA Astrophysics Data System (ADS)

Bell, R. J.; Gray, S. L.; Jones, O. P.

2017-04-01

The relationship between storms and extreme ocean waves in the North Sea is assessed using a long-period wave data set and storms identified in the Interim ECMWF Re-Analysis (ERA-Interim). An ensemble sensitivity analysis is used to provide information on the spatial and temporal forcing from mean sea-level pressure and surface wind associated with extreme ocean wave height responses. Extreme ocean waves in the central North Sea arise due to intense extratropical cyclone winds from either the cold conveyor belt (northerly-wind events) or the warm conveyor belt (southerly-wind events). The largest wave heights are associated with northerly-wind events which tend to have stronger wind speeds and occur as the cold conveyor belt wraps rearward round the cyclone to the cold side of the warm front. The northerly-wind events provide a larger fetch to the central North Sea to aid wave growth. Southerly-wind events are associated with the warm conveyor belts of intense extratropical cyclones that develop in the left upper tropospheric jet exit region. Ensemble sensitivity analysis can provide early warning of extreme wave events by demonstrating a relationship between wave height and high pressure to the west of the British Isles for northerly-wind events 48 h prior. Southerly-wind extreme events demonstrate sensitivity to low pressure to the west of the British Isles 36 h prior.

Osan AB, Korea. Revised Uniform Summary of Surface Weather Observations (RUSSWO). Parts A-F.

DTIC Science & Technology

1982-06-14

USAFETAC SURFACE WINDS2 AIR WATHER SERVICE/MAC PERCENTAGE FREQUENCY OF WIND DIRECTION AND SPEED (FROM HOURLY OBSERVATIONS) 1471220 OSAN AS KO 73-S1 FED...BRANCHusAF’TAC SURFACE WINDS AIR WATHER SERVICE/MAC PERCENTAGE FREQUENCY OF WIND DIRECTION AND SPEED (FROM HOURLY OBSERVATIONS) 47122’ OSAN AS KO 73-81 NOV _RLL

Heat waves in Senegal : detection, characterization and associated processes.

NASA Astrophysics Data System (ADS)

Gnacoussa Sambou, Marie Jeanne; Janicot, Serge; Badiane, Daouda; Pohl, Benjamin; Dieng, Abdou L.; Gaye, Amadou T.

2017-04-01

Atmospheric configuration and synoptic evolution of patterns associated with Senegalese heat wave (HW) are examined on the period 1979-2014 using the Global Surface Summary of the Day (GSOD) observational database and ERA-Interim reanalysis. Since there is no objective and uniform definition of HW events, threshold methods based on atmospheric variables as daily maximum (Tmax) / minimum (Tmin) temperatures and daily mean apparent temperature (AT) are used to define HW threshold detection. Each criterion is related to a specific category of HW events: Tmax (warm day events), Tmin (warm night events) and AT (combining temperature and moisture). These definitions are used in order to characterize as well as possible the warm events over the Senegalese regions (oceanic versus continental region). Statistics on time evolution and spatial distribution of warm events are carried out over the 2 seasons of maximum temperature (March-May and October-November). For each season, a composite of HW events, as well as the most extended event over Senegal (as a case study) are analyzed using usual atmospheric fields (sea level pressure, geopotential height, total column water content, wind components, 2m temperature). This study is part of the project ACASIS (https://acasis.locean-ipsl.upmc.fr/doku.php) on heat waves occurrences over the Sahel and their impact on health. Keywords: heat wave, Senegal, ACASIS.

Some calculated effects of non-uniform inflow on the radiated noise of a large wind turbine

NASA Technical Reports Server (NTRS)

Greene, G. C.; Hubbard, H. H.

1980-01-01

Far field computations were performed for a large wind turbine to evaluate the effects of non-uniform aerodynamic loading over the rotor disk. A modified version of the Farassat/Nystrom propeller noise prediction program was applied to account for the variations in loading due to inflow interruption by the upstream support tower. The computations indicate that for the uniform inflow case, relatively low noise levels are generated and the first rotational harmonic dominated the spectrum. For cases representing wake flow deficiences due to the tower structure, subtantially increased noise levels for all harmonics are indicated, the greatest increases being associated with the higher order harmonics.

Taylor dispersion in wind-driven current

NASA Astrophysics Data System (ADS)

Li, Gang; Wang, Ping; Jiang, Wei-Quan; Zeng, Li; Li, Zhi; Chen, G. Q.

2017-12-01

Taylor dispersion associated with wind-driven currents in channels, shallow lakes and estuaries is essential to hydrological environmental management. For solute dispersion in a wind-driven current, presented in this paper is an analytical study of the evolution of concentration distribution. The concentration moments are intensively derived for an accurate presentation of the mean concentration distribution, up to the effect of kurtosis. The vertical divergence of concentration is then deduced by Gill's method of series expansion up to the fourth order. Based on the temporal evolution of the vertical concentration distribution, the dispersion process in the wind-driven current is concretely characterized. The uniform shear leads to a special symmetrical distribution of mean concentration free of skewness. The non-uniformity of vertical concentration is caused by convection and smeared out gradually by the effect of diffusion, but fails to disappear even at large times.

Uniformly wound superconducting coil and method of making same

DOEpatents

Mookerjee, S.; Weijun, S.; Yager, B.

1994-03-08

A coil of superconducting wire for a superconducting magnet is described having a relatively dense and uniformly spaced winding to enhance the homogeneity and strength of the magnetic field surrounding the coil and a method of winding the same wherein the mandrel used to wind said coil comprises removable spacers and retainers forming a plurality of outwardly opening slots, each of said slots extending generally about the periphery of the mandrel and being sized to receive and outwardly align and retain successive turns of the superconducting wire within each slot as the wire is wound around and laterally across the mandrel to form a plurality of wire ribbons of a predetermined thickness laterally across the mandrel. 8 figures.

Uniformly wound superconducting coil and method of making same

DOEpatents

Mookerjee, Sumit; Weijun, Shen; Yager, Billy

1994-01-01

A coil of superconducting wire for a superconducting magnet having a relaely dense and uniformly spaced winding to enhance the homogeneity and strength of the magnetic field surrounding the coil and a method of winding the same wherein the mandrel used to wind said coil comprises removable spacers and retainers forming a plurality of outwardly opening slots, each of said slots extending generally about the periphery of the mandrel and being sized to receive and outwardly align and retain successive turns of the superconducting wire within each slot as the wire is wound around and laterally across the mandrel to form a plurality of wire ribbons of a predetermined thickness laterally across the mandrel.

A comparison of methods for assessing power output in non-uniform onshore wind farms

DOE PAGES

Staid, Andrea; VerHulst, Claire; Guikema, Seth D.

2017-10-02

Wind resource assessments are used to estimate a wind farm's power production during the planning process. It is important that these estimates are accurate, as they can impact financing agreements, transmission planning, and environmental targets. Here, we analyze the challenges in wind power estimation for onshore farms. Turbine wake effects are a strong determinant of farm power production. With given input wind conditions, wake losses typically cause downstream turbines to produce significantly less power than upstream turbines. These losses have been modeled extensively and are well understood under certain conditions. Most notably, validation of different model types has favored offshoremore » farms. Models that capture the dynamics of offshore wind conditions do not necessarily perform equally as well for onshore wind farms. We analyze the capabilities of several different methods for estimating wind farm power production in 2 onshore farms with non-uniform layouts. We compare the Jensen model to a number of statistical models, to meteorological downscaling techniques, and to using no model at all. In conclusion, we show that the complexities of some onshore farms result in wind conditions that are not accurately modeled by the Jensen wake decay techniques and that statistical methods have some strong advantages in practice.« less

A comparison of methods for assessing power output in non-uniform onshore wind farms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staid, Andrea; VerHulst, Claire; Guikema, Seth D.

Wind resource assessments are used to estimate a wind farm's power production during the planning process. It is important that these estimates are accurate, as they can impact financing agreements, transmission planning, and environmental targets. Here, we analyze the challenges in wind power estimation for onshore farms. Turbine wake effects are a strong determinant of farm power production. With given input wind conditions, wake losses typically cause downstream turbines to produce significantly less power than upstream turbines. These losses have been modeled extensively and are well understood under certain conditions. Most notably, validation of different model types has favored offshoremore » farms. Models that capture the dynamics of offshore wind conditions do not necessarily perform equally as well for onshore wind farms. We analyze the capabilities of several different methods for estimating wind farm power production in 2 onshore farms with non-uniform layouts. We compare the Jensen model to a number of statistical models, to meteorological downscaling techniques, and to using no model at all. In conclusion, we show that the complexities of some onshore farms result in wind conditions that are not accurately modeled by the Jensen wake decay techniques and that statistical methods have some strong advantages in practice.« less

Windstorm Impact Reduction Implementation Plan

DTIC Science & Technology

2007-01-01

wind events, including hurricanes, tornadoes and straight line winds from thunderstorms. This information is repeated in brief during severe weather...event documentation and damage analyses. Better understanding of atmospheric dynamics of straight - line winds Wind observing systems and...Developed techniques for improved extreme wind speed maps Investigation of straight - line winds Wind speed and direction analysis for input to

Radiometric correction of scatterometric wind measurements

NASA Technical Reports Server (NTRS)

1995-01-01

Use of a spaceborne scatterometer to determine the ocean-surface wind vector requires accurate measurement of radar backscatter from ocean. Such measurements are hindered by the effect of attenuation in the precipitating regions over sea. The attenuation can be estimated reasonably well with the knowledge of brightness temperatures observed by a microwave radiometer. The NASA SeaWinds scatterometer is to be flown on the Japanese ADEOS2. The AMSR multi-frequency radiometer on ADEOS2 will be used to correct errors due to attenuation in the SeaWinds scatterometer measurements. Here we investigate the errors in the attenuation corrections. Errors would be quite small if the radiometer and scatterometer footprints were identical and filled with uniform rain. However, the footprints are not identical, and because of their size one cannot expect uniform rain across each cell. Simulations were performed with the SeaWinds scatterometer (13.4 GHz) and AMSR (18.7 GHz) footprints with gradients of attenuation. The study shows that the resulting wind speed errors after correction (using the radiometer) are small for most cases. However, variations in the degree of overlap between the radiometer and scatterometer footprints affect the accuracy of the wind speed measurements.

C3Winds: A Novel 3D Wind Observing System to Characterize Severe Weather Events

NASA Astrophysics Data System (ADS)

Kelly, M. A.; Wu, D. L.; Yee, J. H.; Boldt, J.; Demajistre, R.; Reynolds, E.; Tripoli, G. J.; Oman, L.; Prive, N.; Heidinger, A. K.; Wanzong, S.

2015-12-01

The CubeSat Constellation Cloud Winds (C3Winds) is a NASA Earth Venture Instrument (EV-I) concept with the primary objective to resolve high-resolution 3D dynamic structures of severe wind events. Rapid evolution of severe weather events highlights the need for high-resolution mesoscale wind observations. Yet mesoscale observations of severe weather dynamics are quite rare, especially over the ocean where extratropical and tropical cyclones (ETCs and TCs) can undergo explosive development. Measuring wind velocity at the mesoscale from space remains a great challenge, but is critically needed to understand and improve prediction of severe weather and tropical cyclones. Based on compact, visible/IR imagers and a mature stereoscopic technique, C3Winds has the capability to measure high-resolution (~2 km) cloud motion vectors and cloud geometric heights accurately by tracking cloud features from two formation-flying CubeSats, separated by 5-15 minutes. Complementary to lidar wind measurements from space, C3Winds will provide high-resolution wind fields needed for detailed investigations of severe wind events in occluded ETCs, rotational structures inside TC eyewalls, and ozone injections associated with tropopause folding events. Built upon mature imaging technologies and long history of stereoscopic remote sensing, C3Winds provides an innovative, cost-effective solution to global wind observations with the potential for increased diurnal sampling via CubeSat constellation.

Northerly surface winds over the eastern North Pacific Ocean in spring and summer

USGS Publications Warehouse

Taylor, S.V.; Cayan, D.R.; Graham, N.E.; Georgakakos, K.P.

2008-01-01

Persistent spring and summer northerly surface winds are the defining climatological feature of the western coast of North America, especially south of the Oregon coast. Northerly surface winds are important for upwelling and a vast array of other biological, oceanic, and atmospheric processes. Intermittence in northerly coastal surface wind is characterized and wind events are quantitatively defined using coastal buoy data south of Cape Mendocino on the northern California coast. The defined wind events are then used as a basis for composites in order to explain the spatial evolution of various atmospheric and oceanic processes. Wind events involve large-scale changes in the three-dimensional atmospheric circulation including the eastern North Pacific subtropical anticyclone and southeast trade winds. Composites of QSCAT satellite scatterometer wind estimates from 1999 to 2005 based on a single coastal buoy indicate that wind events typically last 72-96 h and result in anomalies in surface wind and Ekman pumping that extend over 1000 kin from the west coast of North America. It may be useful to consider ocean circulation and dependent ecosystem dynamics and the distribution of temperature, moisture, and aerosols in the atmospheric boundary layer in the context of wind events defined herein. Copyright 2008 by the American Geophysical Union.

THE EFFECT OF INTERMITTENT GYRO-SCALE SLAB TURBULENCE ON PARALLEL AND PERPENDICULAR COSMIC-RAY TRANSPORT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Roux, J. A.

