TY - JOUR

T1 - The Diurnal Path to Persistent Convective Self-Aggregation

AU - Jensen, Gorm G.

AU - Fievet, Romain

AU - Haerter, Jan O.

PY - 2022/5/5

Y1 - 2022/5/5

N2 - Clustering of tropical thunderstorms constitutes an important climate feedback because it influences the radiative balance. Convective self-aggregation (CSA) is a profound modeling paradigm for explaining the clustering of tropical oceanic thunderstorms. However, CSA is hampered in the realistic limit of fine model resolution when cold pools-dense air masses beneath thunderstorm clouds-are well-resolved. Studies on CSA usually assume the surface temperature to be constant, despite realistic surface temperatures varying significantly between night and day. Here we mimic the diurnal cycle in cloud-resolving numerical experiments by prescribing a surface temperature oscillation. Our simulations show that the diurnal cycle enables CSA at fine resolutions, and that the process is even accelerated by finer resolutions. We attribute these findings to vigorous combined cold pools emerging in symbiosis with mesoscale convective systems. Such cold pools suppress buoyancy in extended regions (similar to 100 km) and enable the formation of persistent dry patches. Our findings help clarify how the tropical cloud field forms sustained clusters under the diurnal forcing and may have implications for the origin of extreme thunderstorm rainfall and tropical cyclones.

AB - Clustering of tropical thunderstorms constitutes an important climate feedback because it influences the radiative balance. Convective self-aggregation (CSA) is a profound modeling paradigm for explaining the clustering of tropical oceanic thunderstorms. However, CSA is hampered in the realistic limit of fine model resolution when cold pools-dense air masses beneath thunderstorm clouds-are well-resolved. Studies on CSA usually assume the surface temperature to be constant, despite realistic surface temperatures varying significantly between night and day. Here we mimic the diurnal cycle in cloud-resolving numerical experiments by prescribing a surface temperature oscillation. Our simulations show that the diurnal cycle enables CSA at fine resolutions, and that the process is even accelerated by finer resolutions. We attribute these findings to vigorous combined cold pools emerging in symbiosis with mesoscale convective systems. Such cold pools suppress buoyancy in extended regions (similar to 100 km) and enable the formation of persistent dry patches. Our findings help clarify how the tropical cloud field forms sustained clusters under the diurnal forcing and may have implications for the origin of extreme thunderstorm rainfall and tropical cyclones.

KW - convection

KW - self-aggregation

KW - diurnal

KW - mesoscale

KW - clouds

KW - CLOUD

KW - PRECIPITATION

KW - EQUILIBRIUM

KW - OCEAN

KW - CYCLE

KW - CIRCULATION

KW - SIMULATIONS

KW - ATMOSPHERE

KW - FREQUENCY

KW - EXPLICIT

U2 - 10.1029/2021MS002923

DO - 10.1029/2021MS002923

M3 - Journal article

C2 - 35865232

VL - 14

JO - Journal of Advances in Modeling Earth Systems

JF - Journal of Advances in Modeling Earth Systems

SN - 1942-2466

IS - 5

M1 - e2021MS002923

ER -