问题
I have downloaded climate model output in the form of netcdf files with one variable (pr) for the whole world with a daily time-step. My final goal is to have monthly data for Europe.
I have never used netcdf files before and all the specific software for netcdf I could find doesn't seems to work in windows. Since I programme in R, I tried using the ncdf4 package but run into memory size problems (my files are around 2Gb)... I am now trying the netCDF4 module in python (first time I am using python - so go easy on me).
I have managed to install everything and found some code online to import the dataset:
nc_fid = Dataset(nc_f, 'r')
# Extract data from NetCDF file
lats = nc_fid.variables['lat'][:]
lons = nc_fid.variables['lon'][:]
time = nc_fid.variables['time'][:]
pp = nc_fid.variables['pr'][:]
However all the tutorials I found are on how to make a netcdf file... I have no idea how to aggregate this daily rainfall (variable pr) into monthly. Also, I have different types of calender in different files, but I don't even know how to access that information:
time.calendar
AttributeError: 'numpy.ndarray' object has no attribute 'calendar'
Please help, I don't want to have to learn Linux just so I can sort-out some data :(
回答1:
Why not avoid programming entirely and use NCO which supplies the ncrcat command that aggregates data thusly:
ncrcat day*.nc month.nc
Voilà. See more ncrcat examples here.
Added 20160628: If instead of a month-long timeseries you want a monthly average then use the same command only with ncra instead of ncrcat. The manual explains things like this.
回答2:
If you have a daily timestep and you want to calculate the monthly mean then you can do
cdo monmean input_yyyy.nc output_yyyy.nc
It sounds as if you have several of these files, so you will need to merge them with
cdo mergetime file_*.nc timeseries.nc
where the * is a wildcard for the years.
来源：https://stackoverflow.com/questions/26240747/how-to-convert-daily-to-monthly-netcdf-files