Earlier work based on nonlinear guiding center (NLGC) theory suggested that perpendicular cosmic-ray transport is diffusive when cosmic rays encounter random three-dimensional magnetohydrodynamic turbulence dominated by uniform two-dimensional (2D) turbulence with a minor uniform slab turbulence component. In this approach large-scale perpendicular cosmic-ray transport is due to cosmic rays microscopically diffusing along the meandering magnetic field dominated by 2D turbulence because of gyroresonant interactions with slab turbulence. However, turbulence in the solar wind is intermittent and it has been suggested that intermittent turbulence might be responsible for the observation of 'dropout' events in solar energetic particle fluxes on small scales.more » In a previous paper le Roux et al. suggested, using NLGC theory as a basis, that if gyro-scale slab turbulence is intermittent, large-scale perpendicular cosmic-ray transport in weak uniform 2D turbulence will be superdiffusive or subdiffusive depending on the statistical characteristics of the intermittent slab turbulence. In this paper we expand and refine our previous work further by investigating how both parallel and perpendicular transport are affected by intermittent slab turbulence for weak as well as strong uniform 2D turbulence. The main new finding is that both parallel and perpendicular transport are the net effect of an interplay between diffusive and nondiffusive (superdiffusive or subdiffusive) transport effects as a consequence of this intermittency.« less

Effects of Cross-axis Wind Jet Events on the Northern Red Sea Circulation

NASA Astrophysics Data System (ADS)

Menezes, V. V.; Bower, A. S.; Farrar, J. T.

2016-12-01

Despite its small size, the Red Sea has a complex circulation. There are boundary currents in both sides of the basin, a meridional overturning circulation, water mass formation in the northern part and an intense eddy activity. This complex pattern is driven by strong air-sea interactions. The Red Sea has one of the largest evaporation rates of the global oceans (2m/yr), an intricate and seasonally varying wind pattern. The winds blowing over the Northern Rea Sea (NRS, north of 20N) are predominantly southeastward along the main axis all year round; in the southern, they reverse seasonally due to the monsoonal regime. Although the winds are mostly along-axis in the NRS, several works have shown that sometimes during the boreal winter, the winds blow in a cross-axis direction. The westward winds from Saudi Arabia bring relatively cold dry air and dust from the desert, enhancing heat loss and evaporation off the Red Sea. These wind-jet events may contribute to increased eddy activity and are a trigger for water mass formation. Despite that, our knowledge about the cross-axis winds and their effect on NRS circulation is still incipient. In the present work we analyze 10-years of Quikscat scatterometer winds and altimetric sea surface height anomalies, together with 2-yrs of mooring data, to characterize the westward wind jet events and their impacts on the circulation. We show that the cross-axis winds are, indeed, an important component of the wind regime, explaining 11% of wind variability of the NRS (well-described by a 2nd EOF mode). The westward events occur predominantly in the winter, preferentially in January (about 15 events in 10-years) and have a mean duration of 4-5 days, with a maximum of 12 days (north of 22N). There are around 6 events per year, but in 2002-2003 and 2007-2008, twice more events were detected. The westward wind events are found to strongly modify the wind stress curl, causing a distinct positive/negative curl pattern along the main axis. This pattern enhances the eddy activity and impacts the NRS circulation.

The Solar Wind Depletion (SWD) event of 26 April 1999: Triggering of an auroral pseudobreakup event

NASA Technical Reports Server (NTRS)

Zhou, X.; Tsurutani, B.; Gonzalez, W.

2000-01-01

The interplanetary solar wind depletion (SWD) event of 26 April 1999 and its magnetospheric consequences are examined. The SWD event is characterized by a solar wind density decrease from [similar to] 3.0 to 0.7 cm(sup -3) leading to a solar wind ram pressure decrease from [similar to] 2.0 to 0.2 nPa. This SWD onset is followed by a dipolarization of nightside magnetospheric fields.

A summary of wind power prediction methods

NASA Astrophysics Data System (ADS)

Wang, Yuqi

2018-06-01

The deterministic prediction of wind power, the probability prediction and the prediction of wind power ramp events are introduced in this paper. Deterministic prediction includes the prediction of statistical learning based on histor ical data and the prediction of physical models based on NWP data. Due to the great impact of wind power ramp events on the power system, this paper also introduces the prediction of wind power ramp events. At last, the evaluation indicators of all kinds of prediction are given. The prediction of wind power can be a good solution to the adverse effects of wind power on the power system due to the abrupt, intermittent and undulation of wind power.

A comparison of three approaches for simulating fine-scale surface winds in support of wildland fire management: Part I. Model formulation and comparison against measurements

Treesearch

Jason M. Forthofer; Bret W. Butler; Natalie S. Wagenbrenner

2014-01-01

For this study three types of wind models have been defined for simulating surface wind flow in support of wildland fire management: (1) a uniform wind field (typically acquired from coarse-resolution (,4 km) weather service forecast models); (2) a newly developed mass-conserving model and (3) a newly developed mass and momentumconserving model (referred to as the...

Wind Energy Conference, Boulder, Colo., April 9-11, 1980, Technical Papers

NASA Astrophysics Data System (ADS)

1980-03-01

Papers are presented concerning the technology, and economics of wind energy conversion systems. Specific topics include the aerodynamic analysis of the Darrieus rotor, the numerical calculation of the flow near horizontal-axis wind turbine rotors, the calculation of dynamic wind turbine rotor loads, markets for wind energy systems, an oscillating-wing windmill, wind tunnel tests of wind rotors, wind turbine generator wakes, the application of a multi-speed electrical generator to wind turbines, the feasibility of wind-powered systems for dairy farms, and wind characteristics over uniform and complex terrain. Attention is also given to performance tests of the DOE/NASA MOD-1 2000-kW wind turbine generator, the assessment of utility-related test data, offshore wind energy conversion systems, and the optimization of wind energy utilization economics through load management.

How Well Can the Observed Flux Ropes in the Solar Wind be Fitted by a Uniform-twist Flux Rope Model?

NASA Astrophysics Data System (ADS)

Wang, Y.

2015-12-01

In the solar wind, flux ropes, e.g., magnetic clouds (MCs), are a frequently observational phenomenon. Their magnetic field configuration or the way that the field lines wind around the flux rope axis is one of the most important information to understand the formation and evolution of the observed flux ropes. Most MCs are believed to be in the force-free state, and widely modeled by the Lundquist force-free solution, in which the twist of the field line increases from zero at the axis to infinity at the boundary. However, Lundquist solution is not the only form of a force-free magnetic field. Some studies based on suprathermal electron observations and models have shown that MCs may carry magnetic field lines more likely to be uniformly twisted. The nonlinear force-free field extrapolation of solar magnetic field also suggests that the field lines of a flux rope twist limitedly. In this study, we have developed a velocity-modified uniform-twist force-free flux rope model, and fit observed MCs with this model. By using this approach, we test how well the observed MCs can be fitted into a uniform-twist flux rope. Some interesting results will be given in this presentation.

Taking advantage of modern turbines

NASA Astrophysics Data System (ADS)

Thresher, Robert

2018-06-01

Wind facilities have generally deployed turbines of the same power and height in regular uniform arrays. Now, the modern generation of turbines, with customer-selectable tower heights and larger rotors, can significantly increase wind energy's economic potential using less land to generate cheaper electricity.

Flowfield measurements in the NASA Lewis Research Center 9- by 15-foot low-speed wind tunnel

NASA Technical Reports Server (NTRS)

Hughes, Christopher E.

1989-01-01

An experimental investigation was conducted in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel to determine the flow characteristics in the test section during wind tunnel operation. In the investigation, a 20-probe horizontally-mounted Pitot-static flow survey rake was used to obtain cross-sectional total and static pressure surveys at four axial locations in the test section. At each axial location, the cross-sectional flowfield surveys were made by repositioning the Pitot-static flow survey rake vertically. In addition, a calibration of the new wind tunnel rake instrumentation, used to determine the wind tunnel operating conditions, was performed. Boundary laser surveys were made at three axial locations in the test section. The investigation was conducted at tunnel Mach numbers 0.20, 0.15, 0.10, and 0.05. The test section profile results from the investigation indicate that fairly uniform total pressure profiles (outside the test section boundary layer) and fairly uniform static pressure and Mach number profiles (away from the test section walls and downstream of the test section entrance) exist throughout in the wind tunnel test section.

Fine-tuning of process conditions to improve product uniformity of polystyrene particles used for wind tunnel velocimetry

NASA Technical Reports Server (NTRS)

Ray, Asit K.

1990-01-01

Monodisperse polymer particles (having uniform diameter) were used for the last two decades in physical, biological, and chemical sciences. In NASA Langley Research Center monodisperse polystyrene particles are used in wind tunnel laser velocimeters. These polystyrene (PS) particles in latex form were formulated at the Engineering Laboratory of FENGD using emulsion-free emulsion polymerization. Monodisperse PS latices particles having different particle diameters were formulated and useful experimental data involving effects of process conditions on particle size were accumulated. However, similar process conditions and chemical recipes for polymerization of styrene monomer have often yielded monodisperse particles having varying diameters. The purpose was to improve the PS latex product uniformity by fine-tuning the process parameters based on the knowledge of suspension and emulsion polymerization.

Main Properties of Forbush Effects Related to High-Speed Streams from Coronal Holes

NASA Astrophysics Data System (ADS)

Melkumyan, A. A.; Belov, A. V.; Abunina, M. A.; Abunin, A. A.; Eroshenko, E. A.; Oleneva, V. A.; Yanke, V. G.

2018-03-01

The IZMIRAN database of Forbush effects and interplanetary disturbances was used to study features of the action of high-speed solar wind streams from coronal holes on cosmic rays. Three hundred and fifty Forbush effects created by coronal holes without other actions were distinguished. The mean values and distributions have been found for different characteristics of events from this group and compared with all Forbush effects and Forbush effects caused by coronal ejections. Despite the great differences in high-speed streams from coronal holes, this group turned out to be more compact and uniform as compared to events related to coronal ejections. Regression dependences and correlation relations between different parameters of events for the studied groups have been obtained. It has been shown that Forbush effects caused by coronal ejections depend considerably more strongly on the characteristics of interplanetary disturbances as compared to Forbush effects related to coronal holes. This suggests a significant difference between the modulation mechanisms of Forbush effects of different types and corroborates earlier conclusions based on indirect data.

Taking advantage of modern turbines

DOE PAGES

Thresher, Robert

2018-05-14

Here, wind facilities have generally deployed turbines of the same power and height in regular uniform arrays. Now, the modern generation of turbines, with customer-selectable tower heights and larger rotors, can significantly increase wind energy's economic potential using less land to generate cheaper electricity.

Taking advantage of modern turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thresher, Robert

Here, wind facilities have generally deployed turbines of the same power and height in regular uniform arrays. Now, the modern generation of turbines, with customer-selectable tower heights and larger rotors, can significantly increase wind energy's economic potential using less land to generate cheaper electricity.

Performance of wind turbines in a turbulent atmosphere

NASA Technical Reports Server (NTRS)

Sundar, R. M.; Sullivan, J. P.

1981-01-01

The effect of atmospheric turbulence on the power fluctuations of large wind turbines was studied. The significance of spatial non-uniformities of the wind is emphasized. The turbulent wind with correlation in time and space is simulated on the computer by Shinozukas method. The wind turbulence is modelled according to the Davenport spectrum with an exponential spatial correlation function. The rotor aerodynamics is modelled by simple blade element theory. Comparison of the spectrum of power output signal between 1-D and 3-D turbulence, shows the significant power fluctuations centered around the blade passage frequency.

10 CFR Appendix A to Subpart K of... - Uniform Test Method for Measuring the Energy Consumption of Distribution Transformers

Code of Federal Regulations, 2014 CFR

2014-01-01

... Uniform Test Method is used to test more than one unit of a basic model to determine the efficiency of... one ampere and the test current is limited to 15 percent of the winding current. Connect the... 10 Energy 3 2014-01-01 2014-01-01 false Uniform Test Method for Measuring the Energy Consumption...

Hospital admissions for asthma and acute bronchitis in El Paso, Texas: do age, sex, and insurance status modify the effects of dust and low wind events?

PubMed

Grineski, Sara E; Staniswalis, Joan G; Bulathsinhala, Priyangi; Peng, Yanlei; Gill, Thomas E

2011-11-01

El Paso County (Texas) is prone to still air inversions and is one of the dust "hot spots" in North America. In this context, we examined the sub-lethal effects of airborne dust and low wind events on human respiratory health (i.e., asthma and acute bronchitis) between 2000 and 2003, when 110 dust and 157 low wind events occurred. Because environmental conditions may not affect everyone the same, we explored the effects of dust and low wind within three age groups (children, adults, and the elderly), testing for effect modifications by sex and insurance status, while controlling for weather and air pollutants. We used a case-crossover design using events matched with referent days on the same day-of-the-week, month, and year with conditional logistic regression to estimate the probability of hospital admission, while controlling for apparent temperature (lag 1), nitrogen dioxide, and particulate matter of 2.5μm or less. Children (aged 1-17) were 1.19 (95% confidence interval: 1.00-1.41) times more likely to be hospitalized for asthma three days after a low wind event, and 1.33 (95% CI: 1.01-1.75) times more likely to be hospitalized for acute bronchitis one day after a dust event than on a clear day. Girls were more sensitive to acute bronchitis hospitalizations after dust events (1.83, 95% CI: 1.09-3.08) than boys, but less sensitive than boys to acute bronchitis hospitalizations after low wind events (0.68, 95% CI: 0.46-1.00). We found general trends with regard to dust and low wind events being associated with increased odds of hospitalization for asthma and bronchitis amongst all ages and adults (aged 18-64). Adults covered by Medicaid and adults without health insurance had higher risks of hospitalization for asthma and acute bronchitis after both low wind and dust events. Results suggest that there were respiratory health effects associated with dust and low wind events in El Paso, with stronger impacts among children and poor adults. Girls and boys with acute bronchitis were differentially sensitive to dust and low wind events. Copyright © 2011 Elsevier Inc. All rights reserved.

Hospital admissions for asthma and acute bronchitis in El Paso, Texas: Do age, sex, and insurance status modify the effects of dust and low wind events?

