# Bug in the sign convention in the TKE OSBL scheme?

**URL:** <https://nemo-ocean.discourse.group/t/bug-in-the-sign-convention-in-the-tke-osbl-scheme/998>\
**Category:** v4.2.x\
**Tags:** DYN, ZDF\
**Created:** [6 March 2026 08:29 UTC](https://nemo-ocean.discourse.group/t/bug-in-the-sign-convention-in-the-tke-osbl-scheme/998 "2026-03-06T08:29:52Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![takachanbo](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@takachanbo](https://nemo-ocean.discourse.group/u/takachanbo)\
**Post date:** [6 March 2026 08:29 UTC](https://nemo-ocean.discourse.group/t/bug-in-the-sign-convention-in-the-tke-osbl-scheme/998/1 "2026-03-06T08:29:52Z")

</div>

I am looking through the turbulent kinetic energy (TKE) ocean surface boundary layer (OSBL) scheme but I am having some confusions pertaining to the term associated with Kolmogorov dissipation. In the snippet of code from `zdftke.F90` pasted below, the term with `dissl` has a `+` sign. Shouldn’t this be minus in order to ensure a reduction in TKE, `en`?

```auto
DO_3D_OVR( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 ) !* Matrix and right hand side in en
   ...
   !
   ! ! right hand side in en
   en(ji,jj,jk) = en(ji,jj,jk) + rn_Dt * ( p_sh2(ji,jj,jk) & ! shear
      & - p_avt(ji,jj,jk) * rn2(ji,jj,jk) & ! stratification
      & + zfact3 * dissl(ji,jj,jk) * en(ji,jj,jk) & ! dissipation
      & ) * wmask(ji,jj,jk)
END_3D

```

The sign of dissipation also seems to contradict Equation (9.1) in the NEMO reference manual.

 ![Screenshot 2026-03-06 at 14.09.39](https://global.discourse-cdn.com/free1/uploads/nemo_ocean/original/1X/976bb30e8eb593f495dac2ca4e6f12e0b3676cb8.png)