Implementation of IFS Cycle 47r3

Timeline of the implementation

Meteorological content

Assimilation

• New RTTOV coefficients for hyperspectral infrared (IR) sounders
• New height reassignment for low level AMVs
• Add representativeness error in the total observation error for Aeolus
• Weak-constraint 4D-Var active in the stratosphere for the EDA system

Observations

• Assimilation of all-sky AMSU-A

Model

• A more consistent formulation of boundary layer turbulence, shallow convection and sub-grid cloud including:
  • Simplified and more consistent treatment of sub-grid cloud saturation adjustment
  • Consistent treatment of subgrid cloud from boundary layer turbulent mixing without separate statistical cloud scheme
  • Consistent computation of mixing height for unstable turbulent boundary layer and convection scheme
  • Change from double to single iteration of turbulent mixing scheme
• New method for computing inversion strength based on moist entropy for distinguishing stratocumulus and cumulus cloud
• Limit to convective overshoot based on tropopause stability
• New parametrized deep convection closure with an additional dependence on total advective moisture convergence
• Change from exponential-exponential cloud vertical overlap to random-exponential overlap in closer agreement with observations
• Include vapour deposition process for growth of falling snow particles 
• Change from linear to cubic interpolation for cloud liquid, ice, rain and snow semi-Lagrangian departure point calculations, including 3D quasi-monotone limiter
• Interpolation of cloud and precipitation to radiation grid changed from in-cloud to grid-mean
• Inclusion of full supersaturation adjustment in the ensemble SPPT stochastic perturbations
• Mass-weighting and relaxation timescale introduced for ensemble SPPT stochastic perturbations
• Revised simplified moist physics and associated tangent-linear and adjoint
• Bug fix for vertical interpolation of 3D aerosol climatology
• Improved calculation of extinction coefficients for near-surface visibility in fog, rain and snow
• Revised gustiness parametrization
• Improved calculation of the peak wave period for multi-peaked ocean wave spectra

Meteorological impact

• Extratropical upper-air geopotential and wind in the first few days of the forecast improved by 1-2%
• Tropical upper-air winds throughout the medium-range improved by 1-4%
• Tropical upper-air temperature improved in HRES, but degraded CRPS in ENS due to small (~0.2K) increase in bias. Low level temperatures (including 850hPa and 2m) temperature approximately neutral versus observations but degraded versus analysis over subtropical ocean.
• Tropical Cyclones: Small improvement in position and central pressure absolute error
• Improved MJO prediction and amplitude
• More realistic precipitation PDF in strongly convective regimes
• Increased convective precipitation (reduced dry bias) in arid regions
• Increase in small scale structure for cloud and precipitation but total cloud cover degraded
• Reduced biases for wind gusts and for visibility in fog, rain and snow

New and changed parameters

New parameters

The table contains the list of parameters expected to be available with the model implementation. They will be available as part of the test data.

Param ID	Short Name	Name	units	Component & type	GRIB edition	Level type	MARS	Added to Catalogue	ecCharts	Dissemination
2280451	trpp	Tropopause pressure	Pa	HRES FC	2	sfc			TBD	TBC
228020	degm10l	-10 degrees C isothermal level (atm)	m	HRES FC ENS CF/PF	1	sfc			TBD	TBC
228131	u10n	Neutral wind at 10 m u-component	m s-1	ENS CF/PF	1	sfc			TBD	TBC
228132	v10n	Neutral wind at 10 m v-component	m s-1	ENS CF/PF	1	sfc			TBD	TBC
228231	mlcape50	Mixed-layer CAPE in the lowest 50 hPa	J kg-1	HRES FC ENS CF/PF	2	sfc			TBD	TBC
228232	mlcin50	Mixed-layer CIN in the lowest 50 hPa	J kg-1	HRES FC ENS CF/PF	2	sfc			TBD	TBC
228233	mlcape100	Mixed-layer CAPE in the lowest 100 hPa	J kg-1	HRES FC ENS CF/PF	2	sfc			TBD	TBC
228234	mlcin100	Mixed-layer CIN in the lowest 100 hPa	J kg-1	HRES FC ENS CF/PF	2	sfc			TBD	TBC
228235	mucape	Most-unstable CAPE	J kg-1	HRES FC ENS CF/PF	2	sfc				TBC
228237	mudlp	Departure level of the most unstable parcel expressed as Pressure	Pa	HRES FC ENS CF/PF	2	sfc			TBD	TBC
260290	cat	Clear air turbulence (CAT)	m2/3 s-1	HRES FC	2	ml			TBD	TBC

¹Please note that the current MARS client, built with MIR 1.7.2, will issue a warning when interpolating parameter 228045 (Tropopause pressure). As MIR uses the default interpolation for this parameter in any case, this warning can be ignored and will be addressed in a future version of the MARS client.

Changes to existing GRIB parameters

In Cycle 47r3 the grid descriptions for the surface fields ci and sst in the analysis are now identical to those of the land-sea mask (lsm). 

Technical content

Changes to GRIB encoding

The GRIB model identifiers (generating process identification number) for cycle 47r3 will be changed as follows:

For all parameters in GRIB 2 the Master Tables Version Number will be changed as follows:

Correct decoding of all 47r3 GRIB 2 parameters requires ecCodes 2.22.1 or newer.

Software

To handle all output from Cycle 47r3 the following software packages will be required:

ecCodes 2.22.1
Magics 4.8.2
Metview 5.12.1

Availability of 47r3 test data

Test data in MARS

IFS Cycle 47r3 beta test data is available from MARS with experiment version 0076 (MARS keyword EXPVER=0076): 

• HRES (class=od, stream=oper, expver=76)
• HRES-WAM (class=od, stream=wave, expver=76)
• ENS (class=od, stream=enfo, expver=76)
• ENS-WAM (class=od, stream=waef, expver=76)

Only registered users of ECMWF computing systems will be able to access the test data sets in MARS. The data should not be used for operational forecasting.  Please report any problems you find with this data via the ECMWF Support Portal.

The release candidate test data and products, which are expected to be made available in September 2021, will be generated daily, shortly behind operational high resolution and ensemble runs and based on the operational dissemination requirements. The availability of the test data does not follow any strict schedule.

Resources

• Bechtold, P. R. Forbes, I. Sandu, S. Lang, M. Ahlgrimm, 2020: A major moist physics upgrade for the IFS. ECMWF Newsletter, 164, pp. 24-32. DOI:10.21957/3gt59vx1pb

• Bechtold, P., M. Bramberger, A. Dörnbrack, M. Leutbecher, L. Isaksen, 2021: Forecasting Clear Air Turbulence (CAT). ECMWF Newsletter, No 168.

• David Duncan et al., Assimilation of AMSU-A in all-sky conditions. EUMETSAT/ECMWF Fellowship Programme Research Report, in preparation, 2021

• All Physics developments and all new Grib parameters (algorithms) described in the IFS scientific documentation