Direction Of Strong Winds Research Articles

Distinguishing Extreme Precipitation Mechanisms Associated with Atmospheric Rivers and Nonatmospheric Rivers in the Lower Yangtze River Basin

Abstract This study investigates the disparity in quantitative moisture contribution and synoptic-scale vertical motion in the lower reaches of the Yangtze River basin (LYRB) for different extreme precipitation (EP) types, which are categorized as EP associated with atmospheric river (AR&EP) or EP associated with nonatmospheric river (non-AR&EP). To analyze moisture contribution, backward tracking using the Water Accounting Model-2layers is performed. In general, the remote moisture contribution is 9.7 times greater than the local contribution, with the ocean contribution being 1.67 times stronger than the land contribution. However, terrestrial and oceanic contributions obviously increase in the EP types, especially for oceanic contribution being double in magnitude. Notably, the west Pacific (WP) contribution emerges as the dominant differentia between the EP types, playing a crucial role in the AR formation. By solving the quasigeostrophic omega equation, the upper-level jet (ULJ) stream acts as the primary dynamic forcing for transverse vertical motion in AR&EP, while the baroclinic trough exhibits a relatively weaker influence. However, both systems have a nearly equal impact on vertical velocity in non-AR&EP. The enhanced shearwise elevation in the non-AR&EP type is the response of the stronger upper-level ridge over the Tibetan Plateau (TP), which induces enhanced Q vector, the divergence pointing toward the LYRB. However, the main dynamic difference is the location of ULJ, which serves as the trigger role although weak. Diabatic forcing proves to be the decisive factor for vertical motion development, the difference attributed to the released excessive latent heating with excess moisture contribution from the WP in AR&EP with enhanced precipitation. Significance Statement The main objective of this study is to investigate quantitative moisture contribution by applying Water Accounting Model-2layers and vertical motion attribution using the quasigeostrophic omega equation for extreme precipitation types based on the presence or absence of atmospheric river. Our findings reveal excessive moisture from the west Pacific serving not only as key in atmospheric river formation but also as the primary trigger for intensified diabatic vertical motion, inducing enhanced precipitation. The direction of strong winds in the north of the Tibetan Plateau holds crucial forecasting implications, which determine the location of the upper-level jet stream downstream. The transverse vertical motion, induced by the upper-level jet stream, plays the dominant dynamic role in both extreme precipitation (EP) types.

Experimental studies on lateral bearing capacity of modified tripod suction caissons for offshore wind turbines in silty clay

In recent years regular tripod suction caissons are commonly used in offshore wind farm projects because of economic feasibility and environment-friendly work principles. The design of a modified tripod suction caisson composed of three caissons with different diameters can improve the capacity behaviour in the direction of strong wind within a considered construction cost. This paper carried out model tests to study the lateral bearing capacity of modified tripod suction caissons in silty clay. Based on the equilibrium equation of vertical force of modified tripod suction caissons the average vertical subgrade reaction modulus is proposed to investigate the relationship between it and rotation, which is of paramount importance to the nonlinear lateral bearing capacity. The results show that the range of bearing capacity factors increases with the increasing effective diameter-height ratio indicating that modified tripod suction caisson with reasonable combinations can effectively improve its bearing capacity in a certain loading direction. The sum of the bearing capacity factors of three monopod suction caissons falls in the range of the capacity factors of the tripod foundation consisting of the above caissons. Suction under the lid increases with the increasing lateral load and seems to be not related to the combinations of suction caissons with different diameters. By fitting the experimental data, it is found that there is a power exponential relationship between the average vertical subgrade reaction modulus and rotation of the foundation.

