Resultant Wind Direction Research Articles

Greedy parabolics: Wind flow direction within the deflation basin of parabolic dunes is governed by deflation basin width and depth

Parabolic dunes are ‘U’ or ‘V’-shaped aeolian landforms that form on pre-existing sand deposits. Their morphology consists of an upwind deflation basin, bordered by often vegetated trailing arms and a downwind depositional lobe. The orientation of parabolic dunes is commonly attributed to the prevailing or resultant wind direction. Consequently, the orientation of parabolic dunes stabilised by vegetation growth has been used as a proxy for wind direction during past climates in several studies. However, the ability or extent of parabolic dune morphology to steer incident wind flow parallel to the orientation of the landform, and thus migrate in the direction of the current landform orientation rather than prevailing wind direction, is unknown. By numerically modelling wind flow within the deflation basin of eight parabolic dunes, we demonstrate for the first time that wind flow direction within the deflation basin of a parabolic dune is highly controlled by the depth and width of the deflation basin. The greater the depth–width ratio of the landform (i.e. the deeper and narrower the deflation basin), the greater the degree of flow steering relative to the axis orientation of the landform. These results demonstrate that future studies must exercise caution when using parabolic dune orientation as a direct proxy for prevailing wind direction, especially where parabolic dunes have a relatively high deflation basin depth–width ratio, as the deflation basin of these landforms may continue to migrate in an antecedent wind direction.

Wireless Wind Speed Measurement Based on Three–Axis Ultrasonic Anemometer

In this paper, a three-axis ultrasonic anemometer is presented which uses six ultrasonic transducers to obtain the wind speed, wind direction, etc. Every two transducers are used as transmitter and receiver of a short sequence of pulses. The time of flight is taken by the ultrasonic sound to travel from the transmitter to the receiver. This can be used to determine the three dimensional vector components of wind—u, v and w. From these components, the resultant wind speed and direction can be obtained. The developed anemometer is intended to be used in the environment monitor demand of tethered aerostat and airship. Also it can support autonomous navigation for a scale model sailboat.

黄土高原水蚀风蚀交错带坡耕地土壤风蚀速率空间分布

Wind erosion is difficult to separate from the total erosion in the wind-water erosion crisscross region of the Loess Plateau, regardless of its spatial distribution. Water erosion also contributes to the total erosion. Water and wind erosions affect each other. The methods and techniques used in current research present the most significant limitation. Therefore, the methods and techniques of the field must be improved. A short-lived radionuclide—7Be—was used to trace wind erosion in this study. Surface soil samples (0–30 mm) were collected from two north-faced farmland slopes with sandy loam and clay loam using the transect approach in the Liudaogou Watershed. This study estimated the rates of soil–wind erosion, analyzed the spatial distribution pattern of soil-wind erosion, and discussed its implication to wind conditions and local microreliefs. Results showed that the average rate of wind erosion was 1560.81 t/(km2 a) on sandy loam slope A and 694.26 t/(km2 a) on clay loam slope B. The wind erosion rate decreased from top to bottom for both slopes. Soil particles were coarser, specific surface areas were smaller, and organic matter contents were lower in the surface layer (0–30 mm) after wind erosion than those before wind erosion. The isolines of the wind erosion rate visually showed the wind erosion distribution and indicated that the north wind was the effective resultant wind direction that caused soil loss. The variation in the shape of the isolines reflected the microreliefs of the slopes, and their variation degree denoted the influence degree and scope of microreliefs on wind erosion.

Spatial Pattern of Ground-Level Ozone Concentration in Dallas-Fort Worth Metropolitan Area

The objective of this study was to analyze spatial patterns of ground-level ozone concentrationin the Dallas-Fort Worth, Texas metropolitan area. Average daily maximum eight-hour ozone concentration,number of days with concentrations exceeding 75 ppb, average outside air temperature, and resultant winddirection at 20 monitoring stations were compiled for January-December, 2013. Recent estimates of populationand vehicle miles traveled were also compiled for 12 counties with ozone monitoring station(s). Ozone levelsand resultant wind directions were mapped for representative months in each season. On several days fromMay-October, eight-hour ozone measurements exceeded 75 ppb. September, followed by August, producedthe highest ozone concentrations, as well as the most observations exceeding 75 ppb. Late spring and summermonths also showed the greatest range in ozone concentrations; during this time period, sustained southeasterlywinds caused distinct clusters of high ozone concentration at the northern perimeter of the study area.However, ozone concentrations at individual monitoring stations were not associated with population orvehicle miles traveled in counties occupied by those stations.

