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  • Transport of chemical trace...
    Pan, Laura L.; Honomichl, Shawn B.; Kinnison, Douglas E.; Abalos, Marta; Randel, William J.; Bergman, John W.; Bian, Jianchun

    Journal of geophysical research. Atmospheres, 16 December 2016, Letnik: 121, Številka: 23
    Journal Article

    Chemical transport associated with the dynamics of the Asian summer monsoon (ASM) system is investigated using model output from the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model run in specified dynamics mode. The 3‐D day‐to‐day behavior of modeled carbon monoxide is analyzed together with dynamical fields and transport boundaries to identify preferred locations of uplifting from the boundary layer, the role of subseasonal‐scale dynamics in the upper troposphere and lower stratosphere (UTLS), and the relationship of ASM transport and the stratospheric residual circulation. The model simulation of CO shows the intraseasonal east‐west oscillation of the anticyclone may play an essential role in transporting convectively pumped boundary layer pollutants in the UTLS. A statistical analysis of 11 year CO also shows that the southern flank of the Tibetan plateau is a preferred location for boundary layer tracers to be lofted to the tropopause region. The vertical structure of a model tracer (E90) further shows that the rapid ASM vertical transport is only effective up to the tropopause level (around 400 K). The efficiency of continued vertical transport into the deep stratosphere is limited by the slow ascent associated with the zonal‐mean residual circulation in the lower stratosphere during northern summer. Quasi‐isentropic transport near the 400 K potential temperature level is likely the most effective process for ASM anticyclone air to enter the stratosphere. Key Points Model results indicate that there is a preferred location of vertical transport from the boundary layer to UTLS Subseasonal‐scale dynamics of the Asian monsoon anticyclone is an important driver of UTLS chemical transport The season's slow ascent in residual circulation limits the efficiency of vertical transport into the stratosphere from the ASM