Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-1065
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
19 Dec 2016
Review status
A revision of this discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Enhanced Stratospheric Water Vapor over the Summertime Continental United States and the Role of Overshooting Convection
Robert L. Herman1, Eric A. Ray2, Karen H. Rosenlof2, Kristopher M. Bedka3, Michael J. Schwartz1, William G. Read1, Robert F. Troy1, Keith Chin1, Lance E Christensen1, Dejian Fu1, Robert A. Stachnik1, T. Paul Bui4, and Jonathan M. Dean-Day5 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
2National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) Chemical Sciences Division, Boulder, Colorado, USA
3NASA Langley Research Center, Hampton, Virginia, USA
4NASA Ames Research Center, Moffett Field, California, USA
5Bay Area Environmental Research Institute, Sonoma, California, USA
Abstract. The NASA ER-2 aircraft sampled the UTLS region over North America during the NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) field mission. This study reports three case studies of convectively-influenced air parcels with enhanced water vapor in the overworld stratosphere over the summertime continental United States. Water vapor mixing ratios greater than 10 ppmv, more than twice the stratospheric background levels, were measured by the JPL Laser Hygrometer (JLH Mark2) at pressure levels between 80 and 160 hPa. Through satellite observations and analysis, we make the connection between these in situ water measurements and overshooting cloud tops. The overshooting tops (OT) are identified from a SEAC4RS OT detection product based on satellite infrared window channel brightness temperature gradients. Back trajectory analysis ties enhanced water to OT one to seven days prior to the intercept by the aircraft. The trajectory paths are dominated by the North American Monsoon (NAM) anticyclonic circulation. This connection suggests that ice is convectively transported to the overworld stratosphere in OT events and subsequently sublimated; such events may irreversibly enhance stratospheric water vapor in the summer over Mexico and the United States. Regional context is provided by water observations from the Aura Microwave Limb Sounder (MLS).

Citation: Herman, R. L., Ray, E. A., Rosenlof, K. H., Bedka, K. M., Schwartz, M. J., Read, W. G., Troy, R. F., Chin, K., Christensen, L. E., Fu, D., Stachnik, R. A., Bui, T. P., and Dean-Day, J. M.: Enhanced Stratospheric Water Vapor over the Summertime Continental United States and the Role of Overshooting Convection, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1065, in review, 2016.
Robert L. Herman et al.
Robert L. Herman et al.

Data sets

NASA JPL JLH - JPL Laser Hygrometer for in-situ water vapor measurement
R. L. Herman, R. F. Troy, R. A. Stachnik, and K. Chin
doi:10.5067/Aircraft/SEAC4RS/Aerosol-TraceGas-Cloud
Robert L. Herman et al.

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Short summary
This study reports new aircraft field observations of elevated water vapor greater than 10 ppmv in the overworld stratosphere over the summertime continental U.S. Back-trajectories from the flight track intersect overshooting convective tops within the previous 1 to 7 days, suggesting that ice is convectively and irreversibly transported to the stratosphere in the most energetic overshooting convective events. Satellite measurements (Aura MLS) indicate such events are uncommon (< 1 %).
This study reports new aircraft field observations of elevated water vapor greater than 10 ppmv...
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