Gridded arrows

This example was taken from the [Cartopy gridded arrow example].

The big idea is to plot arrows from one CRS in another!

using GeoMakie, CairoMakie

xs = LinRange(311.9, 391.1, 30)
ys = LinRange(-23.6, 24.8, 20)

us = @. 1 * (2 * cos(2 * deg2rad(xs) + 3 * deg2rad(ys' + 30)) ^ 2)
vs = @. 2 * cos(6 * deg2rad(xs)) .+ ys' * 0 # that last part is just to establish the shape

pole_longitude=177.5
pole_latitude=37.5
arrow_crs = "+proj=ob_tran +o_proj=latlon +o_lon_p=0 +o_lat_p=$(pole_latitude) +lon_0=$(180+pole_longitude) +to_meter=$(deg2rad(1) * 6378137.0)"

f, a, p = arrows(
    xs, ys, us, vs;
    arrowsize = 4,
    source = arrow_crs,
    axis = (; type = GeoAxis, dest = "+proj=ortho +lon_0=-10 +lat_0=45")
)

Now we plot the background:

ep = surface!(a,
    -180..180, -90..90,
    zeros(axes(rotr90(GeoMakie.earth())));
    shading = NoShading, color = rotr90(GeoMakie.earth())
)
translate!(ep, 0, 0, -1)
f

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