## Difference between T_2M and T_2M_AV

Added by Sven Karsten 2 months ago

Dear all,

currently I’m evaluating some of my model results against E-OBS data for a time span of 30 years. I consider e.g. the seasonal mean of the surface temperature. I figured that when I use the T_2M field for comparison, the model is too cold by roughly 2°C (especially pronounced in summer). However, when I use the T_2M_AV field, the results fit much better to observations. I’m prinitng both fields with daily resolution.

As the name suggests, I guess T_2M_AV is the time average of the T_2M field (actually the documentation https://www.cosmo-model.org/content/model/documentation/core/cosmo_io_guide_6.0.pdf does not know T_2M_AV). What is not quite clear to me is

1. over which time this average is exactly performed

2. and to which time instance the printed T_2M field corresponds?

Is it like the average is performed over a period of an output (e.g. for me one day) and the field T_2M is a snapshot at one border of that interval (e.g. at 0:00)?

Does this imply that if one is interested in comparing time means against observations one should use T_2M_AV and if one wants to use the model data for forcing another model one should use T_2M?

Thank you very much in advance and with best regards,

Sven

### Replies (1)

#### RE: Difference between T_2M and T_2M_AV - Added by Burkhardt Rockel 2 months ago

1. T_2M_AV is averaged over the output time interval (similar as the radiation outputs starting with an “A”)

2. T_2M is an instantaneous value at the end of the output interval

When you use T_2M for comparison the output interval should be 3h or less.