MARS request

A MARS request is the way to specify an action on a set of fields or observations. The directives specified in a MARS request have the following syntax:

verb,
   keyword1 = value 1,
   ...      = ...,
   keywordN = value N

Where:

verb:

identifies the action to be taken, e.g. retrieve or list.

keyword:

is a known MARS variable, e.g. type or date

value:

is the value assigned to the keyword, e.g. Analysis or temperature.

Keywords may be assigned a single value, a list of values or a range of values.

A list is indicated by the separator /

A range is indicated by using the keywords to as well as / and by.

Examples of different formats for values are given in the table below.

Format	Example
single value	param = temperature/SSRD
list of values	step = 12/24/48
range of values	date = 19990104/to/19990110/by/2

The following example shows a retrieve request with a mix of single, list and range of values:

retrieve,
   class    = od,
   stream   = oper,
   expver   = 1,
   date     = -1,
   type     = analysis,
   levtype  = model levels,
   levelist = 1/to/91,
   param    = temperature,
   grid     = 0.1/0.1

Retrieve requests have to specify, at least, directives to identify the data. The ones to identify fields are defined in the MARS Catalogue. Data manipulation (post-processing, such as grid) directives are optional, depending on user needs.