NC文件按时序维度拆分

最近拿到了nc文件，每个nc文件里包括了一年多的数据，使用的时候无法识别时间维度，需要把nc文件按时间维度拆分为很多个nc文件。
nc文件的结构
拆分代码如下

import xarray as xr
import os
from netCDF4 import Dataset
import numpy as np
in_folder = r"F:\Data\流场数据\data"
out_folder = r"F:\Data\OceanCurrent"

#First import the netcdf4 library
from netCDF4 import Dataset  # http://code.google.com/p/netcdf4-python/

# Read en existing NetCDF file and create a new one
# f is going to be the existing NetCDF file from where we want to import data
# and g is going to be the new file.

def ChangeNC(in_folder,out_folder):
    for root, dirs, files in os.walk(in_folder):
        for f in files:
            path = os.path.join(root, f)
            print(path)
            file_in = Dataset(path, 'r')  # r is for read only
            time = file_in.variables["time"][:]  # read time variable
            u1 = file_in.variables["uwnd"][:]
            v1 = file_in.variables["vwnd"][:]
            latList = file_in.variables["latitude"][:]
            lonList = file_in.variables["longitude"][:]

            # print(u1,v1,time)
            for i in range(len(time)):
                # print(time[i])
                print(v1[i][0], u1[i][0])
                # print(i,type(f))
                newName = f[:-3] + "_" + str(i) + ".nc"

                pathOut = os.path.join(out_folder, newName)  # output file
                # g = Dataset(pathOut, 'w')  # w if for creating a file
                outputfile = Dataset(pathOut, 'w', format='NETCDF3_CLASSIC')

                outputfile.createDimension('lat', 628)
                outputfile.createDimension('lon', 1440)
                outputfile.createDimension('time', 1)

                lat = outputfile.createVariable('lat', np.float32, ('lat'))
                lon = outputfile.createVariable('lon', np.float32, ('lon'))
                time = outputfile.createVariable('time', np.float32, ('time'))
                u = outputfile.createVariable('U', np.float32, ('lat', 'lon'))
                v = outputfile.createVariable('V', np.float32, ('lat', 'lon'))

                lat.units = 'degrees_north'
                lat.long_name = 'latitude'
                # _FillValue = NaN; // double
                # :units = "degrees_north";
                # :long_name = "Latitude";
                lat.standard_name = "latitude"
                lat.point_spacing = "even"
                lat.axis = "Y";
                # :NAVO_code = 1; // int
                lat._CoordinateAxisType = "Lat"

                lon.units = 'degrees_east'
                lon.long_name = 'longitude'
                lon.standard_name = "longitude";
                # lon.modulo = "360 degrees";
                lon.axis = "X";
                # :NAVO_code = 2; // int
                lon._CoordinateAxisType = "Lon";
                time.units = "hours since 1987-01-01 00:00:00"
                time.long_name = "Time of analysis"
                # u(time=72, depth=1, latitude=481, longitude=1201);
                u.units = "m s-1";
                u.long_name = "u-wind vector component at 10 meters"
                u.coordinates = "latitude longitude";
                u.height = "10 meters above sea-surface";
                u.standard_name = "eastward_wind";

                v.units = "m s-1"
                v.long_name = "v-wind vector component at 10 meters"
                v.standard_name = "northward_wind"
                v.height = "10 meters above sea-surface"

                # missing_value = NaN; // double
                outputfile.variables['lon'][:] = lonList
                # np.linspace(0, 360, 1201)
                # outputfile.variables['lon'][:] = np.linspace(-180 + 0.5, 180 - 0.5, 1201)
                outputfile.variables['lat'][:] = latList
                # np.linspace(80, -80 , 481)
                # np.array()file_in.variables['longitude'][:]
                # np.linspace(-80, 80 , 481)
                outputfile.variables['U'][:] = u1[i]
                outputfile.variables['V'][:] = v1[i]
                outputfile.variables['time'][:] = time[i:i + 1]
                outputfile.close()
            file_in.close()
if __name__ == '__main__':
    in_folder = "F:\\Data\\CCMP"
    out_folder = "F:\\Data\\CCMP\\Daily"
    for year in range(2019,2010,-1):
        folder = in_folder + "\\" + str(year)
        ChangeNC(folder, out_folder)