Download ECMWF MARS data

These steps to download ECMWF data are based on their instructions here: https://software.ecmwf.int/wiki/display/WEBAPI/Access+MARS

ECMWF parameters are described here: http://apps.ecmwf.int/codes/grib/param-db

Create a directory for mars:
```
mkdir -p ~/mars/bin
mkdir -p ~/mars/lib
```

Download mars:

cd ~/mars/bin
wget https://software.ecmwf.int/wiki/download/attachments/56664858/mars
export PATH=~/mars/bin/:$PATH
chmod +x ~/mars/bin/mars

Install ECMWF KEY
- You need an ECMWF account.
- Login: https://apps.ecmwf.int/auth/login/
- Save your key: https://api.ecmwf.int/v1/key/ to ~/.ecmwfapirc

Install client libraries

Download to ~/mars/lib:

cd ~/mars/lib
wget https://software.ecmwf.int/wiki/download/attachments/56664858/ecmwf-api-client-python.tgz
tar -xzf ecmwf-api-client-python.tgz
export PYTHONPATH=~/mars/lib:$PYTHONPATH

Put your MARS request into a file e.g. test.req:

retrieve,
  class   = od,
  stream  = oper,
  expver  = 1,
  date    = 20020501/to/20020510,
  time    = 00/06/12/18,
  type    = an,
  levtype = sfc,
  param   = sea surface temperature,
  target  = "sst.grib"

Request data:
```
mars test.req
```
Check your MARS request using the online catalogue before submitting a request: http://apps.ecmwf.int/mars-catalogue/
There can be long delays. Check your queue here: http://apps.ecmwf.int/webmars/joblist/
Check MARS activity. If there are lots of “queued” requests, it’s busy!
Some useful hints on using MARS here: https://software.ecmwf.int/wiki/display/UDOC/MARS+FAQ
https://software.ecmwf.int/wiki/display/WEBAPI/WebAPI+FAQ