High and low pressure indicated by lines of equal pressure called isobars.
Although we cannot actually see the air moving we can measure its motion by the force that it applies on objects. We use a wind vane to indicate the wind’s direction and an anemometer to measure the wind’s speed. But even without those instruments we can determine the direction.
For example, a flag points in the opposite direction of the wind. The wind blows leaves opposite the direction from which the wind is blowing. Airplanes taking off and landing at airports will be into the direction of the wind.
The vertical direction of wind motion is typically very small (except in thunderstorm updrafts) compared to the horizontal component, but is very important for determining the day to day weather. Rising air will cool, often to saturation, and can lead to clouds and precipitation. Sinking air warms causing evaporation of clouds and thus fair weather.
You have probably seen weather maps marked with H’s and L’s which indicate high- and low-pressure centers. Usually surrounding these “highs” and “lows” are lines called isobars. “Iso” means “equal” and a “bar” is a unit of pressure so an isobar means “equal pressure”. So everywhere along each line is the pressure has the same value.
Pressure gradient force extends from high pressure to low pressure.
With high-pressure systems, the value of air pressure along each isobar increases toward the center with each concentric line. The opposite is true for low-pressure systems in that with each concentric line toward the center represents lower pressure. Isobars maybe be close together or far apart.
The closer the isobars are drawn together the quicker the air pressure changes. This change in air pressure is called the “pressure gradient”. Pressure gradient is just the difference in pressure between high- and low-pressure areas.
The speed of the wind is directly proportional to the pressure gradient meaning that as the change in pressure increases (i.e. pressure gradient increases) the speed of the wind also increases at that location.
Also, notice that the wind direction (yellow arrows) is clockwise around the high-pressure system and counter-clockwise around the low-pressure system. In addition, the direction of the wind is across the isobars slightly, away from the center of the high-pressure system and toward the center of the low-pressure system.
Why does this happen? To understand we need to examine the forces that govern the wind. There are three forces that cause the wind to move as it does. All three forces work together at the same time.
The pressure gradient force (Pgf) is a force that tries to equalize pressure differences. This is the force that causes high pressure to push air toward low pressure. Thus, air would flow from high to low pressure if the pressure gradient force was the only force acting on it.
One way to see this force in action is to see what happens when a straight line becomes a curve. Picture the Earth as a turntable (see number 1) spinning counter-clockwise. A ruler is placed over the turntable (see number 2) and a pencil will move in a straight line from the center to the edge while the turntable spins underneath. The result is a curved line on the turntable (see number 3).
When viewed from space, wind travels in a straight line. However, when viewed from the Earth, air (as well as other things in flight such as planes and birds) is deflected to the right in the northern hemisphere (red arrow on image at right). The combination of the two forces would cause the wind to blow parallel to straight isobars with high pressure on the right.
So why does air spiral out from highs and into lows? There is one other force, called friction, which is the final component to determining the flow of wind. The surface of the earth is rough and it not only slows the wind down but it also causes the diverging winds from highs and converging winds near lows.
Airflow around highs and lows.
What happens to the converging winds near a low? A property called mass continuity states that mass cannot be created or destroyed in a given area. So air cannot “pile up” at a given spot.
It has to go somewhere so it is forced to rise. As it rises it cools. When air cools, condensation begins to exceed evaporation so the invisible vapor condenses, forming clouds and then precipitation. That is why there is often inclement weather near low-pressure areas.
What about the diverging air near a high? As the air spreads away from the high, air from above must sink to replace it. Sinking air warms. As air warms, evaporation begins to exceed condensation which means that clouds will tend to evaporate. That is why fair weather is often associated with high
Wind is almost entirely caused by the effects of the sun which, each hour, delivers 175 million million watts of energy to the earth. This energy heats the planet’s surface, most intensively at the equator, which causes air to rise. This rising air creates an area of low pressure at the surface into which cooler air is sucked, and it is this flow of air that we know as “wind”.
