Seasonal forecast monthly statistics on single levels from 2017 to present: Product type

Seasonal forecast monthly statistics on single levels from 2017 to present: Product type

I am going to download data of total precipitation from: "Seasonal forecast monthly statistics on single levels from 2017 to present"

I don't know exactly what are the differences between "Ensemble" and "Individual members" under the "Product type" menu.

I am going to download hindcast of each of six models for period 1993-2016. All leads are needed. Also the members are not important for me so I like to average over the members.

When I select "Ensemble mean", selecting the hindcast years disables.

Dear Morteza,

The "Individual members" include statistics computed using data only from a particular ensemble member (we can have monthly mean, monthly minimum, monthly maximum or monthly standard deviation). This individual member statistics is computed for both hindcast and forecast start dates. For example, extracting ECMWF system 5 monthly mean will result in 51 values, one for each individual member.

The "Ensemble mean" is the average over the monthly means from all individual ensemble members. This is computed only for the forecast start dates.

The "Hindcast climate mean" is the average over the monthly means from all individual ensemble members (so it is an ensemble mean), but averaged also over all years in the hindcast (climate) period. That's why this is not available for each hindcast start date in part. To retrieve it, you have to associate it with a particular forecast start date. For example,  retrieving ECMWF system 5 January 2020 start date will give a Hindcast climate mean which is an average over the  monthly means from all individual ensemble members and over all January start dates in the hindcast period 1993-2016.

For most recent systems of the models, hindcast period is 1993-2016, with the only exception of Met Office January start date which has 1994-2016. But some of the past systems had hindcast period ending in 2014 or 2015. For more info you can see the page Summary of available data.

If Hindcast climate mean is not useful for you, and you want each start date individually, then I suggest you extract the Individual members monthly means and after you compute the ensemble mean for each of the six models.

I hope this helps,

Simona

Dear Simona

Thanks for illustration. Suppose that P(.) stands for precipitation. I nee the previous values of Precipitation as a function of Lat, Lon, Year, Month and Lead, I mean:

P(Lat, Lon,Year, Month, Lead) wherein     1993<=Y<=2016  and Lead depends on the model and system. Also 1<=Month<=12.

As you can see the members are not important for me. So it's better to average over all members. Based on your advice, I must download data in Monthly Mean (under individual member menu) and calculate the average over all members myself.


Thanks

Regards

Dear Morteza,


Yes, you have to download Individual members Monthly mean and calculate the average over all members yourself. You should download model data from the same system, so don't mix data from different systems of a model.

Meteo-France system 7 and NCEP system 2 have been recently introduced and not all hindcast months are ready, we plan to process them as soon as we have the data from the providers.


Regards,

Simona

Dear Simona,

Based on your descriptions regarding"Hindcast climate mean":

I should select also a  particular forecast start date. If this data calculates monthly means from all individual ensemble members and averaged also over all years  in the hindcast (climate) period 1993-2016, what is the role of forecast start date? For example, what is the difference between selecting Nov 2021 and Nov 2018 or Nov 2019 as forecast start date? Would you provide examples?


Thanks

Dear Simona

Thanks for illustration.

I also have another problem. I downloaded the following file:

import cdsapi

c = cdsapi.Client()

c.retrieve(
'seasonal-monthly-single-levels',
{
'originating_centre':'ukmo',
'system': '13',
'variable':'total_precipitation',
'product_type':'monthly_mean',
'year':'2016',
'month':'12',
'leadtime_month':[
'1','2','3',
'4','5','6'
],
'area' : [40, 44, 24, 64],
'format':'grib'
},
"UKMO2016_month12.grib" )


I also downloaded the same file in netcdf format. Unfortunately the "UKMO2016_month12.grib" doesn't show the members while "UKMO2016_month12.nc" shows the members correctly. Please let me know if any command in my code is not safe.


Best Regards

Morteza


Dear Morteza,

Your download script is correct, I used it and obtained 168 grib messages, i.e. 28 ensemble members (numbered from 0 to 27)  for each of the 6 leadtimes.

Maybe you can try to repeat the retrieval.

After you can use ecCodes tools to list the files, for example "grib_ls -m UKMO2016_month12.grib".

Best regards,

Simona

Thanks Simona

Can I use ecCodes in a Windows based Pyhton?

Bests,

Morteza

Dear Morteza,

I have found some information about ECMWF software under Windows here:

Microsoft Windows (experimental)

ECMWF software under Windows

However, I am not a specialist in using the ECMWF software in Windows. If the information I found does not help you, I suggest you create a new forum issue where you ask Copernicus user support what software can be used in Windows for accessing grib files.

Best regards,

Simona