Radar Characteristics and Causal Analysis of Two Consecutive Tornado Events Associated with Heavy Precipitation during the Mei-Yu Season

This paper comprehensively analyzed two consecutive tornado events associated with heavy precipitation during the Mei-yu season (a period of continuous rainy weather that occurs in the middle and lower reaches of the Yangtze River in China from mid-June to mid-July each year) and detailed the formation and development process of the tornadoes using Doppler weather radar, wind profiler radar, ERA5 reanalysis data, ground automatic station data and other multi-source data. The results showed that: (1) Small-scale vortices were triggered and developed during the eastward movement of the low vortex, forming two tornadoes successively on the eastern section of the Mei-yu front. (2) The presence of a gap on the front side of the reflectivity factor profile indicated that strong incoming airflow entered the updraft. Mesocyclones were detected with decreasing heights and increasing shear strengths. The bottom height of the tornado vortex signature (TVS) dropped to 0.7 km, and the shear value increased to 55.4 × 10−3 s−1. Tornado debris signatures (TDSs) could be seen with a low cross-correlation coefficient (CC) value area of 0.85–0.9 in the mesocyclone. The difference between the lowest-level difference velocity (LLDV) and the maximum difference velocity (MXDV) reached the largest value when a tornado occurred. (3) The continuously enhanced low-level jet propagated downward to form a super-low-level jet, and the strong wind direction and wind speed convergence in the boundary layer created a warm, moist and unstable atmosphere in Suzhou. With the entrainment of dry air, the northwest dry jet and the southeast moist jet stimulated the formation of a miniature supercell. (4) The low-level vertical wind shear of 0–1 km increased significantly upon tornado occurrence, which was more conducive to the formation and intensification of horizontal vorticity tubes. Encountering updrafts and downdrafts, the vorticity tubes might have been stretched and intensified. The first lightning jumps appeared 15 min and 66 min earlier than the Kunshan Bacheng tornado and the Taicang Liuhe tornado. The Liuhe tornado occurred during the stage when the lightning frequency reached its peak and then fell back.

Impacts of stronger winds and less sea ice on Canadian Beaufort Sea shelf ecosystems since the late 1990s

Continuous and multi-decadal records of faunal abundance and diversity helping to identify the impacts of ongoing global warming on aquatic ecosystems are rare in the coastal Arctic. Here, we used a 50-year-long microfaunal record from a sediment core collected in the Herschel Basin (YC18-HB-GC01; 18 m water depth) to document some aspects of the environmental responses of the southern Canadian coastal Beaufort Sea to climate change. The microfaunal indicators include benthic foraminiferal assemblages, ostracods and tintinnids. The carbonate shells of two foraminiferal species were also analyzed for their stable isotope signatures (δ13C and δ18O). We compiled environmental parameters from 1970 to 2019 for the coastal region, including sea ice data (break-up date, freeze-up date, open season length and mean summer concentration), the wind regime (mean speed, direction of strong winds and the number of storms), hydrological data (freshet date, freshet discharge and mean summer discharge of the Firth and the Mackenzie rivers), and air temperature. Large-scale atmospheric patterns were also taken into consideration. Time-constrained hierarchal clustering analysis of foraminiferal assemblages and environmental parameters revealed a near-synchronous shift around the late 1990s. The microfaunal shift corresponds to an increased abundance of taxa tolerant to variable salinity, turbulent bottom water conditions, and turbid waters towards the present. The same time interval is marked by stronger easterly winds, more frequent storms, reduced sea-ice cover, and a pervasive anticyclonic circulation in the Arctic Ocean (positive Arctic Ocean Oscillation; AOO+). Deeper vertical mixing in the water column in response to intensified winds was fostered by increased open surface waters in summer leading to turbulence, increased particle loading and less saline bottom waters at the study site. Stronger easterly winds probably also resulted in enhanced resuspension events and coastal erosion in addition to a westward spreading of the Mackenzie River plume, altogether contributing to high particulate-matter transport. Increase food availability since ∼2000 was probably linked to enhanced degradation of terrestrial organic carbon, which also implies higher oxygen consumption. The sensitivity of microfaunal communities to environmental variations allowed capturing consequences of climate change on a marine Arctic shelf ecosystem over the last 50 years.

