AIFS Historical Archive and Hindcasts?

AIFS, IFS and OpenIFS
1

Hi,

I’m interested in testing the performance of AIFS against alternative datasets for some applications. This requires historical data and ideally hindcasts showing how the model would have performed previously.

However, as of right now, it appears that AIFS data is only published on a 4-day rolling window, so even historical data from its February release is inaccessible.

Does ECMWF have plans to openly release historical AIFS data and/or hindcasts at any point? I recognize that right now the priority must be publishing AIFS ensembles but I’m a little surprised historical data at least isn’t available.

Kind regards,
Robert

2

Hi Robert,
Sorry for the delay in the reply.
Currently historical data is not available in the Open Data dataset in the ECMWF server.
Historical data available in MARS is under CCBY4 licence (which means open), however access to the MARS archive is not free.
However, AIFS data is available in AWS servers from the date it was operational (February 2025).
What you can do is replace ‘ecmwf’ as source in ecmwf-opendata python api request with ‘aws’ and you should be able to download data from 25 February onwards.
The request should look something like this:

from ecmwf.opendata import Client
client = Client("aws", beta=False)
pl_parameters = ['u', 'v']
pl_filename = 'aifs_single_medium-wind850_pl.grib'

client.retrieve(
    date='20250301',
    time=0,
    step=12,
    stream="oper",
    type="fc",
    levtype="pl",
    levelist=850,
    model="aifs-single",
    param=pl_parameters,
    target=pl_filename
)

I hope this helps.
Best regards,
Milana

3

Hi @Milana_Vuckovic ,

Thanks for the thorough reply, this is very helpful. A small follow-up question: if ECMWF is now hosting data on AWS, is it (or will it be) possible for users to access the AWS S3 buckets directly through standard cloud-access tools? For instances the s3fs library in Python.

Many thanks,
Robert

4

Hi Robert,
I’m no expert on S3, but let me try.
You can find info about the data on AWS here: AWS Marketplace: ECMWF real-time forecasts

You can download directly from S3 using earthkit.data, like this:

ekd.from_source("s3", {
    "endpoint": "s3.amazonaws.com",
    "region": "eu-central-1",
    "bucket": "ecmwf-forecasts",
    "objects": "20250603/00z/aifs-single/0p25/oper/20250603000000-120h-oper-fc.grib2"
}, anon=True)

Best regards,
Milana