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@ARTICLE{Ueyama:884281,
author = {Ueyama, R. and Jensen, E. J. and Pfister, L. and Krämer,
M. and Afchine, A. and Schoeberl, M.},
title = {{I}mpact of {C}onvectively {D}etrained {I}ce {C}rystals on
the {H}umidity of the {T}ropical {T}ropopause {L}ayer in
{B}oreal {W}inter},
journal = {Journal of geophysical research / D},
volume = {125},
number = {14},
issn = {2169-8996},
address = {Hoboken, NJ},
publisher = {Wiley},
reportid = {FZJ-2020-03173},
pages = {e2020JD032894},
year = {2020},
abstract = {Deep convection detraining in the uppermost tropical
troposphere is capable of transporting water vapor and ice
into the tropical tropopause layer (TTL), but the impact of
deep convection on the global and regional TTL water vapor
budget remains uncertain. In particular, the role of
convectively detrained ice crystals that remain suspended
after active convection has subsided is not well understood.
These ice crystals represent aging cirrus anvils detached
from the convective core. We use a cloud microphysical model
that tracks individual ice crystals throughout their
lifetimes to quantify the impact of detrained ice on the
humidity of the TTL during boreal winter. Convective
influence of air parcels near the wintertime cold point
tropical tropopause is determined by tracing thousands of
backward trajectories through satellite‐derived, global,
3‐hourly convective cloud‐top altitude fields. Detrained
ice, most of which is found over the tropical western
Pacific, experiences cooling on the order of 1 K day−1
downstream of convection. Downstream cooling increases
relative humidity and explains the observed supersaturated
TTL over this region. Vapor in excess of saturation
condenses onto the detrained ice, which ultimately brings
the relative humidity down to saturation. Thus, convectively
detrained ice crystals in aging anvils predominantly
dehydrate the TTL, but the effect is small (0.01 ppmv).
Moistening by active convection (0.30 ppmv), including the
rapid sublimation of convectively lofted ice crystals near
the tops of core anvils, overwhelms the dehydration by aging
anvil ice crystals detrained from the core. The net effect
is moistening by convective core anvils during boreal
winter.},
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)},
pid = {G:(DE-HGF)POF3-244},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000556876500027},
doi = {10.1029/2020JD032894},
url = {https://juser.fz-juelich.de/record/884281},
}