PubMed Central

Staniswalis, Joan G.; Bulathsinhala, Priyangi; Peng, Yanlei; Gill, Thomas E.

2013-01-01

Background El Paso County (Texas) is prone to still air inversions and is one of the dust “hot spots” in North America. In this context, we examined the sub-lethal effects of airborne dust and low wind events on human respiratory health (i.e., asthma and acute bronchitis) between 2000 and 2003, when 110 dust and 157 low wind events occurred. Because environmental conditions may not affect everyone the same, we explored the effects of dust and low wind within three age groups (children, adults, and the elderly), testing for effect modifications by sex and insurance status, while controlling for weather and air pollutants. Methods We used a case-crossover design using events matched with referent days on the same day-of-the-week, month, and year with conditional logistic regression to estimate the probability of hospital admission, while controlling for apparent temperature (lag 1), nitrogen dioxide, and particulate matter of 2.5 micrometers or less. Results Children (aged 1–17) were 1.19 (95% confidence interval: 1.00–1.41) times more likely to be hospitalized for asthma three days after a low wind event, and 1.33 (95% CI: 1.01–1.75) times more likely to be hospitalized for acute bronchitis one day after a dust event than on a clear day. Girls were more sensitive to acute bronchitis hospitalizations after dust events (1.83, 95% CI: 1.09–3.08) than boys, but less sensitive than boys to acute bronchitis hospitalizations after low wind events (0.68, 95% CI: 0.46–1.00). We found general trends with regard to dust and low wind events being associated with increased odds of hospitalization for asthma and bronchitis amongst all ages and adults (aged 18–64). Adults covered by Medicaid and adults without health insurance had higher risks of hospitalization for asthma and acute bronchitis after both low wind and dust event Conclusions Results suggest that there were respiratory health effects associated with dust and low wind events in El Paso, with stronger impacts among children and poor adults. Girls and boys with acute bronchitis were differentially sensitive to dust and low wind events. PMID:21782162

Modeling Planetary Atmospheric Energy Deposition By Energetic Ions

NASA Astrophysics Data System (ADS)

Parkinson, Christopher; Bougher, Stephen; Gronoff, Guillaume; Barthelemy, Mathieu

2016-07-01

The structure, dynamics, chemistry, and evolution of planetary upper atmospheres are in large part determined by the available sources of energy. In addition to the solar EUV flux, the solar wind and solar energetic particle (SEP) events are also important sources. Both of these particle populations can significantly affect an atmosphere, causing atmospheric loss and driving chemical reactions. Attention has been paid to these sources from the standpoint of the radiation environment for humans and electronics, but little work has been done to evaluate their impact on planetary atmospheres. At unmagnetized planets or those with crustal field anomalies, in particular, the solar wind and SEPs of all energies have direct access to the atmosphere and so provide a more substantial energy source than at planets having protective global magnetic fields. Additionally, solar wind and energetic particle fluxes should be more significant for planets orbiting more active stars, such as is the case in the early history of the solar system for paleo-Venus and Mars. Therefore quantification of the atmospheric energy input from the solar wind and SEP events is an important component of our understanding of the processes that control their state and evolution. We have applied a full Lorentz motion particle transport model to study the effects of particle precipitation in the upper atmospheres of Mars and Venus. Such modeling has been previously done for Earth and Mars using a guiding center precipitation model. Currently, this code is only valid for particles with small gyroradii in strong uniform magnetic fields. There is a clear necessity for a Lorentz formulation, hence, a systematic study of the ionization, excitation, and energy deposition has been conducted, including a comparison of the influence relative to other energy sources (namely EUV photons). The result is a robust examination of the influence of energetic ion transport on the Venus and Mars upper atmosphere which will be discussed in this presentation.

Ensemble Forecasting of Coronal Mass Ejections Using the WSA-ENLIL with CONED Model

NASA Technical Reports Server (NTRS)

Emmons, D.; Acebal, A.; Pulkkinen, A.; Taktakishvili, A.; MacNeice, P.; Odstricil, D.

2013-01-01

The combination of the Wang-Sheeley-Arge (WSA) coronal model, ENLIL heliospherical model version 2.7, and CONED Model version 1.3 (WSA-ENLIL with CONED Model) was employed to form ensemble forecasts for 15 halo coronal mass ejections (halo CMEs). The input parameter distributions were formed from 100 sets of CME cone parameters derived from the CONED Model. The CONED Model used image processing along with the bootstrap approach to automatically calculate cone parameter distributions from SOHO/LASCO imagery based on techniques described by Pulkkinen et al. (2010). The input parameter distributions were used as input to WSA-ENLIL to calculate the temporal evolution of the CMEs, which were analyzed to determine the propagation times to the L1 Lagrangian point and the maximum Kp indices due to the impact of the CMEs on the Earth's magnetosphere. The Newell et al. (2007) Kp index formula was employed to calculate the maximum Kp indices based on the predicted solar wind parameters near Earth assuming two magnetic field orientations: a completely southward magnetic field and a uniformly distributed clock-angle in the Newell et al. (2007) Kp index formula. The forecasts for 5 of the 15 events had accuracy such that the actual propagation time was within the ensemble average plus or minus one standard deviation. Using the completely southward magnetic field assumption, 10 of the 15 events contained the actual maximum Kp index within the range of the ensemble forecast, compared to 9 of the 15 events when using a uniformly distributed clock angle.

On WKB expansions for Alfven waves in the solar wind

NASA Technical Reports Server (NTRS)

Hollweg, Joseph V.

1990-01-01

The WKB expansion for 'toroidal' Alfven waves in solar wind, which is described by equations of Heinemann and Olbert (1980), is examined. In this case, the multiple scales method (Nayfeh, 1981) is used to obtain a uniform expansion. It is shown that the WKB expansion used by Belcher (1971) and Hollweg (1973) for Alfven waves in the solar wind is nonuniformly convergent.

On WKB expansions for Alfven waves in the solar wind

NASA Astrophysics Data System (ADS)

Hollweg, Joseph V.

1990-09-01

The WKB expansion for 'toroidal' Alfven waves in solar wind, which is described by equations of Heinemann and Olbert (1980), is examined. In this case, the multiple scales method (Nayfeh, 1981) is used to obtain a uniform expansion. It is shown that the WKB expansion used by Belcher (1971) and Hollweg (1973) for Alfven waves in the solar wind is nonuniformly convergent.

Elemental abundances in corotating events

NASA Technical Reports Server (NTRS)

Vonrosenvinge, T. T.; Mcguire, R. E.

1986-01-01

Large, persistent solar-wind streams in 1973 and 1974 produced corotating interaction regions which accelerated particles to energies of a few MeV/nucleon. The proton to helium ratio (H/He) reported was remarkably constant at a value (22 + or - 5) equal to that in the solar wind (32 + or - 3), suggesting that particles were being accelerated directly out of the solar wind. Preliminary results from a similar study approximately 11 years (i.e., one solar cycle) later are reported. Corotating events were identified by surveying the solar wind data, energetic particle time-histories and anisotropies. This data was all obtained from the ISEE-3/ICE spacecraft. These events also show H/He ratios similar to that in the solar wind. In addition, other corotating events were examined at times when solar flare events could have injected particles into the corresponding corotating interaction regions. It was found that in these cases there is evidence for H/He ratios which are significantly different from that of the solar wind but which are consistent with the range of values found in solar flare events.

Severe flooding along the eastern Adriatic coast: the case of 1 December 2008

NASA Astrophysics Data System (ADS)

Međugorac, Iva; Pasarić, Miroslava; Orlić, Mirko

2015-06-01

This paper addresses an extraordinary storm surge in the Northern Adriatic that was more pronounced on the eastern than on the western shore. On 1 December 2008, Adriatic monitoring stations detected exceptionally high sea levels; the oldest Croatian tide gauge station recorded the highest water level in its operating history at the time. Apart from the Northern Adriatic, large portion of the Dalmatian Coast was also exposed to high water levels, while Venice experienced a less-dramatic event. This marine storm was different from the capital storm of 4 November 1966 during which the surge had the highest impact ahead of Venice and along the north-western coastline. The 2008 event is studied here in detail, and the mechanisms that resulted in the different flooding of the two shores are identified. The study is based on hourly sea level, air pressure and wind data measured along both basin sides together with ECMWF reanalysis fields. Four components of sea-level evolution are identified: the storm surge, tide, Adriatic seiche and, low-frequency variability. The 2008 event was the outcome of a fine interplay between the first three components, which were all superimposed on the raised sea level due to low-frequency variability. The marine storm differed from the 1966 storm in the atmospheric forcing and relative timing of all contributing processes. The 2008 flooding of the eastern coast was mainly due to the Sirocco-wind shear, whereas the 1966 flooding of the western coast was due to the combined effect of almost uniform Sirocco and bottom slope.

Randolph AFB, San Antonio, Texas. Revised Uniform Summary of Surface Weather Observations (RUSSWO)

DTIC Science & Technology

1976-03-19

FoRM ARE oUsoIII ’, " ’ . . . " " -,, ’:,,,:t."," *4 -- ".°" "- . . . " ’ * "- : ; Ir , ( DATA PROCESSING BRANCH EtAC/USAF SURFACE WINDS AIR" WATHER ...FORM ARI OS$Oitlt_ ___ _zT z __ __ ___......- ___ _ _ _ .4. .. . II DATA PROCESSIN G BRASFCH FTAC/USAF SURFACE WINDS AiR WATHER SERVICE/MAC PERCENTAGE...SURFACE WINDS 1 A/R WATHER SERVICE/MAC PERCENTAGE FREQUENCY OF WIND DIRECTION AND SPEED (FROM HOURLY OBSERVATIONS) ( 12911- RANDOLPH AFBJTEXAS/SAN

Wind turbine rotor simulation using the actuator disk and actuator line methods

NASA Astrophysics Data System (ADS)

Tzimas, M.; Prospathopoulos, J.

2016-09-01

The present paper focuses on wind turbine rotor modeling for loads and wake flow prediction. Two steady-state models based on the actuator disk approach are considered, using either a uniform thrust or a blade element momentum calculation of the wind turbine loads. A third model is based on the unsteady-state actuator line approach. Predictions are compared with measurements in wind tunnel experiments and in atmospheric environment and the capabilities and weaknesses of the different models are addressed.

Reconnection-Driven Coronal-Hole Jets with Gravity and Solar Wind

NASA Technical Reports Server (NTRS)

Karpen, J. T.; Devore, C. R.; Antiochos, S. K.; Pariat, E.

2017-01-01

Coronal-hole jets occur ubiquitously in the Sun's coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry,gravity, and solar wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagation is sustained through the outer corona, in the form of a traveling nonlinear Alfven wave front trailed by slower-moving plasma density enhancements that are compressed and accelerated by the wave. This finding agrees well with observations of white-light coronal-hole jets, and can explain microstreams and torsional Alfven waves detected in situ in the solar wind. We also use our numerical results to deduce scaling relationships between properties of the coronal source region and the characteristics of the resulting jet, which can be tested against observations.

Observations and predictability of gap winds in a steep, narrow, fire-prone canyon in central Idaho, USA

NASA Astrophysics Data System (ADS)

Wagenbrenner, N. S.; Forthofer, J.; Gibson, C.; Lamb, B. K.

2017-12-01

Frequent strong gap winds were measured in a deep, steep, wildfire-prone river canyon of central Idaho, USA during July-September 2013. Analysis of archived surface pressure data indicate that the gap wind events were driven by regional scale surface pressure gradients. The events always occurred between 0400 and 1200 LT and typically lasted 3-4 hours. The timing makes these events particularly hazardous for wildland firefighting applications since the morning is typically a period of reduced fire activity and unsuspecting firefighters could be easily endangered by the onset of strong downcanyon winds. The gap wind events were not explicitly forecast by operational numerical weather prediction (NWP) models due to the small spatial scale of the canyon ( 1-2 km wide) compared to the horizontal resolution of operational NWP models (3 km or greater). Custom WRF simulations initialized with NARR data were run at 1 km horizontal resolution to assess whether higher resolution NWP could accurately simulate the observed gap winds. Here, we show that the 1 km WRF simulations captured many of the observed gap wind events, although the strength of the events was underpredicted. We also present evidence from these WRF simulations which suggests that the Salmon River Canyon is near the threshold of WRF-resolvable terrain features when the standard WRF coordinate system and discretization schemes are used. Finally, we show that the strength of the gap wind events can be predicted reasonably well as a function of the surface pressure gradient across the gap, which could be useful in the absence of high-resolution NWP. These are important findings for wildland firefighting applications in narrow gaps where routine forecasts may not provide warning for wind effects induced by high-resolution terrain features.

Low loss pole configuration for multi-pole homopolar magnetic bearings

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A. (Inventor); Hakun, Claef F. (Inventor)

2001-01-01

A new pole configuration for multi-pole homopolar bearings proposed in this invention reduces rotational losses caused by eddy-currents generated when non-uniform flux distributions exist along the rotor surfaces. The new homopolar magnetic bearing includes a stator with reduced pole-to-pole and exhibits a much more uniform rotor flux than with large pole-to-pole gaps. A pole feature called a pole-link is incorporated into the low-loss poles to provide a uniform pole-to-pole gap and a controlled path for pole-to-pole flux. In order to implement the low-loss pole configuration of magnetic bearings with small pole-to-pole gaps, a new stator configuration was developed to facilitate installation of coil windings. The stator was divided into sector shaped pieces, as many pieces as there are poles. Each sector-shaped pole-piece can be wound on a standard coil winding machine, and it is practical to wind precision layer wound coils. To achieve maximum actuation efficiency, it is desirable to use all the available space for the coil formed by the natural geometric configuration. Then, the coils can be wound in a tapered shape. After winding, the sectored-pole-pieces are installed into and fastened by bonding or other means, to a ring of material which encloses the sectored-pole-pieces, forming a complete stator.

