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(RESOLVED) ERA-Interim downloading large file problem for ungrib purpose

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Dear WRF Community,

I am trying to run WRF using ERA-Interim as boundary condition. However, when downloading data, I have met a problem. I used three separated grib files for WPS processing.


When downloading Model Level Variables ERA-ML-201503.grib, I used the following script:

#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
"class": "ei",
"dataset": "interim",
"date": "2015-03-01/to/2015-03-30",
"expver": "1",
"grid": "0.75/0.75",
"levelist": "1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/34/35/36/37/38/39/40/41/42/43/44/45/46/47/48/49/50/51/52/53/54/55/56/57/58/59/60",
"levtype": "ml",
"param": "130.128/131.128/132.128/133.128",
"step": "0",
"stream": "oper",
"time": "00:00:00/06:00:00/12:00:00/18:00:00",
"type": "an",
"target": "ERA-ML-201503.grib",

It accounts ~6.5G for ERA-ML-201503.grib, and this script fails to download a whole year since the output is a very large file.

My question is: it is necessary to download such a large file? How to adopt the above script for downloading ERA-ML (only WRF run purpose)?
As this problem is specific to the data, and not the model, I would advise contacting the group that issues & supports the data for advice. It shouldn't be necessary to have such large data files. You should be able to get a subset of the data, as long as they are not on a Gaussian grid (WPS is incapable of processing a subset on that grid). If it helps, take a look here to see which variables are mandatory and recommended: