Ice Particles over the Asian Monsoon:Observations during the Field Campaign StratoClim 2017

The StratoClim field campaign with the Russian high-flying aircraft M55-Geophysica took place out
of Nepal 2017 in the monsoon period July to August to investigate, amongst others, size
distributions and number concentrations (N ice) of ice particles in the sub-tropical upper
troposphere/lower stratosphere (UTLS) region. The measurements are performed by means of the
cloud spectrometer NIXE-CAPS (Krämer et al., 2016), capable to detect aerosol and ice particles in
the size range 0.6 to 937 um. Ice water content (IWC) was additionally determined from total and gas
phase water measurements with the hygrometers FISH and FLASH (Meyer et al., 2015)
5.5 hours of ice clouds in the temperature range 185 to 240 K are observed during 8 flights in the
altitude range 10–19 km in and over the Asian monsoon anticyclone. We found that exceptional ice
clouds are observed in comparison to the comprehensive climatology of cirrus clouds, which is part of
the Jülich in-situ airborne data base (JULIA). JULIA contains 131 hours of IWC and 80 hours of N ice
from 19 field campaigns between 75 N and 25 S. At temperatures lower than 200 K, the StratoClim
IWC as well as Nice are frequently about a factor of 10 to 100 higher than in the total climatology.
IWCs are higher than ever recorded. These cirrus most probably originate from frozen liquid drops
(liquid origin cirrus, Krämer et al., 2016) that are uplifted in deep convection. A part of this type of ice
clouds is observed above the cold point of the temperature profile, that means that overshooting events
in the deep convection are observed. Another part of the measurements show very low N ice , which
are reported and discussed also earlier in the literature. We interpret these clouds as in-situ cirrus
formed in the outflow of the Asian monsoon.
We will present the StratoClim cirrus observation of IWC and N ice as well as RHice in comparison to
the JULIA climatology. Also, the vertical distribution of cirrus clouds in the Asian monsoon will be
presented, in particular ice particle size distributions at different distances to the atmospheric cold
point of matured in-situ cirrus and cirrus near the core of strong deep convection.
References

Krämer et al. (2016): A microphysics guide to cirrus clouds – Part 1: Cirrus types, Atmos. Chem.
Phys., 16, 3463-3483, doi:10.5194/acp-16-3463-2016.
Meyer, J., Rolf, C., Schiller, C., Rohs, S., Spelten, N., Afchine, A., Zöger, M., Sitnikov, N.,
Thornberry, T. D., Rollins, A. W., Bozóki, Z., Tátrai, D., Ebert, V., Kühnreich, B., Mackrodt, P.,
Möhler, O., Saathoff, H., Rosenlof, K. H., and Krämer, M.: Two decades of water vapor
measurements with the FISH fluorescence hygrometer: a review, Atmos. Chem. Phys., 15, 8521–
8538, doi:10.5194/acp-15-8521-2015, 2015.