Characterisation of a windbreak system on the south coast of Western Australia. 1. Microclimate and wind erosion

2002 ◽  
Vol 42 (6) ◽  
pp. 703 ◽  
Author(s):  
R. A. Sudmeyer ◽  
P. R. Scott
Keyword(s):  
Wind Speed ◽  
Western Australia ◽  
Wind Direction ◽  
Vapour Pressure ◽  
Wind Erosion ◽  
Vapour Pressure Deficit ◽  
Growing Season ◽  
Soil Movement ◽  
Air Temperatures ◽  
Prevailing Wind Direction

The lack of data relating changes in microclimate and wind erosion to crop growth in shelter is a constraint to the adoption of windbreak systems in Australia. In this experiment microclimate and soil movement were measured in a 450 m wide bay between 2 Pinus pinaster windbreaks in south-western Australia over 4 years. Changes in wind speed and microclimate as a result of wind shelter varied spatially and temporally. When the wind direction was perpendicular to the windbreaks, wind-run reductions greater than 20% extended 18 times the height of the windbreak (H) downwind. However, over the whole growing season wind-run reductions greater than 20% only extended 3–6 H from the windbreaks, and were confined to within 4 H over the whole year. Over the growing season, atmospheric vapour pressure and average daily temperature and potential evaporation in the most sheltered part of the windbreak bay were generally within ± 5–10% of unsheltered values. While growing conditions were generally improved, there were periods at the end of the growing season when sheltered crops experienced increased air temperatures and vapour pressure deficit. The principal benefit of the windbreaks appeared to be reducing wind speed during periods with short duration erosive winds. More than 1 H from the windbreaks, wind erosion was reduced for 36 H downwind of the windbreak that provided most shelter during the period of maximum soil movement. Browsing stock increased the porosity of the lower 1.5 m of the windbreaks, which allowed wind to funnel under the windbreaks. This study highlights the difficulty of maintaining constant shelter in an environment where the prevailing wind direction changes throughout the year and the need to orient windbreaks to provide shelter during those times when strong winds are most damaging to soils or crops.

Management of excess water in duplex soils

1992 ◽  
Vol 32 (7) ◽  
pp. 857 ◽  
Author(s):  
DJ McFarlane ◽  
JW Cox
Keyword(s):  
Groundwater Recharge ◽  
Water Flow ◽  
Western Australia ◽  
Soil Structure ◽  
Wind Erosion ◽  
Growing Season ◽  
Water Levels ◽  
Storm Runoff ◽  
Cereal Crops ◽  
Excess Water

Excess water in duplex soils can be removed by drains. In soils in which drainage is impractical, some success has been obtained by deep ripping and by gypsum amendment. These practices can increase profile storage or drainage. Interceptor drains are suitable for duplex soils with slopes of more than about 1.5%. On more gentle slopes, relief drains are used to remove excess water. Subsurface tube and mole drains have been used successfully to drain cereal crops in Victoria, but in Western Australia open drains are preferred because they can carry storm runoff as well as seepage waters. The greatest cost of open drains is the land removed from production. Over 35% of the rain falling during the growing season has been removed by drains in Victoria and Western Australia in wet years. Drainage was almost entirely downslope of monitored interceptor drains in Western Australia, which is not predicted from the theory. Simulation of water levels between drains and of drain flows using the DRAINMOD model indicated significant, preferred pathways for water flow to drains. The pathways explain the predominantly downslope effect of interceptor drains and the wide drain spacings which can be used. Deep ripping and the incorporation of gypsum can reduce waterlogging in some soils, but has had no effect in several others. The effect of deep ripping on recharge is unclear. Drains may decrease groundwater recharge, water and wind erosion, and soil structure decline. Their effect on phosphate export from catchments is unclear.

scholarly journals Water in a warmer world – is atmospheric evaporative demand changing in viticultural areas?

