Portal de Periódicos da CAPES

An estimate of the stratospheric contribution to springtime tropospheric ozone maxima using TOPSE measurements and beryllium‐7 simulations

2003; American Geophysical Union; Volume: 108; Issue: D4 Linguagem: Inglês

10.1029/2001jd001428

2156-2202

D. J. Allen, Jack E. Dibb, B. A. Ridley, Kenneth Pickering, R. W. Talbot,

Atmospheric and Environmental Gas Dynamics

Measurements of tropospheric ozone (O 3 ) between 30°N and 70°N show springtime maxima at remote locations. The contribution of seasonal changes in stratosphere–troposphere exchange (STE) to these maxima was investigated using measurements from the Tropospheric Ozone Production about the Spring Equinox Experiment (TOPSE) campaign and the beryllium‐7 ( 7 Be) distribution from a calculation driven by fields from the Goddard Earth Observing System Data Assimilation System (GEOS DAS). Comparison with TOPSE measurements revealed that upper tropospheric model‐calculated 7 Be mixing ratios were reasonable (a change from previous calculations) but that lower tropospheric mixing ratios were too low most likely due to an overestimation of scavenging. Temporal fluctuations were well captured although their amplitudes were often underestimated. Analysis of O 3 measurements indicated that O 3 mixing ratios increased by 5–10% month −1 for θ < 300 K (the underworld) and by 10–15% month −1 for θ > 300 K (the tropospheric middleworld). 7 Be mixing ratios decreased with time for θ < 290 K and increased with time for θ > 300 K. Model‐calculated middleworld increases of 7 Be were a factor of 2 less than measured increases. 7 Be with a stratospheric source (strat‐ 7 Be) increased by 4.6–8.8% month −1 along TOPSE flight paths within the tropospheric middleworld. Increases in strat‐ 7 Be were not seen along TOPSE flight paths in the underworld. Assuming changes in tropospheric O 3 with a stratospheric source are the same as changes in strat‐ 7 Be and that 50% of O 3 in the region of interest is produced in the stratosphere, changes in STE explain 20–60% of O 3 increases in the tropospheric middleworld and less than 33% of O 3 increases in the underworld.