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Table of Contents

Introduction

This is a brief introduction of the main request parameter syntax.

Note

We recommend that you get familiar with datasets and their availability using http://apps.ecmwf.int/datasets/

You can also get the request syntax using "View MARS request" feature.

...

Syntax

Code Block
languagebash
verb,
 keyword1 = value1,
      ... = value2,
 keywordN = valueN
  • verb: action to be taken (e.g. retrieve, list, read)
  • keyword: a known MARS variable, e.g. type or date
  • value: value assigned to the keyword, e.g. Analysis or temperature

Retrieve example from "View MARS request":


Code Block
titleMARS request
retrieve,
 stream=oper,
 levtype=sfc,
 param=165.128/41.128,

...

dataset

...

=interim,
 step=0,
 grid=0.75/0.75,
 time=00,
 date=2013-09-01/to/2013-09-30,
 type=an,
 class=ei

...



Code Block
Keyword
language
definition
py
datasetSee Dataset section of pDate & Timetime

Base time (00, 06, 12 and 18)

Observation time (HHMM or HH:MM: ie 09:30)

date

Specifies the Analysis date, the Forecast base date or Observations date. Formats

  • Absolute as YYYY-MM-DD, YYYYMMDD. The day of the year can also be used: YYYY-DDD
  • Relative as -n ; n is the number of days before today (i.e., -1 = yesterday )
  • Name of month (e.g. january for Climatology data)
  • Operational monthly means are retrieved by setting day (DD) to 00.
stepSpecifies the forecast time step from forecast base time. Valid values are hours (HH)Fieldstype

Determines the type of field to be retrieved:

This keyword makes the selection between observations, images or fields, and it determines some of the valid remaining keywords of the request.
  • Analysis (an)
  • Forecast (fc)
  • Perturbed Forecast (pf)
  • Control Forecast (cf)
levtype

Denotes type of level:

  • Model level (ml)
  • Pressure level (pl)
  • Surface (sfc)
  • Potential vorticity (pv)
  • Potential temperature (pt)
  • Depth (dp)
levelistLevels for the specified levtype. (off if levtype=sfc)param

Meteorological parameter. (t, temprerature, 130, 30.128, ...)

Storagetarget
specifies a Unix file into which data is to be written after retrieval or manipulation. Path names should always be enclosed in double quotes:
target = "analysis.grb"
titlePython equivalence
 #!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
   
server = ECMWFDataServer()
   
server.retrieve({
    'dataset' : "interim",
	'time'    : "00",
	'date'    : "2013-09-01/to/2013-09-30",
    'step'    : "0",
    'type'    : "an",
    'levtype' : "sfc",    
    'param'   : "165.128/41.128",
    'grid'    : "0.75/0.75",
    'target'  : "interim201309.grib"
    })


Keyword

In the Dataset service there is an extra mandatory keyword called dataset which does not appear in normal MARS requests.

Keyworddefinition
dataset See Available Datasets
formatYou can add 'format' : "netcdf" to retrieve the data in NetCDF format.

the other possible MARS keywords are explained in the MARS keywords documentation.