Outflow from the Asian Summer Monsoon and Transport in the UTLS based on GLORIA Measurements during the PHILEAS Campaign 2023

This thesis investigates the origin, uplift mechanisms, and transport pathways of air masses enriched
in Dichloromethane (CH$_2$Cl$_2$) and Peroxyacetyl Nitrate (PAN) observed over the Northeast Pacific
during the PHILEAS aircraft campaign in late summer 2023. The main objective is to identify
the dominant transport processes responsible for the observed enhancements in PAN and CH$_2$Cl$_2$,
determine their source regions within the Asian Summer Monsoon (ASM), and assess the role of
vertical and horizontal transport mechanisms such as uplift into the Asian Monsoon Anticyclone
... mehr
(AMA) with subsequent eddy shedding and Warm Conveyor Belts (WCBs). The analysis is based
on high-resolution atmospheric composition data retrieved from the Gimballed Limb Observer
for Radiance Imaging of the Atmosphere (GLORIA) aboard the HALO aircraft, complemented
by model-based ICON-ART surface tracers and HYSPLIT backward trajectories driven by ERA5
reanalysis.
The results show that observed CH$_2$Cl$_2$ and, to a large fraction, PAN concentration maxima across
four research flights originated predominantly from East China. The maxima in CH$_2$Cl$_2$ and PAN
during Flight 8 on 26–27 August 2023 are observed in the upper troposphere as well as in the
lower stratosphere. The uplift associated with the tropospheric maximum occurred mainly below
the flanks of the AMA over the continent and Northwest Pacific. Its transport pathway into the
upper troposphere is characterized by a horizontal export of monsoon outflow across the North
Pacific. Although some uplift characteristics for the tropospheric maximum resemble WCB-related
transport, the evidence remains incomplete. A consistent explanation for the transport of air
belonging to the stratospheric maxima is the transport through deep convention into the AMA and
subsequent eddy shedding related to the West Pacific Anticyclone (WPA). This raises the question
of whether both WCBs and deep convective ascent within the AMA can simultaneously contribute
to tropospheric as well as stratospheric filaments of monsoon air over the northeastern Pacific.
Further investigation, particularly involving shorter-lived tracers and PV-based diagnostics, is
needed to refine the attribution of uplift mechanisms and mixing events influencing the extratropical
UTLS.

This thesis investigates the origin, uplift mechanisms, and transport pathways of air masses enriched
in Dichloromethane (CH2Cl2) and Peroxyacetyl Nitrate (PAN) observed over the Northeast Pacific
during the PHILEAS aircraft campaign in late summer 2023. The main objective is to identify
the dominant transport processes responsible for the observed enhancements in PAN and CH2Cl2,
determine their source regions within the Asian Summer Monsoon (ASM), and assess the role of
vertical and horizontal transport mechanisms such as uplift into the Asian Monsoon Anticyclone
... mehr
(AMA) with subsequent eddy shedding and Warm Conveyor Belts (WCBs). The analysis is based
on high-resolution atmospheric composition data retrieved from the Gimballed Limb Observer
for Radiance Imaging of the Atmosphere (GLORIA) aboard the HALO aircraft, complemented
by model-based ICON-ART surface tracers and HYSPLIT backward trajectories driven by ERA5
reanalysis.
The results show that observed CH2Cl2 and, to a large fraction, PAN concentration maxima across
four research flights originated predominantly from East China. The maxima in CH2Cl2 and PAN
during Flight 8 on 26–27 August 2023 are observed in the upper troposphere as well as in the
lower stratosphere. The uplift associated with the tropospheric maximum occurred mainly below
the flanks of the AMA over the continent and Northwest Pacific. Its transport pathway into the
upper troposphere is characterized by a horizontal export of monsoon outflow across the North
Pacific. Although some uplift characteristics for the tropospheric maximum resemble WCB-related
transport, the evidence remains incomplete. A consistent explanation for the transport of air
belonging to the stratospheric maxima is the transport through deep convention into the AMA and
subsequent eddy shedding related to the West Pacific Anticyclone (WPA). This raises the question
of whether both WCBs and deep convective ascent within the AMA can simultaneously contribute
to tropospheric as well as stratospheric filaments of monsoon air over the northeastern Pacific.
Further investigation, particularly involving shorter-lived tracers and PV-based diagnostics, is
needed to refine the attribution of uplift mechanisms and mixing events influencing the extratropical
UTLS.