AIR MAIL
Where today’s air came from
The air arriving over Paris about 5,000 feet above the ground was over British Columbia three days ago, and over the Great Lakes a day ago, about 1,840 miles back along its path. It came down from about 14,700 feet up, warming and drying as it sank. Near the ground the air came from a point about 430 miles to the west; at 10,000 feet, from the California coast. It feels dry all the same. Traced back 72 hours through NOAA’s hourly RAP analyses, nine paths at each of three heights.