In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 19, No. 17 ( 2019-09-12), p. 11525-11543
Kurzfassung:
Abstract. We use airborne measurements of water vapor
(H2Ov) stable isotopologues and complementary meteorological
observations to examine how boundary layer (BL) dynamics, cloud processing, and
atmospheric mixing influence the vertical structure of δD, δ18O, and deuterium excess (d excess =δD–8×δ18O) in the BL, inversion layer (INV), and lower free
troposphere (FT). Flights were conducted around two continental US cities in
February–March 2016 and included vertical profiles extending from near
the surface to ≤2 km. We examine observations from three unique case
study flights in detail. One case study shows observations that are
consistent with Rayleigh isotopic distillation theory coinciding with clear
skies, dry adiabatic lapse rates within the boundary layer, and relatively
constant vertical profiles of wind speed and wind direction. This suggests
that the air mass retained the isotopic fingerprint of dehydration during
moist adiabatic processes upwind of the study area. Also, observed d-excess
values in the free troposphere were sometimes larger than Rayleigh theory
predicts, which may indicate mixing of extremely dehydrated air from higher
altitudes. The two remaining case studies show isotopic anomalies in the
d-excess signature relative to Rayleigh theory and indicate cloud processes
and complex boundary layer development. The most notable case study with
stratocumulus clouds present had extremely low (negative) d-excess values at
the interface of the inversion layer and the free troposphere, which is
possibly indicative of cloud or rain droplet evaporation. We discuss how in situ
H2Ov stable isotope measurements, and d excess in particular,
could be useful for improving our understanding of water phase changes,
transport, and mixing that occurs between the BL, INV, and FT.
Materialart:
Online-Ressource
ISSN:
1680-7324
DOI:
10.5194/acp-19-11525-2019
DOI:
10.5194/acp-19-11525-2019-supplement
Sprache:
Englisch
Verlag:
Copernicus GmbH
Publikationsdatum:
2019
ZDB Id:
2092549-9
ZDB Id:
2069847-1
