QUANTIFYING TRANSPORT BETWEEN THE TROPICAL AND MIDLATITUDE LOWER STRATOSPHERE

Airborne in situ observations of molecules with a wide range of lifeti mes (methane, nitrous oxide, reactive nitrogen, ozone, chlorinated hal ocarbons, and halon-1211), used in a tropical tracer model, show that mid-latitude air is entrained into the tropical lower stratosphere wit hin about 13.5 months; transport is faster in the reverse direction, B ecause exchange with the tropics is slower than global photochemical m odels generally assume, ozone at mid-latitudes appears to be more sens itive to elevated levels of industrial chlorine than is currently pred icted, Nevertheless, about 45 percent of air in the tropical ascent re gion at 21 kilometers is of mid-latitude origin, implying that emissio ns from supersonic aircraft could reach the middle stratosphere.