2019 ◽  
Vol 12 ◽  
pp. 01011
Author(s):  
H.R. Schultz
Keyword(s):  
Wind Speed ◽  
Solar Radiation ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Strong Increase ◽  
Simultaneous Increase ◽  
Evaporative Demand ◽  
Precipitation Patterns ◽  
Napa Valley ◽  
Rhone Valley

The predicted developments in climate are region-specific and adaptation can only be successful considering the regional characteristics with its diverse technical, environmental, economic and social implications. One of the key concerns for many regions is the availability of water through precipitation, the distribution of precipitation throughout the year, and possible changes in evaporative demand of the atmosphere and thus water use. From rising temperatures it is mostly assumed that water holding capacity of the atmosphere will increase in the future as a function of the Clausius-Clapeyron law, which predicts an increase in the saturation vapour pressure of the atmosphere of 6–7% per degree Celsius. As a consequence, a simultaneous increase in potential evapotranspiration (ETp, the amount of water that could potentially be evaporated from soils and transpired by plants due to changes in climatic factors such as temperature, vapour pressure deficit, radiation and wind speed) is assumed in many cases, which would alter soil and plant water relations. However, the same underlying principles also predict an increase in precipitation by 1–2% per degree warming. Additionally, model predictions for many regions forecast altered precipitation patterns and thus in combination with the possibility of increased ETp, farmers around the world fear an increase in the likelyhood of water deficit and a reduction in the availability of water for irrigation. Contrary to expectations, there have been reports on a reduction in evaporative demand worldwide despite increasing temperatures. In many cases this has been related to a decrease in solar radiation observed for many areas on earth including wine growing regions in Europe until the beginning of the 80th (global dimming) of the last century. However, since then, solar radiation has increased again, but ETp did not always follow and a worldwide decrease in wind speed and pan evaporation has been observed. In order to evaluate different grape growing regions with respect to observed changes on precipitation patterns and ETp, the data of seven wine-growing areas in five countries in the Northern and Southern hemisphere across a large climatic trans-sect were analyzed (Rheingau, Germany, Burgundy, Rhone Valley, France, Napa Valley, USA, Adelaide Hills, Tasmania, Australia, Marlborough, New Zealand) were analyzed. Precipitation patterns differed vastly between locations and showed very different trends over observation periods ranging from 23 to 60 years. The ETp has increased continuously in only two of the seven wine growing areas (Rheingau and Marlborough). In most other areas, ETp has been stable during winter and summer for at least 22 years (Rhone Valley, Napa Valley, Tasmania), sometimes much longer (45 years Adelaide Hills), and has been declining in Burgundy after a period of strong increase for the last 13 years. The potential underlying factors are discussed in relation to observed shifts in precipitation patterns.

Abundance and Temporal and Spatial Distribution of Culicoides Brevitarsis Kieffer (Diptera: Ceratopogonidae) on Cattle in South-East Queensland.

1979 ◽  
Vol 27 (2) ◽  
pp. 251 ◽  
Author(s):  
MM Campbell ◽  
DS Kettle
Keyword(s):  
Spatial Distribution ◽  
Wind Speed ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Negative Temperature ◽  
Direct Sunlight ◽  
Temporal And Spatial Distribution ◽  
Small Areas ◽  
Temporal And Spatial ◽  
Time Of Year

Numbers of C. brevitarsis on cattle in south-east Queensland increased rapidly from zero at 0.5 h before sunset, to a peak during the half hour after sunset, then decreased to zero in the following 5-6 h and remained at zero throughout the day. On standing animals abundance was greatest on the ridgeline at the tail, decreasing rapidly down the flank and less rapidly towards the head. On mature animals abundance after sunset halved with each increase of 0.53 m s-1 in wind speed, each increase of 6.4�C, each decrease of 158 Pa vapour pressure deficit, and each additional 38 min after sunset. Only females were collected from cattle; 97% of nullipars were mated. They did not always feed at their first attempt and were much less likely to feed on some hosts than others. Close shaving did not alter the number of flies on small areas and did not prevent feeding. Before sunset C. brevitarsis were observed more frequently on hosts in the absence of direct sunlight. In direct sunlight, abundance was influenced most by wind speed (positive), minutes before sunset (negative) and temperature (negative), in order of decreasing importance. Without direct sunlight, the factors were minutes before sunset (negative), temperature (positive), and wind speed (negative); after sunset the factors were wind speed (negative), vapour pressure deficit (positive), minutes after sunset (negative) and minor effects from time of year and temperature.