Wind-forced modulations in crossing sea states over infinite depth water

NASA Astrophysics Data System (ADS)

Debsarma, Suma; Senapati, Sudipta; Das, K. P.

2014-09-01

The present work is motivated by the work of Leblanc ["Amplification of nonlinear surface waves by wind," Phys. Fluids 19, 101705 (2007)] which showed that Stokes waves grow super exponentially under fair wind as a result of modulational instability. Here, we have studied the effect of wind in a situation of crossing sea states characterized by two obliquely propagating wave systems in deep water. It is found that the wind-forced uniform wave solution in crossing seas grows explosively with a super-exponential growth rate even under a steady horizontal wind flow. This is an important piece of information in the context of the formation of freak waves.

An extreme wind erosion event of the fresh Eyjafjallajökull 2010 volcanic ash

PubMed Central

Arnalds, Olafur; Thorarinsdottir, Elin Fjola; Thorsson, Johann; Waldhauserova, Pavla Dagsson; Agustsdottir, Anna Maria

2013-01-01

Volcanic eruptions can generate widespread deposits of ash that are subsequently subjected to erosive forces which causes detrimental effects on ecosystems. We measured wind erosion of the freshly deposited Eyjafjallajökull ash at a field site the first summer after the 2010 eruption. Over 30 wind erosion events occurred (June-October) at wind speeds > 10 m s−1 in each storm with gusts up to 38.7 m s−1. Surface transport over one m wide transect (surface to 150 cm height) reached > 11,800 kg m−1 during the most intense storm event with a rate of 1,440 kg m−1 hr−1 for about 6½ hrs. This storm is among the most extreme wind erosion events recorded on Earth. The Eyjafjallajökull wind erosion storms caused dust emissions extending several hundred km from the volcano affecting both air quality and ecosystems showing how wind erosion of freshly deposited ash prolongs impacts of volcanic eruptions. PMID:23409248

An extreme wind erosion event of the fresh Eyjafjallajökull 2010 volcanic ash.

PubMed

Arnalds, Olafur; Thorarinsdottir, Elin Fjola; Thorsson, Johann; Waldhauserova, Pavla Dagsson; Agustsdottir, Anna Maria

2013-01-01

Volcanic eruptions can generate widespread deposits of ash that are subsequently subjected to erosive forces which causes detrimental effects on ecosystems. We measured wind erosion of the freshly deposited Eyjafjallajökull ash at a field site the first summer after the 2010 eruption. Over 30 wind erosion events occurred (June-October) at wind speeds > 10 m s(-1) in each storm with gusts up to 38.7 m s(-1). Surface transport over one m wide transect (surface to 150 cm height) reached > 11,800 kg m(-1) during the most intense storm event with a rate of 1,440 kg m(-1) hr(-1) for about 6½ hrs. This storm is among the most extreme wind erosion events recorded on Earth. The Eyjafjallajökull wind erosion storms caused dust emissions extending several hundred km from the volcano affecting both air quality and ecosystems showing how wind erosion of freshly deposited ash prolongs impacts of volcanic eruptions.

Elemental abundances in corotating events

NASA Technical Reports Server (NTRS)

Vonrosenvinge, T. T.; Mcguire, R. E.

1985-01-01

Large, persistent solar-wind streams in 1973 and 1974 produced corotating interaction regions which accelerated particles to energies of a few MeV/nucleon. The proton to helium ratio (H/He) was remarkably constant at a value (22 + or 5) equal to that in the solar wind (21 + or - 3), suggesting that particles were being accelerated directly out of the solar wind. Preliminary results were presented from a similar study approximately 11 years (i.e., one solar cycle) later. Corotating events have been identified by surveying the solar wind data, energetic particle time-histories and anisotropies. This data was all obtained from the ISEE-3/ICE spacecraft. These events also show H/He ratios similar to that in the solar wind. It is flund that in these cases there is evidence for H/He ratios which are significantly different from that of the solar wind but which are consistent with the range of values found in solar flare events.

Numerical Investigation of the Flow Angularity Effects of the NASA Langley UPWT on the Ares I DAC1 0.01-Scale Model

NASA Technical Reports Server (NTRS)

Lee, Henry C.; Klopfer, Goetz H.; Onufer, Jeff T.

2011-01-01

Investigation of the non-uniform flow angularity effects on the Ares I DAC-1 in the Langley Unitary Plan Wind Tunnel are explored through simulations by OVERFLOW. Verification of the wind tunnel results are needed to ensure that the standard wind tunnel calibration procedures for large models are valid. The expectation is that the systematic error can be quantified, and thus be used to correct the wind tunnel data. The corrected wind tunnel data can then be used to quantify the CFD uncertainties.

Characteristic Paths of Extratropical Cyclones that Cause High Wind Events in the Northeast United States

NASA Astrophysics Data System (ADS)

Booth, J. F.; Rieder, H. E.; Lee, D.; Kushnir, Y.

2014-12-01

This study analyzes the association between wintertime high wind events (HWEs) in the northeast United States US and extratropical cyclones. Sustained wind maxima in the Daily Summary Data from the National Climatic Data Center's Integrated Surface Database are analyzed for 1979-2012. For each station, a Generalized Pareto Distribution (GPD) is fit to the upper tail of the daily maximum wind speed data, and probabilistic return levels at intervals of 1, 3 and 5-years are derived from the GPD fit. At each interval, wind events meeting the return level criteria are termed HWEs. The HWEs occurring on the same day are grouped into multi-station events allowing the association with extratropical cyclones, which are tracked in the European Center for Medium-Range Weather Forecast ERA-Interim reanalysis. Using hierarchical clustering analysis, this study finds that the HWEs are most often associated with cyclones travelling from southwest to northeast, usually originating west of the Appalachian Mountains. The results show that a storm approaching from the southwest is four times more likely to cause strong surface winds than a Nor'easter. A series of sensitivity analyses confirms the robustness of this result. Next, the relationship between the strength of the wind events and the corresponding storm minimum sea level pressure is analyzed. No robust relationship between these quantities is found for strong wind events. Nevertheless, subsequent analysis shows that a relationship between deeper storms and stronger winds emerges if the analysis is extended to the entire set of wintertime storms.

Modulation of equatorial Pacific westerly/easterly wind events by the Madden-Julian oscillation and convectively-coupled Rossby waves

NASA Astrophysics Data System (ADS)

Puy, Martin; Vialard, J.; Lengaigne, M.; Guilyardi, E.

2016-04-01

Synoptic wind events in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (ENSO) evolution. This paper characterizes the spatio-temporal distribution of Easterly (EWEs) and Westerly Wind Events (WWEs) and quantifies their relationship with intraseasonal and interannual large-scale climate variability. We unambiguously demonstrate that the Madden-Julian Oscillation (MJO) and Convectively-coupled Rossby Waves (CRW) modulate both WWEs and EWEs occurrence probability. 86 % of WWEs occur within convective MJO and/or CRW phases and 83 % of EWEs occur within the suppressed phase of MJO and/or CRW. 41 % of WWEs and 26 % of EWEs are in particular associated with the combined occurrence of a CRW/MJO, far more than what would be expected from a random distribution (3 %). Wind events embedded within MJO phases also have a stronger impact on the ocean, due to a tendency to have a larger amplitude, zonal extent and longer duration. These findings are robust irrespective of the wind events and MJO/CRW detection methods. While WWEs and EWEs behave rather symmetrically with respect to MJO/CRW activity, the impact of ENSO on wind events is asymmetrical. The WWEs occurrence probability indeed increases when the warm pool is displaced eastward during El Niño events, an increase that can partly be related to interannual modulation of the MJO/CRW activity in the western Pacific. On the other hand, the EWEs modulation by ENSO is less robust, and strongly depends on the wind event detection method. The consequences of these results for ENSO predictability are discussed.

Influence of orographically steered winds on Mutsu Bay surface currents

NASA Astrophysics Data System (ADS)

Yamaguchi, Satoshi; Kawamura, Hiroshi

2005-09-01

Effects of spatially dependent sea surface wind field on currents in Mutsu Bay, which is located at the northern end of Japanese Honshu Island, are investigated using winds derived from synthetic aperture radar (SAR) images and a numerical model. A characteristic wind pattern over the bay was evidenced from analysis of 118 SAR images and coincided with in situ observations. Wind is topographically steered with easterly winds entering the bay through the terrestrial gap and stronger wind blowing over the central water toward its mouth. Nearshore winds are weaker due to terrestrial blockages. Using the Princeton Ocean Model, we investigated currents forced by the observed spatially dependent wind field. The predicted current pattern agrees well with available observations. For a uniform wind field of equal magnitude and average direction, the circulation pattern departs from observations demonstrating that vorticity input due to spatially dependent wind stress is essential in generation of the wind-driven current in Mutsu Bay.

Meso-beta scale numerical simulation studies of terrain-induced jet streak mass/momentum perturbations

NASA Technical Reports Server (NTRS)

Lin, Yuh-Lang; Kaplan, Michael L.

1993-01-01

The first section is on 3-D numerical modeling of terrain-induced circulations and covers the following: (1) additional insights into gravity wave generation mechanisms based on the control simulation; (2) ongoing nested-grid numerical simulations; (3) work to be completed during the remainder of FY-93; and (4) work objectives for FY-94. The second section is on linear theory and theoretical modeling and covers the following: (1) the free response of a uniform barotropic flow to an initially stationary unbalanced (ageostrophic) zonal wind anomaly; and (2) the free response of a uniform barotropic flow to an initially stationary balanced zonal wind anomaly.

Climatology and Predictability of Cool-Season High Wind Events in the New York City Metropolitan and Surrounding Area

NASA Astrophysics Data System (ADS)

Layer, Michael

Damaging wind events not associated with severe convective storms or tropical cyclones can occur over the Northeast U.S. during the cool season and can cause significant problems with transportation, infrastructure, and public safety. These non-convective wind events (NCWEs) events are difficult for operational forecasters to predict in the NYC region as revealed by relatively poor verification statistics in recent years. This study investigates the climatology of NCWEs occurring between 15 September and 15 May over 13 seasons from 2000-2001 through 2012-2013. The events are broken down into three distinct types commonly observed in the region: pre-cold frontal (PRF), post-cold frontal (POF), and nor'easter/coastal storm (NEC) cases. Relationships between observed winds and some atmospheric parameters such as 900 hPa height gradient, 3-hour MSLP tendency, low-level wind profile, and stability are also studied. Overall, PRF and NEC events exhibit stronger height gradients, stronger low-level winds, and stronger low-level stability than POF events. Model verification is also conducted over the 2009-2014 time period using the Short Range Ensemble Forecast system (SREF) from the National Centers for Environmental Prediction (NCEP). Both deterministic and probabilistic verification metrics are used to evaluate the performance of the ensemble during NCWEs. Although the SREF has better forecast skill than most of the deterministic SREF control members, it is rather poorly calibrated, and exhibits a significant overforecasting, or positive wind speed bias in the lower atmosphere.

Climate projection of synoptic patterns forming extremely high wind speed over the Barents Sea

NASA Astrophysics Data System (ADS)

Surkova, Galina; Krylov, Aleksey

2017-04-01

Frequency of extreme weather events is not very high, but their consequences for the human well-being may be hazardous. These seldom events are not always well simulated by climate models directly. Sometimes it is more effective to analyze numerical projection of large-scale synoptic event generating extreme weather. For example, in mid-latitude surface wind speed depends mainly on the sea level pressure (SLP) field - its configuration and horizontal pressure gradient. This idea was implemented for analysis of extreme wind speed events over the Barents Sea. The calendar of high surface wind speed V (10 m above the surface) was prepared for events with V exceeding 99th percentile value in the central part of the Barents Sea. Analysis of probability distribution function of V was carried out on the base of ERA-Interim reanalysis data (6-hours, 0.75x0.75 degrees of latitude and longitude) for the period 1981-2010. Storm wind events number was found to be 240 days. Sea level pressure field over the sea and surrounding area was selected for each storm wind event. For the climate of the future (scenario RCP8.5), projections of SLP from CMIP5 numerical experiments were used. More than 20 climate models results of projected SLP (2006-2100) over the Barents Sea were correlated with modern storm wind SLP fields. Our calculations showed the positive tendency of annual frequency of storm SLP patterns over the Barents Sea by the end of 21st century.

Improved high power/high frequency inductor

NASA Technical Reports Server (NTRS)

Mclyman, W. T. (Inventor)

1990-01-01

A toroidal core is mounted on an alignment disc having uniformly distributed circumferential notches or holes therein. Wire is then wound about the toroidal core in a uniform pattern defined by the notches or holes. Prior to winding, the wire may be placed within shrink tubing. The shrink tubing is then wound about the alignment disc and core and then heat-shrunk to positively retain the wire in the uniform position on the toroidal core.

