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What is CAMSiRA?

CAMS interim Reanalysis (CAMSiRA) is a global reanalysis data set of atmospheric composition (AC), produced by CAMS. CAMSiRA covers the period 2003–2018 and is not going to be continued any further. CAMSiRA data were made available as an interim product  before the comprehensive CAMS Reanalysis became available and users are advised to switch to the CAMS reanalysis.

For further information on CAMSiRA please see Flemming et al. (2017).

How to access CAMSiRA data

CAMSiRA data is hosted on ECMWF's Meteorological Archiving and Retrieval System (MARS).

Users with direct access to MARS (check your access rights here) can access the CAMSiRA data on MARS as stream=oper, class=mc, expver=eac3. eac3  has the following CAMS fields:







 param=aermr01,aermr02,aermr03,aermr04,aermr05,aermr06,aermr07,aermr08,aermr09,aermr10,aermr11,aermr12,co,go3,hno3,n2o5,no,no2,o3,pan,q,so2 # ! ( same aerosols but fewer chemical species than gbst)


 levelist=1,2,3,5,7,10,20,30,50,70, 100/to/300/by/50, 400/to/800/by/100, 850,900,925,950,1000  




step=3,6,9,12   # ! note that all surface fields are also available also for step=0 BUT xxxaod550 is zero for time step 0, so it should not be retrieved  



Non-MARS users, including users of the ECMWF data server web interface and WebAPI please contact for access to the CAMSiRA data.

In addition to the data described above a control run (CR, without data assimilation) is available. If parameters are unavailable in the main dataset, try the control run data.

Control run data is available as class=rd, expver=gbst (2003-2017), expver=gm7p (2018,branch: std_CY41R1_broadwell_20161121_modisaer_bugfix)

gbst has the following CAMS fields, all timestamped to the first of the month (YYYYMM01), time=0, step=0/to/744/by/3 (31 day months) or step=0/to/720/by/3 (30 day months):






levelist=1,2,3,5,7,10,20,30,50,70, 100/to/300/by/50, 400,500,700,850,925,1000




Known issues

PM 2.5 values are incorrect

PM 2.5 values are incorrect and should not be used. This issue will be corrected in the next CAMS reanalysis.

OH has only one step per day

For OH (Hydroxyl radical) only one step per day is archived. OH features a strong diurnal cycle, thus a dataset including at least 4 steps per day is required to produce a reliable OH climatology.

As a workaround we recommend using OH data from the control as described above.


Flemming, J., and Coauthors, 2017: The CAMS interim Reanalysis of Carbon Monoxide, Ozone and Aerosol for 2003–2015, Atmos. Chem. Phys., 17, 1945–1983,

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