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@ARTICLE{Clark:903139,
      author       = {Clark, Hannah and Bennouna, Yasmine and Tsivlidou, Maria
                      and Wolff, Pawel and Sauvage, Bastien and Barret, Brice and
                      Le Flochmoën, Eric and Blot, Romain and Boulanger, Damien
                      and Cousin, Jean-Marc and Nédélec, Philippe and Petzold,
                      Andreas and Thouret, Valérie},
      title        = {{T}he effects of the {COVID}-19 lockdowns on the
                      composition of the troposphere as seen by {I}n-service
                      {A}ircraft for a {G}lobal {O}bserving {S}ystem ({IAGOS}) at
                      {F}rankfurt},
      journal      = {Atmospheric chemistry and physics},
      volume       = {21},
      number       = {21},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-04863},
      pages        = {16237 - 16256},
      year         = {2021},
      abstract     = {The European research infrastructure IAGOS (In-service
                      Aircraft for a Global Observing System) equips commercial
                      aircraft with a system for measuring atmospheric
                      composition. A range of essential climate variables and air
                      quality parameters are measured throughout the flight, from
                      take-off to landing, giving high-resolution information in
                      the vertical in the vicinity of international airports and
                      in the upper troposphere–lower stratosphere during the
                      cruise phase of the flight. Six airlines are currently
                      involved in the programme, achieving a quasi-global coverage
                      under normal circumstances. During the COVID-19 crisis, many
                      airlines were forced to ground their fleets due to a fall in
                      passenger numbers and imposed travel restrictions. Deutsche
                      Lufthansa, a partner in IAGOS since 1994 was able to operate
                      an IAGOS-equipped aircraft during the COVID-19 lockdown,
                      providing regular measurements of ozone and carbon monoxide
                      at Frankfurt Airport. The data form a snapshot of an
                      unprecedented time in the 27-year time series. In May 2020,
                      we see a $32 \%$ increase in ozone near the surface with
                      respect to a recent reference period, a magnitude similar to
                      that of the 2003 heatwave. The anomaly in May is driven by
                      an increase in ozone at nighttime which might be linked to
                      the reduction in NO during the COVID-19 lockdowns. The
                      anomaly diminishes with altitude becoming a slightly
                      negative anomaly in the free troposphere. The ozone
                      precursor carbon monoxide shows an $11 \%$ reduction in
                      MAM (March–April–May) near the surface. There is only a
                      small reduction in CO in the free troposphere due to the
                      impact of long-range transport on the CO from emissions in
                      regions outside Europe. This is confirmed by data from the
                      Infrared Atmospheric Sounding Interferometer (IASI) using
                      retrievals performed by SOftware for a Fast Retrieval of
                      IASI Data (SOFRID), which display a clear drop of CO at
                      800 hPa over Europe in March but otherwise show little
                      change to the abundance of CO in the free troposphere.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {2111 - Air Quality (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2111},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000715751600001},
      doi          = {10.5194/acp-21-16237-2021},
      url          = {https://juser.fz-juelich.de/record/903139},
}