Wind Speed Patterns Research Articles

Wind speed and relative humidity influence spatial patterns of burn severity in boreal forests of northeastern China

We investigated relationships between the spatial patterns of burn severity in Chinese boreal forests and weather parameters. Patch size, shape and arrangement differed between high-severity and low/moderate-severity patches. Wind speed and relative humidity were dominant weather parameters of spatial variation in burn severity. Patch size negatively correlated with relative humidity; patch complexity and aggregation positively correlated with wind speed. Spatial patterns of burn severity strongly control post-fire succession and numerous ecological processes in fire-prone boreal forests. Burn-severity patterns are strongly tied to weather conditions. Understanding how weather influences spatial patterns of burn severity is critical for predicting burn severity and fire management strategies. We investigated relationships between spatial patterns of burn severity and weather variables in the Chinese boreal forests. Using satellite imagery, we mapped burn severity for 22 fires that occurred between 2000 and 2005. For each fire, we calculated metrics of spatial pattern. Using Random Forest models, we quantified the relative importance of weather variables in determining spatial patterns of burn severity. High-severity fire patch, averaged 570.5 ha (SD = 1530.6), was the dominant outcome, occupying 67.8% of all area burned across the 22 fires. High-severity patches were larger, more aggregated, and simpler in shape than low- and moderate-severity patches. Patch size of high-severity fires increased in drier and less humid conditions, and patches were more complex and aggregated with higher wind speeds. With drier conditions predicted with climate change, spatial patterns of burn severity in Chinese boreal forests may become increasingly homogeneous, possibly affecting long term ecological functions.

Wind Speed Patterns Mining Based on Multiple Views

There are different patterns for wind speed variation in different seasons. The patterns are not only related to the statistical characteristics, but also to the trends of wind speed fluctuation and variation. However, the classical clustering can’t take the trend information as an independent overall feature in the algorithm. In this paper, multi-view clustering is introduced to extract patterns of wind speed variation from both statistical information and the trends. For about 1.5-year historical data, the trends of wind speed variation and fluctuation, and other five statistical characteristics are selected as features to characterize patterns of wind speed variation. Then four patterns are obtained with multiple clustering. It is found that mean wind speed and fluctuation level are very important and the behavior of wind speed is significantly different in the past states in different clusters. Forecasting model performs worse for the cluster with large mean wind speed and fluctuation range.

What are the main local drivers determining richness and fishery yields in tropical coastal fish assemblages?

Seasonal ecological effects caused by temperature and photoperiod are typically considered minimal in the tropics. Nevertheless, annual climate cycles may still influence the distribution and abundance of tropical species. Here, we investigate whether seasonal patterns of precipitation and wind speed influence the structure of coastal fish assemblages and fishing yields in northeast Brazil. Research trips were conducted during the rainy and dry seasons using commercial boats and gear to sample the fish community. Diversity was analyzed using abundance Whittaker curves, diversity profiles and the Shannon index. Principal Component Analysis (PCA) was used to analyze associations between the abundance of species and various environmental variables related to seasonality. A total of 2,373 fish were collected, representing 73 species from 34 families – 20 of which were classified as both frequent and abundant. Species richness was greater and more equitable during the rainy season than the dry season – driven by changes in the precipitation rather than to wind speed. Species diversity profiles were slightly greater during the rainy season than the dry season, but this difference was not statistically significant. Using PCA was identified three groups of species: the first associated with wind speed, the second with precipitation, and the third with a wide range of sampling environments. This latter group was the largest and most ecologically heterogeneous. We conclude that tropical coastal fish assemblages are largely influenced by local variables, and seasonally mediated by annual changes related to precipitation intensity and wind speed, which in turn influences fishery yields.

What are the main local drivers determining richness and fishery yields in tropical coastal fish assemblages?

