Sub-cloud Rain Evaporation in the North Atlantic Ocean

• Main Authors: Sarkar, Mampi, Bailey, Adriana, Blossey, Peter, Szoeke, Simon P., Noone, David, Quinones Melendez, Estefania, Leandro, Mason, Chuang, Patrick
• Format: Text
• Language: English
• Published: 2023
• Subjects: North Atlantic
• Online Access: https://doi.org/10.5194/egusphere-2022-1143; https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1143/

Sub-cloud rain evaporation in the trade wind region significantly influences the boundary layer mass and energy budgets. Parameterizing it is, however, difficult due to the sparsity of well-resolved rain observations and the challenges of sampling short-lived marine cumulus clouds. In this study, sub-cloud rain evaporation is analyzed using a steady-state, one-dimensional model that simulates changes in drop sizes, relative humidity, and rain isotopic composition. The model is initialized with relative humidity, raindrop size distributions, and water vapor isotope ratios (e.g., δ D v , δ 18 O v <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="31pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="da8f46eeb884e5f67877552a16157ec3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-12671-2023-ie00001.svg" width="31pt" height="16pt" src="acp-23-12671-2023-ie00001.png"/></svg:svg> ) sampled by the NOAA P3 aircraft during the Atlantic Tradewind Ocean–Atmosphere Mesoscale Interaction Campaign (ATOMIC), which was part of the larger EUREC 4 A (ElUcidating the RolE of Clouds–Circulation Coupling in ClimAte) field program. The modeled surface precipitation isotope ratios closely match the observations from EUREC 4 A ground-based and ship-based platforms, lending credibility to our model. The model suggests that 63 % of the rain mass evaporates in the sub-cloud layer across 22 P3 cases. The vertical distribution of the evaporated rain flux is top heavy for a narrow ( σ ) raindrop size distribution (RSD) centered over a small geometric mean diameter ( D g ) at the cloud base. A top-heavy profile has a higher rain-evaporated fraction (REF) and larger changes in the rain deuterium excess ( d = δ D - 8 × δ 18 O <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="92pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9a5282d21666df35dd87a12b2ee29626"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-12671-2023-ie00002.svg" ...