Atmospheric forcing of sea ice anomalies in the Ross Sea polynya region

NASA Astrophysics Data System (ADS)

Dale, Ethan R.; McDonald, Adrian J.; Coggins, Jack H. J.; Rack, Wolfgang

2017-01-01

We investigate the impacts of strong wind events on the sea ice concentration within the Ross Sea polynya (RSP), which may have consequences on sea ice formation. Bootstrap sea ice concentration (SIC) measurements derived from satellite SSM/I brightness temperatures are correlated with surface winds and temperatures from Ross Ice Shelf automatic weather stations (AWSs) and weather models (ERA-Interim). Daily data in the austral winter period were used to classify characteristic weather regimes based on the percentiles of wind speed. For each regime a composite of a SIC anomaly was formed for the entire Ross Sea region and we found that persistent weak winds near the edge of the Ross Ice Shelf are generally associated with positive SIC anomalies in the Ross Sea polynya and vice versa. By analyzing sea ice motion vectors derived from the SSM/I brightness temperatures we find significant sea ice motion anomalies throughout the Ross Sea during strong wind events, which persist for several days after a strong wind event has ended. Strong, negative correlations are found between SIC and AWS wind speed within the RSP indicating that strong winds cause significant advection of sea ice in the region. We were able to partially recreate these correlations using colocated, modeled ERA-Interim wind speeds. However, large AWS and model differences are observed in the vicinity of Ross Island, where ERA-Interim underestimates wind speeds by a factor of 1.7 resulting in a significant misrepresentation of RSP processes in this area based on model data. Thus, the cross-correlation functions produced by compositing based on ERA-Interim wind speeds differed significantly from those produced with AWS wind speeds. In general the rapid decrease in SIC during a strong wind event is followed by a more gradual recovery in SIC. The SIC recovery continues over a time period greater than the average persistence of strong wind events and sea ice motion anomalies. This suggests that sea ice recovery occurs through thermodynamic rather than dynamic processes.

Low Probability Tail Event Analysis and Mitigation in BPA Control Area: Task 2 Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Shuai; Makarov, Yuri V.; McKinstry, Craig A.

Task report detailing low probability tail event analysis and mitigation in BPA control area. Tail event refers to the situation in a power system when unfavorable forecast errors of load and wind are superposed onto fast load and wind ramps, or non-wind generators falling short of scheduled output, causing the imbalance between generation and load to become very significant.

Coupled effects of wind-storms and drought on tree mortality across 115 forest stands from the Western Alps and the Jura mountains.

PubMed

Csilléry, Katalin; Kunstler, Georges; Courbaud, Benoît; Allard, Denis; Lassègues, Pierre; Haslinger, Klaus; Gardiner, Barry

2017-12-01

Damage due to wind-storms and droughts is increasing in many temperate forests, yet little is known about the long-term roles of these key climatic factors in forest dynamics and in the carbon budget. The objective of this study was to estimate individual and coupled effects of droughts and wind-storms on adult tree mortality across a 31-year period in 115 managed, mixed coniferous forest stands from the Western Alps and the Jura mountains. For each stand, yearly mortality was inferred from management records, yearly drought from interpolated fields of monthly temperature, precipitation and soil water holding capacity, and wind-storms from interpolated fields of daily maximum wind speed. We performed a thorough model selection based on a leave-one-out cross-validation of the time series. We compared different critical wind speeds (CWSs) for damage, wind-storm, and stand variables and statistical models. We found that a model including stand characteristics, drought, and storm strength using a CWS of 25 ms -1 performed the best across most stands. Using this best model, we found that drought increased damage risk only in the most southerly forests, and its effect is generally maintained for up to 2 years. Storm strength increased damage risk in all forests in a relatively uniform way. In some stands, we found positive interaction between drought and storm strength most likely because drought weakens trees, and they became more prone to stem breakage under wind-loading. In other stands, we found negative interaction between drought and storm strength, where excessive rain likely leads to soil water saturation making trees more susceptible to overturning in a wind-storm. Our results stress that temporal data are essential to make valid inferences about ecological impacts of disturbance events, and that making inferences about disturbance agents separately can be of limited validity. Under projected future climatic conditions, the direction and strength of these ecological interactions could also change. © 2017 John Wiley & Sons Ltd.

Critical role of wind-wave induced erosion on the morphodynamic evolution of shallow tidal basins

NASA Astrophysics Data System (ADS)

D'Alpaos, Andrea; Carniello, Luca; Rinaldo, Andrea

2014-05-01

Wind-wave induced erosion processes are among the chief processes which govern the morphodynamic evolution of shallow tidal basins, both in the vertical and in the horizontal plane. Wind-wave induced bottom shear stresses can promote the disruption of the polymeric microphytobenthic biofilm and lead to the erosion of tidal-flat surfaces and to the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Moreover, the impact of wind-waves on salt-marsh margins can lead to the lateral erosion of marsh boundaries thus promoting the disappearance of salt-marsh ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind wave-induced resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind waves and tidal currents on the hydrodynamic circulation in shallow basins. Our analyses of the characteristics of combined current and wave-induced exceedances in bottom shear stress over a given threshold for erosion, suggest that wind wave-induced resuspension events can be modeled as a marked Poisson process. The interarrival time of wave-induced erosion events is, in fact, an exponentially distributed random variable, as well as the duration and intensity of overthreshold events. Moreover, the analysis of wind-wave induced resuspension events for different historical configurations of the Venice Lagoon from the 19th to the 21st century, shows that the interarrival times of erosion events have dramatically decreased through the last two centuries, whereas the intensities of erosion events have experienced a surprisingly high increase. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.

Impact of the Assimilation of Hyperspectral Infrared Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

NASA Technical Reports Server (NTRS)

Berndt, Emily B.; Zavodsky, Bradley T; Jedlovec, Gary J.; Elmer, Nicholas J.

2013-01-01

Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), North American Regional Reanalysis (NARR) reanalysis, and Rapid Refresh analyses.

Wind erosion in semiarid landscapes: Predictive models and remote sensing methods for the influence of vegetation

NASA Technical Reports Server (NTRS)

Musick, H. Brad; Truman, C. Randall; Trujillo, Steven M.

1992-01-01

Wind erosion in semi-arid regions is a significant problem for which the sheltering effect of rangeland vegetation is poorly understood. Individual plants may be considered as porous roughness elements which absorb or redistribute the wind's momentum. The saltation threshold is the minimum wind velocity at which soil movement begins. The dependence of the saltation threshold on geometrical parameters of a uniform roughness array was studied in a wind tunnel. Both solid and porous elements were used to determine relationships between canopy structure and the threshold velocity for soil transport. The development of a predictive relation for the influence of vegetation canopy structure on wind erosion of soil is discussed.

Impact of roof height non-uniformity on pollutant transport between a street canyon and intersections.

PubMed

Nosek, Štěpán; Kukačka, Libor; Jurčáková, Klára; Kellnerová, Radka; Jaňour, Zbyněk

2017-08-01

This paper presents an extension of our previous wind-tunnel study (Nosek et al., 2016) in which we highlighted the need for investigation of the removal mechanisms of traffic pollution from all openings of a 3D street canyon. The extension represents the pollution flux (turbulent and advective) measurements at the lateral openings of three different 3D street canyons for the winds perpendicular and oblique to the along-canyon axis. The pollution was simulated by emitting a passive gas (ethane) from a homogeneous ground-level line source positioned along the centreline of the investigated street canyons. The street canyons were formed by courtyard-type buildings of two different regular urban-array models. The first model has a uniform building roof height, while the second model has a non-uniform roof height along each building's wall. The mean flow and concentration fields at the canyons' lateral openings confirm the findings of other studies that the buildings' roof-height variability at the intersections plays an important role in the dispersion of the traffic pollutants within the canyons. For the perpendicular wind, the non-uniform roof-height canyon appreciably removes or entrains the pollutant through its lateral openings, contrary to the uniform canyon, where the pollutant was removed primarily through the top. The analysis of the turbulent mass transport revealed that the coherent flow structures of the lateral momentum transport correlate with the ventilation processes at the lateral openings of all studied canyons. These flow structures coincide at the same areas and hence simultaneously transport the pollutant in opposite directions. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the Improvement of Convergence Performance for Integrated Design of Wind Turbine Blade Using a Vector Dominating Multi-objective Evolution Algorithm

NASA Astrophysics Data System (ADS)

Wang, L.; Wang, T. G.; Wu, J. H.; Cheng, G. P.

2016-09-01

A novel multi-objective optimization algorithm incorporating evolution strategies and vector mechanisms, referred as VD-MOEA, is proposed and applied in aerodynamic- structural integrated design of wind turbine blade. In the algorithm, a set of uniformly distributed vectors is constructed to guide population in moving forward to the Pareto front rapidly and maintain population diversity with high efficiency. For example, two- and three- objective designs of 1.5MW wind turbine blade are subsequently carried out for the optimization objectives of maximum annual energy production, minimum blade mass, and minimum extreme root thrust. The results show that the Pareto optimal solutions can be obtained in one single simulation run and uniformly distributed in the objective space, maximally maintaining the population diversity. In comparison to conventional evolution algorithms, VD-MOEA displays dramatic improvement of algorithm performance in both convergence and diversity preservation for handling complex problems of multi-variables, multi-objectives and multi-constraints. This provides a reliable high-performance optimization approach for the aerodynamic-structural integrated design of wind turbine blade.

Influence of Convective Effect of Solar Winds on the CME Transit Time

NASA Astrophysics Data System (ADS)

Sun, Lu-yuan

2017-10-01

Based on an empirical model for predicting the transit time of coronal mass ejections (CMEs) proposed by Gopalswamy, 52 CME events which are related to the geomagnetic storms of Dst < -50 nT, and 10 CME events which caused extremely strong geomagnetic storms (Dst < -200 nT) in 1996- 2007 are selected, and combined with the observational data of the interplanetary solar winds that collected by the ACE satellite at 1AU, to analyze the influence of convective effect of ambient solar winds on the prediction of the CME transit time when it arrives at a place of 1 AU. After taking the convective effect of ambient solar winds into account, the standard deviation of predictions is reduced from 16.5 to 11.4 hours for the 52 CME events, and the prediction error is less than 15 hours for 68% of these events; while the standard deviation of predictions is reduced from 10.6 to 6.5 hours for the 10 CME events that caused extremely strong geomagnetic storms, and the prediction error is less than 5 hours for 6 of the 10 events. These results show that taking the convective effect of ambient solar winds into account can reduce the standard deviation of the predicted CME transit time, hence the convective effect of solar winds plays an important role for predicting the transit times of CME events.

3D electroplated inductors with thickness variation for improved broadband performance

NASA Astrophysics Data System (ADS)

Farm-Guoo Tseng, Victor; Bedair, Sarah S.; Lazarus, Nathan

2017-01-01

The performance of an RF spiral inductor is based on the balance between ohmic losses in the outer turns and eddy current losses dominant in the inner turns where the magnetic field is the strongest. In this work, air-core spiral inductors with winding trace thicknesses decreasing towards the center are demonstrated, achieving quality factor improvement over a wide frequency range compared to uniform thickness inductors. A custom 3D copper electroplating process was used to produce spiral inductors with varying winding thicknesses in a single plating step, with patterned gaps in a seed layer used to create delays in the vertical plating. The fabricated center-lowered coil inductors were 80 nH within a one square millimeter area with thickness varying from 60 µm to 10 µm from outer to inner winding. Within the 16 MHz-160 MHz range, the center-lowered inductors were shown to have a maximum to minimum quality factor improvement of 90%-10% when compared to uniform thickness inductors with thicknesses ranging from 60 µm to 10 µm. Compared to the 20 µm uniform thickness inductor which has the optimal performance among all uniform thickness inductors in this frequency range, the center-lowered inductors were shown to achieve a maximum quality factor improvement of 20% at the edge frequencies of 16 MHz and 160 MHz, and a minimum quality factor improvement of 10% near the geometric mean center frequency of 46 MHz.

Galactic cluster winds in presence of a dark energy

NASA Astrophysics Data System (ADS)

Bisnovatyi-Kogan, G. S.; Merafina, M.

2013-10-01

We obtain a solution for the hydrodynamic outflow of the polytropic gas from the gravitating centre, in the presence of the uniform dark energy (DE). The antigravity of DE is enlightening the outflow and makes the outflow possible at smaller initial temperature, at the same density. The main property of the wind in the presence of DE is its unlimited acceleration after passing the critical point. In application of this solution to the winds from galaxy clusters, we suggest that collision of the strongly accelerated wind with another galaxy cluster, or with another galactic cluster wind, could lead to the formation of a highest energy cosmic rays.

Rotating electric machine with fluid supported parts

DOEpatents

Smith, Jr., Joseph L.; Kirtley, Jr., James L.

1981-01-01

A rotating electric machine in which the armature winding thereof and other parts are supported by a liquid to withstand the mechanical stresses applied during transient overloads and the like. In particular, a narrow gap is provided between the armature winding and the stator which supports it and this gap is filled with an externally pressurized viscous liquid. The liquid is externally pressurized sufficiently to balance the static loads on the armature winding. Transient mechanical loads which deform the armature winding alter the gap dimensions and thereby additionally pressurize the viscous liquid to oppose the armature winding deformation and more nearly uniformly to distribute the resulting mechanical stresses.

Wind Effects on Flow Patterns and Net Fluxes in Density-Driven High-Latitude Channel Flow

NASA Astrophysics Data System (ADS)

Huntley, Helga S.; Ryan, Patricia

2018-01-01

A semianalytic two-dimensional model is used to analyze the interplay between the different forces acting on density-driven flow in high-latitude channels. In particular, the balance between wind stress, viscous forces, baroclinicity, and sea surface slope adjustments under specified flux conditions is examined. Weak winds are found not to change flow patterns appreciably, with minimal (<7%) adjustments to horizontal velocity maxima. In low-viscosity regimes, strong winds change the flow significantly, especially at the surface, by either strengthening the dual-jet pattern, established without wind, by a factor of 2-3 or initiating return flow at the surface. A nonzero flux does not result in the addition of a uniform velocity throughout the channel cross section, but modifies both along-channel and cross-channel velocities to become more symmetric, dominated by a down-channel jet centered in the domain and counter-clockwise lateral flow. We also consider formulations of the model that allow adjustments of the net flux in response to the wind. Flow patterns change, beyond uniform intensification or weakening, only for strong winds and high Ekman number. Comparisons of the model results to observational data collected in Nares Strait in the Canadian Archipelago in the summer of 2007 show rough agreement, but the model misses the upstream surface jet on the east side of the strait and propagates bathymetric effects too strongly in the vertical for this moderately high eddy viscosity. Nonetheless, the broad strokes of the observed high-latitude flow are reproduced.

