Long-Term Beach and Shoreface Changes, NW Jutland, Denmark: Effects of a Change in Wind Direction

1990 ◽  
pp. 113-122 ◽  
Author(s):  
Christian Christiansen ◽  
Dan Bowman
Keyword(s):  
Wind Direction

scholarly journals Simultaneous generalized and low-layer SCIDAR turbulence profiles at san pedro mártir observatory

2019 ◽  
Vol 490 (1) ◽  
pp. 1397-1405 ◽  
Author(s):  
R Avila ◽  
O Valdés-Hernández ◽  
L J Sánchez ◽  
I Cruz-González ◽  
J L Avilés ◽  
...  
Keyword(s):  
High Altitude ◽  
Wind Direction ◽  
Close Agreement ◽  
Baja California ◽  
Ground Level ◽  
Combined Effect ◽  
Moderate Altitude ◽  
San Pedro ◽  
Simultaneous Measurements

ABSTRACT We present optical turbulence profiles obtained with a Generalized SCIDAR (G-SCIDAR) and a low-layer SCIDAR (LOLAS) at the Observatorio Astronómico Nacional in San Pedro Mártir (OAN-SPM), Baja California, Mexico, during three observing campaigns in 2013, 2014, and 2015. The G-SCIDAR delivers profiles with moderate altitude-resolution (a few hundred metres) along the entire turbulent section of the atmosphere, while the LOLAS gives high altitude resolution (on the order of tens of metres) but only within the first few hundred metres. Simultaneous measurements were obtained on 2014 and allowed us to characterize in detail the combined effect of the local orography and wind direction on the turbulence distribution close to the ground. At the beginning of several nights, the LOLAS profiles show that turbulence peaks between 25 and 50 m above the ground, not at ground level as was expected. The G-SCIDAR profiles exhibit a peak within the first kilometre. In 55 per cent and 36 per cent of the nights stable layers are detected between 10 and 15 km and at 3 km, respectively. This distribution is consistent with the results obtained with a G-SCIDAR in 1997 and 2000 observing campaigns. Statistics computed with the 7891 profiles that have been measured at the OAN-SPM with a G-SCIDAR in 1997, 2000, 2014, and 2015 campaigns are presented. The seeing values calculated with each of those profiles have a median of 0.79, first and third quartiles of 0.51 and 1.08 arcsec, which are in close agreement with other long term seeing monitoring performed at the OAN-SPM.

scholarly journals The Importance of Climate Variability to Wind-Driven Modulation of Hypoxia in Chesapeake Bay

2010 ◽  
Vol 40 (6) ◽  
pp. 1435-1440 ◽  
Author(s):  
Malcolm E. Scully
Keyword(s):  
Time Series ◽  
Climate Variability ◽  
Chesapeake Bay ◽  
Wind Direction ◽  
Large Scale ◽  
Nitrogen Loading ◽  
Nutrient Inputs ◽  
Westerly Direction ◽  
Hypoxic Volume

Abstract Extensive hypoxia remains a problem in Chesapeake Bay, despite some reductions in estimated nutrient inputs. An analysis of a 58-yr time series of summer hypoxia reveals that a significant fraction of the interannual variability observed in Chesapeake Bay is correlated to changes in summertime wind direction that are the result of large-scale climate variability. Beginning around 1980, the surface pressure associated with the summer Bermuda high has weakened, favoring winds from a more westerly direction, the direction most correlated with observed hypoxia. Regression analysis suggests that the long-term increase in hypoxic volume observed in this dataset is only accounted for when both changes in wind direction and nitrogen loading are considered.

scholarly journals Desert Locust in India: The 2020 invasion and associated risks

2020 ◽  
Author(s):  
Sayantan Ghosh ◽  
arindam roy
Keyword(s):  
Wind Direction ◽  
Desert Locust ◽  
Breeding Ground ◽  
Indian States ◽  
Kharif Season ◽  
Reverse Migration ◽  
Super Cyclone ◽  
Controlling Measures ◽  
Local Ecology

Wind direction, often used in forecasting locust migration, indicates a non-zero probability of desert locust invasion in eastern Indian states. Apart from present controlling measures, we are additionally suggesting to be cautious about the eggs of locust as the rainfall associated with Super Cyclone Amphan has created a favorable breeding ground for the gregarious locust. Also reverse migration of these locusts might affect the Indian states for the second time. Long-term controlling policy (till Kharif season; June to October) is required to minimize the damage. Also, increasing the farmers awareness and sensitized local ecology groups might be helpful in desert locust reporting.