Numerical Simulation of Wind Waves and calculation of planning wave factors in the East Taihu Lake, Jiangsu Province, China

Taihu Lake is a large shallow lake in the lower Yangtze River Delta. The wave action in Taihu Lake plays an important role in coastal port construction. In this paper, based on the 10 min average wind speed at 10 m above the water surface recorded hourly from August 14 to August 17, 2014, the SWAN wave model is used to simulate the wind waves of the Taihu Lake in the corresponding period. Due to the lack of long-time series of wave observation data in the project area, the relationship between design wind speed and wind wave is used to calculate wave elements in different return periods. The results show that the strong wind direction and strong wave direction of the East Taihu Lake are NNW. The waves in the proposed Qidu harbor are mainly from the waves outside the permeable breakwater. Under the action of the most unfavorable wave direction NE, the effective wave height of most waters in the harbor is below 0.4m, which can meet the requirements of avoiding waves for fishing boats.

Surface ozone exceedances in Melbourne, Australia are shown to be under NOx control, as demonstrated using formaldehyde:NO2 and glyoxal:formaldehyde ratios

Two and a half years of multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of nitrogen dioxide (NO2), formaldehyde (HCHO) and glyoxal (CHOCHO) are presented alongside in-situ ozone (O3) measurements in Melbourne, Australia. Seasonal and diurnal cycles, vertical profiles and relationships with key meteorological variables are provided. NO2 and CHOCHO were found at highest concentration for low wind speeds implying that their sources were predominantly localised and anthropogenic. HCHO showed an exponential relationship with temperature and a strong wind direction dependence from the northern and eastern sectors, and therefore most likely originated from oxidation of biogenic volatile organic compounds (VOCs) from surrounding forested and rural areas. The glyoxal:formaldehyde ratio (Rgf), reported for the first time in Australia, was consistently high compared to values elsewhere in the world with a mean of 0.105 ± 0.0503 and tended to increase with increasing anthropogenic influence. The HCHO:NO2 ratio (Rfn) was used to characterise tropospheric ozone formation conditions. A strong relationship was found between high temperature, low Rgf, high Rfn and high ozone surface concentrations. Therefore, we propose that both Rgf and Rfn may be useful indicators of tropospheric ozone production regimes and concentrations. The Rfn showed that the vast majority of high ozone production episodes occurred under NOx-limited conditions, suggesting that surface ozone pollution events in Melbourne could be curtailed using NOx emission controls.

Tafoni show postglacial and modern wind azimuths that are similar at Bunger Hills

AbstractThe directions of strong winds are important for the distribution of marine salt spray, rock weathering, lake chemistry and the distribution of vegetation in Bunger Hills, a coastal ice-free oasis in East Antarctica. Present-day strong winds (> 10 m s−1) dominantly blow from 118 ± 21 degrees true (°T; ± 1 SD). Orientated tafoni (weathering pits) might form in bedrock surfaces by salt and ice crystallization, thermal stress and saltating sand particles, recording the orientation of a strongly directional wind field since the last deglaciation, which commenced > 30 000 years ago. The orientations of these tafoni, at 101 ± 18°T for 686 measurements at 28 sites, are indistinguishable from the direction of modern-day strong winds (> 10 m s−1), indicating that the orientation of the slope of the ice sheet has been stable throughout the last 10 000 years during the Holocene.

Numerical simulation of the oil spilling diffusion in waterway engineering

Taking Guangli waterway engineering of Dongying Port as background, based on hydrodynamic and Euler-Lagrange theory, a numerical model of two-dimensional tidal current and oil spill diffusion is established and verified by measured data. According to different meteorological conditions, choose representative scenes, the drift range of oil film after oil spill accident and its influence on the surrounding water environment are predicted. Results show that: the range and track of oil film are closely related to the oil spilling time and wind direction. Under no wind condition, the oil sweep area is between 45 km2 and 65 km2 in 24h; Under strong wind direction of NW, the furthest distance to the southeast can be up to 23 km, and the oil sweep area is between 70 km2 and 135 km2 in 24h. Oil spills will have different effects on adjacent reserves. It is suggested that emergency response measures should be taken quickly in case of oil spills to minimize the adverse effects on the surrounding marine environment.