Clonal Responses of Tea Shoot Extension to Temperature in Malawi

1993 ◽  
Vol 29 (1) ◽  
pp. 47-60 ◽  
Author(s):  
R. I. Smith ◽  
F. J. Harvey ◽  
M. G. R. Cannell
Keyword(s):  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Field Measurements ◽  
Empirical Method ◽  
Shoot Length ◽  
Extension Rate ◽  
Base Temperature ◽  
Growing Seasons ◽  
Air Temperatures ◽  
Tea Shoot

SummaryAlthough the relationship between the length of a growing tea shoot and time is not truly exponential, the exponential relative shoot extension rate (ERSER) can be used for comparisons when both the initial shoot lengths and the periods of measurement are identical. An empirical method to adjust ERSER for variations in initial shoot length was developed for weekly field measurements of seven tea clones in Malawi. ERSERs, measured throughout the two growing seasons after the bushes had been pruned, were standardized to an initial shoot length of 2.5 cm and were then related to mean weekly air temperatures and to vapour pressure deficits. There were large clonal differences in the response of ERSER to temperature within the range 18–23°C. Shoots of the vigorous Malawi clone SFS 150 elongated rapidly at all temperatures, but notably at the lower temperatures (18–20°C). Two Kenyan clones, BB/35 and K6/8, did not grow well at about 18°C, which is normal for growth in Kenya but which coincides with the period of short daylengths (less than 12 h) in Malawi. A significant decrease in ERSER was found with increased vapour pressure deficit over the whole range of field measurements and ERSERs were uniformly lower in the second year after pruning. The results suggest that the usual calculations to derive an inherent base temperature for elongation are not valid unless elongation is truly exponential and therefore, in general, base temperatures should not be used for comparisons between experiments.

scholarly journals A Study on Characteristics and Comparison of Evaporation Estimation Methods in Bandung

2021 ◽  
Vol 53 (2) ◽  
pp. 182-199
Author(s):  
Rusmawan Suwarman ◽  
Novitasari Novitasari ◽  
I Dewa Gede Agung Junnaedhi
Keyword(s):  
Regression Analysis ◽  
Wind Speed ◽  
Relative Humidity ◽  
Solar Radiation ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Estimation Methods ◽  
Observation Data ◽  
Weather Factor ◽  
Better Than

This study aims to understand the characteristic of evaporation and to evaluate the evaporation estimation methods to be employed in Bandung by using observation data at three different land cover characteristics sites, namely, densely vegetated area (Baleendah), densely built-up area (Ujung Berung), and mix of buildings and vegetation area (ITB). Observation data used are hourly evaporation, vapour pressure deficit, temperature, relative humidity, wind speed, and radiation. The analysis was done mostly by using statistical methods such as regression analysis and error comparison. The result shows the dominant weather factor affecting the evaporation in ITB and Ujung Berung is vapour pressure deficit, and in Baleendah is solar radiation. The methods of evaporation estimations used in this study are Trabert, Schendel, Turc, and CIMIS-Penman methods. The result shows that the original constant values of those methods are significantly correlated. However, the Schendel is found the most overestimated, and the second is Turc. The best estimated evaporation in Baleendah, ITB, and Ujung Berung is calculated using CIMIS-Penman with one hour lag of radiation, Trabert, and Calibrated Schendel, respectively. The improvement of constant value was applied to Schendel and the result is better than the original constants.

scholarly journals Spatiotemporal Characteristics of Near-Surface Wind in Shenzhen

2020 ◽  
Vol 12 (2) ◽  
pp. 739 ◽  
Author(s):  
Cheng Liu ◽  
Qinglan Li ◽  
Wei Zhao ◽  
Yuqing Wang ◽  
Riaz Ali ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Surface Wind ◽  
Prevailing Wind ◽  
Average Wind Speed ◽  
Near Surface ◽  
Average Wind ◽  
Prevailing Wind Direction ◽  
Seasonal Wind ◽  
The Mean

