The influence of convective aggregation on the stable isotopic
composition of water vapor: Implications for the humidity of the
troposphere
Abstract
Remote sensing datasets of water vapor isotopic composition are used
along with objective measures of convective aggregation to better
understand the impact of convective aggregation on the atmospheric
hydrologic cycle in the global tropics
($30^{\circ}$N to
$30^{\circ}$S) for the period 2015-2020. When
convection is unaggregated, vertical velocity profiles are top-heavy,
mixing ratios increase and water vapor $\delta D$
decreases as the mean precipitation rate increases, consistent with
partial hydrometeor evaporation below anvils into a relatively humid
atmospheric column. Aggregated convection is associated with
bottom-heavy vertical velocity profiles and a positive correlation
between mixing ratio and $\delta D$, a result that is
consistent with isotopic enrichment from detrainment of shallow
convection near the observation level. Intermediate degrees of
aggregation do not display significant variation in
$\delta D$ with mixing ratio or precipitation rate.
Convective aggregation provides a useful paradigm for understanding the
relationships between mixing ratio and isotopic composition across a
range of convective settings. The results presented here may have
utility for a variety of applications including the interpretation of
paleoclimate archives and the evaluation of numerical simulations of
convection.