排列netCDF4文件中的数据

Question

I am trying to figure out how to use Python module for netCDF4 handling. I would like to save simulation data into a file, such that for every time I have a grid of values of a certain field. I adapted an example that I have found for my use:

from netCDF4 import Dataset
import numpy as np

root_grp = Dataset('py_netcdf4.nc', 'w', format='NETCDF4')
root_grp.description = 'Example simulation data'

ndim = 128 # Size of the matrix ndim*ndim
xdimension = 0.75
ydimension = 0.75
# dimensions
root_grp.createDimension('time', None)
root_grp.createDimension('x', ndim)
root_grp.createDimension('y', ndim)

# variables
prec = root_grp.createVariable('time', 'f8', ('time',))
x = root_grp.createVariable('x', 'f4', ('x',))
y = root_grp.createVariable('y', 'f4', ('y',))
field = root_grp.createVariable('field', 'f8', ('time', 'x', 'y',))

# data
x_range =  np.linspace(0, xdimension, ndim)
y_range =  np.linspace(0, ydimension, ndim)
x[:] = x_range
y[:] = y_range
for i in range(5):
    field[i,:,:] = np.random.uniform(size=(len(x_range), len(y_range)))


root_grp.close

My question is - what is the preferred way now to add mode information that I would like to calculate for each time - such as the mean, max, and min values of the field every time?

Answer 1

You can add attributes to variables simply with:

field.mean=np.mean(field)

This is rather limited of course, for more data You should probably just create new variables like field_mean, field_max or similar. I do not think it is described in http://cfconventions.org/ or https://geo-ide.noaa.gov/wiki/index.php?title=NetCDF_Attribute_Convention_for_Dataset_Discovery but You may want to browse through different NetCDF conventions mentioned here http://www.unidata.ucar.edu/software/netcdf/conventions.html .