Reposting this. List setup makes it very easy to fail to post to the list.
Actually, I think that direction of wind flow, and currents, would tend to govern the ash flow, and not a whole lot else - by a couple of weeks after any given event. I think that conceivably it would matter if events were at mid latitude, equatorial, or elsewhere, because I think that it did in the case of the Sumatra volcano that caused the Year Without a Summer. (Sumatra had more than one catastrophic volcano in the 19th century.) Otherwise, once dust and gas got into the atmosphere, it was everywhere.
If it can assumed that the Deccan Traps and the Chicxulub impact took place at approximately the same time,
Again: no, they did not. The main episode of eruptions was over 100,000 years before the impact, and smaller episodes happened long before and after.