So, you’ve heard ‘ECWMF is far better than NCEP’, and you want a piece of some ECMWF data action. Where do you get get it? How do you find it?. Here’s a list to help you (me) out.
There are multiple routes to ECMWF data heaven. The most flexible and powerful, but most complicated is MARS. To use MARS fully you need the client, a piece of open-source software covered by a GPL licences, but costs £100. It is used to communicate with the data servers at ECMWF, and can subset data on the server side to reduce the volume of data needed to be transferred. Quicker way to MARS is via Web MARS.
Some links on MARS
The other route is the ECMWF data server. This gives you straight access, no software needed, no (not many) questions asked. It is actually just a linux server sitting outside the ECMWF firewall running MARS, but only allowing access to the disk archive, and not the tape archive.
To grab a dataset requires a request. Some fields used in the request are:
|class||ECMWF classification (od, rd, e4, …)|
|stream||originating forecasting system(oper, wave, enfo, seas, …)|
|expver||version of the experiment (01 operational, 11, aaaa)|
|domain||area covered by the data (Global, Mediterranean, …)|
|system||seasonal forecast operational system (1, 2, 3)|
|type||type of field (an, fc, …)|
|levtype||type of level (pl, ml, sfc, pt, pv)|
|levelist||levels for the specified levtype (off if levtype=sfc)|
|param||meteorological parameter (t, temperature, 130, 30.128)|
|number||ensemble member (1, 2, …)|
|channel||brightness temperature frequency band|
|diagnostic||iteration sensitivity forecast products|
|frequency||direction 2-d wave spectra products|
An example of a MARS request is:
class = ei,
stream = oper,
expver = 1,
date = 20071201/to/20071231,
time = 00/06/12/18,
type = an,
levtype = sfc,
param = sd,
target = “era-int.200712.sd”
The request is used to build a MARS tree, which describes the data hierachy to work through.
To subset an area use the boundaries North/West/South/East.