In reality atmospheric circulation is much more complicated and, after rising at the equator air travels polewards. As it travels the air cools and eventually descends to the earth’s surface at about 30° latitude (north and south), from where it returns once again to the equator (a closed loop known as a Hadley Cell). Similar cells exist between 30° and 60° latitude (the Ferrel Cells) and between 60° latitude and each of the poles (the Polar Cells).
Within these cells, the flow of air is further impacted by the rotation of the earth or the “Coriolis Effect”. This effect creates a sideways force which causes air to circulate anticlockwise around areas of low pressure in the northern hemisphere and clockwise in the southern hemisphere
While these mechanisms are responsible for the creation of winds at a global level, those at the level of an individual wind farm are in practice also impacted by more local effects. The most significant of these are:
During the day, the earth heats up more quickly than the sea. This causes air to rise over the land and in turn air to be “sucked in” from over the sea – an effect known as a sea breeze. During the night, the earth cools down more quickly than the sea and the effect is reversed. Overall, average wind speeds on the coast can be ~0.5 m/sec higher than those just a few kilometres inland.
During the day, the earth heats up more quickly than the sea. This causes air to rise over the land and in turn air to be “sucked in” from over the sea – an effect known as a sea breeze. During the night, the earth cools down more quickly than the sea and the effect is reversed. Overall, average wind speeds on the coast can be ~0.5 m/sec higher than those just a few kilometres inland.
wind is a clean, free, and readily available renewable energy source. Each day, around the world, wind turbines are capturing the wind’s power and converting it to electricity. Wind power generation plays an increasingly important role in the way we power our world – in a clean, sustainable manner.
But how is wind energy created? Wind turbines allow us to harness the power of the wind and turn it into energy. When the wind blows, the turbine’s blades spin clockwise, capturing energy. This triggers the main shaft of the wind turbine, connected to a gearbox within the nacelle, to spin. The gearbox sends that wind energy to the generator, converting it to electricity. Electricity then travels to a transformer, where voltage levels are adjusted to match with the grid.
The proposed location of the Dutch “Windwheel” is the international port of the city of Rotterdam. This modern, dynamic and international metropolis is the architectural capital of the Netherlands and continues to renew itself. It adds a unique landmark to the city, making the skyline even more spectacular.
The US hotel industry recorded single digit growth in all three performance metrics during the week beginning 23 January 2011, compared with the corresponding week last year, according to a report by STR Global. In year-over-year comparisons, hotel occupancy during the week increased
EC Harris has finished the construction of the Grand Millennium Al Wahda hotel for the Al Wahda Sports Club in Abu Dhabi, UAE. The hotel, which is located adjacent to the Al Wahda Mall in Abu Dhabi, features 588 guestrooms and 262 apartments. The property also houses seven b
Wyndham Worldwide’s profit increased by 7% to $78m during the fourth quarter of 2010, compared with the $73m profit reported during the corresponding quarter in 2009. The US-based hotel group’s revenue for 2010 rose to $937m, a 3% increase on the same period in 2009.
The US hotel industry recorded single digit growth in all three performance metrics during the week beginning 23 January 2011, compared with the corresponding week last year, according to a report by STR Global. In year-over-year comparisons, hotel occupancy during the week increased b
EC Harris has finished the construction of the Grand Millennium Al Wahda hotel for the Al Wahda Sports Club in Abu Dhabi, UAE. The hotel, which is located adjacent to the Al Wahda Mall in Abu Dhabi, features 588 guestrooms and 262 apartments. The property also houses seven b
The Dutch Wind Wheel is an innovative and sustainable development concept proposed in the city of Rotterdam in the Netherlands. It comprises residential, hotel, dining and tourism facilities in addition to a clean-energy generating mechanism that highlights the Dutch clean technology and innovation in renewable energy.
The project is a collaborative effort from, Doepel Strijkers Architects, technology development firm BLOC, and leisure destinations development firm Meysters. Dutch Windwheel Corporation, a consortium formed by the three companies, initiated the project.
