#newfcsystem

Description of the upgrade

A wide-ranging upgrade of ECMWF’s Integrated Forecasting System (IFS) including changes in data assimilation (both in the EDA and the 4DVAR), in the use of observations, and in modelling. The new cycle only includes meteorological changes; there are no technical changes, e.g. new resolutions.

Cycle 45r1 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.

News

Timeline of the

implementation

The planned timetable for the implementation of the

IFS Cycle 45r1 is as follows:

The timetable represents current expectations and may change in light of actual progress made.

Datasets affected

• HRES
• ENS
• HRES-WAM
• HRES-SAW
• ENS-WAM

Resolution

Unchanged from previous IFS cycle.

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

• Coupling of the 3-

• dimensional ocean and atmosphere: introduction of the coupling to the NEMO 3-

• dimensional ocean model also in the high-resolution

• forecast (HRES), with the same ocean model version used in the medium-range/monthly ensemble (ENS): NEMO3.4 in ORCA025_Z75 configuration; upgrade of the NEMO-IFS coupling strategy in both ENS and HRES to a full-coupling in the tropical region (partial-coupling-extra-tropics);
• 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 below.
• Modified parameter for non-orographic gravity-wave drag scheme for 91 levels;
• Model error changes:

• • Stochastically perturbed parametrization tendency scheme (SPPT): improved flow-dependent error representation via reduced spread in clear skies regions (due to unperturbed radiative-tendency in clear sky), activation of tendency perturbations in stratosphere, and weaker tapering of perturbations in boundary layer; amplitude reduction of the SPPT perturbations patterns (by 20%);
  • EDA: cycling of stochastic physics random fields in the EDA, and adoption of the same SPPT configuration in EDA as in ENS;

• • Stochastic kinetic energy backscatter scheme (SKEB): deactivation of the stochastic backscatter (SKEB) scheme due to improved model error representation by the SPPT scheme (see above), leading to a 2.5% cost saving in

• • the ENS;

New bathymetry in wave models

With the IFS Cycle 45r1, we have upgraded the bathymetry (water depth) used in the wave models (HRES-WAM, HRES-SAW and ENS-WAM) based on ETOPO1.

The figures below show the new bathymetry used for HRES-WAM and ENS-WAM for Europe together with the difference with the previously used bathymetry (ETOPO2).

HRES-WAM

ENS-WAM

This change was in part driven by users pointing out that the previous bathymetry for the Baltic Sea was quite erroneous at few places. Change in water depth will mostly affect the wave fields in coastal area, generally resulting in higher wave heights where the water has become deeper and vice-versa.. Moreover, some WAM grid points have changed from sea to land (i.e. no waves at those points),  and vice versa. These locations are respectively shown in the right figures above , with green and black shadings (you may need to zoom into the pictures). This change of land/sea points will be visible for some coastal locations in the Wave ENSgrams and for users relying exclusively on the wave model values at those locations.

Meteorological impact and evaluation

The following evaluation of the new cycle is based on the alpha testing. 

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. The latter is mainly a result of changes to the analysis, as confirmed by corresponding neutral results against observations. Upper-air improvements are more pronounced in the tropics, especially for wind and temperature. Verified against observations, upper-air changes are overall positive in the tropics except for relative humidity, and neutral to slightly positive in the extratropics. Upper-air results for the ENS verified against analysis are mostly positive in the tropics but more neutral in the extratropics. The negative signal for temperature in the lower troposphere at shorter lead times is again mainly due to changes in the analysis. Against observations, results are mostly negative in the extratropics at early lead times and significantly positive in the tropics, with the exception of relative humidity at 700hPa. The negative impact in the extratropics is partly due to a slight reduction in ensemble spread associated with the transition to a physically more realistic SPPT scheme. Whether or not this reduced spread is genuinely detrimental depends on whether observation errors are taken into account in the verification which has not been done routinely so far. Experimental verification against radiosonde data that takes observation error into account indicates that a large fraction of the negative ENS results disappear or become statistically non-significant.

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 underspread, 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.

Evaluation

Scorecards of the new cycle are now available.

New and changed parameters

New

parameters

Extended output have been added in cycle 45r1, including precipitation rates, CAPE indices and a total

lightning flash density.

			TBC
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			TBC
151131	ocu	Eastward sea water velocity	Ocean current zonal component	m s-1	1	HRES / ENS			TBC
151132	ocv	Northward sea water velocity	Ocean current meridional component	m s-1	1	HRES / ENS			TBC

For more details on the new lightning parameters, please read the Newsletter article "Promising results for lightning predictions".

