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Quantifying Transport Between the Tropical and Mid-Latitude Lower Stratosphere
1C. M. Volk, G. S. Dutton, and J. M. Gilligan are with the Climate Monitoring and Diagnostics Laboratory (CMDL), National Oceanic and Atmospheric Administration (NOAA), Boulder, CO 80303, and the Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309, USA. J. W. Elkins is with NOAA/CMDL, Boulder, CO 80303, USA. D. W. Fahey is with the NOAA Aeronomy Laboratory, Boulder, CO 80303, USA. R. J. Salawitch and J. J. Margitan are with the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. M. H. Proffitt is with the NOAA Aeronomy Laboratory, Boulder, CO 80303, and CIRES, University of Colorado, Boulder, CO 80309, USA. M. Loewenstein, J. R. Podolske, and K. R. Chan are with the NASA Ames Research Center, Moffett Field, CA 94035, USA. K. Minschwaner is with the Department of Physics, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA.
Mid-latitude air enters the tropical stratosphere slower than assumed, making mid-latitude ozone more sensitive to industrial chlorine. This finding impacts predictions for ozone depletion and supersonic aircraft emissions.
Area of Science:
- Atmospheric Chemistry
- Stratospheric Science
- Global Transport
Background:
- Stratospheric composition is influenced by air exchange between mid-latitudes and the tropics.
- Accurate modeling of this exchange is crucial for understanding ozone layer dynamics and atmospheric pollution.
Purpose of the Study:
- To quantify the rate of air mass exchange between the mid-latitude and tropical lower stratosphere.
- To assess the implications of this exchange rate for ozone sensitivity to industrial chlorine and potential impacts of supersonic aircraft.
Main Methods:
- Airborne in situ observations of long-lived molecules (methane, nitrous oxide, ozone, etc.).
- Utilized a tropical tracer model to analyze atmospheric transport pathways and timescales.
Main Results:
- Mid-latitude air entrainment into the tropical lower stratosphere occurs within approximately 13.5 months.
- Stratospheric transport from the tropics to mid-latitudes is faster than the reverse.
- Approximately 45% of air at 21 km in the tropical ascent region originates from mid-latitudes.
Conclusions:
- Global photochemical models may underestimate the sensitivity of mid-latitude ozone to industrial chlorine due to slower-than-assumed tropical exchange.
- Emissions from supersonic aircraft could potentially reach the middle stratosphere given the observed mid-latitude air contribution.