- The objective of this example is to demonstrate how to iterate efficiently over some dates (eg '2014-10-01' and '2014-11-01') two requests for 'perturbed forecast', 'pressure' and 'sfc' level, for TIGGE, ECMWF Center.
- It can be used as a starting point,however you need to please keep in mind that you have to adapt it to your needseg to set the keyword, values according to your requirements ('param', 'levtype', 'step' etc).
- In this way you can extend these requests to download more data or a longer period of TIGGE.
 The most efficient way to organise your requests is per dates and times
ie select a set of 'dates' and 'times' and add the 'steps', 'origins', 'levels' and 'parameters' that you need.  It is not efficient to organise your requests per parameter, per origin or per step. (eg to submit a different request per parameter or per origin for a list of dates)
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