Assessing precipitation over the Amazon basin as simulated by a
storm-resolving model
Abstract
In this study we investigate whether a better representation of
precipitation in the Amazon basin arises through an explicit
representation of convection and whether it is related to the
representation of organized systems. In addition to satellite data, we
use ensemble simulations of the ICON-NWP model at storm-resolving
(2.5-5.0 km) scales with explicit convection (E-CON) and coarse
resolutions, with parameterized convection (P-CON). The main
improvements in the representation of Amazon precipitation by E-CON are
in the spatial pattern of precipitation, the distribution of
precipitation intensity and the spatial distribution in the diurnal
cycle. By isolating precipitation from organized convective systems
(OCS), it is shown that many of the well simulated precipitation
features in the Amazon arise from the distribution of these systems. The
simulated and observed OCS are classified into 6 clusters which
distinguish nocturnal and diurnal OCS. While the E-CON ensembles capture
the OCS, especially their diurnal cycle, their frequency is reduced
compared to observations. Diurnal clusters are influenced by surface
processes such as cold pools, which aid to the propagation of OCS.
Nocturnal clusters are rather associated with strong low-level
easterlies, possibly related to the Amazonian low-level jet. These
particular environmental conditions provide insights on the processes
that are important for OCS in the Amazon and should be further improved.