Abstract. Both frequency and intensity of rainfall affect aerosol wet
deposition. With a stochastic deep convection scheme implemented into two
state-of-the-art global climate models (GCMs), a recent study found that
aerosol burdens are increased globally by reduced climatological mean wet
removal of aerosols due to suppressed light rain. Motivated by their work, a
novel approach is developed in this study to detect what rainfall rates are
most efficient for wet removal (scavenging amount mode) of different aerosol
species of different sizes in GCMs and applied to the National Center for
Atmospheric Research Community Atmosphere Model version 5 (CAM5) with and
without the stochastic convection cases. Results show that in the standard
CAM5, no obvious differences in the scavenging amount mode are found among
different aerosol types. However, the scavenging amount modes differ in the
Aitken, accumulation and coarse modes, showing around 10–12, 8–9 and 7–8 mm d−1, respectively, over the tropics. As latitude increases poleward, the
scavenging amount mode in each aerosol mode is decreased substantially. The
scavenging amount mode is generally smaller over land than over ocean. With
stochastic convection, the scavenging amount mode for all aerosol species in
each mode is systematically increased, which is the most prominent along the
Intertropical Convergence Zone, exceeding 20 mm d−1 for small particles.
The scavenging amount modes in the two cases are both smaller than
individual rainfall rates associated with the most accumulated rain
(rainfall amount mode), further implying precipitation frequency is more
important than precipitation intensity for aerosol wet removal. The notion
of the scavenging amount mode can be applied to other GCMs to better
understand the relation between rainfall and aerosol wet scavenging, which
is important to better simulate aerosols.
Southern Ocean deep convection in global climate models: A driver for variability of subpolar gyres and Drake Passage transport on decadal timescales
