English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

. Raindrops interact with water vapour in ambient air while sedimenting fromthe cloud base to the ground. They constantly exchange water molecules withthe environment and, in sub-saturated air, they evaporate partially orentirely. The latter of these below-cloud processes is important forpredicting the resulting surface rainfall amount. It also influences theboundary layer profiles of temperature and moisture through evaporativelatent cooling and humidity changes. However, despite its importance, it isvery difficult to quantify this process from observations. Stable waterisotopes provide such information, as they are influenced by both rainevaporation and equilibration (i.e. the exchange of isotopes betweenraindrops and ambient air). This study elucidates this option by introducinga novel interpretative framework for stable water isotope measurementsperformed simultaneously at high temporal resolution in both near-surfacevapour and rain. We refer to this viewing device as the ΔδΔd-diagram, which shows the isotopic composition (δ2H,d-excess) of equilibrium vapour from precipitation samples relative to theambient vapour. It is shown that this diagram facilitates the diagnosis ofbelow-cloud processes and their effects on the isotopic composition of vapourand rain since equilibration and evaporation lead to different pathways inthe two-dimensional phase space of the ΔδΔd-diagram, asinvestigated with a series of sensitivity experiments with an idealizedbelow-cloud interaction model. The analysis of isotope measurements for aspecific cold front in central Europe shows that below-cloud processes leadto distinct and temporally variable imprints on the isotope signal in surfacerain. The influence of evaporation on this signal is particularly strongduring periods with a weak precipitation rate. After the frontal passage, thenear-surface atmospheric layer is characterized by higher relative humidity,which leads to weaker below-cloud evaporation. Additionally, a lower meltinglayer after the frontal passage reduces time for exchange between vapour andrain and leads to weaker equilibration. Measurements from four cold frontalevents reveal a surprisingly similar slope of ΔdΔδ=-0.30 in the phase space, indicating a potentiallycharacteristic signature of below-cloud processes for this type of rainevent.

A new interpretative framework for below-cloud effects on stable water isotopes in vapour and rain