Windthrown trees on the Kings River Ranger District, Sierra National Forest: meteorological aspects

Treesearch

Michael A. Fosberg

1986-01-01

Blowdown in shelterwood, sanitation cuts, and other partial cuts on the Kings River Ranger District, Sierra National Forest, are due to Mono winds. Both winter storm and Mono winds were considered as causes of winter blowdown. All evidence, e.g., direction of tree-fall and occurrence of high wind events, point to Mono wind events as the cause of blowdown. Only 12...

Calibration of the Naval Postgraduate School 3.5 X 5.0 Academic Wind Tunnel

DTIC Science & Technology

1990-09-01

design of the wind tunnel great care is taken to ensure undisturbed, uniform flow through the test section. Even so, there will exist some disturbances...the longitudinal pressure gradient will determine if there is flow leakage in the test section doors. The information obtained also makes possible an...turbulence calibrations were performed. At the completion of these measurements it was determined that the flow quality could be improved by wind tunnel

A near uniform basin-wide sea level fluctuation over the Japan/East Sea: A semienclosed sea with multiple straits

NASA Astrophysics Data System (ADS)

Kim, Seung-Bum; Fukumori, Ichiro

2008-06-01

Sea level of the Japan/East Sea observed by the TOPEX/Poseidon (T/P) satellite altimeter is analyzed using a 1/4°-resolution ocean general circulation model. A significant fraction of the Japan/East Sea sea level variability is found to be spatially uniform with periods ranging from 20 d to a year. The model simulation is consistent with T/P records in terms of the basin-wide sea level fluctuation's spectral energy and coherence. The simulation indicates that the changes are barotropic in nature and controlled, notably at high frequencies, by the net mass transport through the straits of the Japan/East Sea driven by winds in the vicinity of the Korea/Tsushima and Soya Straits. A series of barotropic simulations suggest that the sea level fluctuations are the result of a dynamic balance at the straits among near-strait winds, friction, and geostrophic control. The basin-wide sea level response is a linear superposition of changes due to winds near the individual straits. In particular, a basin-wide sea level response can be established by winds near either one of the straits alone. For the specific geometry and winds, winds near the Soya Strait have a larger impact on the Japan/East Sea mean sea level than those near the Korea/Tsushima Strait.

Climatological attribution of wind power ramp events in East Japan and their probabilistic forecast based on multi-model ensembles downscaled by analog ensemble using self-organizing maps

NASA Astrophysics Data System (ADS)

Ohba, Masamichi; Nohara, Daisuke; Kadokura, Shinji

2016-04-01

Severe storms or other extreme weather events can interrupt the spin of wind turbines in large scale that cause unexpected "wind ramp events". In this study, we present an application of self-organizing maps (SOMs) for climatological attribution of the wind ramp events and their probabilistic prediction. The SOM is an automatic data-mining clustering technique, which allows us to summarize a high-dimensional data space in terms of a set of reference vectors. The SOM is applied to analyze and connect the relationship between atmospheric patterns over Japan and wind power generation. SOM is employed on sea level pressure derived from the JRA55 reanalysis over the target area (Tohoku region in Japan), whereby a two-dimensional lattice of weather patterns (WPs) classified during the 1977-2013 period is obtained. To compare with the atmospheric data, the long-term wind power generation is reconstructed by using a high-resolution surface observation network AMeDAS (Automated Meteorological Data Acquisition System) in Japan. Our analysis extracts seven typical WPs, which are linked to frequent occurrences of wind ramp events. Probabilistic forecasts to wind power generation and ramps are conducted by using the obtained SOM. The probability are derived from the multiple SOM lattices based on the matching of output from TIGGE multi-model global forecast to the WPs on the lattices. Since this method effectively takes care of the empirical uncertainties from the historical data, wind power generation and ramp is probabilistically forecasted from the forecasts of global models. The predictability skill of the forecasts for the wind power generation and ramp events show the relatively good skill score under the downscaling technique. It is expected that the results of this study provides better guidance to the user community and contribute to future development of system operation model for the transmission grid operator.

Interplanetary ions during an energetic storm particle event - The distribution function from solar wind thermal energies to 1.6 MeV

NASA Technical Reports Server (NTRS)

Gosling, J. T.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Zwickl, R. D.; Paschmann, G.; Sckopke, N.; Hynds, R. J.

1981-01-01

An ion velocity distribution function of the postshock phase of an energetic storm particle (ESP) event is obtained from data from the ISEE 2 and ISEE 3 experiments. The distribution function is roughly isotropic in the solar wind frame from solar wind thermal energies to 1.6 MeV. The ESP event studied (8/27/78) is superposed upon a more energetic particle event which was predominantly field-aligned and which was probably of solar origin. The observations suggest that the ESP population is accelerated directly out of the solar wind thermal population or its quiescent suprathermal tail by a stochastic process associated with shock wave disturbance. The acceleration mechanism is sufficiently efficient so that approximately 1% of the solar wind population is accelerated to suprathermal energies. These suprathermal particles have an energy density of approximately 290 eV cubic centimeters.

Statistical characterization of wind-wave induced sediment resuspension events in shallow tidal basins

NASA Astrophysics Data System (ADS)

D'Alpaos, A.; Carniello, L.; Rinaldo, A.

2013-12-01

Wind-wave induced erosion processes play a critical role on the morphodynamic evolution of shallow tidal landscapes. Both in the horizontal and in the vertical planes, patterns of wind-induced bottom shear stresses contribute to control the morphological and biological features of the tidal landscape, through the erosion of tidal-flat surfaces and of salt-marsh margins, the disruption of the polymeric microphytobenthic biofilm, and the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind wave-induced resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind waves and tidal currents on the hydrodynamic circulation in shallow basins. Our analysis of the characteristics of combined current and wave-induced exceedances in bottom shear stress over a given threshold for erosion, suggest that wind wave-induced resuspension events can be modeled as a marked Poisson process. Moreover, the analysis of wind-wave induced resuspension events for different historical configurations of the Venice Lagoon shows that the interarrival times of erosion events have decreased through the last two centuries, whereas the intensities of erosion events have increased. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.

An Update to the Warm-Season Convective Wind Climatology of KSC/CCAFS

NASA Technical Reports Server (NTRS)

Lupo, Kevin

2012-01-01

Total of 1100 convective events in the 17-year warm-season climatology at KSC/CCAFS. July and August typically are the peak of convective events, May being the minimum. Warning and non-warning level convective winds are more likely to occur in the late afternoon (1900-2000Z). Southwesterly flow regimes and wind directions produce the strongest winds. Storms moving from southwesterly direction tend to produce more warning level winds than those moving from the northerly and easterly directions.

Joint probabilities of extreme precipitation and wind gusts in Germany

NASA Astrophysics Data System (ADS)

von Waldow, H.; Martius, O.

2012-04-01

Extreme meteorological events such as storms, heavy rain, floods, droughts and heat waves can have devastating consequences for human health, infrastructure and ecosystems. Concomitantly occurring extreme events might interact synergistically to produce a particularly hazardous impact. The joint occurrence of droughts and heat waves, for example, can have a very different impact on human health and ecosystems both in quantity and quality, than just one of the two extreme events. The co-occurrence of certain types of extreme events is plausible from physical and dynamical considerations, for example heavy precipitation and high wind speeds in the pathway of strong extratropical cyclones. The winter storm Kyrill not only caused wind gust speeds well in excess of 30 m/s across Europe, but also brought 24 h precipitation sums greater than the mean January accumulations in some regions. However, the existence of such compound risks is currently not accounted for by insurance companies, who assume independence of extreme weather events to calculate their premiums. While there are established statistical methods to model the extremes of univariate meteorological variables, the modelling of multidimensional extremes calls for an approach that is tailored to the specific problem at hand. A first step involves defining extreme bivariate wind/precipitation events. Because precipitation and wind gusts caused by the same cyclone or convective cell do not occur at exactly the same location and at the same time, it is necessary to find a sound definition of "extreme compound event" for this case. We present a data driven method to choose appropriate time and space intervals that define "concomitance" for wind and precipitation extremes. Based on station data of wind speed and gridded precipitation data, we arrive at time and space intervals that compare well with the typical time and space scales of extratropical cyclones, i.e. a maximum time lag of 1 day and a maximum distance of about 300 km between associated wind and rain events. After modelling extreme precipitation and wind separately, we explore the practicability of characterising their joint distribution using a bivariate threshold excess model. In particular, we present different dependence measures and report about the computational feasibility and available computer codes.

The Use of Red Green Blue Air Mass Imagery to Investigate the Role of Stratospheric Air in a Non-convective Wind Event

NASA Technical Reports Server (NTRS)

Berndt, E. B.; Zavodsky, B. T.; Jedlovec, G. J.; Molthan, A. L.

2013-01-01

Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis, and Rapid Refresh analyses.

The Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

NASA Technical Reports Server (NTRS)

Berndt, Emily; Zavodsky, Bradley; Jedlovec, Gary; Elmer, Nicholas

2013-01-01

Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis, and Rapid Refresh analyses.

Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

NASA Technical Reports Server (NTRS)

Berndt, E. B.; Zavodsky, B. T.; Folmer, M. J.; Jedlovec, G. J.

2014-01-01

Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), 32-km North American Regional Reanalysis (NARR) interpolated to a 12-km grid, and 13-km Rapid Refresh analyses.

Impact of the Assimilation of Hyperspectral Infrared Retrieved Profiles on Advanced Weather and Research Model Simulations of a Non-Convective Wind Event

NASA Technical Reports Server (NTRS)

Berndt, E. B.; Zavodsky, B. T.; Jedlovec, G. J.

2014-01-01

Non-convective wind events commonly occur with passing extratropical cyclones and have significant societal and economic impacts. Since non-convective winds often occur in the absence of specific phenomena such as a thunderstorm, tornado, or hurricane, the public are less likely to heed high wind warnings and continue daily activities. Thus non-convective wind events result in as many fatalities as straight line thunderstorm winds. One physical explanation for non-convective winds includes tropopause folds. Improved model representation of stratospheric air and associated non-convective wind events could improve non-convective wind forecasts and associated warnings. In recent years, satellite data assimilation has improved skill in forecasting extratropical cyclones; however errors still remain in forecasting the position and strength of extratropical cyclones as well as the tropopause folding process. The goal of this study is to determine the impact of assimilating satellite temperature and moisture retrieved profiles from hyperspectral infrared (IR) sounders (i.e. Atmospheric Infrared Sounder (AIRS), Cross-track Infrared and Microwave Sounding Suite (CrIMSS), and Infrared Atmospheric Sounding Interferometer (IASI)) on the model representation of the tropopause fold and an associated high wind event that impacted the Northeast United States on 09 February 2013. Model simulations using the Advanced Research Weather Research and Forecasting Model (ARW) were conducted on a 12-km grid with cycled data assimilation mimicking the operational North American Model (NAM). The results from the satellite assimilation run are compared to a control experiment (without hyperspectral IR retrievals), Modern Era-Retrospective Analysis for Research and Applications (MERRA) reanalysis, and Rapid Refresh analyses.

RECONNECTION-DRIVEN CORONAL-HOLE JETS WITH GRAVITY AND SOLAR WIND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karpen, J. T.; DeVore, C. R.; Antiochos, S. K.

Coronal-hole jets occur ubiquitously in the Sun's coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry, gravity, and solarmore » wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagation is sustained through the outer corona, in the form of a traveling nonlinear Alfvén wave front trailed by slower-moving plasma density enhancements that are compressed and accelerated by the wave. This finding agrees well with observations of white-light coronal-hole jets, and can explain microstreams and torsional Alfvén waves detected in situ in the solar wind. We also use our numerical results to deduce scaling relationships between properties of the coronal source region and the characteristics of the resulting jet, which can be tested against observations.« less

Nearshore circulation on a sea breeze dominated beach during intense wind events

NASA Astrophysics Data System (ADS)

Torres-Freyermuth, Alec; Puleo, Jack A.; DiCosmo, Nick; Allende-Arandía, Ma. Eugenia; Chardón-Maldonado, Patricia; López, José; Figueroa-Espinoza, Bernardo; de Alegria-Arzaburu, Amaia Ruiz; Figlus, Jens; Roberts Briggs, Tiffany M.; de la Roza, Jacobo; Candela, Julio

2017-12-01

A field experiment was conducted on the northern Yucatan coast from April 1 to April 12, 2014 to investigate the role of intense wind events on coastal circulation from the inner shelf to the swash zone. The study area is characterized by a micro-tidal environment, low-energy wave conditions, and a wide and shallow continental shelf. Furthermore, easterly trade winds, local breezes, and synoptic-scale events, associated with the passage of cold-fronts known as Nortes, are ubiquitous in this region. Currents were measured concurrently at different cross-shore locations during both local and synoptic-scale intense wind events to investigate the influence of different forcing mechanisms (i.e., large-scale currents, winds, tides, and waves) on the nearshore circulation. Field observations revealed that nearshore circulation across the shelf is predominantly alongshore-directed (westward) during intense winds. However, the mechanisms responsible for driving instantaneous spatial and temporal current variability depend on the weather conditions and the across-shelf location. During local strong sea breeze events (W > 10 m s-1 from the NE) occurring during spring tide, westward circulation is controlled by the tides, wind, and waves at the inner-shelf, shallow waters, and inside the surf/swash zone, respectively. The nearshore circulation is relaxed during intense land breeze events (W ≈ 9 m s-1 from the SE) associated with the low atmospheric pressure system that preceded a Norte event. During the Norte event (Wmax≈ 15 m s-1 from the NNW), westward circulation dominated outside the surf zone and was correlated to the Yucatan Current, whereas wave breaking forces eastward currents inside the surf/swash zone. The latter finding implies the existence of large alongshore velocity shear at the offshore edge of the surf zone during the Norte event, which enhances mixing between the surf zone and the inner shelf. These findings suggest that both sea breezes and Nortes play an important role in sediment and pollutant transport along/across the nearshore of the Yucatan shelf.

