Ryd-Scherhag effect

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Schematic representation of the processes in converging and diverging air currents. Explanation of the force diagram: pressure gradient force (G), Coriolis force (C), movement of an air parcel (v). The black lines represent isobars , mass shifts are indicated by "+" and "-".

The Ryd-Scherhag effect (after Valdemar Hansen Ryd and Richard Scherhag ) describes processes in meteorology that occur in flowing air masses in areas with increasing or decreasing pressure gradients . It therefore plays an important role in the creation of dynamic printed structures.

Explanation

In the case of an air parcel that moves under geostrophic conditions, the gradient force causing the movement and the Coriolis force acting on the moving air parcel balance each other out. The greater the gradient force, the faster the air parcel moves and the greater the Coriolis force. Geostrophic conditions only exist in higher layers of the troposphere due to the frictional influence of the earth's surface .

If the air parcel now flows into an area with a higher pressure gradient, the Coriolis force follows the increase in the gradient force with a delay due to the inertia of the air. The greater influence of the pressure gradient force in this convergence area leads to an ageostrophic blowing of the wind. In the direction of the gradient force, which always acts in the direction of the lower pressure, there is an anisobaric mass displacement , i.e. across the isobars .

In contrast, there is a mass flow in the direction of the higher pressure when an air parcel moves into a divergence area . The adjustment of the wind speed to the local conditions is delayed again due to the inertia, so the Coriolis force also decreases more slowly than the gradient force, i.e. H. the influence of the Coriolis force on the movement increases. The mass displacement in the flow delta is greater than the processes of movement in a convergence area, since the initial velocity of the air when moving into the divergence area is higher than when entering the convergence area. Overall, there is thus a gain in mass in the direction of the higher pressure. The resulting increase in air pressure leads to the development of a dynamic high pressure area on the ground, on the opposite side the ground pressure is reduced due to the loss of mass and a dynamic low pressure area is created .

meaning

For the weather over Europe, the Ryd-Scherhag effect plays an important role , especially in the formation of the Azores highs and Iceland lows . The areas of convergence and divergence lie in the meanders of the planetary frontal zone , the Rossby waves . The resulting dynamic pressure areas play a decisive role in balancing out the radiation- related energy differences on earth.

Individual evidence

  1. ^ Meteorology and climatology : an introduction, page 172 uf, Horst Malberg, Springer-Verlag Berlin, ISBN 3-540-42919-0

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