The Chemical Weather

2005 ◽  
Vol 2 (1) ◽  
pp. 6 ◽  
Author(s):  
Mark G. Lawrence ◽  
Øystein Hov ◽  
Matthias Beekmann ◽  
Jørgen Brandt ◽  
Hendrik Elbern ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Atmospheric Chemistry ◽  
Wind Direction ◽  
Strong Influence ◽  
Trace Gases ◽  
Short Term ◽  
Chemical Complexity ◽  
Chemical Climate ◽  
Short Term Variability

Environmental Context. Meteorological weather—temperature, pressure, wind direction—is familiar to all, and contrasts with meteorological climate in short-term (weather) versus long-term (climate) influence. From the atmospheric chemistry side, the focus has largely been on the chemical climate, the long-term mean concentrations of important trace gases and aerosols. An emerging new focus of study is the chemical weather—the tremendous short-term variability of the atmospheric chemical composition, resulting from the strong influence of meteorological variability, chemical complexity, and regionally and temporally varying emissions.

scholarly journals Differences in mid-latitude stratospheric winds between reanalysis data and versus radiosonde observations at Prague

2014 ◽  
Vol 32 (4) ◽  
pp. 353-366 ◽  
Author(s):  
M. Kozubek ◽  
J. Laštovička ◽  
P. Križan
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Historical Data ◽  
Reanalysis Data ◽  
Atmospheric Dynamics ◽  
Data Series ◽  
Stratospheric Wind ◽  
Long Term Trends

Abstract. Reanalysis data are very useful for studying the stratosphere. They can be used for analysis of long-term trends (temperature, wind speed, humidity, etc.) or analysis of global atmospheric dynamics, etc. There are various reanalysis projects that provide outputs which are not identical. In this paper, we mutually compare three of them, ERA-40, ERA-Interim and NCEP/NCAR, and compare them with balloon radiosonde observations from Prague, Port Hardy and Valentia stations. This comparison is done for wind speed and direction at pressure levels 100 and 10 hPa and for various periods between 1957 and 2009. The results show that the differences between reanalysis vary. Wind speed data from all three analyses reasonably agree except for the 10 hPa historical data before 1966 and particularly ERA-40 data at the end of the data series (1998–2001). The quality of the ERA-40 10 hPa stratospheric wind data has been proven to be substantially worse over the last four ERA-40 years of 1998–2001 (2002) compared to previous years, both in wind speed and wind direction. The reanalysis data results are compared with radiosonde observations from Prague, Port Hardy and Valentia stations at 10 hPa for the months of February between 1989 and 2009. The results show that there are sometimes surprisingly large differences, more for ERA-Interim versus Prague measurements. Differences in wind direction greater than 45° (outliers) between the reanalysis data and Prague observations in wind direction occur in Februaries predominantly when winds in Prague are in "minor" sectors, such as north, northeast and east (easterlies), whereas "major" sectors, particularly the dominant W (westerlies) wind sector, exhibit almost no outliers.

Forecasting the wind direction by using time series models with long-term memory (case study: Nayer region)

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Paria Soleimani ◽  
Bahareh Emami ◽  
Meysam Rafei ◽  
Hooman Shahrasbi
Keyword(s):  
Time Series ◽  
Wind Energy ◽  
Wind Direction ◽  
Fossil Fuels ◽  
Moving Average ◽  
Maximum Energy ◽  
Long Term Memory ◽  
Term Memory ◽  
Content Type

Purpose Today, because of the increasing need for the energy resources and the reduction of fossil fuels, renewable energy, especially wind energy, has attracted special attention. The precise forecasting of such energy will be the main factor in designing and investing in this field. On the other hand, the wind energy forecast provides the possibility of optimal use of available resources. In addition, the produce maximum energy would be possible by identifying wind direction and putting wind turbines in the best position. Design/methodology/approach Time series forecasting methods with long-term memory in this research have been used. Findings Eventually, the autoregressive fractionally integrated moving average (3,0,0)-FIGARCH (1,0,1) long-term memory model has more acceptable performance. The obtained error is based on the RMSE (0.2889) and the TIC (0.2605) values. Practical implications In this paper, the forecast wind direction belongs to Ardebil province and Nayer city in Iran. Originality/value The speed and direction of wind are variables that constantly change; hence, it will be difficult to predict the exact wind energy. In recent years, some studies have been conducted on wind speed forecasting, whereas wind direction forecasting has been done in a fewer number of studies. Most studies are related to low-lying areas. As the height of the wind turbine is directly related to the energy generation, 78 m height has been considered in this study.

Long-Term Extreme Response Analysis for a Fixed Offshore Wind Turbine Considering Blade-Pitch-Actuator Fault and Normal Transient Events

2014 ◽  
Author(s):  
Qinyuan Li ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Direction ◽  
Normal Operation ◽  
Offshore Wind Turbine ◽  
Bending Moments ◽  
Start Up ◽  
Extreme Response ◽  
Transient Events