Effect of Planetary Rotation on Oceanic Surface Boundary Layer Turbulence

AbstractA large-eddy simulation (LES) model is configured to investigate the effect of the horizontal (northward) component of Earth’s rotation on upper-ocean turbulence. The focus is on the variability of the effect with latitude/hemisphere in the presence of surface gravity waves and when capped by a stable stratification beneath the surface layer. When is included, the mean flow, turbulence, and vertical mixing depend on the wind direction. The value and effect of are the largest in the tropics and decrease with increasing latitudes. The variability in turbulent flows to wind direction is different at different latitudes and in opposite hemispheres. When limited by stable stratification, the variability in turbulence intensity to wind direction reduces, but the entrainment rate changes with wind direction. In wave-driven Langmuir turbulence, the variability in mean current to wind direction is reduced, but the variability of turbulence to wind direction is evident. When there is wind-following swell, the variability in the mean current to wind direction is further reduced. When there is strong wind-opposing swell so that the total wave forcing is opposite to the wind, the variability in the mean current to wind direction is reduced, but the variability of turbulence to wind direction is enhanced, compared to in Ekman turbulence. The profiles of eddy viscosity, including its shape and its value, show a strong wind direction dependence for both stratified wind-driven and wave-driven Langmuir turbulence. Our study demonstrates that wind direction is an important parameter to upper-ocean mixing, though it is overlooked in existing ocean models.

Monitoring snowpack evolution using interferometric synthetic aperture radar on the North Slope of Alaska, USA

This research investigates the use of Interferometric Synthetic Aperture Radar (InSAR) to generate a time-series of snow water equivalent (SWE) for dry snow within the Kuparuk watershed, North Slope, Alaska, during the winter of 1993/1994. Maps depicting relative change in phase and the theoretical relative change in SWE between satellite acquisitions are created for 3-day periods at the end of March 1994 using both ascending and descending ERS-1 overpasses. The theoretical coefficient relating relative change in phase and relative change in SWE for C-band is found to be at least twice as large as what is expected when using a simple single-layer snow model for this study area and time period. Without any direct measurements of SWE on the ground, station measurements of snow depth and hourly wind are linked to each 3-day relative change in phase map. Along with a qualitative assessment, quantitative measures of the rate and magnitude of phase change around these stations are directly compared to the hourly wind data for a given 3-day period. InSAR-derived maps acquired around a measured precipitation event show a considerable relationship to the predominant direction of strong winds over each 3-day period while maps acquired around no measureable precipitation depict much less correlation between phase change and predominant direction of strong winds. Despite limited ground measurements to infer snowpack conditions, these results show continued promise for the InSAR technique to measure changes in snowpack conditions (e.g. SWE) at much higher resolutions than manual sampling methods or passive microwave remote sensing. The extension of this technique to current L-band InSAR satellite platforms is also discussed.

Design wind loads for a low-rise building taking into account directional effects

The basic idea of a directional design is to optimize the orientation of a building, e.g. to have the strong axis in the strong wind direction and to have the weak axis in the direction of the weaker storms. However, it has to be understood that the wind load depends on two key random variables: the extreme wind speeds and the extremes of the wind-induced actions or action effects. Generally, the complex interaction of the corresponding directionalities does not allow separating the two variables. A consistent analysis is presented on the example of a low-rise building.

