How the wind shapes our lives.
Posted on 31 Jan 2023
The wind around us is a seemingly invisible hand that can shape our planet, lives and society. Even though we cannot see the wind, we can certainly see the results of its work - from helping to dry our clothes, to spreading populations around our planet. As we mentioned in our previous article, it can also be seen as the driving force for other weather, transporting and shaping systems both locally and globally, one of the fundamentals of our weather systems.
Our wind is generated by differences in atmospheric pressure caused by the interaction of the sun’s energy and the shape, geography and rotation of our planet. The front, or boundary between areas of similar pressure creates the vast array of weather conditions that we experience. The Coriolis effect, caused by the rotation of our planet, makes wind systems twist counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
The wind may seem to be a free-flowing energy source that varies at its own whim, however it does follow patterns, and can be categorized, compartmentalized and, thankfully predicted.
There are generally three ways that winds can be classified, depending on how frequently, and where they appear:
Primary (prevailing, planetary) winds tend to be constant and consistent throughout the year. Examples include Trade winds, westerlies and easterlies.
Secondary (seasonal, periodic) winds change direction during different seasons. These winds are influenced by the unique geography of a particular area, an example being the monsoon.
Tertiary winds are generally local to a certain area and time of the day, and are influenced by specific temperature and pressure characteristics of a small area. For example, the Loo is a hot and dry local wind of the northern plains of India, and the Mistral, which is a strong, cold, northwesterly wind that blows from southern France.
There are a number of ‘wind zones’, some that have been argued to have been of critical importance to the spread of human populations throughout the planet. Most notably are the Trade Winds that are generally regarded as being predictable, and which blow from the east across the tropics. They have been instrumental in the history of exploration, communication, and trade. Ships relied on trade winds to establish quick and reliable routes across the vast Atlantic and, later, Pacific Oceans. Even today, shipping depends on trade winds and the ocean currents they drive.
In 1947, the famous explorer and experimental archaeologist Thor Hyerdahl led a perilous journey aboard the Kon-Tiki, in essence a wind-powered raft to prove that it was at least possible to travel from the coast of Peru to the coral reefs of French Polynesia, more than 6,920 kilometers (4,300 miles) using only the power of the wind. Although his specific theory has been largely discredited today, his inspirational adventure nevertheless showed that it was possible to complete such a long journey in what we would see today as a very rudimentary sail-powered craft.
There are two types of Trade Winds - continental - which form over land, and which are generally warmer and dryer than their sea-based counterparts, the maritime trade winds. Tropical storms tend to develop as trade winds due to differences in air pressure over the ocean. As the dense, moisture-filled winds of the storm encounter the drier winds of the coast, the storm can increase in severity.
Strong trade winds do not tend to carry moisture inland, however the weaker varieties are capable of transporting large levels of rainfall inland, and are the main cause of the Southeast Asian monsoon season.
The summer monsoon is of critical importance to agriculture and the general economic development of areas in Southeast Asia and India. These areas do not tend to have large irrigation systems, lakes or large underground aquifers (such as in the UK), and rely on the monsoon rain to fill the smaller aquifers and wells that supply the irrigation for the tea and rice crops for the year. The monsoon also keeps the dairy herds healthy, enabling India to be the largest milk producing nation in the world.
Energy production also relies on the monsoon rains - hydroelectric power plants generate energy from the downpours, which power hospitals, schools and businesses in the area.
The severity of the monsoon can also have an effect on the local economy. Cities such as Mumbai are used to dealing with flooded streets, however when the floods are excessive, crops are ruined and some villages can even be completely submerged by mudslides.
However when the rains are too weak, local communities cannot grow enough food for their own use, and governments are forced to import food. The larger agribusinesses are also affected, creating a damaging effect to the national economy.
The winter monsoon that runs from October to April is less intense than the summer equivalent. The dry winter monsoon blows from the northeast, with the winds starting in Mongolia and northwestern China. Winter monsoons are less powerful than summer monsoons in Southeast Asia, due in part to the Himalaya Mountains preventing much of the wind and moisture of the monsoons from reaching the coast.
The Himalayas also prevent much of the cool air from reaching places like southern India and Sri Lanka, keeping them warm all year, and having an influence on droughts in the area.
Both current, historical and forecast rainfall can be reliably and easily viewed using the OpenWeather Global Precipitation Maps History and Forecast product. Featuring a 10-minute step, global precipitation can be easily incorporated into applications with this easy-to-use API.
The trade winds from the planet’s two hemispheres meet at what is known as the intertropical convergence zone (ITCZ). Surrounding the ITCZ is an area famous for its analogy with a feeling of boredom, lethargy and unease, the Doldrums.
This belt around the Earth extends approximately five degrees north and south of the equator, with very weak prevailing winds, and unusually calm seas, creating an area infamous amongst ancient mariners who relied solely on the wind to power their craft.
Different types of wind can be seen to both create inspirational journeys as well as be the byword for inactivity and boredom. It can create devastation, but also be a source of food, power and healthcare. In our next article we will look at other wind phenomena such as cyclones, blizzards and tornadoes.
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Wind information can be obtained from the OpenWeather Weather Maps 2.0, which gives visual map layers that include a separate wind layer to allow users to visualize wind directions, anywhere in the world.
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