`uv2vxvy` documentation

`uv2vxvy` is part of Antarctic Mapping Tools for Matlab (Greene et al., 2017). Click here for a complete list of functions in AMT.

This function transforms georeferenced (zonal and meridional) vector components to cartesian (polar stereographic) coordinate components.

## Contents

## Syntax

[vx,vy] = uv2vxvy(lat,lon,U,V) [vx,vy] = uv2vxvy(x,y,U,V)

## Description

`[vx,vy] = uv2vxvy(lat,lon,U,V)` transforms zonal `U` and meridional `V` components of a vector field to cartesian horizontal `vx` and vertical `vy` components. Inputs `lat` and `lon` define locations of each point in `U` and `V`.

`[vx,vy] = uv2vxvy(x,y,U,V)` transforms zonal `U` and meridional `V` components of a vector field to cartesian horizontal `vx` and vertical `vy` components. Inputs `lat` and `lon` define locations of each point in `vx` and `vy`. Polar stereographic coordinates are automatically determined if any value in the first two inputs of `uv2vxvy` exceed normal geographic coordinate values.

## Example

Let's create an approximate vector field, call it wind. Use `psgrid` to get a 50 km resolution, 800 km wide grid centered on the South Pole. Then make up some zonal `U` and meridional `V` wind speed data and plot it on a map:

[lat,lon] = psgrid('south pole',8000,50); U = 10*ones(size(lat)).*cosd((lat+65)*3).^3; V = 3*sind(lon); speed = hypot(U,V); antmap('northernlimit',-55) pcolorm(lat,lon,speed) bedmap2 'patchshelves' bedmap2 'patchgl' quivermc(lat,lon,U,V,'density',15)

Above initialized a map with `antmap`, plotted wind speed as a pseudocolor field with `pcolorm`, laid the outlines of ice shelves and the continent with the Bedmap2 plotting function, and showed the vector field with `quivermc`. I downsample the field to 15% of its original density to reduce clutter.

close

Those zonal and meridional components can be converted to grid vx and vy components like this:

[vx,vy] = uv2vxvy(lat,lon,U,V);

Now the arrows can be displayed in cartesian coordinates. Get the correct locations for the arrows by

[x,y] = ll2ps(lat,lon);

and plot on cartesian coordinates like this:

quiver(x,y,vx,vy)

Ugh, that's ugly! Too crowded to see much, so let's overlay a Bedmap2 grounding line for context and then zoom in on the Antarctic Peninsula:

hold on bedmap2('gl','xy') axis([-3002352 -1453605 921398 2142910])

## Citing AMT

If this function or any other part of Antarctic Mapping Tools is useful for you, please cite the paper that describes AMT.

Greene, C. A., Gwyther, D. E., & Blankenship, D. D. Antarctic Mapping Tools for Matlab. *Computers & Geosciences*. 104 (2017) pp.151-157. doi:10.1016/j.cageo.2016.08.003.

## Author Info

The `uv2vxvy` function and supporting documentation were written by Chad A. Greene of the University of Texas at Austin's Institute for Geophysics (UTIG), September 2015.