Plattsburgh, AFB, New York. Revised Uniform Summary of Surface Weather Observations (RUSSWO). Parts A-F.

DTIC Science & Technology

1984-01-24

GLOCAL CLIMATOLOGY 3RANCH LSAFETAC SURFACE WINDS 410 wrATHER SERVICE/MAC PERCENTAGE FREQUENCY OF WIND...oeux1I, . .p 4. A i € * GLOcAL CLIMATCLOGY RANCH L’AFETAC CEILING VERSUS VISIBILITY AIP ’-EATHFR SRVlCE/MAC 72(7Z_ PLATTSBURSH AFS NV 74-97 *A

An experimental study of several wind tunnel wall configurations using two V/STOL model configurations. [low speed wind tunnels

NASA Technical Reports Server (NTRS)

Binion, T. W., Jr.

1975-01-01

Experiments were conducted in the low speed wind tunnel using two V/STOL models, a jet-flap and a jet-in-fuselage configuration, to search for a wind tunnel wall configuration to minimize wall interference on V/STOL models. Data were also obtained on the jet-flap model with a uniform slotted wall configuration to provide comparisons between theoretical and experimental wall interference. A test section configuration was found which provided some data in reasonable agreement with interference-free results over a wide range of momentum coefficients.

Wind-tunnel modelling of the tip-speed ratio influence on the wake evolution

NASA Astrophysics Data System (ADS)

Stein, Victor P.; Kaltenbach, Hans-Jakob

2016-09-01

Wind-tunnel measurements on the near-wake evolution of a three bladed horizontal axis wind turbine model (HAWT) in the scale 1:O(350) operating in uniform flow conditions and within a turbulent boundary layer at different tip speed ratios are presented. Operational conditions are chosen to exclude Reynolds number effects regarding the turbulent boundary layer as well as the rotor performance. Triple-wire anemometry is used to measure all three velocity components in the mid-vertical and mid-horizontal plane, covering the range from the near- to the far-wake region. In order to analyse wake properties systematically, power and thrust coefficients of the turbine were measured additionally. It is confirmed that realistic modelling of the wake evolution is not possible in a low-turbulence uniform approach flow. Profiles of mean velocity and turbulence intensity exhibit large deviations between the low-turbulence uniform flow and the turbulent boundary layer, especially in the far-wake region. For nearly constant thrust coefficients differences in the evolution of the near-wake can be identified for tip speed ratios in the range from 6.5 to 10.5. It is shown that with increasing downstream distances mean velocity profiles become indistinguishable whereas for turbulence statistics a subtle dependency on the tip speed ratio is still noticeable in the far-wake region.

Ion-driven instabilities in the solar wind: Wind observations of 19 March 2005

DOE PAGES

Gary, S. Peter; Jian, Lan K.; Broiles, Thomas W.; ...

2016-01-16

Intervals of enhanced magnetic fluctuations have been frequently observed in the solar wind. However, it remains an open question as to whether these waves are generated at the Sun and then transported outward by the solar wind or generated locally in the interplanetary medium. Magnetic field and plasma measurements from the Wind spacecraft under slow solar wind conditions on 19 March 2005 demonstrate seven events of enhanced magnetic fluctuations at spacecraft-frame frequencies somewhat above the proton cyclotron frequency and propagation approximately parallel or antiparallel to the background magnetic field B o. The proton velocity distributions during these events are characterizedmore » by two components: a more dense, slower core and a less dense, faster beam. In conclusion, observed plasma parameters are used in a kinetic linear dispersion equation analysis for electromagnetic fluctuations at k x B o = 0; for two events the most unstable mode is the Alfvén-cyclotron instability driven by a proton component temperature anisotropy T ⊥/T || > 1 (where the subscripts denote directions relative to B o), and for three events the most unstable mode is the right-hand polarized magnetosonic instability driven primarily by ion component relative flows. Thus, both types of ion anisotropies and both types of instabilities are likely to be local sources of these enhanced fluctuation events in the solar wind.« less

Ion-driven instabilities in the solar wind: Wind observations of 19 March 2005

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gary, S. Peter; Jian, Lan K.; Broiles, Thomas W.

Intervals of enhanced magnetic fluctuations have been frequently observed in the solar wind. However, it remains an open question as to whether these waves are generated at the Sun and then transported outward by the solar wind or generated locally in the interplanetary medium. Magnetic field and plasma measurements from the Wind spacecraft under slow solar wind conditions on 19 March 2005 demonstrate seven events of enhanced magnetic fluctuations at spacecraft-frame frequencies somewhat above the proton cyclotron frequency and propagation approximately parallel or antiparallel to the background magnetic field B o. The proton velocity distributions during these events are characterizedmore » by two components: a more dense, slower core and a less dense, faster beam. In conclusion, observed plasma parameters are used in a kinetic linear dispersion equation analysis for electromagnetic fluctuations at k x B o = 0; for two events the most unstable mode is the Alfvén-cyclotron instability driven by a proton component temperature anisotropy T ⊥/T || > 1 (where the subscripts denote directions relative to B o), and for three events the most unstable mode is the right-hand polarized magnetosonic instability driven primarily by ion component relative flows. Thus, both types of ion anisotropies and both types of instabilities are likely to be local sources of these enhanced fluctuation events in the solar wind.« less

Ion-driven instabilities in the solar wind: Wind observations of 19 March 2005.

PubMed

Gary, S Peter; Jian, Lan K; Broiles, Thomas W; Stevens, Michael L; Podesta, John J; Kasper, Justin C

2016-01-01

Intervals of enhanced magnetic fluctuations have been frequently observed in the solar wind. But it remains an open question as to whether these waves are generated at the Sun and then transported outward by the solar wind or generated locally in the interplanetary medium. Magnetic field and plasma measurements from the Wind spacecraft under slow solar wind conditions on 19 March 2005 demonstrate seven events of enhanced magnetic fluctuations at spacecraft-frame frequencies somewhat above the proton cyclotron frequency and propagation approximately parallel or antiparallel to the background magnetic field B o . The proton velocity distributions during these events are characterized by two components: a more dense, slower core and a less dense, faster beam. Observed plasma parameters are used in a kinetic linear dispersion equation analysis for electromagnetic fluctuations at k x B o  = 0; for two events the most unstable mode is the Alfvén-cyclotron instability driven by a proton component temperature anisotropy T ⊥ /T ||  > 1 (where the subscripts denote directions relative to B o ), and for three events the most unstable mode is the right-hand polarized magnetosonic instability driven primarily by ion component relative flows. Thus, both types of ion anisotropies and both types of instabilities are likely to be local sources of these enhanced fluctuation events in the solar wind.

Ion‐driven instabilities in the solar wind: Wind observations of 19 March 2005

PubMed Central

Jian, Lan K.; Broiles, Thomas W.; Stevens, Michael L.; Podesta, John J.; Kasper, Justin C.

2016-01-01

Abstract Intervals of enhanced magnetic fluctuations have been frequently observed in the solar wind. But it remains an open question as to whether these waves are generated at the Sun and then transported outward by the solar wind or generated locally in the interplanetary medium. Magnetic field and plasma measurements from the Wind spacecraft under slow solar wind conditions on 19 March 2005 demonstrate seven events of enhanced magnetic fluctuations at spacecraft‐frame frequencies somewhat above the proton cyclotron frequency and propagation approximately parallel or antiparallel to the background magnetic field B o. The proton velocity distributions during these events are characterized by two components: a more dense, slower core and a less dense, faster beam. Observed plasma parameters are used in a kinetic linear dispersion equation analysis for electromagnetic fluctuations at k x B o = 0; for two events the most unstable mode is the Alfvén‐cyclotron instability driven by a proton component temperature anisotropy T⊥/T|| > 1 (where the subscripts denote directions relative to B o), and for three events the most unstable mode is the right‐hand polarized magnetosonic instability driven primarily by ion component relative flows. Thus, both types of ion anisotropies and both types of instabilities are likely to be local sources of these enhanced fluctuation events in the solar wind. PMID:27818854

Low-cost wind tunnel for aerosol inhalation studies.

PubMed

Chung, I P; Dunn-Rankin, D; Phalen, R F; Oldham, M J

1992-04-01

A low-cost wind tunnel for aerosol studies has been designed, constructed, and evaluated for aerosol uniformity with 2- and 0.46-micron particles. A commercial nebulizer was used to produce the suspended test particles, and a custom-made, four-hole injector was used to introduce the aerosol into the wind tunnel. A commercially available optical particle counter measured the particle concentration. Performance tests of the velocity profile and particle concentration distribution at two flow rates showed that the system performs well for small particles.

Gap winds and their effects on regional oceanography Part II: Kodiak Island, Alaska

NASA Astrophysics Data System (ADS)

Ladd, Carol; Cheng, Wei; Salo, Sigrid

2016-10-01

Frequent gap winds, defined here as offshore-directed flow channeled through mountain gaps, have been observed near Kodiak Island in the Gulf of Alaska (GOA). Gap winds from the Iliamna Lake gap were investigated using QuikSCAT wind data. The influence of these wind events on the regional ocean was examined using satellite and in situ data combined with Regional Ocean Modeling System (ROMS) model runs. Gap winds influence the entire shelf width (> 200 km) northeast of Kodiak Island and extend an additional 150 km off-shelf. Due to strong gradients in the along-shelf direction, they can result in vertical velocities in the ocean of over 20 m d-1 due to Ekman pumping. The wind events also disrupt flow of the Alaska Coastal Current (ACC), resulting in decreased flow down Shelikof Strait and increased velocities on the outer shelf. This disruption of the ACC has implications for freshwater transport into the Bering Sea. The oceanographic response to gap winds may influence the survival of larval fishes as Arrowtooth Flounder recruitment is negatively correlated with the interannual frequency of gap-wind events, and Pacific Cod recruitment is positively correlated. The frequency of offshore directed winds exhibits a strong seasonal cycle averaging 7 days per month during winter and 2 days per month during summer. Interannual variability is correlated with the Pacific North America Index and shows a linear trend, increasing by 1.35 days per year. An accompanying paper discusses part I of our study (Ladd and Cheng, 2016) focusing on gap-wind events flowing out of Cross Sound in the eastern GOA.

Synoptic forcing of wind relaxations at Pt. Conception, California

NASA Astrophysics Data System (ADS)

Fewings, Melanie R.; Washburn, Libe; Dorman, Clive E.; Gotschalk, Christopher; Lombardo, Kelly

2016-08-01

Over the California Current upwelling system in summer, the prevailing upwelling-favorable winds episodically weaken (relax) or reverse direction for a few days. Near Pt. Conception, California, the wind usually does not reverse, but wind relaxation allows poleward oceanic coastal flow with ecological consequences. To determine the offshore extent and synoptic forcing of these wind relaxations, we formed composite averages of wind stress from the QuikSCAT satellite and atmospheric pressure from the North American Regional Reanalysis (NARR) using 67 wind relaxations during summer 2000-2009. Wind relaxations at Pt. Conception are the third stage of an event sequence that repeatedly affects the west coast of North America in summer. First, 5-7 days before the wind weakens near Pt. Conception, the wind weakens or reverses off Oregon and northern California. Second, the upwelling-favorable wind intensifies along central California. Third, the wind relaxes at Pt. Conception, and the area of weakened winds extends poleward to northern California over 3-5 days. The NARR underestimates the wind stress within ˜200 km of coastal capes by a factor of 2. Wind relaxations at Pt. Conception are caused by offshore extension of the desert heat low. This synoptic forcing is related to event cycles that cause wind reversal as in Halliwell and Allen (1987) and Mass and Bond (1996), but includes weaker events. The wind relaxations extend ˜600 km offshore, similarly to the California-scale hydraulic expansion fan shaping the prevailing winds, and ˜1000 km alongshore, limited by an opposing pressure gradient force at Cape Mendocino.

Low Probability Tail Event Analysis and Mitigation in BPA Control Area: Task One Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Shuai; Makarov, Yuri V.

This is a report for task one of the tail event analysis project for BPA. Tail event refers to the situation in a power system when unfavorable forecast errors of load and wind are superposed onto fast load and wind ramps, or non-wind generators falling short of scheduled output, the imbalance between generation and load becomes very significant. This type of events occurs infrequently and appears on the tails of the distribution of system power imbalance; therefore, is referred to as tail events. This report analyzes what happened during the Electric Reliability Council of Texas (ERCOT) reliability event on Februarymore » 26, 2008, which was widely reported because of the involvement of wind generation. The objective is to identify sources of the problem, solutions to it and potential improvements that can be made to the system. Lessons learned from the analysis include the following: (1) Large mismatch between generation and load can be caused by load forecast error, wind forecast error and generation scheduling control error on traditional generators, or a combination of all of the above; (2) The capability of system balancing resources should be evaluated both in capacity (MW) and in ramp rate (MW/min), and be procured accordingly to meet both requirements. The resources need to be able to cover a range corresponding to the variability of load and wind in the system, additional to other uncertainties; (3) Unexpected ramps caused by load and wind can both become the cause leading to serious issues; (4) A look-ahead tool evaluating system balancing requirement during real-time operations and comparing that with available system resources should be very helpful to system operators in predicting the forthcoming of similar events and planning ahead; and (5) Demand response (only load reduction in ERCOT event) can effectively reduce load-generation mismatch and terminate frequency deviation in an emergency situation.« less

Measurement of Non-Stationary Characteristics of a Landfall Typhoon at the Jiangyin Bridge Site.

