Simulation & Animations

Info: In order to see the animations below, you simply click on the particular image.

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Computation of the Seasonal Climatology of Stream Function and Velocity Potential Derived from the Wind Field

Analysis and Reconstructed Codes by Sandro Lubis 
Graduate Student of Leipzig Institute for Meteorology, University of Leipzig, Germany

All computations are made using
[ NCAR Command Language (NCL)]

Velocity potential is a good indicator to comprehend the irrotational flows in the atmosphere. The velocity potential is a scalar field that describes the quantity of  divergent irrotational part of the horizontal velocity field. A question that naturally arises is “Where do we find irrotational flows?”. A uniform flow is definitely irrotational. But one hardly finds a uniform flow in nature.  In general, centers of regions of positive potential (negative Laplacian) have converging winds at 200hPa and subsidence beneath. Regions of negative potential have diverging winds and rising air motion beneath [DOMEX 2011]. Recent research has also indicated that  there is strong relationship between the Streamfunction and Velocity Potential to the Madden–Julian Oscillation and other tropical waves.

The following figures are calculated from the ERA Interim Dataset  1979-2013

In this experiment, data is retrieved from ECMWF ERA-Interim 6-hourly datasets of wind field.  Stream function and velocity potential are computed via spherical harmonics at given zonal and meridional wind on a fixed grid with on the condition that input values must be in ascending latitude order and input array must be on a global grid.

[ANIMATION]