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This icon returns GRIB fields of one of the following :

  • divergent wind vectors from input data of Divergence
  • rotational wind vectors from input data of Vorticity
  • U/V wind vectors from input data of Vorticity and Divergence

The generated fields can be simply visualised or saved as GRIB files.

The macro language equivalents are divrot(),  divwind() and uvwind().

The Rotational Wind / Divergent Wind Editor

The RotationalWind/DivergentWind editor belongs to a type of editor known as family editor which allows related sets of input specifications to be grouped in the same icon editor, each in its own tabbed pane. The available working input panes are :

RotWind - To derive rotational wind vector fields from input of vorticity

DivWind - To derive divergent wind vector fields from input of divergence

UvWind - To derive U/V wind vector fields from input of vorticity and divergence

To operate with this icon first you need to select which output you want to produce by clicking the tab of the corresponding pane. In this icon the input panes contain identical sets of input parameters :

Data

Specifies the data required for the application. The icon field assist button provides a tailor made MARS request in case you need some guidance in the data specification. The requested data is Divergence in the Divwind pane, Vorticity in the Rotwind pane and both in the Uvwind pane. All input data are specified in spherical harmonics.

Truncation

Specifies the truncation to be applied to the spherical harmonics input data prior to conversion to lat/long.

Smoothing

Specifies whether to apply spatial smoothing to the spherical harmonics prior to transformation to grid points. This operation is performed after the truncation specified in Truncation . The smoothing filter is of the form :

 sn = exp (-(n*(n+1)/fltc*(fltc+1))**mfltexp)

this is roughly equivalent to a  \( \nabla^{2 \times mfltexp} \)

operator in grid point space.

Fltc

Specifies the value of the parameter fltc to be used in the smoothing filter. Only available if Smoothing set to Yes . The default value is 19.4.

Mfltexp

Specifies the value of the parameter mfltexp to be used in the smoothing filter. Only available if Smoothing is set to Yes . The default value is 2, roughly equivalent to a  \( \nabla^4 \)

operator in grid point space.