Tropical Oceanic Mesoscale Cold Pools in a High-Resolution Global
Cloud-Resolving Model from DYAMOND Initiative
Abstract
In recent years, global kilometer-scale convection-permitting models
have shown promising results in producing realistic convection and
precipitation. Cold pools, which can be represented by km-scale models,
are identified as one of the significant mesoscale processes responsible
for modulating the life cycle of mesoscale organized convection.
However, there is still a lack of understanding about cold pool
properties across the spatio-temporal scales, as well as their
representation in models. In this study, a 2.5 km global Icosahedral
Nonhydrostatic (ICON) model simulation run for 40 days (06 UTC 01 Aug -
23 UTC 10 Sep 2016) from the Dynamics of the Atmospheric general
circulation Modeled On Non-hydrostatic Domains (DYAMOND) initiative is
used to identify thermal cold pools (using Tv)
over the tropical oceans. The diurnal cycle of simulated thermal cold
pools is compared against NASA’s RapidScat-observed gradient feature
(GF) frequency and IMERG precipitation. ICON and IMERG exhibit morning
peaks in cold pool activity similar to RapidScat GF frequency but miss
the afternoon peak. Advanced Scatterometer (ASCAT) and RapidScat GF
spatial climatology is also compared to ICON cold pools, where ICON
shows more cold pools over the Indo-Pacific and western Atlantic basins.
Random forest regression is applied to identify critical
environmental properties with column water vapor found to be most
important for controlling cold pool properties. Regional differences
between cold pool properties are explored, where easterly waves dominate
the eastern Pacific and Atlantic cold pool activity. The western Pacific
and the Indian Ocean cold pools are controlled by local mesoscale
forcing and intraseasonal oscillations.