We used the Lagrangian model FLEXPART to identify the moisture sources of 110 tropical cyclones with cyclogenesis within an area comprised between 15 – 45 W and 8 – 20 N. The model computes changes in the specific humidity from a 10-day period before the day of cyclogenesis of each tropical cyclone is and its contribution to the moisture budget of the region of interest. We calculated the values of the anomalies of the moisture budget to identify the main regions of moisture sources: the African coasts in the North Atlantic, the continental region over western Africa and along the South African coast. We also calculated the contribution of moisture sources from the South Atlantic to the cyclogenesis. The frequency distribution of these percentages shows two main peaks, one in ~20% and other in ~50%. The result shows that the path of tropical cyclones with ~50% of moisture contribution from the South Atlantic made landfall more often than those with ~20%.
I have the following questions/comments on your presentation:
1) Regarding results shown in Fig. 2 you point out two source regions: (i) the north Atlantic front to the African
coast, over west Africa, and (ii) the area extended along the south Atlantic from the equator through the southern African coast. Would you accept seeing three different regions: (i) the north Atlantic (in association with warmer SSTs?), (ii) the Sub-Saharan region (in association with the African Jet and Tropical Easterly Waves, TEW), and (iii) the South Tropical Atlantic (in association with a strong transport by the trade winds?). In particular, please discuss the role of TEW.
2) It is unclear what Figure 3 represents. A figure denoting Frequency (such as a histogram) should add up to 1.0 (or 100%). Please clarify what you are trying to convey, more so having in mind Figure 4.
Thank you very much for your contribution to the Conference.
This is a very interesting research topic.
My comment is on the technical details from the methodology, having in mind a future publication.
If I understood well, you have a six by six-degree box centered at each of the 110 cyclogenesis points given, from the 1979-2012 period. I think it would be worth discussing in more detail this 6-degree choice. Have you performed a sensitivity analysis to this box dimension?
I will be looking forward to reading your future work on mechanisms.