Coastal Boundary Layer Characteristics of Wind, Turbulence, and Surface Roughness Parameter over the Thumba Equatorial Rocket Launching Station, India

The study discusses the features of wind, turbulence, and surface roughness parameter over the coastal boundary layer of the Peninsular Indian Station, Thumba Equatorial Rocket Launching Station (TERLS). Every 5 min measurements from an ultrasonic anemometer at 3.3 m agl from May 2007 to December 2012 are used for this work. Symmetries in mesoscale turbulence, stress off-wind angle computations, structure of scalar wind, resultant wind direction, momentum flux (M), Obukhov length (L), frictional velocity (u*), w-component, turbulent heat flux (H), drag coefficient (CD), turbulent intensities, standard deviation of wind directions (σθ), wind steadiness factor-σθrelationship, bivariate normal distribution (BND) wind model, surface roughness parameter (z0),z0and wind direction (θ) relationship, and variation ofz0with the Indian South West monsoon activity are discussed.

The wind regime of Romania – Characteristics, trends and North Atlantic oscillation influences

The present study attempts to develop a comprehensive perspective of the wind regime on the Romanian territory, focusing on the characteristics and tendencies encountered over the past 50 years, as well as on the NAO projection on it, using several data categories gathered from 167 meteorological stations. Based on the recorded multiannual averages and on the strong correlation (r = 0.87) established between altitude and wind speed in wind exposed areas, we created the map of mean (multi)annual wind speed. The highest aeolian potential corresponds to the Carpathians (7-10 m/s on the ridges and 3-7 m/s on the slopes and within valleys) and the Black Sea Shore (5-7 m/s); nevertheless, the two areas develop extreme values of the wind turbulence – maximum in the Carpathians and minimum in the coastal units. Tablelands in Moldova and Dobrogea, as well as the northern part of Baragan show ideal conditions for the development of aeolian parks (moderate and strong winds, low turbulences). On a country-size scale, the month with the highest mean wid speed is March, whereas August is the calmest one. For the first time, the map of resultant wind direction (DRV) was designed, expressing both the resultant wind orrientation and its intensity (high intensity = low directional variability). Concerning NAO, a negative correlation is observed between its indices and the wind speed (mean speed, frequency and intensity of the stromic events) at a multiannual and multidecadal scale. The correlation coefficients present high values in the extra-carpathian areas and small or moderate values in the intra-carpathian areas. The positive (negative) NAO associated with low (high) cyclogenesis over the Mediterranean area induce low (high) winds over the Romanian territory due to diminished (enhanced) frequency of cyclones reaching Romanian regions.

Model Representation of Local Air Quality Characteristics

Abstract Daily (24 h) and hourly air quality data at several sites are used to examine the performance of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5)–Community Multiscale Air Quality Model (CMAQ) system over a 3-month period in 2003. A coarse (36 km) model grid was expected to provide relatively poor performance for ozone and comparatively better performance for fine particles, especially the more regional sulfate and carbonaceous aerosols. However, results were different from this expectation. Modeling showed significant skill for ozone at several locations but very little skill for particulate species. Modeling did poorly identifying surface wind directions associated with the highest and lowest pollutant exposures at most sites, although results varied widely by location. Model skill appeared to be better for ozone when spatial–temporal (S–T) patterns were examined, due in part to the ability of the model to reproduce much of the temporal variance associated with the diurnal photochemical cycle. At some sites the modeling even performed well in replicating the directional variability of hourly ozone despite relatively low spatial resolution. MM5–CMAQ spatial (directional) representation of 24-h-average particulate data was not good in most cases, but model skill improved somewhat when hourly data were examined. Modeling exhibited skill for sulfate at only one of nine sites using 24-h data averaged by daily resultant wind direction, at two of six sites when hourly data were averaged by direction, and at four of six sites when the combined spatial and temporal variance of sulfate was examined. Results were generally poorer for total carbon aerosol mass and total mass of particulate matter with diameter of less than 2.5 μm (PM2.5). The primary result of this study is that an S–T analysis of pollutant patterns reveals model performance insights that cannot be realized by only examining model error statistics as is typically done for regulatory applications. Use of this S–T analysis technique is recommended for better understanding model performance during longer simulation periods, especially when using grids of finer spatial resolution for applications supporting local air quality management studies. Of course, using this approach will require measuring semicontinuous fine particle data at more sites and for longer periods.

