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Development of the deterministic forecast system (June 2006). Martin Miller (Head of Model Division) with input from many colleagues. Operational changes from June 2004 up to June 2005 (the last User Meeting). 29 June 2004 – Early Delivery System 28 September 2004 – IFS cycle 28r3

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development of the deterministic forecast system june 2006
Development of the deterministic forecast system (June 2006)

Martin Miller

(Head of Model Division)

with input from many colleagues

operational changes from june 2004 up to june 2005 the last user meeting
Operational changesfrom June 2004 up to June 2005(the last User Meeting)
  • 29 June 2004 – Early Delivery System
  • 28 September 2004 – IFS cycle 28r3
  • 18 October 2004 – IFS cycle 28r4
  • 5 April 2005 – IFS cycle 29r1
  • 28 June 2005 – IFS cycle 29r2 (examples)

Anomaly correlation of 500hPa forecasts for Europe

Mean from 1 Dec 2004 to 28 June 2005

Cycle 29r2

Cycle 29r1



Hurricane Charley

Track forecasts from 12 UTC 11 Aug 2004

Comparison of cycle 29r2

e-suite and operations

with independent TCWV retrievals from Jason

microwave radiometer

e-suite ops

Global 1.74 1.90

N. Hemisphere 1.63 1.71

Tropics 2.12 2.43

S. Hemisphere 1.53 1.62

N. Atlantic 1.63 1.69

N. Pacific 1.57 1.69

Rain Asm

Assimilation of rain-affected microwave radiances

and improvement of humidity analysis

bias correction of surface pressure observations
Bias-correction of surface-pressure observations

December 2004

April 2005

Altamera, Brazil

use of baltic sea ice analysis from smhi

Use of Baltic Sea Ice Analysis from SMHI

Mean sea-ice concentration 5 - 24 January 2004

NCEP analysis

Local analysis

also included
Also included :
  • Refinements to use of ATOVS and AIRS
  • Improved use of TEMP and SYNOP humidity observations
  • Lower surface-pressure observation errors for automatic stations
  • Use of Meteosat-8 (MSG) winds
  • Statistics for Wavelet Jb from new ensemble data assimilation
  • Small revisions to surface, convection and cloud schemes
  • Better vertical diffusion in first minimization of 4D-Var
1 february 2006 ifs cycle 30r1
1 February 2006 – IFS cycle 30r1
  • T799 horizontal resolution for deterministic forecast
  • 4D-Var increments at T255 (30min time step)

- Use of grid-point humidity and ozone

- Revised ozone chemistry

  • 91-level vertical resolution
  • Changes to the wave model
    • Grid spacing reduced from 0.5° to 0.36°
    • Use of Jason altimeter wave height data and ENVISAT ASAR spectra in the wave model assimilation
  • T399 L62 resolution for EPS
    • Wave model grid unchanged at 1°, but number of frequencies increased from 25 to 30, and number of directions from 12 to 24
vertical resolution increase



Position of levels and pressure layer thickness of L60 (blue) and L91 (red)



Vertical Resolution Increase
  • The number of vertical levels for analysis and deterministic model

increased from 60 to 91.

  • Largest resolution increase near the tropopause
  • Model top raised from 0.1hPa (~65km) to 0.01hPa (~80km).

Fit to Aircraft data:

V-wind in NH extra-tropics

statistical significance t test for z 500hpa scores from 304 forecast
Statistical significance (t-test) for Z 500hPa scores from 304 forecast

Green numbers: T799L91 better than T511L60,red numbers: T799L91 is worse

00utc 12 december 2005 pmsl and 10m windspeed
00UTC 12 December 2005: Pmsl and 10m windspeed











00utc 9 january 2005 pmsl and 10m windspeed
00UTC 9 January 2005: Pmsl and 10m windspeed











forecasts of katrina for 12 utc monday 29 august
Forecasts of Katrina for 12 UTC, Monday 29 August



36h forecast


T511 L60


T799 L91



72h forecast


T511 L60


T799 L91


26th 00UTC 3.5 days

26th 12UTC

27th 00UTC 2.5 days


This upgraded forecasting system provides:

  • more accurate analyses and forecasts leading to better medium-range forecast guidance from both the deterministic and ensemble prediction systems
  • improved input to limited area forecasting in the Member States
  • more skilful forecasts of most types of severe weather
  • a better (more accurate) system on which to base research and development to further the expectations of the ECMWF longer-term strategy
7 february 2006 new radiance bias correction
7 February 2006 – New radiance bias correction

Applied statically, but derived from variational scheme to be implemented with cycle 31r1

Sonde-bg Control

Sonde-bg New bias correction

Sonde-an Control

Sonde-an New bias correction

RMS error of 300hPa tropical temperature forecasts


pressure (hPa)