The spatiotemporal characteristics of near-surface wind in Shenzhen were investigated in this study by using hourly observations at 92 automatic weather stations (AWSs) from 2009 to 2018. The results show that during the past 10 years, most of the stations showed a decreasing trend in the annual mean of the 10 min average wind speed (avg-wind) and the mean of the 3 s average wind speed (gust wind). Over half of the decreasing trends at the stations were statistically significant (p < 0.05). Seasonally, the decrease in wind speed was the most severe in spring, followed by autumn, winter, and summer. The distribution of wind speed tends to be greater in the east and coastal areas for both avg-wind and gust wind. From September to March of the following year, the prevailing wind direction in Shenzhen was northerly, and from April to August, the prevailing wind direction was southerly. The seasonal wind speed distribution exhibited two different types, spring–summer type and autumn–winter type, which may be induced by their different prevailing wind directions. The analysis by the empirical orthogonal function (EOF) method confirmed the previous findings that the mean wind speed was decreasing in Shenzhen and that two different seasonal wind speed spatial distribution patterns existed. Such a study could provide references for wind forecasting and risk assessment in the study area.

scholarly journals Wind turbine wake measurements with automatically adjusting scanning trajectories in a multi-Doppler lidar setup

2018 ◽  
Vol 11 (6) ◽  
pp. 3801-3814 ◽  
Author(s):  
Norman Wildmann ◽  
Nikola Vasiljevic ◽  
Thomas Gerz
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Direction ◽  
Sonic Anemometer ◽  
Prevailing Wind Direction ◽  
Wide Range ◽  
Novel Method ◽  
Approach Velocity ◽  
German Aerospace ◽  
First Time

Abstract. In the context of the Perdigão 2017 experiment, the German Aerospace Center (DLR) deployed three long-range scanning Doppler lidars with the dedicated purpose of investigating the wake of a single wind turbine at the experimental site. A novel method was tested for the first time to investigate wake properties with ground-based lidars over a wide range of wind directions. For this method, the three lidars, which were space- and time-synchronized using the WindScanner software, were programmed to measure with crossing beams at individual points up to 10 rotor diameters downstream of the wind turbine. Every half hour, the measurement points were adapted to the current wind direction to obtain a high availability of wake measurements in changing wind conditions. The linearly independent radial velocities where the lidar beams intersect allow the calculation of the wind vector at those points. Two approaches to estimating the prevailing wind direction were tested throughout the campaign. In the first approach, velocity azimuth display (VAD) scans of one of the lidars were used to calculate a 5 min average of wind speed and wind direction every half hour, whereas later in the experiment 5 min averages of sonic anemometer measurements of a meteorological mast close to the wind turbine became available in real time and were used for the scanning adjustment. Results of wind speed deficit measurements are presented for two measurement days with varying northwesterly winds, and it is evaluated how well the lidar beam intersection points match the actual wake location. The new method allowed wake measurements to be obtained over the whole measurement period, whereas a static scanning setup would only have captured short periods of wake occurrences.

scholarly journals Identifying meteorological drivers of extreme impacts: an application to simulated crop yields

2021 ◽  
Author(s):  
Jakob Zscheischler ◽  
Johannes Vogel ◽  
Pauline Rivoire ◽  
Cristina Deidda ◽  
Leila Rahimi ◽  
...  
Keyword(s):  
United States ◽  
Vapour Pressure ◽  
Crop Yields ◽  
Model Performance ◽  
Vapour Pressure Deficit ◽  
Growing Season ◽  
The United States ◽  
Climate Extreme ◽  
Crop Failure ◽  
Grid Points