Seasonal ecological effects caused by temperature and photoperiod are typically considered minimal in the tropics. Nevertheless, annual climate cycles may still influence the distribution and abundance of tropical species. Here, we investigate whether seasonal patterns of precipitation and wind speed influence the structure of coastal fish assemblages and fishing yields in northeast Brazil. Research trips were conducted during the rainy and dry seasons using commercial boats and gear to sample the fish community. Diversity was analyzed using abundance Whittaker curves, diversity profiles and the Shannon index. Principal Component Analysis (PCA) was used to analyze associations between the abundance of species and various environmental variables related to seasonality. A total of 2,373 fish were collected, representing 73 species from 34 families – 20 of which were classified as both frequent and abundant. Species richness was greater and more equitable during the rainy season than the dry season – driven by changes in the precipitation rather than to wind speed. Species diversity profiles were slightly greater during the rainy season than the dry season, but this difference was not statistically significant. Using PCA was identified three groups of species: the first associated with wind speed, the second with precipitation, and the third with a wide range of sampling environments. This latter group was the largest and most ecologically heterogeneous. We conclude that tropical coastal fish assemblages are largely influenced by local variables, and seasonally mediated by annual changes related to precipitation intensity and wind speed, which in turn influences fishery yields.

Kalman Filter bank post-processor methodology for the Weather Research and Forecasting Model wind speed grid model output correction

ABSTRACTThe performance of the Weather Research and Forecasting (WRF) model, coupled with a bank of eight Kalman Filters (KFB) as a post-processor toolbox for the three hourly average WRF wind speed forecasts, is investigated and compared to the output of the WRF model alone. Two model set-ups, WRF and WRF+KFB, have been tested for the period January to December 2008 on nine locations corresponding to gradient wind towers of the Cuban Eolic program. Tests demonstrated that the KFB post-processing technique, using a third-order polynomial, combined with a four-point a priori moving window averager for covariance matrix computation, was the best configuration for improving the WRF grid model day-ahead wind speed forecast output. The WRF+KFB approach investigated has been shown to adapt to changing wind speed patterns and to offer improved wind speed forecasts for each location considered, whilst only requiring a limited data set for training purposes.

Wind speed pattern in Nigeria (a case study of some coastal and inland areas)

In this study, wind speeds were analysed using the daily wind data obtained from Nigeria Meteorological Agency, Oshodi Lagos at the height of 10m at the different stations during the period of 2000-2010. Weibull , lognormal and normal probability density functions were employed. It was found that the daily mean wind speed groups and percentage frequency of occurrence in brackets in the inland locations (Jos, Kano, and Ilorin) and in the coastal locations (Lagos, and Port Harcourt) ranged from (13-18) ms -1 (70.6%), (8-12)ms -1 (84.4%), (45)ms -1 (67%) and (8-12)ms -1 75.8% to (4-7)ms -1 97% of the observations respectively. Weibull shape parameters K ranged from 3.07 to 3.82. While the scale parameter C ranged from 9.91 to 15.07ms -1 for Kano; K ranged from 2.75 to 4.04 while C ranged from 12.75 to 17.44ms -1 for Jos; K ranged from 2.61 to 2.76 while C ranged from 10.58 to 10.79ms -1 for Lagos; K ranged from 1.95 to 1.98 while C ranged from 6.10 to 6.35ms -1 for Port Harcourt; and K ranged from 3.10 -5.60 while C ranged from 3.80 to 6.00ms -1 for Ilorin. Keywords: Weibull, Ikeja, Jos, Kano and Port Harcourt

Numerical Study on the Effect of Air–Sea–Land Interaction on the Atmospheric Boundary Layer in Coastal Area

We have performed large-eddy simulations (LES) to study the effect of complex land topography on the atmospheric boundary layer (ABL) in coastal areas. The areas under investigation are located at three beaches in Monterey Bay, CA, USA. The sharp-interface immersed boundary method is employed to resolve the land topography down to grid scale. We have considered real-time and what-if cases. In the real-time cases, measurement data and realistic land topographies are directly incorporated. In the what-if cases, the effects of different scenarios of wind speed, wind direction, and terrain pattern on the momentum flux at the beach are studied. The LES results are compared with simulations using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) and field measurement data. We find that the land topography imposes a critical influence on the ABL in the coastal area. The momentum fluxes obtained from our LES agree with measurement data. Our results indicate the importance of capturing the effects of land topographies in simulations.

