# ERA5 data December 2023

**URL:** <https://forum.ecmwf.int/t/era5-data-december-2023/1933>\
**Category:** Datasets and Usage\
**Tags:** era5\
**Created:** [20 February 2024 15:45 UTC](https://forum.ecmwf.int/t/era5-data-december-2023/1933 "2024-02-20T15:45:35Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Omar\_Mostafa](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/o/7ea924/32.png) [@Omar\_Mostafa](https://forum.ecmwf.int/u/Omar_Mostafa)\
**Post date:** [20 February 2024 15:45 UTC](https://forum.ecmwf.int/t/era5-data-december-2023/1933/1 "2024-02-20T15:45:35Z")

</div>

Hello, I have been downloading monthly data from ERA5 for the area of Germany without any problems. However, I recently downloaded the data for the month of December 2023 and found the file filled with NaN values, although the previous months contain values without any problems. Also, the file size is approximately double the usual size compared to previous months.

Is there any explanation for this?

Here is the request:

```auto
    import cdsapi
    c = cdsapi.Client()
    c.retrieve(
               'reanalysis-era5-single-levels',
                {
                    'product_type': 'reanalysis',
                    'format': 'netcdf',
                    'variable': [
                                            'total_sky_direct_solar_radiation_at_surface',
                                            'surface_solar_radiation_downwards',
                                            'surface_net_solar_radiation',
                                            ],
                    'year': '2023',
                    'month': '12',
                    'day': [
                                    '01', '02', '03',
                                    '04', '05', '06',
                                    '07', '08', '09',
                                    '10', '11', '12',
                                    '13', '14', '15',
                                    '16', '17', '18',
                                    '19', '20', '21',
                                    '22', '23', '24',
                                    '25', '26', '27',
                                    '28', '29', '30',
                                    '31',
                        ],
                    'time': [
                                    '00:00', '01:00', '02:00',
                                    '03:00', '04:00', '05:00',
                                    '06:00', '07:00', '08:00',
                                    '09:00', '10:00', '11:00',
                                    '12:00', '13:00', '14:00',
                                    '15:00', '16:00', '17:00',
                                    '18:00', '19:00', '20:00',
                                    '21:00', '22:00', '23:00',
                                    ],
                    'area': [59.0, 4.0 ,40.0, 17.0],
                    'grid': [0.025, 0.025],
                },
                'output.nc'
                )

```

Thank you in advance!

---

<div class="post-metadata">

**Author:** ![Kevin\_Marsh](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/kevin_marsh/32/368_2.png) [@Kevin\_Marsh](https://forum.ecmwf.int/u/Kevin_Marsh)\
**Post date:** [21 February 2024 06:34 UTC](https://forum.ecmwf.int/t/era5-data-december-2023/1933/2 "2024-02-21T06:34:04Z")

</div>

Hi Omar,  
The December 2023 data probably currently contains a mixture of ERA5 and ERA5T data, leading to an extra dimension (expver) in the netCDF file. See this post for details and workarounds

> [@ERA5 CDS requests which return a mixture of ERA5 and ERA5T data](https://prod.ecmwf-forum-prod.compute.cci2.ecmwf.int/t/era5-cds-requests-which-return-a-mixture-of-era5-and-era5t-data/781):
>
> The ERA5 hourly and monthly data are made available with a 3 month delay. This means that after a month has passed, another month's worth of ERA5 data is written to the dataset. ERA5T (near real time) preliminary data are used to fill the gap between the end of the ERA5 data and 5 days before the present date. The oldest month of these is overwritten each month as new ERA5 data become available. So as an example, say we have a current date&nbsp; of 15th February 2020: ERA5 data are currently fro…

Hope that helps  
Kevin