nocturnal boundary layer problem simulations – in #9: CCLM

  @mikhailvarentsov in #7fddb9d

<p> Dear colleges, hello again! </p> <p> I’ve successfully tested model with some of your previous suggestions during last months. Idea to use lower values of tkhmin, ktmmin and pat_len was really helpful. Now I continue my investigation with high-resolution domain (1 km), and I faced problem that model becomes numerically unstable and fails with nan-values (If I use reduced values of tkhmin, ktmmin and pat_len). Anso I made some tests with newer turbulent schemes (itype_turb = 5/7). In these tests results were better (in terms of the errors for nocturnal temperatures) than with itype_turb=3 and standard tuning parameters, but worse than with itype_turb=3 and tunned parameters (tkhmin, ktmmin and pat_len). And also experiments with itype_turb = 5/7 seems to have higher numerical stability that with itype_turb=3. In addition, this new schemes seems to be completely insensitive to tuning parameters that I used before. </p> <p> No I have two main questions: <br/> 1) what model options I can use to avoid problems with numerical stability in case of itype_turb = 3 and corrected tuning parameters (dx = 1km, pat_len=50, tkhmin=tkmmin=0.05, dt = 5/10 sec). <br/> 2) are there any tuning parameters (ore some constants in the code), which can reduce mixing rates under stable conditions in case of usage itype_turb = 5/7? </p> <p> Thanks in advance for your advices! </p>