Numerical Simulation Of Fog Occurrences Over A Southern Part Of Nigeria West Africa

Numerical prediction of fog evolution remains difficult due to its complex processes that require adequate representation of the local perturbations in weather models despite the progress made in advance weather prediction models. The performance and sensitivity of the Weather Research and Forecasting (WRF) model in reproducing fog episodes over Akwa Ibom international airport (AKIA) Nigeria for the first time in West Africa was studied. Some real cases of radiation fog over AKIA were simulated using a set of parameterization schemes to simulate warm fog and visibility limits. Seven fog events were selected for model validation and sensitivity studies in this research work. The use of Kunkel (1984) empirical relationship result showed good agreement between simulated horizontal visibility limits using Liquid Water Content (LWC) when compared with observation. The modeled diurnal patterns of temperature, relative humidity and wind speed were also evaluated with the observed. It was found out that the model also captures the diurnal pattern and the value with very slight biases. These slight biases however, do not affect model results except where overestimation of wind speed and temperature could give rise to an earlier dissipation of fog. Fog estimation through temperature and relative humidity profile is as a result of the turbulent mixing within fog that causes the homogenization of the layers where the fog is present. The result showed evolution of fog through quasi-saturated state between temperature and relative humidity defining fog characteristic onset pronounced by surface inversion.

Estimation of wind speed over lakes in Central Europe using spaceborne C-band SAR

ABSTRACTThe Sentinel-1 satellite mission provides high-resolution, all-weather, day and night Synthetic Aperture Radar images. Studies about wind parameters above the ocean are frequent, inland lakes were seldom investigated. The objective of this article is to investigate the potential of C-band SAR for wind retrieval over lakes for evaluation of representativeness of meteorological station data. A number of lakes from Austria and Hungary (lakes in Salzkammergut, Lake Neusiedl and Lake Balaton), where wind measurements from automatic weather stations are available from the surroundings, has been selected for this study. Functions for speed retrieval are developed from empirical relationships for both available polarizations, VV and VH. Meteorological station data are used for calibration and validation. Best results were obtained for VV although with a dependency on incidence angle. Functions for different incidence angles according to the wind speed were, therefore, determined. There is a good correlation between the measured and the calculated wind speed (R of 0.71–0.91 for calibration sites; average R 0.71 for all sites). Average wind speed patterns for the lakes can be derived, but need to be analyzed separately for descending and ascending acquisitions due to difference in daytime (morning versus late afternoon).

Season-dependent size distribution of aerosols over the tropical coastal environment of south-west India

This paper presents the results of a detailed study on the size characteristics of aerosols at the tropical coastal site Thiruvananthapuram based on the in-situ measurements of size resolved aerosol number density using an aerosol spectrometer, covering a period of 28 months from September 2011 to December 2013. The diurnal pattern of aerosol number density is characterized by day time low and a two-fold increase during nighttime and these changes are closely associated with the strong mesoscale features namely the sea breeze and land breeze prevailing at the site. Aerosol Number Size Distribution (NSD) depicts a multi-modal nature with two prominent modes, one ≤0.1 μm and other ∼1 μm. Two other less pronounced modes are also observed in the NSD, one ∼0.3–0.5 μm and other ∼5–8 μm. The NSDs also exhibited strong seasonal changes linked with the synoptic meteorological feature of this region namely the South Asian monsoon. The seasonal NSDs were parameterized and analyzed. In addition to this, the effects of meteorological parameters temperature, relative humidity, and wind speed and airflow patterns on aerosol number density as revealed by partial correlation analysis were found to be aerosol size dependent.

