Airborne observations and modeling of springtime stratosphere-to-troposphere transport over California E. L. Yates1, L. T. Iraci1, M. C. Roby2, R. B. Pierce3, M. S. Johnson4, P. J. Reddy5, J. M. Tadić1,*, M. Loewenstein1, and W. Gore1 1Atmospheric Science Branch, NASA Ames Research Center, Moffett Field, CA 94035, USA 2Department of Meteorology, San Jose State University, San Jose, CA 95192-0104, USA 3NOAA/NESDIS Advanced Satellite Products Branch Madison, WI 53706, USA 4Biospheric Science Branch, NASA Ames Research Center, Moffett Field, CA 94035, USA 5Air Pollution Control Division, Colorado Department of Public Health & Environment, Denver, CO 80246, USA *now at: Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305, USA
Abstract. Stratosphere-to-troposphere transport (STT) results in air masses of
stratospheric origin intruding into the free troposphere. Once in the free
troposphere, ozone (O3)-rich stratospheric air can be transported and
mixed with tropospheric air masses, contributing to the tropospheric O3
budget. Evidence of STT can be identified based on the differences in the
trace gas composition of the two regions. Because O3 is present in such
large quantities in the stratosphere compared to the troposphere, it is
frequently used as a tracer for STT events.
This work reports on airborne in situ measurements of O3 and other
trace gases during two STT events observed over California, USA. The first,
on 14 May 2012, was associated with a cutoff low, and the second, on 5 June
2012, occurred during a post-trough, building ridge event. In each STT
event, airborne measurements identified high O3 within the
stratospheric intrusion, which were observed as low as 3 km above sea level.
During both events the stratospheric air mass was characterized by elevated
O3 mixing ratios and reduced carbon dioxide (CO2) and water vapor.
The reproducible observation of reduced CO2 within the stratospheric
air mass supports the use of non-conventional tracers as an additional
method for detecting STT. A detailed meteorological analysis of each STT
event is presented, and observations are interpreted with the Realtime Air
Quality Modeling System (RAQMS). The implications of the two STT events are
discussed in terms of the impact on the total tropospheric O3 budget
and the impact on air quality and policy-making.
Citation: Yates, E. L., Iraci, L. T., Roby, M. C., Pierce, R. B., Johnson, M. S., Reddy, P. J., Tadić, J. M., Loewenstein, M., and Gore, W.: Airborne observations and modeling of springtime stratosphere-to-troposphere transport over California, Atmos. Chem. Phys., 13, 12481-12494, doi:10.5194/acp-13-12481-2013, 2013.