The influence of wind forcing on across-shelf transport in the Florida Keys

Acoustic Doppler current profiles and current meter data are combined with wind observations to describe the transport of water leaving Florida Bay and moving onto the inner shelf on the Atlantic side of the Florida Keys. A 275-day study in the Long Key Channel reveals strong tidal exchanges, but the average ebb tide volume leaving Florida Bay is 19% greater than the average flood tide volume entering the bay. The long-term net outflow averages 472 m 3 s −1. Two studies in shelf waters describe the response to wind forcing during spring and summer months in 2004 and during fall and winter months in 2004–2005. During the spring–summer study, southeasterly winds have a distinct shoreward component, and a two-layer pattern appears. Surface layers move shoreward while near-bottom layers move seaward. During the winter study, the resultant wind direction is parallel to the Keys and to the local isobaths. The entire water column moves in a nearly downwind direction, and across-shelf transport is relatively small. During the summer wet season, Florida Bay water should be warmer, fresher, and thus less dense than Atlantic shelf waters. Ebbing bay water should move onto the shelf as a buoyant plume and be held close to the Keys by southeasterly winds. During the winter dry season, colder and saltier Florida Bay water should leave the tidal channels with relatively high density and be concentrated in the near-bottom layers. But little across-shelf flow occurs with northeasterly winds. The study suggests that seasonally changing wind forcing and hydrographic conditions serve to insulate the reef tract from the impact of low-quality bay water.

Monitoring sand dune advance in the Taklimakan Desert

The migration rate of sand dunes is important for the design of the sand-control system in the Taklimakan Desert. Sand dune movement was monitored in a sample plot along the desert-crossing highway by means of a topographical survey in late 1991, 1992 and 1993. The results reveal that most of the morphometric parameters of the dunes are not as well correlated as they are generally supposed to be. The mean advance rate of the dunes was 7.29 and 5.56 m year −1 in 1992 and 1993, respectively. The advance direction is towards the SW, approximately in accordance with the local resultant wind direction. The advance rate of the dunes was controlled by the local wind regime and dune morphometry. However, the relationships between advance rate and the morphometric parameters of the dunes are variable for the immature dunes. The small scale and immaturity of the dunes, insufficient sand supply, and complex wind modes are responsible for the complex dune parameter relationship, involving frequent changes of dune morphology, as well as changes of dune advance rate.

Recognition of ancient eolian longitudinal dunes; a case study in upper Bhander Sandstone, Son Valley, India

ABSTRACT Straight-crested and internally bipolar cross-stratified eolian dunes are common in the upper part of progradational cycles within the late Proterozoic Upper Bhander Sandstone, Son Valley, India. The Sandstone formed in a coastal setting, and it encompasses supralittoral storm, eolian sand sheet, draa, pond, and ephemeral stream deposits. Ripples of three different size and vector populations typically occur within the dune deposits. The smallest population shows migration parallel to the dune crests, and other two show migration obliquely towards the dune crests. Simple interpolation reveals only 9° deviation of the dune trend from the long-term resultant wind direction. In addition to the two primary wind vectors that control the duneforms, the sand transport ratio less than 1.2 suggests that these are longitudinal dunes. Forward computer modeling and calculation of the maximum gross bedform-normal transport direction further corroborate that the dunes were longitudinal. The dunes are smaller and architecturally simpler than most other longitudinal dunes described in the literature. The methodology adopted here is a useful approach to evaluate longitudinal dunes in the rock record.

Superposition of aeolian dust ripple patterns as a result of changing wind directions

AbstractThe effect of a change of wind direction on the orientation (and some other morphometric characteristics) of aeolian dust ripples is investigated. Ripple formation is simulated in a wind tunnel on surfaces that are already characterized by a previously established rippling. The effect of a wind rotation of 45 degrees, 90 degrees, and 180 degrees is examined. It is found that wind rotations of 45 and 180 degrees will lead towards a ripple alignment perpendicular to the last air flow. A wind rotation of 90 degrees, however, leads towards a ripple alignment perpendicular to the resultant wind direction. The faster the wind blows, the more this effect is expressed. No distinct relationship exists between the asymmetry of a dust ripple (and a dust ripple field) and the direction of the wind blowing as the ripples formed. As the orientation and asymmetry of aeolian dust ripples do not necessarily reflect the air flow direction during which the ripples formed, great care should be taken when reconstructing wind directions from such aeolian ripples.

