# Blow up in deep layers with NBQ and 20 m resolution

**URL:** <https://forum.croco-ocean.org/t/blow-up-in-deep-layers-with-nbq-and-20-m-resolution/344>\
**Category:** dynamics-numerics-params\
**Tags:** non-hydro, dynamics-numerics\
**Created:** [April 1, 2022, 9:50am UTC](https://forum.croco-ocean.org/t/blow-up-in-deep-layers-with-nbq-and-20-m-resolution/344 "2022-04-01T09:50:59Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![jihaihappy](https://forum.croco-ocean.org/letter_avatar_proxy/v4/letter/j/ea666f/32.png) [@jihaihappy](https://forum.croco-ocean.org/u/jihaihappy)\
**Post date:** [April 1, 2022, 9:50am UTC](https://forum.croco-ocean.org/t/blow-up-in-deep-layers-with-nbq-and-20-m-resolution/344/1 "2022-04-01T09:50:59Z")

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Hi,

```
 I am runing a extreme high simulation with 20 m (a one-way nesting from 7.5 km 1.5 km 500 m 100 m down to 20 m) reoslution and NBQ turning on. However, I have tried a number of tests, but it always blows up with noise growing in the deep layers. Please see the figure below. Does someone have any idea what the problem is? The details of the configuration is also shown below. Some other information may be helpful:

```

(1) The model runs safely with 3s time step if I just turn NBQ off.  
(2) Time steps I have used: 0.1s and 0.3s. All failed with the same problem.

# Here is a figure of u in the deep layers (very close the bottom, 150 layers in 5000 m water depth) ![image description](https://forum.croco-ocean.org/uploads/default/original/1X/506ad5304e231dafbb161fee4f706665326e0853.jpeg)

# REGIONAL KuroSI MPI NBQ DIAG\_CFL OBC\_EAST OBC\_WEST OBC\_NORTH OBC\_SOUTH W\_HADV\_TVD W\_VADV\_TVD GLS\_MIX2017\_3D CURVGRID SPHERICAL MASKING NEW\_S\_COORD SOLVE3D UV\_COR UV\_ADV SALINITY NONLIN\_EOS SPLIT\_EOS UV\_HADV\_TVD UV\_VIS2 UV\_VIS\_SMAGO UV\_MIX\_S UV\_VADV\_TVD TS\_HADV\_WENO5 TS\_DIF2 TS\_MIX\_ISO TS\_VADV\_WENO5 SPONGE GLS\_MIXING GLS\_KEPSILON CANUTO\_A ANA\_DIURNAL\_SW QCORRECTION SFLX\_CORR FRC\_BRY Z\_FRC\_BRY M2\_FRC\_BRY M3\_FRC\_BRY T\_FRC\_BRY OBC\_NBQ OBC\_M3ORLANSKI OBC\_TORLANSKI ANA\_BSFLUX ANA\_BTFLUX OBC\_M2CHARACT M2FILTER\_NONE TRACERS TEMPERATURE M3FAST NBQ\_IMP HZR NBQ\_PERF NBQ\_GRID\_SLOW NBQ\_HZCORRECT OBC\_NBQORLANSKI OBC\_WORLANSKI VAR\_RHO\_2D VIS\_COEF\_3D TS\_MIX\_IMP TS\_MIX\_ISO\_FILT NTRA\_T3DMIX SPONGE\_GRID SPONGE\_DIF2 SPONGE\_VIS2 NF\_CLOBBER