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Numerical models of the atmosphere usually have their first atmospheric grid level well above 2 m, but the temperature at 2 m above ground level is something one often wants to calculate with such a model.

These models have some surface scheme to calculate temperatures at / in the ground and solve (approximated) Navier–Stokes equations on the atmospheric grid. Heat fluxes between these model components are usually parameterized with the help of Monin–Obukhov similarity theory. Hence, a diagnostic calculation of the 2 m temperature is needed.

What needs to be done to get a reasonable 2 m temperature? Is a simple use of a diagnostic formula using surface layer similarity again enough? What could be done based on data, assuming many simulations and observations are available?

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    $\begingroup$ You tagged your question mos. What is mos? $\endgroup$
    – gerrit ♦
    Apr 16, 2014 at 22:40
  • $\begingroup$ @gerrit MOS is model output statistics en.wikipedia.org/wiki/Model_output_statistics $\endgroup$
    – casey
    Apr 17, 2014 at 0:31
  • $\begingroup$ @casey I'm not sure mos a meaningful tag, it's already tagged as models, and even if it deserves its own tag than perhaps are better name can be thought of. For example, models-output-statistics is at least more understandable. $\endgroup$
    – hugovdberg
    Apr 17, 2014 at 12:21
  • $\begingroup$ @BHF are other answers for this question welcome ? $\endgroup$
    – gansub
    Nov 10, 2015 at 5:56
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    $\begingroup$ Based on the content of the question, I am going to guess the @BHF meant Monin-Obukhov Similarity Theory as MOS. But that is merely a speculation. $\endgroup$
    – BarocliniCplusplus
    Aug 22, 2016 at 21:58

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Your premise is incorrect.

Numerical models normally have:

  • A full temperature profile
  • A specific field for the 2 metre temperature
  • A specific field for the skin temperature

For example, see ERA-40 daily fields, which both 2 metre temperature and Skin temperature, or CFS reanalysis 6-hour fields, which has Air temperature, Skin temperature, and Surface air temperature, (I think surface air temperature means 2-metre temperature, but check their full documentation to be sure).

It is not accurate to take the lowest temperature level in the temperature profile for either of the two, nor to interchange skin temperature with 2-m temperature. But, in some cases, the data distribution may be such that either or both of these are actually attached to the temperature profile. For example, the CFS hourly timeseries has the question:

Where is Sea Surface Temperature (SST) in CFSR? Where is Skin Temperature?

CFSR does not label SST and skin temperature grids differently than temperature grids on other levels. Select the parameter 'Temperature' and the level 'Ground or water surface' to obtain the SST/skin temperature grids, and then use the land/sea mask to determine whether a gridpoint is over water (SST) or land (skin temperature).

(I had the opposite problem, needing skin temperature, and being tempted to use 2 metre temperature instead, until I realised where the data were).

If you encounter a model that really only has the full temperature profile, then I would contact the authors to inquire. Maybe it is a model that really only does well in the free atmosphere, and is not suitable for the extraction of (near-) surface temperatures. The boundary layer can be a hard thing to model!

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