Research results from Antarctic automatic weather stations

Automatic weather station (AWS) units have been deployed in Antarctica since 1980 by the U.S. Antarctic Research Program. As of June 1987, 25 AWS units are operating in Antarctica in support of meteorological research. The AWS units measure air temperature, wind speed, and wind direction at a nominal height of 3 m above the surface and air pressure at the height of the electronics enclosure. Some AWS units measure relative humidity at 3 m and air temperature difference between 3 m and 0.5 m above the surface. Three to five values for each sensor are updated at 10‐min intervals and transmitted at 200‐s intervals to data collection systems on the NOAA series of polar‐orbiting satellites. The AWS units in Antarctica are sited to support research on katabatic winds, barrier winds, surface heat fluxes, and climate. Results from the katabatic wind experiment along a line upslope from the Adelie Coast show that the katabatic wind is stronger in winter than in summer and is strongest inland from the coast. The potential temperature difference from the south pole to the Adelie Coast has the largest negative value in winter, supporting the stronger katabatic winds. The katabatic flow down the glaciers of the Transantarctic Mountains to the Ross Ice Shelf requires synoptic support because the potential temperatures on the Ross Ice Shelf are lower than at higher elevations such as the south pole. Data from AWS sites on the Ross Ice Shelf along the Transantarctic Mountains generally have southerly monthly resultant wind directions along the mountains. Ross Island with its 3000‐m‐high volcanoes deflects the southerly wind flow, resulting in an easterly wind direction at McMurdo Station. AWS units equipped to measure vertical air temperature difference and relative humidity provide estimates of the latent and sensible heat flux on the Ross Ice Shelf. Generally, the sensible heat flux is negative, and the latent heat flux is small. The collection of the AWS data by a local user terminal at McMurdo Station makes possible the use of the AWS data to support air operations.

Anthropogenic nitrogen oxide transport and deposition in Eastern North America

A long-range atmospheric transport and transformation model is presented for nitrogen oxides emitted by man-made sources. The model parameters are optimized by matching the model output—annual average nitrate (NO − 3) wet deposition—to observed deposition at 109 precipitation sampling stations in eastern N America that operated continuously in the years 1980–1982. The root-mean-square residual between observations and predictions is 2.9 kg NO − 3 ha −1 y −1 or 19.7% of the root-mean-square observed value. The trend of estimated annual average NO − 3 concentrations in precipitation at Hubbard Brook, New Hampshire compares well with the observations from 1964 to 1981. Transfer coefficients decay nearly exponentially with distance with length scales of 200–800 km, depending on source-receptor orientation with respect to the resultant annual wind direction. The model is used for source apportionment of NO − 3 wet deposition at several receptors and for estimating a nitrogen budget for eastern N America, including the transboundary fluxes between the U.S. and Canada.

Mesoscale variation of average airflow in application to time integrated concentration gaussian models

Average annual airflow directions have been estimated by a simple method which makes use only of wind direction data measured at standard meteorological stations. Resultant wind directions can be applied to estimate the most probable direction of pollutant transport inside a relatively small region of several tens of km.

The Diurnal Wind Variation in the Lowest 1500 ft in Central Oklahoma. June 1966–May 1967

One year of wind data from a television tower in northern Oklahoma City has been analyzed an a diurnal basis. The annual mean speeds below the third level at 296 ft are lowest at night and highest during the day, and conversely the speeds up to the seventh level at 1458 ft are lowest during the day and highest at night. Generally, speed changes occur in short time periods shortly after sunrise and near sunset. Resultant wind directions veer most with height between 1700–1000 CST and least during midday. At all levels winds veer with time between 2100 and approximately 1100 CST and then back with time during the remaining hours.

