Subseasonal Forecasting
with an Icosahedral, Vertically Quasi-Lagrangian Coupled Model:
Systematic Errors and Deterministic/Probabilistic Forecast Skill
Shan Sun
ESRL
23 Mar, Noon, in 2155
Abstract:
The FIM-iHYCOM coupled model has been running real-time for NOAA’s
Subseasonal Experiment (SubX) since July 2017. It couples the
atmospheric Flow-following finite volume Icosahedral Model (FIM) to an
icosahedral version of the Hybrid Coordinate Ocean Model (HYCOM). This
coupled model is unique in terms of its grid structure: in the
horizontal, both atmospheric and ocean model operate on a common
icosahedral mesh, eliminating the need for a flux interpolator; in the
vertical, both models use an adaptive ALE (Arbitrary
Lagrangian-Eulerian)coordinate. FIM uses GFS physics package, with an
option of Grell-Freitas scale aware convective parameterization.
For SubX, FIM-iHYCOM initializes four time-lagged ensemble members
around each Wednesday, and integrates for 32 days. Preliminary results
from the multi-year hindcasts indicate that both deterministic and
probabilistic forecast skill of week-3-4 from FIM-iHYCOM are comparable
to those of the operational model CFSv2. Moreover, we will discuss
model skills in simulating Madden-Julian Oscillation index, blocking
frequency and sudden stratospheric warming events.