TC trajectory data for 50r1

AIFS, IFS and OpenIFS
1

Hi,

I’ve been checking the test ensemble TC trajectory data for 50r1 in MARS (experiment 80), and I’ve noticed that it contains only the deterministic member (number 52) and the perturbed members (numbers 1 to 50).

However, the implementation page states:

“Tropical cyclone ensemble products currently contain 52 members (50 perturbed members, 1 control member and 1 ex-HRES). After the upgrade 51 will remain (50 perturbed members and control forecast).”

From this description, my understanding is that the trajectory data should include the control member and the perturbed members, but not the deterministic member. This does not seem to match what is currently in the BUFR files in MARS.

Am I misinterpreting the implementation page?
Will the ensemble membership in the test trajectory BUFR files be the same as what will be provided once cyclone 50 is fully implemented?

Thanks.

2

Hi Rabi,

Thank you for your feedback.

I have checked, and the ensemble TC tracks data are not entirely correct in MARS archive for test data of IFS Cycle 50r1. This is why we have stopped archiving them a few days ago.
We have fixed the problem and now the test data is available in dissemination, but not yet in MARS archive.

Currently in the BUFR files there are 52 members, and control and ex-HRES, should be identical.
They have the following Type of ensemble forecast parameters:
EnsembleMemberType = 0 - Unperturbed high-resolution control forecast for the ex-HRES and
EnsembleMemberType = 1 - Unperturbed low-resolution control forecast for the Control forecast.

In the upgraded version (IFS Cycle 50r1) we will keep the 50 perturbed members and the one that has EnsembleMemberType = 0.

Technically, neither is correct, as we don’t have high and low resolution any more, and 9km is considered high resolution for global model.

This is in line with the other change that we are making, moving the Ensemble Control forecast under stream = oper, type=fc, in other words ex-HRES is becoming the Control forecast from IFS Cycle 50r1.

This part is correct in the test data.

What is not correct is the EnsembleMemberNumber=52 in the MARS Archive. This should be 51.

I will be updating the documentation to make this more clear.

Best regards,
Milana