In this paper, the 50-year long-term 1-hour extreme responses of a fixed jacket-type offshore wind turbine with consideration of one-blade-pitch-actuator-stuck fault and the effect of normal transient events such as normal shut-down and start-up process is studied. The long-term extreme results are found based on each short-term extreme response distributions at different environmental conditions. Structure responses such as tower and jacket bottom shear and bending moments as well as blade root bending moments will be focused in this paper. To study the long-term effect of the fault and transient events, the service life of a wind turbine is divided into normal part, faulted part, and transient part. Normal part includes both normal operation and parking of the wind turbine at different wind speed range without any faults. Faulted part includes the parked and emergency shut-down condition of the wind turbine under the fault assuming that the faults are detected soon after they occur but require a longer time before fully repaired. Transient part includes the start-up and shut-down process during the normal operation when wind speed is beyond operation range. The contribution of each part to the long-term extreme response distribution is calculated by weighting factors based on the probability of occurrence of each part. From the results, it is found that in general, the blade-pitch-actuator-stuck fault and the normal transient events generally increase the extreme responses of the wind turbine. The jacket wind turbine is more affected compared to its land based counterpart. In this study since the wind direction is aligned with wind turbine, it is found that the fault primarily increases the tower bottom shear force perpendicular to the wind direction and the bending moments with the axis parallel to the wind as well as the torsional moment, while normal transient events, especially the start-up process at cut-out speed, causes a much greater increase compared to the fault. It contribute mostly to the shear forces parallel and bending moment with axis perpendicular to the wind direction. The azimuth of the blades is found to be very important for blade responses during start-up process especially at higher wind speed.

scholarly journals A Long-term synoptic-scale climate study over Mariepskop, Mpumalanga, South Africa

2012 ◽  
Vol 22 (2) ◽  
pp. 2-6
Author(s):  
I. Pretorius ◽  
H. Rautenbach
Keyword(s):  
Global Warming ◽  
Surface Temperature ◽  
Wind Direction ◽  
Mountain Range ◽  
Linear Temperature ◽  
Near Surface ◽  
National Centre ◽  
Synoptic Wind ◽  
June July

Mariepskop forms part of the northernmost edge of the Drakensberg Mountain range and is known for its complex topography associated with meso-scale atmospheric circulation, and therefore its numerous climatic zones. The mountain hosts a high biodiversity. The peak of Mariepskop lies at approximately 1900m Above Mean Sea Level (AMSL), which is higher than the surrounding escarpment to the east. Its foothills also extend well into the Lowveld at about 700 m AMSL. Mariepskop is therefore ideal for studying airflow exchange between the industrial Highveld and the Lowveld with its diversity of natural resources. It is also ideal for detecting global warming signals on altitudinal gradients extending from the Lowveld to altitudes above the Highveld escarpment. In this study long-term National Centre for Atmospheric Research / National Centre for Environmental Prediction (NCAR/NCEP) wind data at two atmospheric pressure levels (850 and 700 hPa), as well as near-surface temperature data, were obtained for the Mariepskop region for the summer (December-January-February: DJF (1981-2011 )) and winter (June-July-August: JJA (1980-2012)) seasons. The data was used to study synoptic wind flow across the mountain in the upper (700 hPa) and lower (800 hPa) atmosphere, as well as near-surface temperature gradients. During the summer season, east-south-easterly and south-easterly winds were found to be the most prominent. These winds are commonly associated with both continental and ridging anticyclonic conditions. During winter, the predominant wind direction at 850 hPa is south-easterly, which is also due to the influence of ridging anticyclones, while at 700 hPa the dominant winter wind direction becomes west-south-west, which is due to the more frequent eastward passing of cyclonic frontal systems across the Highveld towards the Lowveld. Long-term near-surface temperatures exhibit a weak increasing linear temperature trend for both seasons, which might be due to global warming.

scholarly journals Ratios among atmospheric trace gases together with winds imply exploitable information for bird navigation: a model elucidating experimental results

2013 ◽  
Vol 10 (7) ◽  
pp. 12451-12489 ◽  
Author(s):  
H. G. Wallraff
Keyword(s):  
Wind Direction ◽  
Spatial Information ◽  
Trace Gases ◽  
Atmospheric Trace Gases ◽  
Spatial Gradients ◽  
Home Site ◽  
Environmental Air ◽  
The Individual ◽  
At Home

Abstract. A model of avian goal-oriented navigation is described that is based on two empirical findings: (1) To orient their courses homeward from distant unfamiliar areas, homing pigeons require long-term exposure to undisturbed winds at the home site and olfactory access to the environmental air at home and abroad. (2) Above Germany, ratios among some atmospheric trace gases vary along differently oriented spatial gradients and in dependence on wind direction. The model emulates finding (1) by utilising the analysed air samples on which finding (2) is based. Starting with an available set of 46 omnipresent compounds, virtual pigeons determine the profile of relative weights among them at each of 96 sites regularly distributed around a central home site within a radius of 200 km and compare this profile with corresponding profiles determined at home under varying wind conditions. Referring to particular similarities and dissimilarities depending on home-wind direction, they try to estimate, at each site, the compass direction they should fly in order to approach home. To make the model working, an iterative algorithm imitates evolution by modifying sensitivity to the individual compounds stepwise at random. In the course of thousands of trial-and-error steps it gradually improves homeward orientation by selecting smaller sets of most useful and optimally weighted substances from whose proportional configurations at home and abroad it finally derives navigational performances similar to those accomplished by real pigeons. It is concluded that the dynamic chemical atmosphere most likely contains sufficient spatial information for home-finding over hundreds of kilometres of unfamiliar terrain. The underlying chemo-atmospheric processes remain to be clarified.

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