Wind

As Wind ( Old High German wint, to Indo-European ue, blow, blow ') is referred to in meteorology directed, stronger air movement in the atmosphere.

Formation

Main cause of wind are differences in air pressure between air masses. Here, the air particles move out of the area with a higher air pressure - the high-pressure area - as long as in the area with the lower air pressure - the low pressure area - until the pressure has been released. It is therefore in a wind at a mass flow which aims at an equal distribution of particles in space and thus a maximum entropy with respect to the second law of thermodynamics. The corresponding force is called the pressure gradient force. The greater the difference between the air pressures, the more violent the air to flow masses in the area with the lower air pressure and the stronger the resulting from the movement of air is wind.

Wind direction

The wind direction, usually expressed in the form of a main wind direction is determined by the location of low pressure and high pressure area. It will do but distracted by the Coriolis force in the direction of movement to the right ( Northern Hemisphere ) or left (Southern Hemisphere ). Below the free atmosphere the wind is additionally influenced by friction and can also by morphological structures such as mountains, valleys and canyons vary greatly (for example, hair dryer or down wind, solar chimney, valley wind, mountain wind). In rotating systems such as hurricanes addition, the centrifugal force plays a crucial role. There are basically the meridional and the zonal component of the wind.

Wind speed and wind speed

The speed of the wind is in meters per second (m / s), kilometers per hour (km / h) or in the maritime, aerospace in knots ( 1 kt = 1.852 km / h ) were measured. The highest ever measured wind speeds of around 500-650 km / h have to date been at high altitudes in the so-called jet streams.

The strength of the wind is - expressed in units of Beaufort ( Beaufort ) - within the very popular Beaufort scale. Winds 2-5 Bft are called breeze. Winds with winds 6-8 Bft wind is called with the graduations of strong, stiff and stormy wind. With winds over 9 Bft one speaks of a storm. Winds with the wind force 12 is called a hurricane. A powerful air movement of short duration is referred to as squall.

The force exerted by the wind on objects ( such as on a viaduct ) takes the square of the wind speed: double the wind speed means four times the force.

Classification

Winds are divided into different groups.

  • Direct Druckgradientwind
  • No Coriolis, centrifugal and frictional force
  • äquatornah (low Coriolis force )
  • Balance between pressure gradient and Coriolis force
  • Isobarenparallel (without bends )
  • Above the bottom friction layer (free atmosphere)
  • Depends only on the horizontal pressure gradient
  • Real compensation component for idealized geostrophic wind
  • Based on fluctuations that lead to the mass balance
  • Balance between pressure gradient, centrifugal and Coriolis force
  • Isobarenparallel ( with bends )
  • Above the bottom friction layer (free atmosphere)
  • Depends only on the horizontal pressure gradient
  • Balance between pressure gradient and centrifugal force
  • Usually äquatornah (low Coriolis force ) or high wind speed
  • Only occur with cyclones
  • Immediate instability of zyklostrophischen balance in anticyclones

Also, a distinction based on the dimension and resistance of the winch is common. There are here three main groups distinguished:

Pressurization Mass flow rate Vertical draft Knot (unit) Synoptic scale meteorology Buys Ballot's law Ekman spiral Trade wind Wind power
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