&lt;p&gt;Compound weather events may lead to extreme impacts that can affect many aspects of society including agriculture. Identifying the underlying mechanisms that cause extreme impacts, such as crop failure, is of crucial importance to improve their understanding and forecasting. In this study we investigate whether key meteorological drivers of extreme impacts can be identified using Least Absolute Shrinkage and Selection Operator (Lasso) in a model environment, a method that allows for automated variable selection and is able to handle collinearity between variables. As an example of an extreme impact, we investigate crop failure using annual wheat yield as simulated by the APSIM crop model driven by 1600 years of daily weather data from a global climate model (EC-Earth) under present-day conditions for the Northern Hemisphere. We then apply Lasso logistic regression to determine which weather conditions during the growing season lead to crop failure.&lt;/p&gt;&lt;p&gt;We obtain good model performance in Central Europe and the eastern half of the United States, while crop failure years in regions in Asia and the western half of the United States are less accurately predicted. Model performance correlates strongly with annual mean and variability of crop yields, that is, model performance is highest in regions with relatively large annual crop yield mean and variability. Overall, for nearly all grid points the inclusion of temperature, precipitation and vapour pressure deficit is key to predict crop failure. In addition, meteorological predictors during all seasons are required for a good prediction. These results illustrate the omnipresence of compounding effects of both meteorological drivers and different periods of the growing season for creating crop failure events. Especially vapour pressure deficit and climate extreme indicators such as diurnal temperature range and the number of frost days are selected by the statistical model as relevant predictors for crop failure at most grid points, underlining their overarching relevance.&lt;/p&gt;&lt;p&gt;We conclude that the Lasso regression model is a useful tool to automatically detect compound drivers of extreme impacts, and could be applied to other weather impacts such as wildfires or floods. As the detected relationships are of purely correlative nature, more detailed analyses are required to establish the causal structure between drivers and impacts.&lt;/p&gt;

scholarly journals Wind Turbine Wake Measurements with Automatically Adjusting Scanning Trajectories in a Multi-Doppler Lidar Setup

2018 ◽  
Author(s):  
Norman Wildmann ◽  
Nikola Vasiljevic ◽  
Thomas Gerz
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Direction ◽  
Sonic Anemometer ◽  
Prevailing Wind Direction ◽  
Wide Range ◽  
Engineering Models ◽  
Novel Method ◽  
German Aerospace ◽  
Turbine Wake

Abstract. In the context of the Perdigão 2017 experiment, the German Aerospace Center (DLR) deployed three long-range scanning Doppler lidars with the dedicated purpose of investigating the wake of a single wind turbine at the experimental site. A novel method was established to investigate wake properties with ground-based lidars over a wide range of wind directions. For this method, the three lidars, which were space- and time-synchronized using the WindScanner software, were programmed to measure with crossing beams at individual points up to ten rotor diameters downstream the wind turbine. Every half hour, the measurement points were adapted to the current wind direction to obtain a high availability of wake measurements in changing wind conditions. The linearly independent radial velocities where the lidar beams intersect allow the calculation of the wind vector at those points. Two approaches to estimate the prevailing wind direction were tested throughout the campaign. In the first approach, VAD scans of one of the lidars were used to calculate a five-minute average of wind speed and wind direction every half hour, whereas later in the experiment, five-minute averages of sonic anemometer measurements of a meteorological mast close to the wind turbine became available in real-time and were used for the scanning adjustment. Results of wind speed deficit measurements are presented for two measurement days with varying westerly winds and it is evaluated how well the lidar beam intersection points match the actual wake location. The new method allowed to obtain wake measurements over the whole measurement period, whereas a static scanning setup would only have captured short periods of wake occurrences. The analysed cases reveal that state-of-the-art engineering models for wakes underestimate the actual wind speed deficit.

Wind analysis at Ganja International Airport

2020 ◽  
Vol 61 (12) ◽  
pp. 162-165
Author(s):  
Ulker Faig Bayramova ◽  
Keyword(s):  
Wind Speed ◽  
Key Words ◽  
Wind Direction ◽  
Maximum Speed ◽  
Prevailing Wind ◽  
Wind Rose ◽  
International Airport ◽  
Wind Analysis ◽  
Prevailing Wind Direction ◽  
The Mean

The article reviews wind conditions at Ganja International Airport and specifies the maximum winds observed during the month and the direction of the winds. The direction of the mean, maximum wind speed of the prevailing wind was analyzed. Based on our analysis, we can see that the prevailing wind direction isnortheast and the maximum speed was recorded in March. Key words: wind, temperature, aviation, wind rose, visibility

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