Results from a comparison of HCN measurements and Lagrangian backtrajectory analyses in the Asian Summer Monsoon Anticyclone

The StratoClim aircraft field campaign took place from Kathmandu, Nepal, in summer 2017 in
order to study the atmospheric composition, chemistry, and dynamics in the Asian Summer
Monsoon Anticyclone (ASMA) which is known to transport surface emissions to the mid-latitude
lower stratosphere and the stratosphere worldwide. Hydrogen cyanide (HCN) which is primarily
emitted from biomass burning and has a UTLS lifetime on the order of 1-2 years is a good tracer for
biomass burning import into the lower and free stratosphere.
HCN in the ASM Upper Troposphere and Lower Stratosphere (UTLS) was measured in-situ
employing the Chemical-Ionization Time-of-Flight Mass Spectrometer FUNMASS on board the
high-altitude research aircraft M55-Geophysica. The observed HCN mixing ratios in and above the
ASMA exhibit interesting vertical and horizontal signatures around the tropopause as well as in the
LS probably resulting from convective activity or air mass origin (AMO). We here compare
measured HCN to Lagrangian simulations by the ClaMS and TRACZILLA models which employ
two different approaches to represent higher-reaching convective events. The simulations succeed to
track some of the observed HCN features back to convective activity or AMO. The quality of the
reproduction and further outcomes on the atmospheric relevance will be discussed in the
presentation.