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Research Progress Report

2007 - 2008

ECMWF

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Impact of forecast system upgrades2008

Nov 6th 2007 IFS Cycle 32r3 (partly discussed last year)

Jun 3rd 2008 IFS Cycle 33r1

Sept 30th 2008 IFS Cycle 35r1

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Nov 6th 2007 IFS cycle 32r3

• Revision of the convection scheme, new formulation of convective

entrainment and relaxation time scale

• Reduction of vertical diffusion in inversions and free atmosphere

• New soil hydrology/runoff (HTESSEL)

• New radio-sonde temperature and humidity bias correction

• Increased amount of radio occultation data from COSMIC

• Assimilation of microwave AMSR-E, TMI and SSMIS window

channels

• Assimilation of ozone SBUV from NOAA-17 and NOAA-18.

• Reduce of initial perturbation amplitude for EPS by 30%, use new

moist physics package in computation of targeted tropical cyclone

singular vectors.

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Normalized Anom Corr diffs

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Tropical Forecast Biases Precipitation against GPCP for different cycles: from 15 year 5 months integrations for 1990-2005.

c 32r2 d 32r3

b 31r1a

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More realistic model activity calculated from T799 deterministic forecasts against own Analysis

Cy32r3 significantly increases the level of activity in midlatitudes and Tropics

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observation(for high pressure days over central Europe (last four winters))

DJF2004/558 cases

DJF2005/660 cases

DJF2007/869 cases

DJF2006/752 cases

ED

MF

PBL

M-O

diffu

sion

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H-TESSEL The revised hydrology includes spatial variability related to

topography (runoff) and soil texture (drainage)

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Improved soil moisture and evaporation

SEBEX (Savannah, Sandy soil)

BERMS (Boreal Forest)

HTESSEL improves soil moisture and evaporation with respect to TESSELin dry climates and leads to a better represented soil moisture inter-annual variability in continental climate

HTESSEL improves soil moisture and evaporation with respect to TESSELin dry climates and leads to a better represented soil moisture inter-annual variability in continental climate

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Feb 3rd 2008 IFS cycle 33r1

• Improved moist physics in tangent linear/adjoint of 4D-Var.

• Physics: Retuned entrainment in convection scheme. Bugfix to

scaling of freezing term in convection scheme. Additional shear

term in diffusion coefficient of vertical diffusion. Increased turbulent

orographic form drag. Fix for soil temperature analysis in areas with

100% snow cover.

• Modified post-processing of 2m T and q.

• Active assimilation of AMSR-E and TMI rainy radiances.

• Use of 4 wind solutions for QuikSCAT.

• Extended coverage and increased resolution of limited area wave

model.

• Improved shallow water physics and modified advection for ocean

wave model.

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enhanced orographic form drag

zonal drag[m2/s2]

RMS wind 850hPa[m/s]

33r1 e-suiteFeb-May 2008

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Sept 30th 2008 IFS cycle 35r1 (aka 33r2)

OSTIA sea surface temperature and sea ice analysis

Conserving interpolation scheme for trajectory

New VARBC bias predictors to allow the correction of IR shortwave channels affected by solar effects

Cleaner cold start of AMSUA channel 14

New physics for melting of falling snow

Increased albedo of permanent snow cover

Cool skin/warm layer SST parametrization

Revised linear physics

Add convective contribution to wind gusts in post-processing

Monitoring of MERIS data

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Interesting improvement of the model climate due to increase of Greenland and Antarctica albedo (from 0.75 to 0.8) (CY33R2)

CY33R1

Rev Snow

ERA-I

ERA-I

Long integrations (13-months) evaluated against several datasets indicate a consistent improvement (RMSE reduction)

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Equitable threat score for European precipitation against SYNOP data

Curves show 12 month running mean of seasonal values

Calendar Years

1 day per 7 years

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Large-scale eg MJO

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Tropical Cyclone Intensity Error(mean of 365 days ending at 15 August)

