The Response of Tropical Cyclone Inner Core and Outer Rainband
Precipitation to Warming in Idealized Convection-Permitting WRF
Abstract
Global mean and extreme tropical cyclone (TC) precipitation has been
increasing and is expected to continue to increase into the future due
to climate change. While climate models project that precipitation will
increase mainly in the TC inner core, data from satellite observations
show a decrease in mean TC inner core precipitation over time and an
increase in the outer rainbands since 1998. This work uses
convection-permitting Weather Research and Forecasting (WRF) model
simulations to investigate if this discrepancy between models and
observations is related to coarse model resolutions used in past
studies. The simulations are idealized, with single TCs initialized from
weak vortices over domain-constant sea surface temperatures (SSTs). In
these simulations, TC intensity and inner core precipitation greatly
increase with SST warming while outer rainband precipitation increases
slightly. More of the inner core is occupied by convection more
frequently in the warmer simulations, while the convective activity
remains constant with warming in the TC outer region. Mixing ratios of
hydrometeors and cloud ice increase with warming in both the inner core
and outer rainbands, while the TCs’ vertical circulations deepen and
mean upward velocities strengthen. Results suggest that even
convection-permitting models do not capture a decrease in TC inner core
precipitation with warming, albeit in an idealized model set-up. This
work demonstrates how analysis of three-dimensional storm mode
structures can provide insight into processes that change TC
precipitation in different regions of the storm, and future work will
include applying this analysis to more realistic convection-permitting
simulations.