[Wrf-users] Negative values in diagonal terms of SGS stress tensor

[Christopher Thomas]

I am trying to use WRF in LES mode, and want to calculate some turbulence
statistics, specifically the subgrid scale TKE. I have set m_opt = 1 in the
namelist so that the components of the SGS stress tensor, m11, m22, m33,
m13, etc are output. I am finding some negative values in m11, m22 and m33.
However I thought that

m11 = <u'u'>, m22 = <v'v'> etc.  (here < ...> is Reynolds averaging)

so I don't understand where these negative values can come from. Can anyone
help?

Chris
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