Cycle 40r1v2

IFS cycle 40r1 was the operational model at ECMWF from 19th November 2013 to 12th May 2015.

These release notes describe the differences between OpenIFS cycle 40r1v2 and 40r1v1.

For differences between 40r1v1 and the previous cycle release based on cycle 38, please see the Release Notes for Cycle 40r1v1.

OpenIFS 40r1v2 will not give the same meteorological results as the previous release 40r1v1. A number of changes have been made that mean the model is not bit identical to the previous release, though the differences are small.

For more information on the IFS 40r1 release, see the description of the IFS 40r1 cycle, more detailed summary of changes in IFS cycle 40r1 is also available.

Model documentation

The IFS cycle 40r1 model documentation (PDF manuals) is available from the main ECMWF website.

Brief summary of changes:

ecCodes now supported. Previous versions did not work with ecCodes.
modified SETTLS scheme for improved stratospheric warming forecasts and various improvements for the semi-Lagrangian interpolation and mass fixers (see below).
fix to bug in qnegat.F90 where negative values of moisture were not reset correctly, leading to a very slow moistening of the atmosphere. Negligible difference for medium range forecasts.
setup routine for coupled runs now added (was missing in previous version).
bugfix to cptime.F for RS7K architecture (with thanks to Siham SBII, Morocco).
new command createEX available to create the experiment directory structure for single or ensemble forecasts (see User guide for more details).
some I/O statistics (from iostream_mix) are now reported correctly in the model log file (NODE.001).
minor efficiency improvements.
some surplus code removed.

Note some features from Fortran 2003 are now used, that may require more recent versions of compilers (allowing support of the ASSOCIATE construct). We also do not recommend version 15 of the Intel compiler which has known issues with the OpenIFS code.

Modified SETTLS scheme for improved stratospheric sudden warming

In 40r1v1, during stratospheric sudden warmings (SSW), noisy flow fields can occur resulting in incorrect temperature forecasts at heights typically above 10hPa. This improved scheme works by identifying gridpoints prone to noise and applies a non-extrapolatory scheme improving the representation of the warming. Below 60hPa, this has a neutral impact.

For reproducibility with the old behaviour in 40r1v1, add the following:

NAMDYN
  LSETTLSTF = false,

Some further passive changes (ie. not enabled by default) are:

a modified quasi-monotone limiter which applies the limiter in all three directions at the end of the interpolation rather than at each direction separately. When applied to the specific humidity it reduces the cold bias error of long-range (climate) forecasts.
alternate gridpoint mass-fixer for pressure, instead of the standard spectral mass fixer, which can enforce global mass conservation to near machine precision.
global mass diagnostics for total air mass and tracers. This is extra diagnostic information that can be useful to see global mass conservation errors per timestep.

For further information on the improvements to the forecasts of SSW, please see the article by Michail Diamantakis in ECMWF Newsletter no. 141, Autumn 2014 (p.30).

Grib-api

Please note that the minimum version of grib-api for use with Cycle 40r1 is 1.11.0.
If you see the following error when compiling, please upgrade your version of grib-api:

Error: There is no specific subroutine for the generic 'grib_write_bytes'

Acknowledgements

The OpenIFS team would like to acknowledge the research and support of ECMWF scientists involved in this release.