Cloud Botany: Shallow cumulus clouds in an ensemble of idealized
large-domain large-eddy simulations of the trades
Abstract
Small shallow cumulus clouds (< 1 km) over the tropical oceans
appear to possess the ability to self-organise into mesoscale (10-100
km) patterns. To better understand the processes leading to such
self-organized convection, we present Cloud Botany, an ensemble of 103
large-eddy simulations on domains of 150 km, produced by the Dutch Large
Eddy Simulation (DALES) model on supercomputer Fugaku. Each simulation
is run in an idealized, fixed, larger-scale environment, controlled by
six free parameters. We vary these over characteristic ranges for the
winter trades, including parameter combinations observed during the
EUREC4A (Elucidating the role of clouds–circulation coupling in
climate) field campaign. In contrast to simulation setups striving for
maximum realism, Cloud Botany provides a platform for studying
idealized, and therefore more clearly interpretable causal relationships
between conditions in the larger-scale environment and patterns in
mesoscale, self-organized shallow convection. We find that any
simulation that supports cumulus clouds eventually develops mesoscale
patterns in their cloud fields. We also find a rich variety in these
patterns as our control parameters change, including cold pools lined by
cloudy arcs, bands of cross-wind clouds and aggregated patches,
sometimes topped by thin anvils. Many of these features are similar to
cloud patterns found in nature. The published data set consists of raw
simulation output on full 3D grids and 2D cross-sections, as well as
post-processed quantities aggregated over the vertical (2D), horizontal
(1D) and all spatial dimensions (time-series). The data set is directly
accessible from Python through the use of the EUREC4A intake catalog.