NBTC Holland Marketing is a partner in the project, while more marketing organisations, development companies, investors and government agencies are being sought to form an alliance for the implementation of the project.
The Dutch Wind Wheel is expected to attract 1.5 million tourists a year and is touted to become an architectural landmark and a major tourist attraction for the biggest port city of Europe.
The Wind Wheel appears similar to a wind turbine, consisting of two three-dimensional (3D) rings with a light, open steel and glass construction. Its underwater foundation lends an illusion of a floating wheel.
The 174m (571ft)-tall structure comprises two rings or wheels that are coiled around each other and merge at the top. The rings are designed based on the principle of triangulation to achieve structural stability.
Forty rotating cabins on rails feature on the perimeter of the outer ring. These form a giant roller coaster, which provides visitors with mesmerising views of Rotterdam and its surrounding areas, including Europe’s biggest port, the Second Maasvlakte, and the sea.
The inner ring is designed to be an unconventional windmill that functions as a silent and motionless wind turbine converting wind energy into electricity using a framework of steel tubes.
The inner ring features a panorama restaurant, a sky lobby, a 160-room hotel on seven floors, 72 apartments and an interactive cinema. Commercial facilities are located at the plinth level of the inner ring.
Circular elevators and staircases are provided in the structural core of the wheel, while a parking space of 1,000 cars is located at the base.
The Dutch Wind Wheel also reduces the travel time to Kinderdijk, a UNESCO World Heritage site where 19 mills dating back to the 18th century are located, by 25 minutes on a fast ferry.
An interactive cinema in the 3D roller coaster takes the riders through the Dutch water management history. The cabin interiors of the giant coaster feature an innovative lighting concept.
The windmill showcases an innovative technology called electrostatic wind energy converter (EWICON), which was created by Delft University of Technology and Wageningen University.
The bladeless wind turbine technology eliminates the need for any moving mechanical parts to produce electricity from wind energy. It uses insulated tubes (cables) in a steel framework that are fitted with electrodes and nozzles, which electro-spray positively-charged water into the air.
The electrical energy of the positively charged particles reaching the negative electrode increases when wind pushes them away. The enhanced electrical energy is captured in a battery. The entire system is cheaper to maintain and causes less wear because of the absence of moving mechanical parts.
The innovative windmill creates no noise and no moving shadows. The Wind Wheel is fitted with photovoltaic thermal hybrid solar collectors (PVTs) and features a climatic façade.
It also integrates an efficient water management system, which captures and uses rain water either inside the facility or store it in a wetland. Biogas is produced by collecting the organic waste from the building.
The entire structure is designed to be disassembled and re-used. Local material from the Rotterdam region, the harbour and the surrounding steel industry is proposed be used to build the structure.
The Global Wind Atlas is a free, web-based application developed to help policymakers, planners, and investors identify high-wind areas for wind power generation virtually anywhere in the world, and then perform preliminary calculations. The Global Wind Atlas facilitates online queries and provides freely downloadable datasets based on the latest input data and modeling methodologies. Users can additionally download high-resolution maps of the wind resource potential, for use in GIS tools, at the global, country, and first-administrative unit (State/Province/Etc.) level in the Download section. Information on the datasets and methodology used to create the Global Wind Atlas can be found in the Methodology and Datasets sections.
We encourage users to provide feedback on their experience with this website and the available resources. Please visit the Contact section to provide feedback or submit technical questions.
Learn more about the background of the Global Wind Atlas application and how to use it in your daily work in the video below.
The current version of the Global Wind Atlas (GWA 3.1) is the product of a partnership between the Department of Wind Energy at the Technical University of Denmark (DTU Wind Energy) and the World Bank Group (consisting of The World Bank and the International Finance Corporation, or IFC). Work on GWA 2.0 and GWA 3.0 was primarily funded by the Energy Sector Management Assistance Program (ESMAP), a multi-donor trust fund administered by The World Bank and supported by 13 official bilateral donors. It is part of the global ESMAP initiative on Renewable Energy Resource Mapping that includes biomass, small hydropower, solar energy, and wind energy. GWA 3.0 builds on an ongoing commitment from DTU Wind Energy to disseminate data and science on wind resources to the international community.
