In this manuscript, Agarwal et al. performed a diagnostic evaluation of the state-of-the-art meteorology chemistry models in their ability to simulate meteorology and air quality over the populous, polluted Indo-Gangetic plain. The simulation is compared to ground and satellite observations as well as reanalysis products. Such an evaluation is useful in that it provides a benchmark for future studies; additionally, the study also shows that more accurate emission inventory and better characterization of boundary layer processes are key for further improvements. The manuscript is overall well-written, and I recommend the publication of the manuscript after minor revisions.

Comments: 

Line 32: The word ‘This’ refers to insufficient aspects of the modelling, but the previous sentence is stating the model is reasonably good.

Line 35: The author should simply point out that better diurnal characterization of the boundary layer processes and emission estimates are necessary. Whether or not such improvement makes the model suitable to understand aerosol feedbacks on meteorology remains to be demonstrated, considering that ‘feedbacks’ is not really discussed in the current study.

Line 164: Can the author say a bit more than ‘satisfactorily’ so that the reader better understands the bias from the inventory?

Line 295: What is the reason for the better correlation in September? Is it due to the monsoon season?

Line 317: ERA-5 has positive bias in RH and is used to drive WRF-CHEM, how does it propagate to the negative bias in the simulations?

Figure 1: The font size of the ticklabels should be increased. Fig 1a. Are there any water grid cells?

Figure 4 is wrongly placed before Figure 3. Also, the caption of Figure 3 is incomplete.

Figures 6&7: The size of panels with similar contents should be adjusted to have the same size.

Fig S2: I find the colors for ERA and MERRA very difficult to distinguish.

Technical:

Line: 285: ‘very slightly low’ -> slightly lower

Line 572: revise the sentence ‘including because…’