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import iris.analysis.cartography
grid_areas = iris.analysis.cartography.area_weights(cube)

area_avg = cube.collapsed(['grid_longitude', 'grid_latitude'], iris.analysis.MEAN, weights=grid_areas)

Exercise 5: What other aggregators are available? Calculate the potential temperature variance with time for the area averaged cube (hint: We want to reduce the vertical dimension, and end up with a cube of length 3). Print the data values of the resulting cube.

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