-5

0

5

10

15

20

25

30

0 12 24 36 48 60 72 84 96 108 120

forecast step (hours)

core

pre

ssu

re (

hP

a)

2005

2006

2007

2008

ECMWF

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Simulated Meteosat imagery

T799 36h forecast from 20080525

(Bechtold 2008)

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Numerical Aspects Continuing optimization of the IFS (about 8% gained),

prepIFS, and various technical tools

In addition a more ambitious project to examine scalability of the IFS on ca 25,000 PEs has started

Continuing tests of the ALADIN non-hydrostatic dynamical core, in cooperation with Meteo-France More stable version developed, and alternative systems under analysis

Cost is 25 to 70% higher than hydrostatic version, more efficient version under study

Results and scores essentially identical for H and NH in the troposphere

In the stratosphere, NH results still inferior, due to lack of finite elements in NH (under development)

NH system under test in a great diversity of configurations (acoustic waves, mountain flows, convective flows, planetary waves)

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The new “5-prognostic” cloud scheme

WATER VAPOUR

CLOUDLiquid/Ice

PRECIP Rain/Snow

Evaporation

Autoconversion

Evaporatio

n

Condensation

CLOUD FRACTION CLOUD

FRACTION

Current Cloud Scheme New Cloud Scheme

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Model Ice Water Path (IWP) (1 year climate)

New 5 prognostic cloud microphysicsIce vs. Snow

CloudSat 1 year climatology

Current scheme with diagnostic snow

New scheme with prognostic snow

Observed Ice Water Path (IWP)

g m-2

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Improvements in linear physics

Longwave radiation: TL/AD code has been developed and will replace soon the neural network approach

Allows more flexibility and variable trace gases

Several improvements in vertical diffusion

Mixed layer depth, fluctuations of diffusion coefficients, adapt to all changes in the NL model

Several improvements in convection

Much closer to NL code, important for rain assimilation

TL/AD of surface processes in development

Lake model (FLAKE) introduced in collaboration with Univ. Lisbonne and under testing, significant impact on surface evaporation expected

H-TESSEL run-off integrated to produce river discharges (TRIP model). Verifications against GRDC data allow to track problems.This module may be re-used by EC-Earth to couple river run-off and ocean salinity.

Representation of wind gusts under convection improved (problem signalled by DWD in May 2008)

Excessive snowfall in localized events during winter 2007/2008: problem identified (depth of the melting layer) and cured in cycle 35r1

As part of the work on assimilation of ground-based radar rainfall, a climatology of ducts and super-refraction has been produced , see www.ecmwf.int/products/forecasts/d/inspect/catalog/research/physics/ducting

Other on-going work on physics

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Ocean waves

Excellent verifications of the maximum wave heights

Improvements in use of Quikscat (4 ambiguous solutions instead of 2, and new data stream from JPL with better quality control)

Monitoring of Jason-2 observations shows excellent quality

Offline experiments show positive impact of currents analyzed by Nansen Centre and Mercator-Ocean on wave heights simulations

Fully coupled use of currents, waves, and winds in IFS shows compensation by small changes in the wind fields (to keep comparable momentum fluxes) This influences the atmospheric forecasts and will require retuning of

some aspects of the physics

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Limited area model (hindcast at 10km resolution): Hs difference (current – reference)

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20°N 20°N

30°N30°N

40°N 40°N

90°W

90°W 80°W

80°W 70°W

70°WAnalysed wave height difference: currents (f05j) - no currents (ezy4)

ECMWF Analysis VT:Saturday 3 November 2007 00UTC Surface: **Significant wave height

-1.05

-0.9

-0.75

-0.6

-0.45

-0.3

-0.15

-0.010.01

0.16

0.31

0.46

0.61

0.76

0.91

1.05

snapshot

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Average difference in surface wind

Current in wind direction:lower stress,but stronger surface wind

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Data Assimilation The Ensemble Data Assimilation system is almost ready

for operational implementation

Initial configuration: 10 members+1 control

Incremental 4D-Var with T399 outer loops, T159 inner loops

Perturbed observations, spectral stochastic backscatter – benefits also from more active model since 32r3

Only short forecasts to provide a background for next cycle.

