Verification of NCEP SFM seasonal climate prediction during 2000-2003

Jae-Kyung E. Schemm

Climate Prediction Center

NCEP/NWS/NOAA

Operational NCEP seasonal climate prediction system(NCEP SFM)

1. Description of AGCM

Dynamics:– Global spectral configuration in T62L28

Model physics:– Relaxed Arakawa-Schubert convection scheme

– M.-D. Chou short wave radiation

– M.-D. Chou long wave radiation

– Original Slingo-type cloud

– Tiedtke shallow convection

– Hong and Pan non-local diffusion

– Alpert, et al. gravity wave drag

– OSU land hydrology model

– Mean smoothed orography

– Leith horizontal diffusion on pressure surface

NCEP seasonal climate prediction system

2. Production Suite

– For each month, 7-month prediction runs of 10 member ensemble initialized in 1979 - 1999 period.

• Initial conditions at 0Z and 12Z of first 5 days of month.

– Observed SST and climatological soil moisture as boundary conditions.

– Model climatology and climatological probability distribution based on the 1979-1999 cases.

– 7-month prediction runs of 20-member ensemble initialized at 0Z and 12Z of last 5-days of previous month and first 5-days of present month.

• Forecast SST from ocean model used as BC.

– Forecast anomaly determined with the model climatology -- model bias removed.

Development in 2002-2003

1. Implementation of the seasonal prediction suite as part of the NWS operational production in December 2001. Data access;

ftp://tgprd.nws.noaa.gov/SL.us008001/ST.opnl/MT.clim_MR.hind

ftp://tgprd.nws.noaa.gov/SL.us008001/ST.opnl/MT.clim_MR.fcst

2. Additional ensemble runs with the constructed analog SST forecast.

3. EMC started working on the next generation coupled model system for seasonal prediction - parallel climate test suite with the operational GFS GCM.

Ref. Websites

http://www.emc.ncep.noaa.gov/cmb/atm_forecast

http://www.cpc.ncep.noaa.gov/schemm/snfcst.html

Anomaly Correlation of SFM Forecast 2m Temperature over US Region (2000-2003)

Anomaly Correlation of SFM Forecast Precipitation over US Region (2000-2003)

Anomaly Correlation of SFM Forecast500 hPa height PNA Region (2000-2003)

Anomaly Correlation of SFM Forecast 500 hPa height NH Ext Region (2000-2003)

Weakness of the current operational production suite

-Model climatology and skill mask from hindcast runs with observed SST.

-Estimate potential predictability.

-Hindcast experiments conducted with forecast SST generated by the constructed analog method (van den Dool and Barnston, 1995).

Anomaly Correlation of Seasonal Precipitation Fcst with Sep. IC’sBC’s with Obs SST (left) and CA Fcst SST (right)

Anomaly Correlation of Seasonal 500 hPa Height Fcst with Sep IC’sBC’s with Obs SST (left) and CA Fcst SST (right)

Summary

• NCEP SFM seasonal predictions evaluated for 2000-2003 in terms of 2m temperature and precipitation over the continental US, and 500hPa height over the NHE sector. All variables exhibit modest skill of ~0.2 in anomaly correlation scores in average over the three year period.

• Seasonal predictability is overestimated when it is based on GCM runs with observed SST as boundary condition. The anomaly correlation of winter season forecast was reduced considerably when forecast SST was utilized.

• Impact less pronounced in surface temperature and precipitation over US. Further improvement in GCM is warranted to resolve the problem. EMC has started testing a fully coupled system with current operational GFS GCM in 2003.