Insights on the Provision of Frequency Support by Wind Power and the Impact on Energy Systems

This paper implements and compares between the key concepts to enable wind power short-term frequency support from electrical and mechanical loads perspectives. Pitch de-loading, kinetic energy extraction, and wind turbine (WTG) over-speeding are investigated, where each concept is integrated as a supplementary controller to the conventional controls of WTG. Different patterns of wind speed are examined, step-change and real intermittent of high resolution. The examined aggregated synchronous area has a relatively high wind penetration with frequency support. The overall dynamic inertia of the system is assessed to analyze the impact of the integrated support methods and their key parameters. The coordination between synchronous areas and wind farms, which are interconnected through a multiterminal high-voltage direct-current network (MT-HVDC) is examined. A novel definition of the virtual inertia of MT-HVDC grid is proposed. Results show that pitch de-loading secures support reserve most of the time, and kinetic energy extraction provides sustainable support for a short interval, while accelerative de-loading could reach a compromise. The three methods are adaptable with the MT-HVDC holistic frequency support controller, with a slight advantage of kinetic energy extraction over the virtual inertia of the MT-HVDC. MATLAB/Simulink is the simulation environment.

Spatiotemporal patterns of sediment transport rate and beach–ocean profile for multi-hazard risk management

Many parameters, interacting differently in time and space, affect a long-shore hydrological and marine ecosystem model, and the water resource management advancement is highly affected by these interactions. Sediment transport in coastal regions is due to interactions between various land forms and different complicated physical processes. What determines coast to storm vulnerability, public/private land ownership legal boundaries, and beach extent that can be used for recreation/habitat is the shape of BOP (beach–ocean profile). This paper addresses an approach that requires a disorder power index (entropy power) for the analyses of spatiotemporal patterns and reports, on the basis of a beach area case study, the suitability of the index for the analyses of the hydrological/marine ecosystem components. The approach uses the 1970–2015 monthly data of six Makran ocean beach sections and investigates such variables as wave high, wind speed, and total beach sediment transport rates (TBSTR) spatiotemporal patterns each of which depends on time and plays an important part in terrestrial hydrological studies. Although these variables often show meaningful spatiotemporal variability, their combined performance is hard to explain. In the framework of this context, using entropy-power index exhibits important signals that help the assessment of water resources and provides a clear understanding of the interactions among hydrological parameters at such large scales as the beach area.

A Coastal Bay Summer Breeze Study, Part 1: Results of the Quiberon 2006 Experimental Campaign

The Quiberon 2006 experiment was launched to document the onset and development of land and sea breezes over a semi-circular coastal bay propitious to inshore sailing competitions. The measurements were taken during the 2 weeks of 16–28 June 2006. Micrometeorological variables were recorded at three shore sites around the bay using turbulence sensors on 10–30-m high masts, on four instrumented catamarans at selected sites within the bay, and at a fourth shore site with a Sodar. Synoptic data and local measurements are analyzed here from the point of view of both micrometeorologists and competition skippers, testing in particular the empirical rules of breeze veering and backing according to the wind direction with respect to the coastline orientation at the mesoscale (the quadrant theory). Our analysis focuses on the patterns of lower-altitude wind direction and speed around the bay and over the water basin, and the temporal variations during the periods of the breeze onset, establishment and thermal reinforcement. In offshore synoptic-flow conditions (quadrants 1 and 2), the clockwise rotation of the surface flow had a very large amplitude, reaching up to 360\(^{\circ }\). The breeze strength was negatively correlated to that of the synoptic wind speed. In conditions of onshore synoptic flow from the west (quadrant 3) at an angle to the mainland coast but perpendicular to the Quiberon peninsula, the rotation of the flow was backwards in the early morning and clockwise during the day with a moderate amplitude (40\(^{\circ }\)–50\(^{\circ }\)) around the synoptic wind direction. As the surface wind speed was much larger than the synoptic wind speed, such a case we have designated as a “synoptic breeze”. The breeze onset was shown to fail several times under the influence of weak non-thermal events, e.g., the passage of an occluded front or clouds or an excess of convection. Finally, several local-scale influences of the complex coastal shape appeared in our measurements, e.g., wind fanning in the lee of the isthmus and airflow skirting around the peninsula forehand.