Spread is still a bit small, but impact on the EPS is positive, especially in the tropics. We will also learn from this initial operational configuration

Work will continue to base the deterministic assimilation on flow dependent background error variances computed from the EnDA. Benefits for severe weather forecasts are expected when this is achieved.

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Day-to-day horizontal layer background error estimates for U-wind have very different structure and amplitude, calculated from operational randomization method and fromthe 2.0*(standard deviation of the 10 ensemble DA members). The ensemble based version is much more flow-dependent.

Operational randomization method 2.0*Stdev of 10 T255 outer loop+T95/T159 inner ensemble members.

Both ~850hPa

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Hurricane Emily 19-20 July 2005

Ensemble Data Assimilation spread for zonal wind at 850hPa

Max. stdev of EnDA spread 19m/s Max. stdev of EnDA spread 30m/s

EPS probability at 00UTC 19 July

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2

2

/ 2

/ 2H x

pk x k

if |x| <= k,

if |x| > k,

Introduction of the Huber norm

Gaussian

Huber

Gaussian + flat

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The Huber-norm and robust estimation

18 months of conventional data

Feb 2006 – Sep 2007

Normalised fit of PDF to data

Best Gaussian fit

Best Huber norm fit

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Comparing optimal observation weightsHuber-norm (red) vs. Gaussian+flat (blue)

More weight in the middle of the distribution

More weight on the edges of the distribution

More influence of data with large departures

Weights: 0 – 25%

25%

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Changes in the IFS

Huber norm parameters for SYNOP, METAR, DRIBU: surface pressure, 10m wind

TEMP, AIREP: temperature, wind

PILOT: wind

Relaxation of the fg-check Relaxed first guess checks when Huber VarQC is done

Relaxation out to ~ 20 Sigma

Retuning of the observation error Smaller observation errors for Huber VarQC

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Other work in progress on data assimilation Removing “balance constraints” (and perhaps gravity

wave penalty as well) seems to improve results – on-going tests

Technical developments for weak-constraint 4D-Var based on a 4D initial state (good scalability)

Scientific aspects of weak-constraint 4D-Var (e.g. need to represent time-correlated model errors) are studied with a simple 2-level QG model

Improvements of interpolations between outer loop and inner loop resolutions (shape-preserving interpolators)

Improvements in moisture assimilation to allow super-saturation in analysis and liquid and ice water in control variable

Preparation for operational Forecast Sensitivity to Observations suite

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Satellite Data Progress in assimilation of rain-affected radiances Large improvements of the fit of TL physics to NL

physics

Improvements in description of scattering aspects in TL radiative transfer (included in RTTOV)

New instruments have been included (AMSR-E, TMI)

Periodic bias of 3K in TMI discovered and explained by 80K variations of temperature of the mirror. A bias correction has been proposed.

Direct 4D-Var is almost ready. Comparison between model and obs is done at model grid points.

Unification of clear and cloudy radiance assimilation in progress: single data flow and comparison at model grid points has been adopted, thinning now will be more consistent

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Impact of 1D+4D-Var vs 4D-VarMean TCWV

analysis difference in %

1D+4D-Varminus

NORAIN

4D-Varminus

NORAIN

(08-09/2007)

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33R1 without microwave imagers

33R1 control

All-sky 4D-Var without microwave imagers

All-sky 4D-Var

Relative Humidity RMS forecast errors

10th Aug to 10th Sept 2007: 24 to 32 samples verified against own analyses.

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Higher resolution (horizontal and vertical):

- T1279 (EPS at T639) planned for later next year

- ~140-150 levels planned for 2010

One week of summer and one week of winter