Observations and Simulations of the Stable Water Isotope Signature of Convective Updrafts and Downdrafts Associated with Different Mesoscale Organization Patterns of Shallow Trade Wind Clouds - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Communication Dans Un Congrès Année : 2021

Observations and Simulations of the Stable Water Isotope Signature of Convective Updrafts and Downdrafts Associated with Different Mesoscale Organization Patterns of Shallow Trade Wind Clouds

Résumé

Water molecules containing a heavy hydrogen or oxygen atom have lower saturation vapor pressures and diffusivities than their light counterparts, which leads to a change in their relative abundance during phase transitions. Each process controlling the water vapor budget of shallow cumulus clouds in the trade wind region such as ocean evaporation, convective and turbulent mixing, condensation and evaporation of hydrometeors is associated with a characteristic isotopic fingerprint. In a recent study, different transport regimes in the trades have been shown to be associated with distinct mesoscale organization patterns and water vapor isotope signals in the sub-cloud layer. The reported isotopic differentiation between various mesoscale organisation patterns is most likely due to variations in the relative contribution of the processes mentioned above to the water vapor budget along the flow. To test this hypothesis and assess the timescales over which the pattern-specific anomalies in water vapor isotopes emerge, we use a combination of airborne measurements of stable water vapor isotopes and high-resolution simulations with the isotope-enabled numerical model COSMOiso. The evolution of the stable isotope signature along the trade wind flow is assessed using three-dimensional back-trajectories calculated based on COSMOiso wind fields. The isotope measurements in water vapor were performed on the French aircraft ATR-42 during 18 flights from 25 January to 13 February 2020 as a part of the international EUREC4A field campaign. The flights were conducted over the tropical ocean near Barbados with the aircraft staying predominantly at the height of cloud base. Complementary cloud radar and lidar data as well as in-situ turbulence and microphysics measurements are used to characterise the physical environment of the studied cloud fields. Our isotope measurements reveal substantial differences between flights, which are related to contrasting large-scale flow situations and mesoscale cloud organizations. This study provides promising process-based insights into the cloud-circulation coupling conundrum and demonstrates the potential of water isotopes to identify relevant processes.

Domaines

Météorologie
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Dates et versions

insu-04464303 , version 1 (18-02-2024)

Identifiants

Citer

Leonie Villiger, Marina Duetsch, Sandrine Bony, Pierre-Etienne Brilouet, Patrick Chazette, et al.. Observations and Simulations of the Stable Water Isotope Signature of Convective Updrafts and Downdrafts Associated with Different Mesoscale Organization Patterns of Shallow Trade Wind Clouds. AGU Fall Meeting 2021, Dec 2021, New Orleans, United States. pp.id. A45G-1927. ⟨insu-04464303⟩
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