Spatial Variation of Soil Seed Bank under Cushion Plants in a Subalpine Degraded Grassland

AbstractCushion plants can affect wind speed and sediment movement patterns that probably modify the water and sediment redistribution along slopes and increase the accumulation of seeds under and around their canopies. This study was carried out to assess the spatial variability of soil seed bank (SSB) and seed bank composition around cushion plants to estimate the SSB potential for restoration of degraded area. Twenty cushions of Onobrychis cornuta were selected in a mountainous rangelands in northern Alborz in Iran, measuring density, richness and composition of SSB at four locations of each cushion (upslope edge, downslope edge, centre and outside). SSB composition and density were determined by seedling emergence method. The results showed that the locations of cushions had significant effect on density and richness of the SSBs. The highest SSB density and richness were observed in the centre and upslope edge of the cushions, while there was no significant differences of density and richness between downslope edge and outside (bare grassland soil) of the cushions. In addition, the results showed that seed bank composition was highly correlated between the four locations in the same cushion. We concluded that cushion plants can act as seed traps specially trapping seeds dispersed by barochory and hydrochory and therefore play an important role in conservation and recovery of degraded areas. Copyright © 2017 John Wiley & Sons, Ltd.

Is Catastrophic Climate Change Turning Britain into a Hurricane Hotspot?

Uncharacteristically strong storm activity in the UK during recent years has focused attention once again upon climatic impacts. Rapid climate change, which in turn affects sea surface temperatures (SST), ocean circulation, and wind speed patterns, is most likely contributing to these unprecedented and prolonged storm events. Previous studies focused on individual factors rather than cumulative effects of climate change; however, a knowledge gap exists. Consequently, this quantitative study analysed the current influence of climate change on UK sea surface and mean air temperatures, together with mean wind speeds. It also assessed whether climate change scenarios will create favourable conditions for the genesis of catastrophic hurricanes in the UK using a 2-path analysis (SST, wind speed, temperatures). Accordingly, in situ SST, mean wind speed, and mean temperatures for the period 2000–2014 are analysed. Primary results revealed that increasing trends in regional SST (0.1–0.7 °C), mean temperature (0.4–0.8 °C), and wind speed (0.5–2 m/s) patterns. It is expected that significant changes in climate will cause sea surface temperature increases between 1 and 4 °C, which will accelerate temperature and wind speed further. These adverse changes would negatively affect future UK weather patterns and create positive conditions for the formation of super storms and high winds in the near future, although not necessarily hurricanes.

On the Annual Cycle of Meteorological and Geographical Potential of Wind Energy: A Case Study from Southwest Germany

Wind energy in Germany has experienced high growth rates over the last few years. The set political target in the German federal state of Baden-Wuerttemberg is to raise the share of wind energy in the overall electricity supply to 10% by 2020. To achieve this goal, detailed information on wind energy potential in Baden-Wuerttemberg is necessary. This study assesses the geographical wind energy potential (GP) in Baden-Wuerttemberg giving a guideline to identify suitable locations for wind energy utilization. The focus of this investigation lies in assessing GP for the mean annual meteorological wind energy potential (MP) as well as for the mean MP in December and August providing information on the seasonal behavior of wind power availability. A GIS-based approach is employed to identify sites without geographical restrictions and with sufficient MP at hub heights of 100 m, 140 m, and 200 m. The study finds that (1) the number of possible sites for wind energy utilization is strongly limited by geographical restrictions, (2) GP is highly dependent on MP and, therefore, (3) GP varies highly throughout a year since MP depends on the seasonal pattern of wind speed in Central Europe, showing high values in winter and low values in summer.

An updated review on recent trends in observational surface atmospheric variables and their extremes over Spain

