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@ARTICLE{Hanumanthu:888184,
      author       = {Hanumanthu, Sreeharsha and Vogel, Bärbel and Müller, Rolf
                      and Brunamonti, Simone and Fadnavis, Suvarna and Li, Dan and
                      Ölsner, Peter and Naja, Manish and Singh, Bhupendra Bahadur
                      and Kumar, Kunchala Ravi and Sonbawne, Sunil and Jauhiainen,
                      Hannu and Vömel, Holger and Luo, Beiping and Jorge, Teresa
                      and Wienhold, Frank G. and Dirkson, Ruud and Peter, Thomas},
      title        = {{S}trong day-to-day variability of the {A}sian {T}ropopause
                      {A}erosol {L}ayer ({ATAL}) in {A}ugust 2016 at the
                      {H}imalayan foothills},
      journal      = {Atmospheric chemistry and physics},
      volume       = {20},
      number       = {22},
      issn         = {1680-7324},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2020-04746},
      pages        = {14273 - 14302},
      year         = {2020},
      abstract     = {The South Asian summer monsoon is associatedwith a
                      large-scale anticyclonic circulation in the upper
                      troposphere and lower stratosphere (UTLS), which confines
                      the airmass inside. During boreal summer, the confinement of
                      thisair mass leads to an accumulation of aerosol between
                      about13 and 18 km (360 and 440 K potential temperature);
                      thisaccumulation of aerosol constitutes the Asian
                      TropopauseAerosol Layer (ATAL). We present balloon-borne
                      aerosolbackscatter measurements of the ATAL performed by
                      theCompact Optical Backscatter Aerosol Detector
                      (COBALD)instrument in Nainital in northern India in August
                      2016,and compare these with COBALD measurements in
                      thepost-monsoon time in November 2016. The
                      measurementsdemonstrate a strong variability of the ATAL’s
                      altitude, vertical extent, aerosol backscatter intensity and
                      cirrus cloudoccurrence frequency. Such a variability cannot
                      be deducedfrom climatological means of the ATAL as they are
                      derivedfrom satellite measurements. To explain this observed
                      variability we performed a Lagrangian back-trajectory
                      analysisusing the Chemical Lagrangian Model of the
                      Stratosphere(CLaMS). We identify the transport pathways as
                      well as thesource regions of air parcels contributing to the
                      ATAL overNainital in August 2016. Our analysis reveals a
                      variety offactors contributing to the observed day-to-day
                      variability ofthe ATAL: continental convection, tropical
                      cyclones (maritime convection), dynamics of the anticyclone
                      and strato-spheric intrusions. Thus, the air in the ATAL is
                      a mixture ofair masses coming from different atmospheric
                      altitude layers. In addition, contributions from the model
                      boundary layeroriginate in different geographic source
                      regions. The location of the strongest updraft along the
                      backward trajectoriesreveals a cluster of strong upward
                      transport at the southernedge of the Himalayan foothills.
                      From the top of the convective outflow level (about 13 km;
                      360 K) the air parcels ascendslowly to ATAL altitudes within
                      a large-scale upward spiral driven by the diabatic heating
                      in the anticyclonic flow ofthe South Asian summer monsoon at
                      UTLS altitudes. Caseswith a strong ATAL typically show
                      boundary layer contributions from the Tibetan Plateau, the
                      foothills of the Hi-malayas and other continental regions
                      below the Asian monsoon. Weaker ATAL cases show higher
                      contributions fromthe maritime boundary layer, often related
                      to tropical cyclones, indicating a mixing of clean maritime
                      and pollutedcontinental air. On the one hand increasing
                      anthropogenicemissions in the future are expected due to the
                      strong growthof Asian economies; on the other hand the
                      implementationof new emission control measures (in
                      particular in China)has reduced the anthropogenic emissions
                      of some pollutantscontributing to the ATAL substantially. It
                      needs to be monitored in the future whether the thickness
                      and intensity of theATAL will further increase, which will
                      likely impact the surface climate.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {244 - Composition and dynamics of the upper troposphere and
                      middle atmosphere (POF3-244) / STRATOCLIM - Stratospheric
                      and upper tropospheric processes for better climate
                      predictions (603557)},
      pid          = {G:(DE-HGF)POF3-244 / G:(EU-Grant)603557},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000591833100002},
      doi          = {10.5194/acp-20-14273-2020},
      url          = {https://juser.fz-juelich.de/record/888184},
}