A New Lens for Evaluating Dynamic Controls on Shallow Convection

摘要

Rising temperatures and changing dynamics can both moisten the air, making it difficult to disentangle these interrelated drivers of water cycle change. However, work by Camille Risi and colleagues presents a new way to distinguish their effects. Using large‐eddy simulations with water isotopic tracers, they show that while warming the sea surface increases the ratio of isotopically heavy‐to‐light water in the tropical marine subcloud layer, strengthening the moisture flux convergence decreases it. This divergent response provides a new framework for examining the complex mechanisms that regulate the development of convection and, ultimately, cloudiness—a target of the 2020 international field campaign EUREC4A (ElUcidating the RolE of Clouds‐Circulation Coupling in ClimAte). Moreover, their findings provide a clearer picture of why water isotopes recorded in tropical paleoproxies are a valuable lens through which to view changes in moisture transport in the past. Plain Language Summary Rising temperatures and changing atmospheric motions can both moisten the air, making it difficult to disentangle these interrelated drivers of water cycle change. However, work by Camille Risi and colleagues presents a new way to distinguish their effects. Using numerical simulations of the atmosphere over tropical oceans, they show that while warming the sea surface increases the ratio of isotopically heavy‐to‐light water vapor (HDO/H2O) below the tropical cloud deck, strengthening the rate at which moisture is imported by winds decreases it. This opposite response provides a new framework for examining the complex mechanisms that regulate the development of tropical convection and clouds—a target of the 2020 international field campaign EUREC4A (ElUcidating the RolE of Clouds‐Circulation Coupling in ClimAte). Moreover, their findings provide a clearer picture of why water isotopes recorded in natural archives, such as the stalagmites and stalactites that form in caves, can reveal variations in atmospheric motion and moisture transport in the past.