Parameter TP - accumulated precip - in 24hr step forecast data

Datasets and Usage
1

Hi ECMWF community,

We receive 15-day 24hr step forecast data, from the 00:00UTC base time ENS forecast.

For example, the data supplied on Jan 1st covers forecasts from 00:00 Jan 1st → Jan 15th.

For accumulated precipitation, the first value is always 0, since there is no preceding accumulation.

We are unclear, however, as to what time period the second value refers to - e.g. 34mm or whatever:

In our example above, is it:

a. accumulated precip for 00:00->23:59 Jan 1st
b. accumulated precip for 00:00->23:59 Jan 2nd?

Would appreciate a clear confirmation. Thanks in advance.

CW

2

This depends on the exact dataset you use and the exact variable requested. COuld you share this?

Based on this & the info provided on each parameters definition, we can find the answer together.

3

Hello,

I think my question is similar so I’m posting it here instead of creating a new thread.
I’m coming from the position of having done some analyses using ERA5 data and now trying to use daily forecast data for some interpretations/inferences based on the ERA5 analysis.

So, for accumulated parameters like “total precipitation” and “solar surface radiation downwards”, from what I understood from the documentation, the ERA5 data corresponds to something akin to
ssrd(t=(2024/1/2 - 14:00), x, y) → total shortwave radiation that hit the area located around point (x,y) from t=(2024/1/2 - 13:00) to (2024/1/2 - 14:00).

Is this correct? Please feel free to correct me here if I am wrong.

Now, imagine we are getting data from the daily forecasts and we want to do some kind of inference and we are at t=(2024/2/1). If we want to do the inference for t=(2024/2/2 14:00), we could think about using the following IFS files corresponding to the 12z calculation:
20240201120000-24h-oper-fc.grib2
20240201120000-27h-oper-fc.grib2
Because our target time point is found at 26=12+14, is this correct?
Now, following the same logic, if we want data that is equivalent to the ERA5 format, how can we get it for this case? I am imagining we would actually need three files instead of two for a simple interpolation. We would need:

20240201120000-21h-oper-fc.grib2
20240201120000-24h-oper-fc.grib2
20240201120000-27h-oper-fc.grib2

Then, to get the hourly accumulation value (like in ERA5) for the grid point at 24h, we do
ssrd(24h) = (file_value(24h) - file_value(21h)) / 3

And then for the grid point at 27h
ssrd(27h) = (file_value(27h) - file_value(24h)) / 3

Then we just do some simple interpolation between ssrd(27h) and ssrd(24h) to get ssrd(26h).

Does this make sense?

Thanks,
Tom

4

Hi,
please have a look at the following page:
https://confluence.ecmwf.int/x/hrTICw

Thanks