MACC’s core global data assimilation and forecasting capabilities are being developed from those built by GEMS and incorporated within ECMWF’s Integrated Forecasting System (IFS) software. The full scientific and technical documentation of this software is available online at

http://www.ecmwf.int/research/ifsdocs/

This documentation is updated at approximately two- to three-year intervals. Intermediate changes are documented at

http://www.ecmwf.int/products/data/technical/model_id

Some further background to the development of the ECMWF forecasting system can be found at

http://www.ecmwf.int/products/data/operational_system

The web gateway to the technical specification of IFS products, including the global greenhouse-gas, reactive-gas and aerosol products from MACC, is:

http://www.ecmwf.int/products/data/technical/

Among the information available from the links provided on this web page are specifications of the vertical resolutions of the available three-dimensional field products. The vertical representation of most of the initial MACC products is the 60-level resolution adopted for operations at ECMWF from October 1999 to January 2006, and used also for ECMWF’s ERA-40 and ERA-Interim reanalyses, and for most GEMS products. This and other possible vertical resolutions are specified at:

http://www.ecmwf.int/products/data/technical/model_levels

The core MACC IFS products initially come from a T159 resolution spectral model employing a ~125km (N80) “reduced points” Gaussian grid as used for the ERA-40 reanalysis and specified at:

http://www.ecmwf.int/products/data/technical/gaussian

The resolution of the model is expected to increase during MACC to T255 with ~80km (N128) "reduced points" Gaussian grid as used for the ERA-Interim reanalysis and specified at the same address. Also specified at this address is the N48 regular grid employed by the T63 MOZART CTM to which the IFS is coupled for the global reactive-gas component of the system. Chemical species from the coupled CTM are products supplementary to those species products available from the IFS and can be provided as an interim measure. During MACC a set of chemistry modules will be incorporated directly into the IFS. Although products from this fully integrated system will not be available during the lifetime of MACC, they are expected to be provided early in the life of the post-MACC operational core GMES Atmospheric Service.

IFS products are coded using the WMO FM-92 GRIB edition 1 or edition 2 standards. Software for GRIB decoding, field interpolation and plotting can be obtained from:

http://www.ecmwf.int/products/data/software

Much of this software is open source and downloadable free of charge. The local tables used in the GRIB code, which include variable names and specifications of units, are listed at:

http://www.ecmwf.int/services/archive/d/table/grib_table_2_versions/

In particular, the table describing the additional IFS variables for which MACC has currently made provision is table number 210:

http://www.ecmwf.int/services/archive/d/parameters/order=grib_parameter/table=210/

It should be noted that this table includes some variables (such as nitrous oxide and sodium hexafluoride) that are not provided, initially at least, by the standard MACC production systems. The set of variables describing the distribution of aerosols is dependent on the aerosol model adopted by MACC. The aerosol model is expected to change during MACC from that incorporated in GEMS to a new (UKCA-mode) model. Other new output fields (such as the maximum or minimum values of model variables occurring between model output times) may be added from time to time. User requests for specific additional model outputs will be considered, and met to the extent permitted by scientific, personnel-resource and computing constraints.

By way of illustration, the fields available from the GEMS reanalysis for 2003-2007, which has been continued through 2008 and into 2009 in MACC, are listed in Appendix 1.

The standard meteorological IFS variables are described in table number 128:

http://www.ecmwf.int/services/archive/d/parameters/order=grib_parameter/table=128/

The “Ozone” and “Total column ozone” variables defined in this table are the products of the highly parametrized ozone scheme incorporated in ECMWF’s standard operational meteorological production, and must not be confused with the ozone variables produced by the interactive MACC reactive-gas component, which are defined in table number 210 where they are referred to as “GMES ozone” and "GMES Total column ozone". Both types of ozone variable may be produced by a single run of the IFS.

In addition to the chemical species available from the IFS, a much richer range of species is provided by the coupled CTM model MOZART used for the main production. Species include Montreal protocol variables and ozone depleting substances such as O3, N2O, CH4, H2O, selected halocarbons, PSC cover, NOy, BrOx and ClOx and selected key tropospheric trace gases (O3, NOx, CO, selected NMVOC and OH). The species provided may be adjusted in response to user requirements.