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1 Development of the deterministic forecast system (June 2006) Martin Miller (Head of Model Division) with input from many colleagues.

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Presentation on theme: "1 Development of the deterministic forecast system (June 2006) Martin Miller (Head of Model Division) with input from many colleagues."— Presentation transcript:

1 1 Development of the deterministic forecast system (June 2006) Martin Miller (Head of Model Division) with input from many colleagues

2 2 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 18 October 2004 – IFS cycle 28r4 5 April 2005 – IFS cycle 29r1 28 June 2005 – IFS cycle 29r2 (examples) Day Anomaly correlation of 500hPa forecasts for Europe Mean from 1 Dec 2004 to 28 June 2005 Cycle 29r2 Cycle 29r1

3 3 Assimilation of rain-affected microwave radiances and improvement of humidity analysis Rain Asm Hurricane Charley Track forecasts from 12 UTC 11 Aug 2004 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 2 ) Comparison of cycle 29r2 e-suite and operations with independent TCWV retrievals from Jason microwave radiometer

4 4 Bias-correction of surface-pressure observations Altamera, Brazil December 2004 April 2005

5 5 Use of Baltic Sea Ice Analysis from SMHI Mean sea-ice concentration 5 - 24 January 2004 NCEP analysis Local analysis

6 6 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

7 7 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

8 8 T799 orog

9 9 T799 grid Globe has 843,490 points (348,528 for the T511 grid) Resolution ~25km

10 10 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). Position of levels and pressure layer thickness of L60 (blue) and L91 (red) L91 L60 0.01hPa 0.1hPa

11 11 Fit to Aircraft data: V-wind in NH extra-tropics

12 12 Fit to Radiosonde Data: U-Wind in the Tropics

13 13 Green numbers: T799L91 better than T511L60, red numbers: T799L91 is worse Statistical significance (t-test) for Z 500hPa scores from 304 forecast Day 1Day 3Day 5Day 7 N Hem AC: RMS: 0.1% 2% 0.2% ---- S Hem AC: RMS: 0.1% 0.2% 0.1% Europe AC: RMS: 0.1% 5% 0.1% - 10%

14 14 00UTC 12 December 2005: Pmsl and 10m windspeed D+3 D+4 D+5 Analysis Operations T799L91

15 15 00UTC 9 January 2005: Pmsl and 10m windspeed D+2 D+3 D+4 Analysis Operations T799L91

16 16 Forecasts of Katrina for 12 UTC, Monday 29 August Operational T511 L60 72h forecast 36h forecast Operational T511 L60 Test T799 L91 Test T799 L91 + + + +

17 17 opsT511 e-suite T799 Hurricane Katrina in operations and e-suite: t+72h

18 18 26 th 00UTC 3.5 days 26 th 12UTC 27 th 00UTC 2.5 days

19 19 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 Remarks

20 20 7 February 2006 – New radiance bias correction Applied statically, but derived from variational scheme to be implemented with cycle 31r1 pressure (hPa) Sonde-bg Control Sonde-bg New bias correction Sonde-an Control Sonde-an New bias correction Temperature (K) N Hem RMS error of 300hPa tropical temperature forecasts New bias correction Control Mean from 8-31 Jan 2006 Day

21 21 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

22 22 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)

23 23 CY31R1: super saturation with respect to ice RH ice 100% 150% RH crit New scheme allows super saturation up to homogeneous nucleation limit in clear sky region But once cloud forms deposition instant: no supersaturation within the cloudy region is allowed.

24 24 Simple ECMWF scheme: comparison to Mozaic aircraft data (from Gierens et al.) New scheme Aircraft data Default

25 25 Impact on relative humidity (RH) climatology 31r1 – 30r1 annual mean difference Largest changes in the tropical upper troposphere

26 26 Analysis, humidity RATIO (new/default)

27 27 CY31R1: New vegetation roughness + turbulent orographic form drag scheme (TOFD) 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 Examples of orographic spectra from 100m data over the USA Measure spectral amplitude from 1 km data. Extrapolate spectrum by making assumption about power law.

28 28 Impact of TOFD + new roughness lengths Smaller drag coefficients: diff stress/wind(level48)^2 Higher 10m wind

29 29 Revised numerics of gust parametrization only (CY31R1) OldNew Without stochastic physics With stochastic physics

30 30 Mean gust averaged over 14 days: gust from 24-36 hour forecasts verifying at 0-12 UTC New (CY31R1) Old (CY30R1) New-Old

31 31 Observed gusts versus model gusts (12 to 24 hour forecasts) New (CY31R1) Old (CY30R1)

32 32 CY31R1: only non-blocked part of subgrid orography excites gravity waves (cutoff mountain) Lott and Miller 1997 Only this height is used to excite gravity waves.

33 33 Impact of cutoff mountain in subgrid orography parametrization 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 Old Error: FC-AN New Diff: FC_new-FC_old

34 34 1d+4d-Var Rain Assimilation Modifications proposed for CY31R1: Inclusion of 10m-wind speed in 1D-Var control vector: x = (t, q, u 10, v 10 ) 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 CY30R2CY31R1

35 35 48-hour Forecast RMSE Difference CY31R1-CY30R2 Relative humidity Temperature >0: CY30R2 better <0: CY31R1 better (August 2005, T511L60)

36 36 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

37 37 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: AMSR-E, CHAMP, COSMIC, FY-2C, METOP ATOVS + …, MET9, MTSAT, SSMIS, TMI

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