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Introduction

The global production system is used to produce the daily forecasts of pollutants, aerosols and greenhouse gases across the globe. Satellite observations of atmospheric composition are merged with a detailed computer simulation of the atmosphere using a method called data assimilation. The resulting analyses, i.e. maps of atmospheric composition, are used as initial conditions for the daily forecasts of atmospheric composition. Analyses and forecasts for aerosols and chemical species are produced twice a day.

A global production system is also used to assimilate re-processed observations from many satellites for the last few decades, using the same data assimilation process. The result is called reanalysis and it provides a consistent data set that can be used for scientific studies and trend analyses. The current atmospheric composition reanalysis produced by the Copernicus Atmosphere Monitoring Service is the CAMS: Reanalysis data documentation (EAC4).

The IFS model and data assimilation system configurations (

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48r1)

The model used in the CAMS Global atmospheric composition forecast is the Integrated Forecasting System (IFS) that also produces ECMWF weather forecasts, but with additional modules enabled for aerosols, reactive gases and greenhouse gases that have been developed within CAMS and precursor projects GEMS and MACC. The following processes of atmospheric composition are considered:

• transport of trace gases and aerosols
• injection of emissions
• uptake and release by vegetation and the land and sea surface
• removal by dry deposition at the surface
• removal by scavenging in precipitation
• chemical conversion in the troposphere (CB05) and stratosphere (BASCOE)
• aerosol microphysics

Emissions and surface fluxes of the trace gases and aerosols used in the global CAMS productions are:

• anthropogenic emissions from the CAMS-_GLOB-ANT inventory (available from the ADS)_ANT v5.3 with sectoral diurnal cycles and injection heights
• natural and biogenic natural and biog The ADS is not an operationally supported service and for any time-critical work users should rely on ECMWF FTP service instead. enic emissions from the CAMS-GLOB-NAT and CAMS-GLOB-BIO data sets (available from the ADS)_GLOB_BIO v3.1 climatologies
• ocean fluxes of DMS from the CAMS_GLOB_OCE v.3.1 climatology
• aircraft emissions of CO₂ and NO_x from the CAMS_GLOB_AIR v3.1 data set
• biomass burning emissions inferred from satellite observations of fire activity (from the CAMS GFAS v1.4 )
• wind-blown desert dust and sea salt emissions modelled by the IFS depending on the meteorological forecasts
• CO2 fluxes from vegetation modelled by the C-TESSEL surface scheme (specifically for the CAMS GHG system) 
• natural and biogenic fluxes provided from additional climatological data sets 
• system
• using IS4FIRES injection heights from the CAMS GFAS v1.4 system

For details about simulations and assimilation of chemistry, carbon dioxide, methane and aerosols please see References.

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The IFS model documentation for various model cycles can be found on https://www.ecmwf.int/en/publications/ifs-documentation, including a new section on atmospheric composition aspects. Please note that note that the IFS cycle changes during the years, and this page documents the current operational cycle (47r248r1); please have a look at the table below for details of changes from previous cycles.

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Satellite observations of fire radiative power (GFAS) from the day before the forecast start are used to derive timely biomass burning emissions for the forecast. 

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import cdsapi

c = cdsapi.Client()

c.retrieve(
    'cams-global-atmospheric-composition-forecasts',
    {
        'date': '2021-03-24',
        'time': [
            '00:00', '06:00', '12:00',
            '18:00',
        ],
        'leadtime_hour': '0',
        'area': [           #North, West, South, East
            70, -18, 69,
            -17,
        ],
        'type':'analysis',
        'variable': 'total_aerosol_optical_depth_670nm',
        'format': 'netcdf_zip',
    },
    'download.netcdf_zip')

A subset of the CAMS Global atmospheric composition forecast data for the latest three days can also be accessed through the FTP service. For a list of variables available on the FTP please see here.

Access to CAMS global air quality forecast and analysis data through the ECMWF public Web API service ended on 30 June 2021.

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Variations in delivery times may occur due to the non-operational nature of this ADS service, as issues may arise which cause delays. For any time-critical work, users should rely on ECMWF FTP service dissemination system instead.

Spatial grid

CAMS Global atmospheric composition forecasts data currently has a resolution of approximately 40 km (approximately 0.35 degrees). The data are archived either as spectral coefficients with a triangular truncation of T511 or on a reduced Gaussian grid with a resolution of N256. These grids are so called "linear grids", sometimes referred to as T_L511. 

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Model level fields are in GRIB2 format. All other fields are in GRIB1, unless otherwise indicated. NetCDF format is available on ADS but it is experimental.

# CCSDS -> simple

grib_set -r -s packingType=grid_simple in.grib2 out.grib

# Simple -> CCSDS

grib_set -r -s packingType=grid_ccsds in.grib out.grib2

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Physical characteristics of the different types of aerosols (i.e mass density, the radius mode and geometric standard deviation of the lognormal size distribution and the bin limits and hygroscopic factor), are available in Rémy et al. (2019).

The suggested reference for the IFS aerosol optical properties and hygroscopic growth tables is Bozzo at al (2020).Parameters labelled as "Fast access" and the new CY48R1 documentation: https://www.ecmwf.int/en/elibrary/81374-ifs-documentation-cy48r1-part-viii-atmospheric-composition, chapter 5.

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Table 1:

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Single level

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Fast access parameters (last reviewed on

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02 Aug 2023 )

Table 2:

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Single level

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Slow access parameters(last reviewed on

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02 Aug 2023 )