Publication Abstracts

Sun et al. 2018

Sun, S., R. Bleck, S.G. Benjamin, B.W. Green, and G.A. Grell, 2018: Subseasonal forecasting with an icosahedral, vertically quasi-Lagrangian coupled model. Part I: Model overview and evaluation of systematic errors. Mon. Weather Rev., 146, no. 5, 1601-1617, doi:10.1175/MWR-D-18-0006.1.

The atmospheric hydrostatic Flow-Following Icosahedral Model (FIM), developed for medium-range weather prediction, provides a unique three-dimensional grid structure — a quasi-uniform icosahedral horizontal grid and an adaptive quasi-Lagrangian vertical coordinate. To extend the FIM framework to subseasonal time scales, an icosahedral-grid rendition of the Hybrid Coordinate Ocean Model (iHYCOM) was developed and coupled to FIM. By sharing a common horizontal mesh, air-sea fluxes between the two models are conserved locally and globally. Both models use similar adaptive hybrid vertical coordinates. Another unique aspect of the coupled model (referred to as FIM-iHYCOM) is the use of the Grell-Freitas scale-aware convective scheme in the atmosphere. A multiyear retrospective study is necessary to demonstrate the potential usefulness and allow for immediate bias correction of a subseasonal prediction model. In these two articles, results are shown based on a 16-yr period of hindcasts from FIM-iHYCOM, which has been providing real-time forecasts out to a lead time of 4 weeks for NOAA's Subseasonal Experiment (SubX) starting July 2017. Part I provides an overview of FIM-iHYCOM and compares its systematic errors at subseasonal time scales to those of NOAA's operational Climate Forecast System version 2 (CFSv2). Part II uses bias-corrected hindcasts to assess both deterministic and probabilistic subseasonal skill of FIM-iHYCOM. FIM-iHYCOM has smaller biases than CFSv2 for some fields (including precipitation) and comparable biases for other fields (including sea surface temperature). FIM-iHYCOM also has less drift in bias between weeks 1 and 4 than CFSv2. The unique grid structure and physics suite of FIM-iHYCOM is expected to add diversity to multimodel ensemble forecasts at subseasonal time scales in SubX.

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BibTeX Citation

@article{su06100q,
  author={Sun, S. and Bleck, R. and Benjamin, S. G. and Green, B. W. and Grell, G. A.},
  title={Subseasonal forecasting with an icosahedral, vertically quasi-Lagrangian coupled model. Part I: Model overview and evaluation of systematic errors},
  year={2018},
  journal={Mon. Weather Rev.},
  volume={146},
  number={5},
  pages={1601--1617},
  doi={10.1175/MWR-D-18-0006.1},
}

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RIS Citation

TY  - JOUR
ID  - su06100q
AU  - Sun, S.
AU  - Bleck, R.
AU  - Benjamin, S. G.
AU  - Green, B. W.
AU  - Grell, G. A.
PY  - 2018
TI  - Subseasonal forecasting with an icosahedral, vertically quasi-Lagrangian coupled model. Part I: Model overview and evaluation of systematic errors
JA  - Mon. Weather Rev.
VL  - 146
IS  - 5
SP  - 1601
EP  - 1617
DO  - 10.1175/MWR-D-18-0006.1
ER  -

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