The Development of the NCEP Global Ensemble Forecast System Version 12

Abstract

The Global Ensemble Forecast System (GEFS) is upgraded to version 12, in which the legacy Global Spectral Model (GSM) is replaced by a model with a new dynamical core - the Finite Volume Cubed-Sphere Dynamical Core (FV3). Extensive tests were performed to determine the optimal model and ensemble configuration. The new GEFS has cubed-sphere grids with a horizontal resolution of about 25-km and an increased ensemble size from 20 to 30. It extends the forecast length from 16 days to 35 days to support subseasonal forecasts. The stochastic total tendency perturbation (STTP) scheme is replaced by two model uncertainty schemes: the Stochastically Perturbed Physics Tendencies (SPPT) scheme and Stochastic Kinetic Energy Backscatter (SKEB) scheme. Forecast verification is performed on a period of more than two years of retrospective runs. The results show that the upgraded GEFS outperforms the operational-at-the-time version by all measures included in the GEFS verification package. The new system has a better ensemble error-spread relationship, significantly improved skills in large-scale environment forecasts, precipitation probability forecasts over CONUS, tropical cyclone track and intensity forecasts, and significantly reduced 2-m temperature biases over Northern America. GEFSv12 was implemented on September 23, 2020.

Quantify the Coupled GEFS Forecast Uncertainty for the Weather and Subseasonal Prediction

“…The GEFSv12 is the first UFS implementation with a reforecast to support weather‐to‐subseasonal probabilistic prediction and hydrology applications. The GEFSv12 reforecast was using the same model configurations including dynamics and physical parameterizations as the operational GEFSv12 (Zhou et al., 2022). The stochastic schemes are using SKEB with an amplitude of 0.6 and SPPT with 5‐scales (total sigma = 0.95) of each coefficient as (0.8; 0.4; 0.2; 0.08; 0.04) (Zhou et al., 2022).…”

Statistical Evaluation of the Temperature Forecast Error in the Lower‐Level Troposphere on Short‐Range Timescales Induced by Aerosol Variability

“…We applied the reforecast data set provided by the NCEP Global Ensemble Forecast System were recently updated to version 12 (GEFSv12; Zhou et al, 2022). The forecast skill of the geopotential height at 500 hPa of GEFSv12 is comparable to that of the operational GFS, especially up to a lead time of 5 days (Zhou et al, 2019).…”

Evaluation of multiple bias correction methods with different satellite rainfall products in the Main Beles Watershed, Upper Blue Nile (Abbay) Basin, Ethiopia

“…The scenario evaluated will include estimations of changes in the climate of the Earth's system as a result of these variables. The current CFSR will be extended in the future as a real-time operating product from the research data archive (RDA) summary on CFSR (Parshotam 2019;Kanwal et al 2022;Zhou et al 2022). CFSR data are available at https://globalweather.tamu.edu/.…”