Changes in the tropical belt and their effect on trace gas distributions in the UTLS

Recent observational evidence suggests that changes have occurred in the position and strength of the subtropical jet/mixing-barrier regions, and the related width of the “tropical belt”. These phenomena play a role in governing the large-scale distributions of trace species in the UTLS, although their precise influence is not well understood. Within this context, we present new methods for quantifying the strength and geographical location of subtropical jet/mixing-barrier regions. These methods are based on tropopause height (pressure) and potential vorticity (PV) from meteorological reanalysis output. The cycles and trends in jet/mixing-barrier properties are presented and compared to previous estimates. We present preliminary research as to how these metrics for the tropical belt are correlated with satellite-observed distributions of ozone and water vapor, and how changes in the UTLS mixing relate to long-term changes in a high-quality data record such as the Boulder balloon water vapor and ozone record.