Changes to existing parameters

Technical content

Changes to GRIB encoding

Model identifiers

The GRIB model identifiers (generating process identification number) for cycle 45r1 will be changed as follows:

Software

We recommend the use of the following versions of ECMWF's software packages to manipulate the cycle 45r1 data.

These versions are available through the module tag 'may18' on the system at ECMWF, e.g. eccodes/may18, and will become the default ones on 22 May.

ecCodes

ecCodes version 2.7.3 provides full support for the new model output parameters introduced in IFS Cycle 45r1.

GRIB API

GRIB API version 1.26.0 provides full support for the new model output parameters introduced in IFS Cycle 45r1.

GRIB API is no longer loaded in the default user environment on the ECMWF systems. We will discontinue support for GRIB API at the end of 2018 and recommend to use ecCodes.

EMOSLIB

The version of EMOSLIB used to interpolate IFS Cycle 43r3 data is suitable to handle 45r1 data.

EMOSLIB is no longer loaded in the default user environment on the ECMWF systems.

Magics/Metview

Magics version 3.0.3 and  Metview version 5.0.2 provide full support for the new model output parameters introduced in IFS Cycle 45r1.

Availability of IFS 47r1 test data

Test data in MARS

Test data from the IFS Cycle 45r1 test suites are available in MARS. The data are available with E-suite experiment version (expver) 0072 (MARS keyword EXPVER=0072) starting from 06 UTC on 18 March 2018.

The data can be accessed in MARS from:

• HRES (class=od, stream=oper, expver=72)
• Wave HRES (class=od, stream=wave, expver=72)
• ENS (class=od, stream=enfo, expver=72)
• ENS Wave (class=od, stream=waef, expver=72)

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 to User Support.

Test data in dissemination

IFS Cycle 45r1 test data from the release candidate testing stage are available through the test dissemination system. Users of ECMWF dissemination products can trigger transmission of test products by logging in to the test ECPDS system at https://ecpds-xmonitor.ecmwf.int/  (or https://msaccess.ecmwf.int:7443) in the usual manner. In order to receive the test products, users have to have their firewall open to the relevant ECPDS Data Movers:

• Internet transfers: 193.61.196.104 ( ecpds-xma.ecmwf.int ), 193.61.196.105 ( ecpds-xmb.ecmwf.int ) and 193.61.196.113 ( ecpds-xmc.ecmwf.int )
  

• RMDCN transfers: 136.156.8.132 ( mspds-dm4.ecmwf.int ) and 136.156.8.133 ( mspds-dm5.ecmwf.int )

The IFS Cycle 45r1 test products are available as version number 72 (file names ending with '72'). The test products are generated daily, shortly behind real-time from both the 00UTC and 12UTC runs and based on the operational dissemination requirements and the IFS Cycle 45r1 test data for HRES, HRES-WAM, HRES-SAW., ENS, ENS-WAM and ENS extended..

Should you require any assistance with IFS Cycle 45r1 test dissemination products, please contact Data Services.

The derived products from the ENS (files named with dissemination stream indicator Y and U) are available in ECPDS. Cycle 45r1Tropical Cyclones data are missing in ECPDS and will be made available as soon as possible. 

The Cycle 45r1 new model output parameters listed above will be available through the dissemination after the implementation date. Users wanting to test these parameters will need to access them through MARS.

On the implementation date, we will freeze the access to the dissemination requirements interface for a few hours.

Graphical display of IFS cycle 45r1 test data using ecCharts

From the run of 9th of May 00UTC onwards, the IFS cycle 45r1 layers are available in ecCharts. Cycle 45r1 layers are identified by the label "0072" in their title.

Web charts based on IFS cycle 45r1 test data

ENS meteograms based on IFS cycle 45r1 test data are available as of 16 May 2018 and can be viewed by selecting the "IFS cycle 45r1' model run in the ENS meteograms interface. Access to remaining web charts is now also available in the Charts Catalogue. Only the 'clickable' charts are available for the IFS cycle 45r1, by selecting the "IFS  cycle 45R1" from the Model run tab above the chart.

Time-critical applications

Option 1 - simple time-critical jobs

Member State users of the  "Simple time-critical jobs" framework can test that their scripts will work with the IFS Cycle 45r1 test data by using the limited ECaccess 'events' set up for this purpose:

For these events, MSJ_EXPVER environment variable is set to 0072 and can be used to specify the IFS Cycle 45r1 test data in any MARS retrievals.

These events are  intended for testing technical aspects only and should not be used for operational forecasting.

Options 2 and 3

Option 2 or 3 time-critical applications can be tested with the IFS Cycle 45r1 test data retrieved from MARS or received in Dissemination.

Resources

Newsletter Number 156: https://www.ecmwf.int/en/newsletter/156/news/improved-precipitation-forecasts-ifs-cycle-45r1

Document versions