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Toward the Improvement of Subseasonal Prediction in the National Centers for Environmental Prediction Global Ensemble Forecast System
Author(s) -
Zhu Yuejian,
Zhou Xiaqiong,
Li Wei,
Hou Dingchen,
Melhauser Christopher,
Sinsky Eric,
Peña Malaquias,
Fu Bing,
Guan Hong,
Kolczynski Walter,
Wobus Richard,
Tallapragada Vijay
Publication year - 2018
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2018jd028506
Subject(s) - predictability , madden–julian oscillation , climatology , forecast skill , extratropical cyclone , environmental science , meteorology , geopotential height , quantitative precipitation forecast , northern hemisphere , sea surface temperature , anomaly (physics) , precipitation , global forecast system , geopotential , forecast period , convection , numerical weather prediction , mathematics , statistics , geography , geology , cash flow , physics , accounting , cash flow statement , condensed matter physics , business
In order to provide ensemble‐based subseasonal (weeks 3 and 4) forecasts to support the operational mission of the Climate Prediction Center, National Centers for Environmental Prediction, experiments have been designed through the Subseasonal Experiment (SubX) project to investigate the predictability in both tropical and extratropical regions. The control experiment simply extends the current operational Global Ensemble Forecast System (GEFS; version 11) from 16 to 35 days. In addition to the control, the parallel experiments will be mainly designed to focus on three areas: (1) improving model uncertainty representation for the tropics through stochastic physical perturbations; (2) considering the impact of the ocean by using a two‐tiered sea surface temperature approach; and (3) testing a new scale‐aware convection scheme to improve the model physics for tropical convection and Madden‐Julian Oscillation (MJO) forecasts. All experiments are initialized every 5 days at 0000 UTC during the period of May 2014–May 2016 (25 months). In the tropics, MJO forecast skill has been improved from an average of 12.5 days (control) to nearly 22 days by combining all three modifications to GEFS. In the extratropics, the ensemble mean anomaly correlation of 500‐hPa geopotential height improved over weeks 3 and 4. In addition, the Continuous Ranked Probability Score (of the Northern Hemisphere raw surface temperature (land only) is improved as well. A similar result is found in the Contiguous United States precipitation, although forecast skill is extremely low. Our results imply that calibration may be important and necessary for surface temperature and precipitation forecast for the subseasonal timescale due to the large systematic model errors.