Case study on the influence of synoptic-scale processes on the paired H 2 O–O 3 distribution in the UTLS across a North Atlantic jet stream

[摘要] During a research flight of the Wave-driven ISentropicExchange (WISE) campaign, which was conducted over the eastern NorthAtlantic on 1 October 2017, the composition of the upper troposphere andlower stratosphere (UTLS) across the North Atlantic jet stream was observedby airborne, range-resolved differential absorption lidar (DIAL) profiles.We investigate how the high variability in the paired H 2 O and O 3 distribution along the two-dimensional lidar cross section is affected bysynoptic-scale weather systems, as revealed by the Lagrangian history of theobserved air masses. To this aim, the lidar observations are combined with10 d backward trajectories along which meteorological parameters andderived turbulence diagnostics are traced. The transport and mixingcharacteristics are then projected to the vertical cross sections of thelidar measurements and to the H 2 O–O 3 phase space to explorelinkages with the evolution of synoptic-scale weather systems and theirinteraction. Tropical, midlatitude, and arctic weather systems in the regionof the jet stream and the related transport and mixing explain the complexH 2 O and O 3 distribution to a large extent: O 3 -richstratospheric air from the high Arctic interacts with midlatitude air fromthe North Pacific in a northward-deflected jet stream associated with ananticyclone over the US and forms a filament extending into the tropopausefold beneath the jet stream. In the troposphere, lifting related toconvection in the intertropical convergence zone (ITCZ) and two tropicalcyclones that continuously injected H 2 O into dry descending air fromthe tropical Atlantic and Pacific form filamentary H 2 O structures. Onetropical cyclone that transitioned into a midlatitude cyclone lifted moistboundary layer air, explaining the highest tropospheric H 2 O values.During the two days before the observations, the air with mixed troposphericand stratospheric characteristics experienced frequent turbulence along theNorth Atlantic jet stream, indicating a strong influence of turbulence on theformation of the extratropical transition layer (ExTL). This investigationhighlights the complexity of stirring and mixing processes and their closeconnection to interacting tropospheric weather systems from the tropics to thepolar regions, which strongly influenced the observed fine-scale H 2 Oand O 3 distributions. The identified non-local character ofmixing should be kept in mind when interpreting mixing lines intracer–tracer phase space diagrams.

[学科分类] 医学（综合）