PubMed

He, Xuhui; Qin, Hongxi; Tao, Tianyou; Liu, Wenshuo; Wang, Hao

2017-09-22

The wind-sensitive long-span suspension bridge is a vital element in land transportation. Understanding the wind characteristics at the bridge site is thus of great significance to the wind- resistant analysis of such a flexible structure. In this study, a strong wind event from a landfall typhoon called Soudelor recorded at the Jiangyin Bridge site with the anemometer is taken as the research object. As inherent time-varying trends are frequently captured in typhoon events, the wind characteristics of Soudelor are analyzed in a non-stationary perspective. The time-varying mean is first extracted with the wavelet-based self-adaptive method. Then, the non-stationary turbulent wind characteristics, e.g.; turbulence intensity, gust factor, turbulence integral scale, and power spectral density, are investigated and compared with the results from the stationary analysis. The comparison highlights the importance of non-stationary considerations of typhoon events, and a transition from stationarity to non-stationarity for the analysis of wind effects. The analytical results could help enrich the database of non-stationary wind characteristics, and are expected to provide references for the wind-resistant analysis of engineering structures in similar areas.

Measurement of Non-Stationary Characteristics of a Landfall Typhoon at the Jiangyin Bridge Site

PubMed Central

Qin, Hongxi; Tao, Tianyou; Liu, Wenshuo

2017-01-01

The wind-sensitive long-span suspension bridge is a vital element in land transportation. Understanding the wind characteristics at the bridge site is thus of great significance to the wind- resistant analysis of such a flexible structure. In this study, a strong wind event from a landfall typhoon called Soudelor recorded at the Jiangyin Bridge site with the anemometer is taken as the research object. As inherent time-varying trends are frequently captured in typhoon events, the wind characteristics of Soudelor are analyzed in a non-stationary perspective. The time-varying mean is first extracted with the wavelet-based self-adaptive method. Then, the non-stationary turbulent wind characteristics, e.g.; turbulence intensity, gust factor, turbulence integral scale, and power spectral density, are investigated and compared with the results from the stationary analysis. The comparison highlights the importance of non-stationary considerations of typhoon events, and a transition from stationarity to non-stationarity for the analysis of wind effects. The analytical results could help enrich the database of non-stationary wind characteristics, and are expected to provide references for the wind-resistant analysis of engineering structures in similar areas. PMID:28937641

Large wind ripples on Mars: A record of atmospheric evolution

NASA Astrophysics Data System (ADS)

Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Day, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.; Herkenhoff, K. E.; Ming, D. W.; Mischna, M. A.; Rice, M. S.; Sumner, D. A.; Vasavada, A. R.; Yingst, R. A.

2016-07-01

Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter- to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

Large wind ripples on Mars: A record of atmospheric evolution

USGS Publications Warehouse

Lapotre, M G; Ewing, R C; Lamb, M P; Fischer, W W; Grotzinger, J P; Rubin, D M; Lewis, K W; Ballard, M; Day, Mitch D.; Gupta, S.; Banham, S G; Bridges, N T; Des Marais, D J; Fraeman, A A; Grant, J A; Herkenhoff, Kenneth E.; Ming, D W; Mischna, M A; Rice, M S; Sumner, D A; Vasavada, A R; Yingst, R A

2016-01-01

Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

Combined effects of total grain-size distribution and crosswind on the rise of eruptive volcanic columns

NASA Astrophysics Data System (ADS)

Girault, F.; Carazzo, G.; Tait, S.; Kaminski, E.

2016-10-01

The maximum height of an explosive volcanic column, H, depends on the 1/4th power of the eruptive mass flux, Q, and on the 3/4th power of the stratification of the atmosphere, N. Expressed as scaling laws, this relationship has made H a widely used proxy to estimate Q. Two additional effects are usually included to produce more accurate and robust estimates of Q based on H: particle sedimentation from the volcanic column, which depends on the total grain-size distribution (TGSD) and the atmospheric crosswind. Both coarse TGSD and strong crosswind have been shown to decrease strongly the maximum column height, and TGSD, which also controls the effective gas content in the column, influences the stability of the column. However, the impact of TGSD and of crosswind on the dynamics of the volcanic column are commonly considered independently. We propose here a steady-state 1D model of an explosive volcanic column rising in a windy atmosphere that explicitly accounts for particle sedimentation and wind together. We consider three typical wind profiles: uniform, linear, and complex, with the same maximum wind velocity of 15 m s- 1. Subject to a uniform wind profile, the calculations show that the maximum height of the plume strongly decreases for any TGSD. The effect of TGSD on maximum height is smaller for uniform and complex wind profiles than for a linear profile or without wind. The largest differences of maximum heights arising from different wind profiles are observed for the largest source mass fluxes (> 107 kg s- 1) for a given TGSD. Compared to no wind conditions, the field of column collapse is reduced for any wind profile and TGSD at the vent, an effect that is the strongest for small mass fluxes and coarse TGSD. Provided that the maximum plume height and the wind profile are known from real-time observations, the model predicts the mass discharge rate feeding the eruption for a given TGSD. We apply our model to a set of eight historical volcanic eruptions for which all the required information is known. Taking into account the measured wind profile and the actual TGSD at the vent substantially improves (by ≈ 30%) the agreement between the mass discharge rate calculated from the model based on plume height and the field observation of deposit mass divided by eruption duration, relative to a model taking into account TGSD only. This study contributes to the improvement of the characterization of volcanic source term required as input to larger scale models of ash and aerosol dispersion.

Seattle FWS, Washington. Revised Uniform Summary of Surface Weather Observations (RUSSWO). Parts A-F

DTIC Science & Technology

1970-08-28

FREQUENCY OF WIND DIRECTION AND SPEED til (FROM HOURLY OBSERVATIONS) 24244 SEATTLE wAHtIGTON FWC __iAR - -ALL WATHER _--- ~ALL -- CONDmON - SPEED 34MEAN (KNTS...10 PERCENTAGE FREQUENCY OF WIND DIRECTION AND SPEED 11J1 (FROM HOURLY OBSERVATIONS) 2.4244 SEATTLE WASHINGTOjN FW -6 C ALL WATHER - -M ~0-0 50O

Directional Characteristics of Inner Shelf Internal Tides

DTIC Science & Technology

2007-06-01

Figure 18. YD 202-206 Current vector plot of significant events. Significant events include internal tidal bores, solibores, and solitons . The upper...Events (Bores, Solibores, and Solitons ): Upper column leading-edge cross-shore current velocity and cross-shore wind regression. The small ellipse...Significant Events (Bores, Solibores, and Solitons ): Upper column leading-edge along-shore current velocity and along-shore wind regression. The small

Scalar Fluxes Near a Tall Building in an Aligned Array of Rectangular Buildings

NASA Astrophysics Data System (ADS)

Fuka, Vladimír; Xie, Zheng-Tong; Castro, Ian P.; Hayden, Paul; Carpentieri, Matteo; Robins, Alan G.

2018-04-01

Scalar dispersion from ground-level sources in arrays of buildings is investigated using wind-tunnel measurements and large-eddy simulation (LES). An array of uniform-height buildings of equal dimensions and an array with an additional single tall building (wind tunnel) or a periodically repeated tall building (LES) are considered. The buildings in the array are aligned and form long streets. The sensitivity of the dispersion pattern to small changes in wind direction is demonstrated. Vertical scalar fluxes are decomposed into the advective and turbulent parts and the influences of wind direction and of the presence of the tall building on the scalar flux components are evaluated. In the uniform-height array turbulent scalar fluxes are dominant, whereas the tall building produces an increase of the magnitude of advective scalar fluxes that yields the largest component. The presence of the tall building causes either an increase or a decrease to the total vertical scalar flux depending on the position of the source with respect to the tall building. The results of the simulations can be used to develop parametrizations for street-canyon dispersion models and enhance their capabilities in areas with tall buildings.

Multi-Instrument Observations of Prolonged Stratified Wind Layers at Iqaluit, Nunavut

NASA Astrophysics Data System (ADS)

Mariani, Zen; Dehghan, Armin; Gascon, Gabrielle; Joe, Paul; Hudak, David; Strawbridge, Kevin; Corriveau, Julien

2018-02-01

Data collected between October 2015 and May 2016 at Environment and Climate Change Canada's Iqaluit research site (64°N, 69°W) have revealed a high frequency (40% of all days for which observations were available) of stratified wind layer events that occur from near the surface up to about 7.2 km above sea level. These stratified wind layers are clearly visible as wind shifts (90 to 180°) with height in range-height indicator scans from the Doppler lidar and Ka-band radar and in wind direction profiles from the Doppler lidar and radiosonde. During these events, the vertical structure of the flow appears to be a stack of 4 to 10 layers ranging in vertical width from 0.1 to 4.4 km. The stratification events that were observed occurred predominantly (81%) during light precipitation and lasted up to 27.5 h. The integrated measurement platforms at Iqaluit permitted continuous observations of the evolution of stratification events in different meteorological conditions.

Inherent Variability in Short-time Wind Turbine Statistics from Turbulence Structure in the Atmospheric Surface Layer

NASA Astrophysics Data System (ADS)

Lavely, Adam; Vijayakumar, Ganesh; Brasseur, James; Paterson, Eric; Kinzel, Michael

2011-11-01

Using large-eddy simulation (LES) of the neutral and moderately convective atmospheric boundary layers (NBL, MCBL), we analyze the impact of coherent turbulence structure of the atmospheric surface layer on the short-time statistics that are commonly collected from wind turbines. The incoming winds are conditionally sampled with a filtering and thresholding algorithm into high/low horizontal and vertical velocity fluctuation coherent events. The time scales of these events are ~5 - 20 blade rotations and are roughly twice as long in the MCBL as the NBL. Horizontal velocity events are associated with greater variability in rotor power, lift and blade-bending moment than vertical velocity events. The variability in the industry standard 10 minute average for rotor power, sectional lift and wind velocity had a standard deviation of ~ 5% relative to the ``infinite time'' statistics for the NBL and ~10% for the MCBL. We conclude that turbulence structure associated with atmospheric stability state contributes considerable, quantifiable, variability to wind turbine statistics. Supported by NSF and DOE.

Eclipse-induced wind changes over the British Isles on the 20 March 2015

PubMed Central

2016-01-01

The British Isles benefits from dense meteorological observation networks, enabling insights into the still-unresolved effects of solar eclipse events on the near-surface wind field. The near-surface effects of the solar eclipse of 20 March 2015 are derived through comparison of output from the Met Office’s operational weather forecast model (which is ignorant of the eclipse) with data from two meteorological networks: the Met Office’s land surface station (MIDAS) network and a roadside measurement network operated by Vaisala. Synoptic-evolution relative calculations reveal the cooling and increase in relative humidity almost universally attributed to eclipse events. In addition, a slackening of wind speeds by up to about 2 knots in already weak winds and backing in wind direction of about 20° under clear skies across middle England are attributed to the eclipse event. The slackening of wind speed is consistent with the previously reported boundary layer stabilization during eclipse events. Wind direction changes have previously been attributed to a large-scale ‘eclipse-induced cold-cored cyclone’, mountain slope flows, and changes in the strength of sea breezes. A new explanation is proposed here by analogy with nocturnal wind changes at sunset and shown to predict direction changes consistent with those observed. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’. PMID:27550759

A numerical study of diurnally varying surface temperature on flow patterns and pollutant dispersion in street canyons

NASA Astrophysics Data System (ADS)

Tan, Zijing; Dong, Jingliang; Xiao, Yimin; Tu, Jiyuan

2015-03-01

The impacts of the diurnal variation of surface temperature on street canyon flow pattern and pollutant dispersion are investigated based on a two-dimensional street canyon model under different thermal stratifications. Uneven distributed street temperature conditions and a user-defined wall function representing the heat transfer between the air and the street canyon are integrated into the current numerical model. The prediction accuracy of this model is successfully validated against a published wind tunnel experiment. Then, a series of numerical simulations representing four time scenarios (Morning, Afternoon, Noon and Night) are performed at different Bulk Richardson number (Rb). The results demonstrate that uneven distributed street temperature conditions significantly alters street canyon flow structure and pollutant dispersion characteristics compared with conventional uniform street temperature assumption, especially for the morning event. Moreover, air flow patterns and pollutant dispersion are greatly influenced by diurnal variation of surface temperature under unstable stratification conditions. Furthermore, the residual pollutant in near-ground-zone decreases as Rb increases in noon, afternoon and night events under all studied stability conditions.

Distribution and solar wind control of compressional solar wind-magnetic anomaly interactions observed at the Moon by ARTEMIS

NASA Astrophysics Data System (ADS)

Halekas, J. S.; Poppe, A. R.; Lue, C.; Farrell, W. M.; McFadden, J. P.

2017-06-01

A statistical investigation of 5 years of observations from the two-probe Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) mission reveals that strong compressional interactions occur infrequently at high altitudes near the ecliptic but can form in a wide range of solar wind conditions and can occur up to two lunar radii downstream from the lunar limb. The compressional events, some of which may represent small-scale collisionless shocks ("limb shocks"), occur in both steady and variable interplanetary magnetic field (IMF) conditions, with those forming in steady IMF well organized by the location of lunar remanent crustal magnetization. The events observed by ARTEMIS have similarities to ion foreshock phenomena, and those observed in variable IMF conditions may result from either local lunar interactions or distant terrestrial foreshock interactions. Observed velocity deflections associated with compressional events are always outward from the lunar wake, regardless of location and solar wind conditions. However, events for which the observed velocity deflection is parallel to the upstream motional electric field form in distinctly different solar wind conditions and locations than events with antiparallel deflections. Consideration of the momentum transfer between incoming and reflected solar wind populations helps explain the observed characteristics of the different groups of events.