In this manuscript, the authors are evaluating whether there is a relationship between marine cold air outbreaks (MCAOs) and Sudden Stratospheric Warmings (SSWs) in the Barents, Norwegian, and Labrador Seas. The authors conclude that changes in the large-scale tropospheric circulation account for 42% of the MCAO variance in the Barents Sea and 31% of the variance in the Norwegian Sea. They also make a convincing case that there is a significant increase in the correlation between the large-scale tropospheric flow pattern and MCAOs after SSWs in the Barents and Norwegian Seas. The connection to the large-scale tropospheric flow to MCAOs is further found to be correlated with the Scandinavian Trough pattern in the Barents and Norwegian Seas and Greenland Blocking pattern in the Labrador Sea. This manuscript fits within the scope of WCD in that it addresses stratosphere-troposphere coupling and prediction on sub-seasonal to seasonal time scales. In this revised manuscript, the authors have diligently addressed the earlier concerns and I now think that this could be published after some minor revisions outlined below.
1 The connection to physical processes linking the stratosphere to the surface has been improved in this version, although after reading again, I am still left wondering what physical feature(s) is(are) transporting the cold air into the regions of focus in this study. It makes sense that the lower 500 hPa heights would be associated with the colder air and the related storminess nearby. Papritz et al. (2019) address these processes that are likely relevant in the Norwegian Sea, particularly the tropopause polar vortex (e.g. Cavallo and Hakim 2010).
2 Line 50: The Labrador Sea is also mentioned in the abstract and on Line 55, but just the Norwegian and Barents Seas here.
3 Line 129: Please provide a justification for choosing M >= 4K to define moderate-to-strong MCAOs in DJFM climatology.
4 Lines 135-160: The interpretation provided that the storminess increases in the Barents, Norwegian and Labrador Seas at the time of MCAOs in the respective regions is not quite accurate. However, the conclusion reached by the authors on lines 142-144 is the correct conclusion. Cold air outbreaks occur when there are northerly winds over those regions, which means that the storms must move slightly east of those regions so that the cold sector (west side) is over the seas themselves. For example, in Figure 2j, there is an increase in storminess in the lower right side of the Barents Sea box but decrease in upper left side (not stated correctly on lines 137-138) and similarly for the Norwegian Sea (Fig. 2k) and Labrador Sea (Fig. 2l). This also applies to the conclusions section on line 265.
5 Line 140: On point (iii), it looks like in Figure 2g that the strongest northerly wind anomalies are over the Barents Sea with weaker northerly wind anomalies over the Norwegian Sea.
6 Lines 180-190: It is nice that the authors have now considered statistical significance in this revision. However, it is not clear on line 187 what "All correlations...are found to be statistically significant" refers to. It is good that the correlations themselves have p < 0:05, but what about the differences in correlations between the SSW and climatology or SSW and no SSW? This seems to be addressed in the Labrador Sea correlations only. It should be stated which correlations are and are not significant; perhaps a table with the corresponding
p-values would be most helpful.
7 Line 209: Where are the authors getting that there is an increase in 15% in the explained variance for the Barents Sea for the ZDI index vs. MCAO? It looks like it should be 18% from Figure 3a.
8 Line 245: It is easier to see from Figure 6a,b that the circulation over the Barents Sea is "anomalously cyclonic" rather than "cyclonic."
1 Figure 2: The caption should state what the black and green boxes are in each of the panels (as it is in Figure 1 caption).
2 It is not necessary to say `historical' on line 90
3 Line 145: enhanced --> moderate-to-strong
Cavallo, S. M. and G. J. Hakim, 2010: The composite structure of tropopause polar cyclones from a mesoscale model. Mon. Wea. Rev., 138 (10), 3840-3857, doi:10.1175/2010MWR3371.1.
Papritz, L., E. Rouges, F. Aemisegger, and H. Wernli, 2019: On the thermodynamic pre-conditioning of arctic air masses and the role of tropopause polar vortices for cold air outbreaks from Fram Strait. J. Geophys. Res.: Atmos.