This article reviewed state-of-the-art findings on recent trends in observed atmospheric variables and their extremes in Spain. Our study screened peer-reviewed articles, published within the last decade, on recent climate variability in Spain, with a particular focus on a range of the essential atmospheric variables. The review focusses on the recent evolution of precipitation and air temperature, but also on other meteorological variables such as solar radiation, wind speed, surface humidity and evapotranspiration. While this review highlights results on changes in the mean state of climate in Spain, it also gives equal attention to findings on extreme weather events (e.g. rainstorms, heat waves and droughts). This paper also reviews trends of the most extreme events, like rainstorms, heat waves and droughts. A detailed review of studies focusing on recent changes in the surface climate of Spain revealed some key findings. Studies demonstrate an overall increase of solar radiation since the 1980s. A similar behaviour was observed for surface air temperature since the 1960s, on the order of +0.3ºC decade-1, with rapid warming rates during summer. Different seasonal trend patterns of wind speed were noted over Spain, with declines in winter-spring and increases in summer-autumn. A remarkable decrease (-5%) in relative humidity was observed from 1961 to 2011. For precipitation, studies suggested a strong variability over both space and time, with a moderate decrease of the annual total precipitation. In accordance with changes in the mean conditions of climate, studies of extreme weather events stressed a notable warming in warm extremes, while changes in cold extremes were generally insignificant.

Structural behaviour of lattice transmission towers subjected to wind load

Hurricane Wilma hit Yucatan Peninsula in 2005, causing substantial damage to local electrical transmission towers. Based on the failure characteristics observed on such towers, an analytical study is performed to reproduce such failures and assess their vulnerability. Two latticed transmission towers are analysed under the action of 14 different wind velocity patterns corresponding to several national and international wind design codes. Displacement-controlled pushover analyses are performed to reproduce impending failure mechanism for considered wind patterns, and associated gradient wind speed is computed. Results illustrate that consistent cyclonic wind speed patterns lead to better estimates of failure mechanism and gradient wind values than traditional non-cyclonic patterns.

Potential contributions of wind power to a stable and highly renewable Swiss power supply

Using data from two measurement networks, we analyse the following aspects of wind speeds over Switzerland to assess the possibility of high wind power penetration: spatial correlation, persistent low wind power conditions and the diurnal and seasonal wind speed patterns. We show that correlation amongst speeds as a function of distance is significantly lower compared to values found in literature. This can be attributed to the complex terrain of the Alps, which has a profound influence on meteorological parameters. Secondly, using extreme value analysis we calculate return levels for low wind power periods. Large differences are found, with return levels ranging from 29 to 1017h of no power production for a return period of 10years. No clear spatial pattern was found that can account for these values. However, the length of no-production periods decreases with increasing elevation. Next, we investigate diurnal and seasonal wind speed patterns and show how the different patterns and their intra-annual variation can be explained by local topography. We also find that with increasing elevation mean wind speeds and power production increase, even when accounting for lower air density. Wind speeds are on average higher in winter, and at elevation the relative increase in winter compared to summer is higher. Notable exceptions are explained from topography and carry implications for wind power development. In view of Switzerland’s electricity shortage in winter, these findings make a strong claim for wind power development, especially at higher elevations.

The Trend of Changes in Surface Wind in the Indian Ocean, in the Period from 1981 to 2015, Using Reanalysis Data, NCEP/NCAR

Knowing the pattern of surface winds on the seas and oceans and how it changes over time is of great importance. In this research, the monthly surface wind fields on the Indian Ocean have been studied and analyzed for a 35-year period (1981-2015), using NCEP/NCAR data reanalysis. The results show that transition from cold to warm pattern happens in May and that the summer monsoon pattern begins in June and continues until August. The wind speed pattern tends to the winter monsoon from November on. The maximum average wind speed in June is 13 m/s and its minimum is 2 m/s in October. Direction of prevailing winds is the southwest in the summer. The highest wind speed happens in the latitude of 10 - 15 degrees. Analysis of the wind distribution shows that the wind speed of 2 - 5 m/s happens in about 60% of the cases. There is probability of blowing 0.5 - 4 m/s wind for all months; but this probability is higher in the autumn (October and November) than that in the summer (July and August). Probability of the monthly over 5 m/s winds shows a definitely opposite distribution; that is, wind speed in July and August is higher than that in October. A long-term survey on the speed of surface water wind and sea surface temperature shows an opposite changing trend in wind speed and sea surface temperature during a 55-year statistical period. Wind speed reduced, while the sea surface temperature was increasing. The wind speed gradient in the upper levels of atmosphere graph has been increasing; this phenomenon confirms the effects of global warming and ocean warming on the monsoon system patterns in the Indian Ocean. Keywords North