Speaker: Jui-Lin Frank Li (NTU)
Time & Venue: 14:20, S101
Title: How Falling-Ice Radiative Effects Shape Tropical Pacific Dynamics, ENSO, and Sea Level: A Satellite and Model-Based Assessment
Abstract:
Falling ice particles — including ice crystals, snow, and other frozen hydrometeors — exert significant but long-underappreciated radiative effects on Earth’s energy budget. In contemporary general circulation models (GCMs), the treatment of ice-phase microphysics and their associated radiative properties remains a leading source of systematic bias, with downstream consequences for simulated tropical circulation, sea surface temperature (SST) variability, sea surface height (SSH) anomalies, and El Niño–Southern Oscillation (ENSO). This talk synthesizes findings from a series of studies that used complementary satellite observations — including CloudSat, CALIPSO, MODIS, AIRS, Jason-1/2, QuikSCAT, and CERES — alongside CMIP5 and CMIP6 multi-model ensembles to diagnose how falling ice radiative effects (FIRE) propagate through the coupled climate system. We demonstrate that FIRE warm the lower troposphere and cool the surface in the tropics, modulating surface wind stress, influence thermocline depth, and SSH anomalies in ways that bias the representation of Central-Pacific (CP) El Niño in models. We further show that CMIP3/CMIP5/CMIP6 models exhibit systematic shortwave and longwave radiation biases over tropical and subtropical oceans attributable to the parameterization of frozen hydrometeor optical properties, and that correcting or constraining these biases substantially alters projected Southern Ocean sea ice trajectories and CP-ENSO statistics under global warming. Taken together, these results highlight FIRE as a critical but underexplored physical mechanism linking cloud microphysics to large-scale ocean–atmosphere variability, with implications for climate projection fidelity.