Case study on the influence of synoptic-scale processes on the paired H<sub>2</sub>O–O<sub>3</sub> distribution in the UTLS across a North Atlantic jet stream
<p>During a research flight of the Wave-driven ISentropic Exchange (WISE) campaign, which was conducted over the eastern North Atlantic on 1 October 2017, the composition of the upper troposphere and lower stratosphere (UTLS) across the North Atlantic jet stream was observed by airborne, range...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/999/2023/acp-23-999-2023.pdf |
| Summary: | <p>During a research flight of the Wave-driven ISentropic
Exchange (WISE) campaign, which was conducted over the eastern North
Atlantic on 1 October 2017, the composition of the upper troposphere and
lower stratosphere (UTLS) across the North Atlantic jet stream was observed
by airborne, range-resolved differential absorption lidar (DIAL) profiles.
We investigate how the high variability in the paired H<span class="inline-formula"><sub>2</sub></span>O and O<span class="inline-formula"><sub>3</sub></span> distribution along the two-dimensional lidar cross section is affected by
synoptic-scale weather systems, as revealed by the Lagrangian history of the
observed air masses. To this aim, the lidar observations are combined with
10 d backward trajectories along which meteorological parameters and
derived turbulence diagnostics are traced. The transport and mixing
characteristics are then projected to the vertical cross sections of the
lidar measurements and to the H<span class="inline-formula"><sub>2</sub></span>O–O<span class="inline-formula"><sub>3</sub></span> phase space to explore
linkages with the evolution of synoptic-scale weather systems and their
interaction. Tropical, midlatitude, and arctic weather systems in the region
of the jet stream and the related transport and mixing explain the complex
H<span class="inline-formula"><sub>2</sub></span>O and O<span class="inline-formula"><sub>3</sub></span> distribution to a large extent: O<span class="inline-formula"><sub>3</sub></span>-rich
stratospheric air from the high Arctic interacts with midlatitude air from
the North Pacific in a northward-deflected jet stream associated with an
anticyclone over the US and forms a filament extending into the tropopause
fold beneath the jet stream. In the troposphere, lifting related to
convection in the intertropical convergence zone (ITCZ) and two tropical
cyclones that continuously injected H<span class="inline-formula"><sub>2</sub></span>O into dry descending air from
the tropical Atlantic and Pacific form filamentary H<span class="inline-formula"><sub>2</sub></span>O structures. One
tropical cyclone that transitioned into a midlatitude cyclone lifted moist
boundary layer air, explaining the highest tropospheric H<span class="inline-formula"><sub>2</sub></span>O values.
During the two days before the observations, the air with mixed tropospheric
and stratospheric characteristics experienced frequent turbulence along the
North Atlantic jet stream, indicating a strong influence of turbulence on the
formation of the extratropical transition layer (ExTL). This investigation
highlights the complexity of stirring and mixing processes and their close
connection to interacting tropospheric weather systems from the tropics to the
polar regions, which strongly influenced the observed fine-scale H<span class="inline-formula"><sub>2</sub></span>O
and O<span class="inline-formula"><sub>3</sub></span> distributions. The identified non-local character of
mixing should be kept in mind when interpreting mixing lines in
tracer–tracer phase space diagrams.</p> |
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| ISSN: | 1680-7316 1680-7324 |