1. Data: way forward GO-ESSP meeting next week in Paris
Will decide whether our ensemble definitions can become CF-approved ‘standard names’
May give other feedback
Need to agree data gridding strategy
Need to prioritize variables to be “served” online
Need to give APCC some volume estimates

2. The plan … Distributed data serving
Should allow easy scaling as more models join
Allows us to get off the ground with limited resources
Reduces political issues / accommodates requirements of funders
Original idea: everyone serve their own data
This is perfectly scalable
BUT we want to allow data producers to do deals with data centres – some regional concentrations of data may be helpful

3. The plan … CF compliant netCDF
There was a strong consensus from the scientists to use netCDF (rather than eg GRIB)
The aim is to use CF compliant netCDF
We want to create netCDF files containing multi-model ensemble forecast data – this means we need the concepts of ensemble member number, and also a “multi-model” dimension allowing an adequate characterization of the models concerned.
A prototype implementation has been created, and is presently being used to serve ENSEMBLES seasonal data at ECMWF, via a THREDDS aggregation server.
Note:
The same metadata could be encoded in other ways in the future

4. The plan … netCDF structure
Document from Paco Doblas-Reyes outlines the approach taken
Two points to highlight:
“forecast_reference_time” and “forecast_period” are independent time variables, needed to cope with forecasts which overlap in time.
An “ensemble” dimension is used to distinguish the ensemble members, and is used in several auxiliary variables, which between them encode sufficient metadata to identify which integration the data come from.
… (But if you look at Paco’s document in detail, you will be able to judge better than me what are the critical points ….)

5. Reference