REGIONAL CLIMATE PREDICTION BY NCEP REGIONAL SPECTRAL MODEL

Jun Wang and Hann-Ming Henry JuangEnvironmental Modeling Center, NCEP, Washington DC

Introduction

NCEP Regional Spectral Model (RSM) nested in Global Forecast System (GFS) has been used for regional climate prediction. A three years experiment was conducted to explore the capability of RSM model on seasonal forecast.

Experiment Setup•Oct 2002 – Sept 2004

Model: Nested GSM+RSM GSM: SFM T62L28 RSM: RSM97 60km, 28 levels Domain: US continental Hindcast 4 month integration for every month for 1982-2004 Initial Condition: the first day of current month Boundary Condition: observational SST Forecast A 5-member ensemble of 4 month integration for every month from Oct, 2004 –current Initial Condition: 00Z of the last two days of previous month and the first three days of current month Boundary Condition: Forecasted SST from operational

• Sep 2004 -- Current Model: Nested GSM+RSM GSM: CFS2003 T62L28 RSM: RSM2004 50km, 28 levels Domain: US continental Hindcast

A 3-member ensemble of 7 month integration for every month for 1982-2004

Initial Condition: Last day of previous month and the first two days of current month

Boundary Condition: Forecasted SST from CFS

Forecast

A 10-member ensemble of 7 month integration for every month from: Oct. 2004 –current

Initial Condition: 00Z and 12Z of the last two days of previous month and the first three days of current month

Boundary Condition: Forecasted SST from CFS

Results

Effect of Initial condition

System Error

Effect of Diurnal cycle

Summary

The forecast of Regional Spectral model of consist with that of global model solution, but with more realistic details. In the experiment year Oct 2002 to Sep 2004, RSM has better score than SFM in summer time. From Sep 2004, RSM has better score than CFS on rain forecast.