关于使用Python xarray将经度数组从0-360更改为-180到180 [英] About changing longitude array from 0 - 360 to -180 to 180 with Python xarray

问题描述

我是一位matlab用户，最近尝试在我的计算中更多地使用Python.我正在使用xarray，并希望将地球物理字段的经度数组从0-360更改为-180到180.但是当我这样做时:

I am a matlab user trying to use Python more for my computations recently. I am using xarray and would like to change my longitude array from 0 - 360 to -180 to 180 of a geophysical field. But when I do that:

df=xr.open_dataset(ecmwf_winds.nc)
u10=df['u10']
lon=df['longitude']
lon = np.where(lon > 180, lon-360, lon)
[X,Y]=np.meshgrid(lon,df.latitude)
plt.contourf(X,Y,u10)

等高线图显示出带有缝隙的混乱，这是没有意义的.任何人都可以帮我.我不确定我在哪里做错了.

the contourplot turns out to messy with gaps, which does not make sense. Can anyone please help me with it. I am not sure where I am doing wrong.

推荐答案

您需要先分配值，然后再沿着新的坐标值对所得的DataArray进行排序:

You need to assign the values as you've done and then also sort the resulting DataArray along the new coordinate values:

lon_name = 'longitude'  # whatever name is in the data

# Adjust lon values to make sure they are within (-180, 180)
ds['_longitude_adjusted'] = xr.where(
    ds[lon_name] > 180,
    ds[lon_name] - 360,
    ds[lon_name])

# reassign the new coords to as the main lon coords
# and sort DataArray using new coordinate values
ds = (
    ds
    .swap_dims({lon_name: '_longitude_adjusted'})
    .sel(**{'_longitude_adjusted': sorted(ds._longitude_adjusted)})
    .drop(lon_name))

ds = ds.rename({'_longitude_adjusted': lon_name})

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