Temperature Tendencies in ERA 5

Hi guys,

In ERA 5 there are 5 variables referring to the mean temperature tendencies due to parametrisation:

1) Mean temperature tendency due to short-wave radiation

2) Mean temperature tendency due to short-wave radiation, clear-sky

3) Mean temperature tendency due to long-wave radiation

4) Mean temperature tendency due to long-wave radiation, clear-sky

5) Mean temperature tendency due to parametrisations

My question:

1) Does the variable "Mean temperature tendency due to parametrisations" contain the effect of all parametrisations, including radiation, or do I have to calculate (Mean temperature tendency due to parametrisations) + (Mean temperature tendency due to short-wave radiation) + (Mean temperature tendency due to long-wave radiation) to get the overall diabatic heating at one grid point?

2) (Mean temperature tendency due to short-wave radiation) minus (Mean temperature tendency due to short-wave radiation, clear-sky) yields the diabatic heating due to clouds, right?

3) Is there also a variable relating to the adiabatic heating rate?

Many thanks,

Amelie

Hello Amelie,

  1. The "Mean temperature tendency due to parametrisations" is the tendency due to all parametrisations, but does not include numerical diffusion.
  2. Yes, that's correct.
  3. The adiabatic heating/cooling can be calculated from parameters we do have (Vertical velocity, (virtual) Temperature, Specific humidity), see the last term on the left hand side of the thermodynamic equation, equ 2.3 in Chapter 2 Basic equations and discretisation of Part III Dynamics and numerical procedures in the ERA5 IFS documentation (CY41R2)  https://www.ecmwf.int/en/publications/ifs-documentation. Note, however,  that Vertical velocity, (virtual) Temperature and Specific humidity are instantaneous parameters, whereas the tendencies you mention above are averages since the previous value, ie in the last hour for ERA5.

Regards,

Paul

Hello Paul,

I am still a bit confused about what is and what is not included in the mean temperature tendency due to parametrisations. Are the long and short-wave radiation temperature tendencies considered to be parametrisations, and thus included in the mean temperature tendency due to parametrisations?

Thanks,

Wim

Hi Paul,

thanks a lot for your answer. That was very helpful!

Hello Wim,

The long and short-wave temperature tendencies are produced by the parametrisations and so are included in the mean temperature tendency due to parametrisations. Look at the thermodynamic equation, equ 2.3 in the above reference: on the left hand side (LHS) you have the local tendency, the horizontal and vertical advection and the adiabatic heating/cooling. On the RHS, there are two terms, Pt and Kt. Pt is due to all the parametrisations and Kt is the numerical diffusion. The parametrisations are described at great length in the ERA5 IFS documentation, Part IV Physical processes (link given above).

Regards,

Paul

Hi Paul Berrisford ,

Hope you are well!

I was wondering if the parametrization terms you describe above are available for download similar to the standard fields in ERA5? 

I'm thinking they are subject to some kind of special availability as I couldn't find them on the Copernicus site.

Thanks!

Rich Neale

Hi Richard Neale ,

Good to hear from you - I hope you are well. I'm fine, thanks.

The model level mean rates/fluxes are listed in Table 13 of the ERA5 data documentation:

ERA5: data documentation

These parameters are not available from the CDS disks but can be accessed using the CDS API to retrieve them from the ECMWF archive, MARS. For information on how to download them, see:

ERA5: data documentation#DataorganisationandhowtodownloadERA5

and

How to download ERA5

Note, that retrieving data from MARS can be slow, particularly for model level data - there are 137 model levels.

Let us know how you get on with this, or if you have problems.

Best wishes,

Paul

Hello Paul Berrisford 

Given the mean temperature tendencies for short and longwave radiation are based on the radiation parametrisations as outlined in IFS Documentation Part IV, does this mean that we would not expected changes in ozone to impact these heating rates (over the 1979-present period), since ozone is prescribed as a climatology?

Thank you,

Kevin

Hello Kevin Bloxam 

Sorry for the late response!

You are correct, the radiation scheme uses a climatological distribution of ozone, so the ozone data that you see in ERA5 does not impact the heating rates.

Best wishes,

Paul

No worries! Thank you for this clarification. Cheers -Kevin