Summer Drought over Western India

Summer Drought over Western India C. S. Ramage* The Indian Ocean and Asia comprise a unique water-land combination : an uninterrupted continental mass, north of about 15° N, bordering a uninterrupted ocean to the south. The differing heat capacities of land and ocean subjected to the annual latitudinal cycle of the sun at its zenith give rise to the immense seasonal wind regimes known as monsoons. Although monsoons develop over other parts of the world, only around the Indian Ocean do they appear as truly massive interruptions and reversals of the normal global atmospheric circulation. Within this region the summer monsoon of the Arabian Sea is outstanding. Strong south and southwest winds of unequaled persistence sweep along the shores of Africa and Arabia and across the sea to western India. To the west and north extends the great yearround desert arc of Somalia, Arabia, Iran, and West Pakistan; in the northeast the arc ends in western India, a desert in winter, usually rain-drenched in summer. Vagaries of summer monsoon rain over western India may have dire results and have so far defied the efforts of countless perspiring meteorologists to forecast them adequately. Of the monsoon onset, the fisherman and the sailor think of winds, light or moderate northeast in the winter, usually shifting during late May to fresh or strong southwest. However, to the landanchored millions, the onset occurs when summer rains break the * Professor of Meteorology at the University of Hawaii, Honolulu, Hawaii, 96822, since 1957, Dr. Ramage is also Chairman of the Department of Geosciences and Associate Director of the Hawaii Institute of Geophysics, from which this is Contribution No. 199. Supported by Grant GA-386 of the Atmospheric Sciences Section, National Science Foundation, this paper was presented at the Fifth Technical Conference on Hurricanes and Tropical Meteorology, Caracas, Venezuela, 20 28 November 1967. 41 42 ASSOCIATION OF pacific coast geographers 1004IOOO 004 008 Figure 1. Summer (July, August, September ): Mean surface pressure in nib (dashed lines); mean resultant wind direction ( solid lines ) . Figure 2. Summer: Mean isochrones of onset of monsoon rains: places mentioned in text (land above 12,000 feet elevation shown by hatching). winter drought. During winter, when dry northeast winds dominate the Indian subcontinent, the weather is dry. One might expect, then, that during summer the rains would begin when air which has crossed thousands of miles of ocean to the southwest moves in over the land. To the contrary, however, the rains may not begin until some weeks after the winds shift. This would indicate that establishment of the wind circulation in response to heating of the desert arc and development of heatlows (Figure 1) is a necessary but not sufficient prerequisite for rain, and that the air must be additionally modified before the moisture of the southwest monsoon can be precipitated. Furthermore, 1.The first rains of the monsoon might be expected to develop over southwest India and spread downstream along the flow toward the northeast. However, the rains start almost simultaneously in the northeast and south of the country, but do not reach the northwest until more than six weeks later (Figure 2). 2.Over the coastal regions of northwest India, north of Bombay , when the on-shore surface monsoon flow is strong, near-desert conditions prevail even at the height of the summer monsoon. Less rain falls here on a coast directly exposed to the monsoon than over the Deccan Plateau of central India, a sheltered area lying in the rain shadow of the Western Ghats (Figure 3). VOLUME 30 YEARBOOK 1968 43 I Figure 3. Summer: Mean rainfall in Figure 4. Summer: Mean frequency of surface depression occurrence (from Ananthakrishnan1 ). Isopleths labeled in inches (solid lines); percentage duration times per season (solid) and in years of rain ( dashed lines ) . between occurrences (dashed). 3.The meteorologist can often relate rain distribution to the distribution of pressure systems. Figure 4, based on 70 years of records ,1 depicts the frequency distribution of surface depressions and storms over the Arabian Sea, the Indian subcontinent, and the Bay of Bengal. The depressions, which generally move west-northwest up the Ganges Valley, readily account for the high precipitation of northeastern India and the...

Development of an Objective Method for Forecasting Gulf Stratus Clouds at Bryan Air Base, Texas in the Summer Season

An objective method of forecasting Gulf stratus clouds at Bryan Air Base, Texas in the summer season is developed using the scatter-diagram technique. The parameters used are (1) resultant wind direction, (2) resultant pressure-gradient magnitude, (3) Houston temperature-dew-point spread, (4) Bryan dew point, and (5) Bryan temperature-dew-point spread. Based on one year of independent data and four years of dependent data, the skill scores are 0.55 and 0.70 respectively.

William Bulkeley's record of the weather of Anglesey 1734–1743, 1747–1760

AbstractThe study of climatic fluctuations before the nineteenth century is hindered by the paucity and poor distribution of instrumental records, and increasing reliance must be placed upon diaries and other descriptive sources. The diary of William Bulkeley of Anglesey, over the period between 1734 and 1760, has been examined. From the information it contains, resultant wind directions and constancy have been calculated. Frequencies of days with rain, snow, hail, frost and thunder are tabulated. A comparison is made between the general monthly rainfall serial values calculated for England and Wales and data derived from the diary. The record of the aurorae observed is given.

Chart II.—Mean Annual Pressure and Resultant Wind Direction for 1893

Chart II.—Mean Annual Pressure and Resultant Wind Direction for 1893

Chart V. Normal Pressure (20 years) and Normal Resultant Wind Direction (15 years) for December

Chart V. Normal Pressure (20 years) and Normal Resultant Wind Direction (15 years) for December