The study investigates a simple and cost-effective but efficient method to reduce spurious mixing associated with vertical advections schemes in numerical ocean models. The method is implemented in a model for the South East Asia, and experiments with this model with and without tides are used to demonstrate the methods ability to improve the water masses representation in the region, with focus in regions where tides-associated mixing plays a dominant role.   

Numerical spurious mixing is known to plague ocean models and hence this study, discussing and providing a simple solution to address it, is of wide interest to the ocean modelling community. In my opinion the model experiments, analysis and methods are appropriate, well executed and well described in the study. To the most part the manuscript is well written and easy to follow. However, I had some very minor queries, mainly in terms of clarifications, that the authors may want to address before publication. Hence, I recommend some minor revisions as I describe below before the study is published.

General comment:

1. Table summarising your experiments. Consider adding a table that summarises your experiments T0, T1, NT0 & NT1. This table can for example include the names of the experiments along with their main differences (e.g., with tides, with no tides, with filtered formulation turned on or off). This in my opinion will help the readers to better follow you study and discussion.

Specific comments:

1. Line 187-188, equation. I may have misunderstood something but to me it is not clear how this equation is derived. Please if you could clarify that would be very helpful. (The rest of the equations are very well described in terms of their derivation.)
2. Lines 192-193: Just for consistency with the rest of the notation I believe you mean k(sj+1-2sj+sj-1)/(Dz)^2, essentially use j instead of i.
3. Lines 332-333. I was wondering why the T1 does not lead to any improvement to the T0 in the salinity near the surface. I suggest maybe you can briefly discuss why this is the case.
4. Line 462. “It builds on the fact … a clear illustration”. I am not sure what this sentence describes and it is a little confusing. Maybe consider clarifying what you mean or erase this text.

Typos

1. Line 7, erase the “is provided”
2. Line 34 and the use of “academic” throughout the text (just a suggestion). I recommend to use instead of “academic” something along the lines of “idealised” simulations or “simulations in a theoretical context”.
3. Line 94. Maybe better “under Boussinesq and hydrostatic approximation” rather than equation.
4. Line 385. Maybe better “Manual modification” (or something similar) rather than “Manual edition”.