# Presentation: 828357

## NCEP Numerical Forecast Systems2003-2009

- Stephen Lord, Zoltan Toth,
- Geoff DiMego & Hua-Lu Pan
- Bob Kistler for OWPDT,  7/15/2003
- NCEP/EMC

## Overview

- GFS performance standing
- Historically
- with respect other centers
- Computing
- Numerical Forecast System Development
- Focus on GFS Issues

##    wwwt.emc.ncep.noaa.gov/gmb/bkistler/scores/CDAS_vs_OPNL.gif

-    wwwt.emc.ncep.noaa.gov/gmb/bkistler/scores/CDAS_vs_OPNL.gif

## http://wwwt.emc.ncep.noaa.gov/gmb/STATS/html/aczhist6.html

## GFS change log

- Sept-Oct 2002: Name changes: The AVN will be referred to as the               Global Forecast System model (GFS).
- 10/29/02 12Z
- Resolution change   old: T170L42 to 180h, T62L28 to 384h   new: T254L64 to 84h, T170L42 to 180h, T126L28 to 384h
- Analysis and observation changes: background error recomputed, AMSU-A channels 12 and 13 from NOAA-15 and NOAA-16 and HIRS from NOAA-16 used, METAR surface pressure observations used, divergence tendency constraint in tropics turned off.
- 03/11/03 12Z: NOAA 17 1B radiances assimilated, NOAA-16 AMSU-A radiances restored, QuikSCAT winds superobbed at 0.5 degrees

## NCEP Central Computer System (CCS)Delivered September 2002Operational May 12, 2003

- Three year initial base period
- Two subsequent three year options
- Each option has upgrade (change every 18 months)
- 70% for weather + 30% for climate
- Formerly 90% weather + 10% climate
- E.g. overall 2.5x increase is
- 1.9 Weather
- 6.5 Climate (Week2 to Seasonal)

## 
Each 3 year period contains an upgrade
Total of 6 major increases ’02-’10
    2.5x, 8x, 12x, 18x, 24x, 48x  current power  
Consistent with Moore’s Law 
		(doubled capability every 1.5 years)

- Each 3 year period contains an upgrade
- Total of 6 major increases ’02-’10
-     2.5x, 8x, 12x, 18x, 24x, 48x  current power
- Consistent with Moore’s Law
- 		(doubled capability every 1.5 years)

**NCEP Computing, cont.**

## Central Computer System (CCS)

| Phase / 
Date /
Increase | Processors
Clock Speed | Memory
 | Disk Space | Tape Storage
 |
| --- | --- | --- | --- | --- |
| Current | 2432 375MHz | 1208 Gb | 30 TB | 200 TB |
| Phase I/
May 2003
2.5 x  | 1408 1.3GHz | 1408 Gb | 42 TB | 1250 TB |
| Phase II/
June 2004
8.0 x | 2752 1.8+1.3GHz | 2752 Gb | 84 TB | 2500 TB |

## Slide 9

## Four Equal Cycles per Day

**Four Equal Cycles per Day**

## Model

- Data
- Assim

- Ensembles

## Highlights – Global System

- 2004
- Tracers (e.g. aerosols, for AQ, data assimilation)
- Improved surface physics, dissipation
- Improved long wave radiation
- AIRS data
- Increased ensemble resolution, membership
- 2005
- Improved analysis technology (background errors, 3D-VAR technique)
- Increase horizontal resolution (45 km)
- 2006
- Improved microphysics
- Absorption, scattering in satellite radiative transfer
- Increased ensemble resolution

## Ensemble Development Plans

- Ensemble must capture uncertainties associated with:
- Synoptic situation (chaos)
- Model bias
- Initial conditions
- Ensembles can be used to:
- Provide flow dependent probabilistic guidance
- Estimate forecast uncertainty

## Ensemble Development Plans (cont)

- Initial perturbations
- Rescale bred vectors by Ensemble Transform Kalman Filter (ETKF)
- Include effect of model errors
- Perturb surface model & conditions
- Multiple physics
- Perturb physics parameters within range of uncertainty
- Multi-model ensembles
- WRF (NCEP, NCAR, FNMOC (?), AFWA (?)
- Global (NCEP, ECMWF, MSC, FNMOC)

## GFS and AWC

- +/- 2 PV levels in 2002
- 3hr 25mb 0.5x0.5 lat/lon grids in 2003
- 3hr > 1hr 2004 ?
- Ellrod index ...
- MCC’s perpetuated (HPC complaint)
- Model Bias

## F120 12Z May 7, 2000

- F126 12Z May 7, 2000

- F132 12Z May 7, 2000

- F138 12Z May 7, 2000

## Slide 17

## Slide 18

## Slide 19

## Slide 20

## RRTM

- Rapid Radiative Transfer Model (LW)
- Developed at AER, Inc., used at ECMWF
- L64 runs 2x current LW
- Will permit more frequent calls, every 2hr vs 3hr
- Includes N2O, methane, up to 4 CFC’s, etc.
- Advanced water vapor absorption
- Consistent with diagnostic Hi Mid Lo clouds
- Testing > increases cold bias in lower stratosphere
- Problematic for data assimilation

## RRTM testing

## Problem:Relative AC Score drop-off

- Dominated by planetary scale waves 1-3

## Slide 24

## Slide 25

## Slide 26

## NH

- AC .843
- RMS 52.5m

- AC .628
- RMS 52.5m