Convergence (meteorology)

Areas of convergence and divergence in the emergence of a hurricane in the Caribbean

In meteorology, convergence describes a horizontal influx of air masses into an area of ​​relatively low air pressure, i.e. a low pressure area . The winds that occur here always flow from the area of ​​higher air pressure to the area of ​​lower pressure. The area in which the convergence movement of these air masses occurs is called the convergence zone and its center, which is characterized by the point of the lowest air pressure, the convergence center .

The direction of movement of the converging air masses is determined in weather maps by evaluating the streamline field and marked by convergence lines. The force on which the convergence phenomenon is based is called the gradient force , with the Coriolis force , ground friction and morphological influences such as valleys and mountains also playing a role.

Other processes can result from the phenomenon of convergence, occur simultaneously with it, or superimpose it, for example:

• Every horizontal convergence phenomenon leads to updrafts or downdrafts due to the conservation of mass .
• Vertical air movements are called convection in meteorology .
• Horizontal air movements above the ground in the direction of higher temperatures are called advection in meteorology .
• When air masses sink towards the earth's surface and finally flow apart, one speaks of divergence .

Expressed in formulas, applies to a convergent air flow

${\displaystyle \operatorname {div} {\vec {V}}_{2}={\frac {\partial u}{\partial x}}+{\frac {\partial v}{\partial y}}<0}$

With

• the divergence operator ${\displaystyle \operatorname {div} }$
• the 2D wind vector ${\displaystyle {\vec {V}}_{2}}$
• the zonal wind component and ${\displaystyle u}$
• the meridional wind component . ${\displaystyle v}$

See also

• Baric wind law
• Intra-tropical convergence zone

Web links

• German Weather Service: Divergences / Convergences (accessed on September 28, 2015)
• Manfred Reiber: Interpretation of cloud images and weather phenomena for pilots and balloonists . (accessed on September 28, 2015)
• Daniel Nicolas Köbele: Analysis of areas of convergence in hail events downstream of low mountain ranges using COSMO model simulations . (accessed on September 28, 2015)