Effect of surface roughness on bidirectional reflectance of Antarctic snow

The angular pattern of sunlight reflected by snow is altered by surface roughness, which in the interior of Antarctica is usually in the form of meter‐scale longitudinal erosional features (sastrugi), whose axes align with the direction of strong winds. The bidirectional reflectance distribution function (BRDF) changes over the course of a day as the solar azimuth changes relative to the sastrugi axis. The normalized BRDF, or “anisotropic reflectance factor” R, was measured at South Pole Station from a 22‐m tower at 600, 660, and 900 nm wavelengths. The R pattern was similar at the three wavelengths; it probably varies little from 300 to 900 nm. Measurements were made at solar zenith angles θ0 from 67° to 90°, over the full range of viewing zenith angle (θr), azimuth angle between Sun and view (ϕ), and azimuth angle between Sun and sastrugi (ϕsas). Variation of R with ϕsas was notable; sastrugi oriented perpendicular to the solar beam cause a reduction of the forward peak, and sastrugi at an oblique angle cause R to lose its symmetry about the solar azimuth. However, the effects of sastrugi are mostly restricted to large viewing zenith angles, so remote sensing of albedo and atmospheric properties can be carried out accurately without knowledge of sastrugi height and orientation if only near‐nadir views are used. This recommendation is opposite that for observations of broken clouds over dark surfaces, for which large θr is preferred. A parameterization of R is developed, valid for viewing angles θr ≤ 50°. Sastrugi can cause a reduction of the snow albedo by altering the angle of incidence and by trapping of photons. For the small sastrugi of the Antarctic Plateau, the albedo is unaffected at visible wavelengths but can be reduced by a few percent at near‐infrared wavelengths when the Sun is low.

Slope effect on saltation over a climbing sand dune

Results from a three-year study are presented that integrate field work (in Israel), physical modeling (wind-tunnel testing at UC Davis), and numerical solutions of grain trajectories to model and explain sand transport over a climbing dune. Field grain-size analyses of surface- and saltation-trap materials taken along various positions of the slope suggest that only smaller particles (< 230 μm in diameter for a friction speed, u ∗ , equal 30 cm/s) were able to climb a 20 degree slope in an escarpment normal to the prevailing strong wind direction. Numerical solutions of the particle trajectories are in good agreement with field measurements and confirm that particle motion is diminished at the base area of the slope and that the motion of larger-sized particles is completely terminated which causes an accumulation of these particles. The results suggest that the transport of the majority of the larger particles (> 230 μm) is by saltation. The model is numerically extended to a general series of slopes, particle sizes, and friction speeds with similar tends exhibited.

Wind-determined sediment distribution and Holocene sediment yield in a small, Danish, kettle lake

Sediment distribution was mapped by multiple corings in a small oligotrophic lake in northwestern Denmark. Sediment cores along a representative West-East transect were dated by 14C and correlated using pollen, mineral magnetics and general lithology. Estimates of whole-lake Holocene sediment accumulation were used to calculate sediment yield (terrestrial erosion). Results indicate that: 1) sediment yield was low 10000–5000 BP and increased strongly 5000–2500 BP and again 2500–1200 BP, 2) sediment focusing and waves and currents induced by strong winds were the major processes controlling sediment distribution throughout the Holocene; 3) the dominant wind direction of strong winds has been westerly throughout the Holocene; and 4) the lake was probably more productive in the last 5000 years than in the period from 10000 to 5000 BP.