New bias correction

N Hem

Mean from 8-31 Jan 2006


Temperature (K)

coming next ifs cycle 31r1 aug 2006
Coming next – IFS cycle 31r1 (Aug 2006)
  • Variational radiance bias correction
  • Thinning of low-level AMDAR data
  • Revisions to the 1D and 4D-Var rain assimilation
  • Improved treatment of ice sedimentation, auto-conversion to snow in cloud scheme and super-saturation with respect to ice
  • Implicit treatment of convective transports
ifs cycle 31r1 continued aug 2006
IFS cycle 31r1 continued (Aug 2006)
  • Introduction of turbulent orographic drag scheme
  • Includes changes for EPS extension to day 15
    • T255 perturbed forecasts from day 10 to day 15
    • T399/255 control to day 10/15
    • Also uniform T399 and T255 controls to day 15
  • To be used in version 3 of Seasonal Forecasting System
  • Also for the Interim reanalysis (1989 onwards)
simple ecmwf scheme comparison to mozaic aircraft data from gierens et al
Simple ECMWF scheme: comparison to Mozaic aircraft data(from Gierens et al.)

Aircraft data

New scheme


impact on relative humidity rh climatology
Impact on relative humidity (RH) climatology

31r1 – 30r1 annual mean difference

Largest changes in the tropical upper troposphere


CY31R1: New vegetation roughness + turbulent orographic form drag scheme (TOFD)

Examples of orographic spectra from 100m data over the USA

  • Vegetation roughness from correspondence table linked to dominant land use type (Mahfouf et al. 1995)
  • Scales of interest are below 5 km
  • Use most recent 1 km orographic data
  • Wood and Mason (1993) parametrization for surface drag
  • Drag distribution over model levels rather than effective roughness length concept (Wood, Brown and Hewer, 2001)
  • Parametrize orographic scales from 5 km to the smallest scales as an integral over an empirical orographic spectrum (Beljaars et al. 2004

Measure spectral amplitude from 1 km data.

Extrapolate spectrum by making assumption about power law.

impact of tofd new roughness lengths
Impact of TOFD + new roughness lengths

Smaller drag coefficients: diff stress/wind(level48)^2

Higher 10m wind

revised numerics of gust parametrization only cy31r1
Revised numerics of gust parametrization only (CY31R1)



Without stochastic physics

With stochastic physics

mean gust averaged over 14 days gust from 24 36 hour forecasts verifying at 0 12 utc

Old (CY30R1)

Mean gust averaged over 14 days: gust from 24-36 hour forecasts verifying at 0-12 UTC


New (CY31R1)

cy31r1 only non blocked part of subgrid orography excites gravity waves cutoff mountain
CY31R1: only non-blocked part of subgrid orography excites gravity waves (cutoff mountain)

Only this height is used to excite gravity waves.

Lott and Miller 1997

impact of cutoff mountain in subgrid orography parametrization
Impact of cutoff mountain in subgrid orography parametrization

Error: FC-AN


T511 average vertically integrated zonal wind error from 96h CY29R1 forecasts from 12Z on each day of January 2005 using the new turbulent orographic drag scheme and cutoff mountain.



Error: FC-AN



1d+4d-Var Rain Assimilation Modifications proposed for CY31R1:

  • Inclusion of 10m-wind speed in 1D-Var control vector: x = (t, q, u10, v10)
  • Revised q/c and replacement of ESSL routines for (B) Eigenvector calculations
  • DMSP satellite specific bias correction; more predictors (TCWV, SST, SWS, RWP)
  • Screening of areas with excessive frozen precipitation (mainly SH)

1D-Var Performance Mean TCWV Increments Mean TCWV Increments

CY30R2 CY31R1


48-hour Forecast RMSE Difference CY31R1-CY30R2

Relative humidity


>0: CY30R2 better

<0: CY31R1 better

(August 2005, T511L60)

also planned for later in 2006
Also planned for later in 2006:
  • Use of surface albedo fields from MODIS
  • Use of high-resolution NCEP SST fields
  • Refinements to stratospheric analysis
  • Recalibrated radiosonde temperature bias corrections
  • Unified medium-range/monthly EPS
and possibly at the end of 2006
And possibly at the end of 2006:
  • 4D-Var changes:
    • 3rd inner loop
    • revised trajectory interpolation
    • revised data usage, including modified Var QC
    • new cloud and convection schemes in minimization
  • Upgrade fast radiative transfer to RTTOV-9
  • Change model short-wave radiation scheme to RRTM-SW
  • Upgrades to ocean wave advection and assimilation

And over course of the year:

  • Monitoring and later assimilation of data from: