Note
This tutorial was generated from an IPython notebook that can be downloaded here.
Create numpy region mask¶
In this tutorial we will show how to create a mask for arbitrary latitude and longitude grids.
Import regionmask and check the version:
'0.2.0'
We define a lon/ lat grid with a 1° grid spacing, where the points define the middle of the grid. Additionally we create a grid that spans the edges of the grid for the plotting.
Again we use the SREX regions. Using xarray=False
tells the code to
output to a numpy array.
mask
is now a n_lon x n_lat
numpy array. Gridpoints that do not
fall in a region are NaN, the gridpoints that fall in a region are
encoded with the number of the region (here 1 to 26).
The function mask
determines if all cominations of points given in
lon
and lat
lies within the polygon making up the region.
We can now plot the mask
:
Finally the mask
can now be used to mask out all data that is not in
a specific region.
Plot the selected data
Finally we can obtain the region mean:
Global mean: -0.00329869391794
Central Europe: 0.0326627413837
Create a mask with a different lon/ lat grid¶
The interesting thing of gridmask
is that you can use any lon/ lat
grid.
Use a 5° x 5° grid:
Now the grid cells are much larger.