In ERA5, "2 metre temperature" is an instantaneous parameter and is available hourly, from both the analyses and the forecasts. The parameters "Maximum temperature at 2 metres since previous post-processing" and "Minimum temperature at 2 metres since previous post-processing" are the maximum and minimum in the last hour, and are available from the forecasts only.
The sub-set of ERA5 data on the CDS disks , contains analysed parameters, if available, otherwise it contains forecast parameters. Therefore, on the CDS disks, the "2 metre temperature" is an analysed parameter, whereas the "Maximum temperature at 2 metres since previous post-processing" and "Minimum temperature at 2 metres since previous post-processing" are forecast parameters.
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