GWA 3.0 represents a major upgrade from GWA 2.0 and the first version of the Global Wind Atlas (GWA 1.0). GWA 1.0 was developed by DTU Wind Energy under the framework of the Clean Energy Ministerial (CEM) and, in particular, the CEM Working Group on Solar and Wind Technologies, led by Germany, Spain and Denmark. GWA 1.0 combined the WAsP microscale model with reanalysis data to provide the first freely available high resolution global map of the wind resource. GWA 1.0 was funded by the Technology Development and Demonstration Program of the Danish Energy Agency (EUDP 11-II, 64011-0347) as the Danish contribution to the objectives of the CEM working group. GWA 1.0 was launched in 2015, and benefitted from collaboration with IRENA and the MASDAR institute. These two partners had a significant impact on the development of GWA 1.0 due to their ability to bring various energy stakeholders together.
In GWA 2.0, the focus was on improving the large-scale wind resource data and the website. To provide improved large-scale wind data, the World Bank Group selected Vortex, a leading commercial provider of wind resource data analysis, to carry out a global mesoscale modeling simulation at 9km resolution using the latest, at the time, ERA Interim reanalysis data, to replace the coarser reanalysis data used in GWA 1.0. The microscale modeling in GWA 2.0 was still performed using the DTU Wind Energy WAsP methodology that was used for GWA 1.0, to carry out microscale model calculations at a 250 m grid spacing. In addition to the data improvements, DTU Wind Energy subcontracted Nazka Mapps to reimagine the GWA web-interface providing an improved user experience and enhancing the value to users of the data.
In GWA 3.0, the wind resources have been calculated even more accurately, using the best available methods and input data. This time, Vortex carried out 10 years of mesoscale time-series model simulations rather than ensemble modeling that cover the globe at a 3 km resolution, forced with the latest ERA5 reanalysis data. In addition to improved atmospheric data, GWA 3.0 used improved elevation and landcover data in the microscale modelling. The mesoscale and microscale model simulations were expanded to include locations up to 200 km from all shorelines , to provide additional information on the offshore wind resource. It also included results at two additional heights 10 m and 150 m to reduce the uncertainty when interpolating the results in the vertical.
To better understand the impacts of the improved modeling in GWA 3.0, DTU Wind Energy carried out a validation of the new dataset. This ongoing task uses data from ESMAP-funded measurement campaigns and other high-quality publicly available wind data. At the time of the GWA 3.0 release, validation has been performed using data from ESMAP-funded measurement campaigns, implemented by the World Bank, for Pakistan, Papua New Guinea, Vietnam, and Zambia. Finally, additional features and functionality have been added to the GWA website by DTU Wind Energy and Nazka Mapps, as part of the 3.0 launch The first feature is an energy yield calculator tool, which allows users to create downloadable GIS data for annual energy production, capacity factor, or full load hours using their own custom wind turbine power curve. The second feature allows users to explore the temporal aspect of the wind resource. The variation of the mean wind speed can be found by year, month, and hour. Users can find areas where the wind resource tends to be load-following, i.e. matching the development in hourly or monthly electricity demand. Users can also combine this information with similar temporal data e.g. solar resources available under the Global Solar Atlas, to identify areas where wind and solar complement each other seasonally or during a typical day.
The GWA website will continue to be developed, owned and operated by DTU Wind Energy. Future upgrades and improvements under the partnership with the World Bank Group and ESMAP are already planned.
DTU wishes to thank all organizations and individuals involved in the development of the Global Wind Atlas, including those not listed above, who have provided important input data, review, and feedback. In particular, DTU would like to acknowledge the funding provided by ESMAP for development of GWA 2.0 and GWA 3.0, and advice, review and other non-financial inputs provided by staff and consultants from DTU, World Bank Group (including ESMAP), and Vortex.