Reconsideration on the Distribution of the Shimagare Phenomenon in Japan

The Shimagare phenomenon which is called ‘wave-regeneration’ in the United States, is characterized some crescent-shaped bands consisted of a mature forest, dead trees and young seedlings. Many ecologists, dendrologists, geographers and others have already examined the phenomenon from their own viewpoints. The purpose of this paper is to reconsider the distribution and the locational condition of this phenomenon in Japan.As a result of aerial photograph analysis, some areas have newly been added to the distribution area of the Shimagare phenomenon. It becomes clear that the reexamined distribution area fundamentally coincides with the geographical distribution area of Abies mariesii and A. veitchii. It is noticeable that the scale of the Shimagare strip, crescent-shaped band, is smaller in Tohoku district (north-eastern Japan) than in central Japan. It can be said that the reasons why the Shimagare strip is smaller in Tohoku district are as follows: 1) the mountain areas are consitituted of small geomorphic surfaces, 2) the sub-alpine forests are dominated by A. mariesii, stronger species, 3) the Shimagare does not appear on southfacing slopes more influenced by sunshine effects.The Shimagare strips mostly appear at upper sub-alpine forest one near the top of the mountains, and also on south-facing gentle slopes except in Tohoku district. These facts point out that the Shimagare strips are distributed where pure fir forests are liable to be formed and to be damaged by the desiccation.On the other hand, the arrangement of the Shimagare strips characterized by dead trees show more concentrated direction. Comparing this direction with the direction of wind-shaped trees, both are not necessarily the same with each region. For example, both directions almost agree on Mt. Hakkoda and Mt. Higashi-azuma in Tohoku district, but not Mt. Nantai in Kanto district. These facts closely correspond to the pattern of seasonal variation of wind direction obtained by instrumental observation. For example, meteorogical records of the Mt. Nantai show the considerable frequency of southerly wind corresponding to the direction of arrangement or movement of the Shimagare strips during warm season, but not during cold season. With these facts, prevailing wind during warm season is considered to act as an important factor for the movement of Shimagare strips. And, if the direction of strong wind coincides with prevailing wind direction during warm season, the Shimagare strips will be moved faster.

A Method of Determining the Direction of Strong Winds: Northwestern Coachella Valley, California

This paper presents a method for determining the direction of strong winds in the desert environment by observing wind-developed geologic landforms and biologic features. Techniques and a case study from southern California are presented to provide the engineering geologist with field methods helpful in evaluating the potential hazards of desert aeolian processes. Three hundred thirty-five strong wind direction measurements were recorded in the northwestern Coachella Valley, California, in order to determine the air movement pattern. Data were gathered between February and July 1975, and were obtained from geomorphic (sand drift deposits and barchan dunes) and biologic (plants) indicators. Air flows southeast from the Whitewater Pass topographic constriction through the Coachella Valley. Local topography appears to be the major factor affecting air movements within the Valley. Techniques presented here provide the engineering geologist with a method to aid in siting structures and highways in strong wind areas.

The Direction of Strong Wind at Sendai Bay Coast

Based on the data of the every hour wind directions (1963-1966) at the Gamocoast along Sendai Bay, the author obtained the diagrams shown in Fig. 1-Fig. 3, showing the appearance frequency of wind according to wind directions. During the winter monsoon season, the stronger the wind, the more sharply the wind from land side tends to converge in certain directions. Regarding the wind from sea-side, on the other hand, the directions in which the strong wind in spring tends to appear differ from that in which the weak one in summer tends to appear.

U-SHAPED DUNES AND EFFECTIVE WIND DIRECTIONS IN ALBERTA

Studies were made of aerial photographs of sand dune areas outlined by the Alberta Soil Survey. The presence of U-shaped, V-shaped, blow-out parabolic dunes indicated the direction of the effective wind responsible for their formation. Descriptions, pictures of such dunes and a sketch map showing the probable effective wind directions are included in the report. The shapes of these dunes indicate that the effective wind direction in the Grande Prairie area was from the southwest. In the central portion of Alberta the effective wind direction was from the northwest, while in the southern and southeastern portion of the province the effective winds were from the southwest. Comparison of the indicated effective wind directions with the average pattern of the direction of strong winds shows a very marked similarity.

Notes and personalia

In the issue of October 1950, Figure 4 in the paper of Wiegel and Kimberley, p. 720, the title “Chromatic charts…” should read “Climatic charts…” as they relate to the frequency and direction of strong winds.