Summary of cycle 45r1

A wide-ranging upgrade of ECMWF’s Integrated Forecasting System (IFS), implemented on 5 June 2018, brings better global weather forecasts, with particularly consistent gains in the extended range. A key plank of the upgrade is enhanced dynamic coupling between the ocean, sea ice and the atmosphere.

Implementation date: 05 June 2018 See News article
Detailed description of changes
Key characteristics of our current forecasting system  
Resolution
Horizontal (unchanged)
Vertical (unchanged)
Data set affected
  • HRES
  • ENS
  • HRES-WAM
  • HRES-SAW
  • ENS-WAM
Scorecard for 45r1
Meteorological content

Assimilation

  • Weakly coupled sea-ice atmosphere assimilation applied with the use of OCEAN5 sea-ice (instead of OSTIA) in the surface analysis of the high-resolution (HRES 4d-Var) and the ensemble of data assimilations (EDA) analyses;

  • Relative humidity increments calculated using temperature instead of virtual temperature

  • Weak constraint model error forcing applied at every time step instead of every hour to avoid shocks in the model integration.

Observations    

  • Assimilation of non-surface-sensitive infra-red (IR) channels over land;

  • Assimilation of all sky micro-wave (MW) sounding channels over coasts;

  • Use of direct broadcast FY-3C MWHS2 data for better timeliness;

  • Introduction of RTTOV-12 and new microwave instrument coefficients;

  • Activation of constrained variational bias correction (VarBC);

  • Retuning of the radiosonde observation error, and introduction of a scheme to account for radiosonde drift;

  • Introduction of temperature bias correction of old-style AIREP observations; aircraft temperature varBC predictor upgraded to a three predictor model (cruise, ascent, descent); reduced thinning of aircraft data;

  • Assimilation of JASON-3 and Sentinel-3A altimeters, and use of new altimeters for wave data assimilation;

Model changes    

  • Coupling of the 3-dimensional ocean and atmosphere

  • Improved numerics for warm-rain cloud microphysics and vertical extrapolation for semi-lagrangian trajectory;

  • Increased methane oxidation rate to improve (increase) water vapour in the stratosphere;

  • Improved representation of super-cooled liquid water in convection, and minor convection updates;

  • Improvements in the tangent forward and adjoint models linked to the convection scheme;

  • Correction of soil thermal conductivity formulation and addition of soil ice dependency;

  • New extended output parameters have been added. See Implementation of IFS cycle 45r1

  • Modified parameter for non-orographic gravity-wave drag scheme for 91 levels;

  • Model error changes:

    • Stochastically perturbed parametrization tendency scheme (SPPT)

    • EDA

    • Stochastic kinetic energy backscatter scheme (SKEB)

New bathymetry in wave models

Upgraded  bathymetry (water depth) used in the wave models based on ETOPO1 in:

  • HRES-WAM
  • HRES-SAW
  • ENS-WAM

See Implementation of IFS cycle 45r1 for details

Meteorological impacts

Upper-air

The new cycle leads to improvements in HRES upper-air fields. Verified against the model analysis, a positive signal is seen throughout the troposphere for most parameters, except temperature in the lower troposphere at shorter ranges.

Weather parameters and waves

There is an overall improvement in 2m temperature both in the HRES and ENS particularly for Europe. 2m humidity is largely neutral for HRES, but positive for ENS, particularly in the tropics. 10 m wind speed is largely neutral in the HRES and slightly negative in the ENS. Precipitation in the HRES is improved in terms of categorical verification (e.g. SEEPS), and near-coastal precipitation in warm-rain dominated situations is significantly improved due to changes in the cloud physics. However, these changes also lead to more activity at higher precipitation rates in active regions such as the East Asian monsoon, and as a result error measures such as RMSE or CRPS (for the ENS) are increased. The negative signal for significant wave height against analysis is a result of changes to the analysis from a large increase in observation usage, and verification against observations (buoys) shows the results are neutral for both HRES and ENS.

Tropical cyclones

The implementation of the ocean-atmosphere coupling in the HRES removes the overall negative bias in tropical cyclone central pressure and thereby reduces the mean absolute intensity error by about 10% in the short range, and about 20% from day 5 onwards. Evaluations so far show statistically neutral results for the position error.

Extended range

Changes in scores for the monthly system are generally positive across the range of parameters, with significance in week 1 for tropical winds. The only indication of a degradation is precipitation in the tropics with a consistent negative signal across all 4 weeks. There is an indication of a positive effect on skill across all parameters in the European domain. The MJO Index was significantly under-spread, but changes in 45r1 to the SPPT scheme have brought the spread and error in close agreement throughout the 30 day forecast range. The underestimation of the MJO Index amplitude error has been significantly improved throughout the forecast.

Technical changes
  • Changes to GRIB model identifiers
New model output There are no new parameters introduced with cycle 43r3.
Model ID
  • Atmospheric: 149
  • Ocean wave:  114
  • HRES standalone ocean wave: 214
New disseminated model output

 (*) Not added to the Real-time Catalogue

Parameter Id Short Name Name Description Units   Grib edition Component
260048 tprate Total precipitation rate Total precipitation rate (instantaneous) kg m-2 s-1 2 HRES / ENS
228058 litota6 Averaged total lightning flash density in the last 6 hours Averaged total (cloud-to-cloud and cloud-to-ground) lightning flash density in the last 6 hours. See also here. km-2 day-1 2 HRES / ENS
228057 litota3 Averaged total lightning flash density in the last 3 hours Averaged total (cloud-to-cloud and cloud-to-ground) lightning flash density in the last 3 hours. See also here. km-2 day-1 2 HRES / ENS
228051 litota1(*) Averaged total lightning flash density in the last hour Averaged total (cloud-to-cloud and cloud-to-ground) lightning flash density in the last hour. See also here. km-2 day-1 2 HRES / ENS
228050 litoti Instantaneous total lightning flash density Instantaneous value of total (cloud-to-cloud and cloud-to-ground) lightning flash density. See also here. km-2 day-1 2

HRES / ENS

228036 mxcapes6 maximum CAPES in the last 6 hours Maximum CAPE-shear in the last 6 hours. See also here. m2 s-2 2

HRES / ENS

228035 mxcape6 maximum CAPE in the last 6 hours Maximum CAPE in the last 6 hours. See also here. J kg-1 2 HRES / ENS
162072 viwvn Vertical integral of northward water vapour flux Vertical integral of northward water vapour flux. See also here. kg m-1 s-1 1 HRES / ENS
162071 viwve Vertical integral of eastward water vapour flux Vertical integral of eastward water vapour flux. See also here. kg m-1 s-1 1 HRES / ENS
151132 ocv Ocean current meridional component Ocean current meridional component m s-1 1 HRES / ENS
151131 ocu Ocean current zonal component Ocean current zonal component m s-1 1 HRES / ENS
e-suite experiment number 0072