# Differences between SO2 and tcSO2

**URL:** <https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350>\
**Category:** CAMS - Datasets and Usage\
**Tags:** cams, eac4, global\_reanalysis\
**Created:** [5 April 2020 20:03 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350 "2020-04-05T20:03:21Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Katarina\_Vargicova](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/k/7ea924/32.png) [@Katarina\_Vargicova](https://forum.ecmwf.int/u/Katarina_Vargicova)\
**Post date:** [5 April 2020 20:03 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350/1 "2020-04-05T20:03:21Z")

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Hello,&nbsp;  
 I am quite new to atmospheric data andI am working with CAMS reanalysis data to do my diploma thesis. I noticed there are two different parameters for SO2 (but the same for CO, NO2, O3..)  
 I would like to know what is the difference between&nbsp;Sulphur dioxide (kg kg^-1) and Total column Sulphur dioxide kg m^-2.&nbsp;  
 The first mentioned can be found in CAMS Model levels, second one is from CAMS surface level.&nbsp;  
  
 Is there any good documentation of the parameters from CAMS reanalysis (except of&nbsp;[https://apps.ecmwf.int/codes/grib/param-db](https://apps.ecmwf.int/codes/grib/param-db))&nbsp;

Thank you very much for your help!  
 K

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**Author:** ![Michela](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/898d66/32.png) [@Michela](https://forum.ecmwf.int/u/Michela)\
**Post date:** [11 November 2020 15:24 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350/2 "2020-11-11T15:24:12Z")

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Hi,

Total column (in kg m-2) is available at the surface (model level 60 for MARS users). Total column refers to the total amount of the selected variable in a column of air extending from the surface of the Earth to the top of the atmosphere (model level 1 for MARS users). Total column can also be referred to as total \<selected variable\>, or vertically integrated \<selected variable\>.

Thanks

Michela

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**Author:** ![Andreas\_Sterl1](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/a/49beb7/32.png) [@Andreas\_Sterl1](https://forum.ecmwf.int/u/Andreas_Sterl1)\
**Post date:** [3 August 2026 15:05 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350/3 "2026-08-03T15:05:14Z")

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Hello,

I have he same question and I am puzzled by the answer. From Michela’s answer the two variables aermssso2 (Vertically integrated mass of sulphur dioxide) and tcso2 (Total column Sulphur dioxide) should be the same. However, they aren’t. I downloaded both variables from ECA4. Here is the difference plot for July 2025.

 ![image](https://forum.ecmwf.int/uploads/default/original/2X/1/1d6dbfc7cdfbe870c05b0a98c6a06449c8db76bd.jpeg)

Obviously, both variables are not the same. So what is their difference?

With kind regards,

Andreas Sterl

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**Author:** ![Michela](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/898d66/32.png) [@Michela](https://forum.ecmwf.int/u/Michela)\
**Post date:** [7 August 2026 15:04 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350/4 "2026-08-07T15:04:55Z")

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Dear Andreas,  
thanks for your comment. Could you please share how you downloaded aermssso2? I can only see vertically integrated mass of sulphate aerosol (aermsssu) on the EAC4 form

 ![image](https://forum.ecmwf.int/uploads/default/original/2X/7/7d97c41b115c886aadfe3bab535e32be3c72c2ca.png)

Thanks

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**Author:** ![Andreas\_Sterl1](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/a/49beb7/32.png) [@Andreas\_Sterl1](https://forum.ecmwf.int/u/Andreas_Sterl1)\
**Post date:** [18 August 2026 10:18 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350/5 "2026-08-18T10:18:56Z")

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Dear Michela,

The API request I used is

```auto
dataset = "cams-global-reanalysis-eac4-monthly"
request = {
    "variable": [
        "2m_temperature",
        "total_aerosol_optical_depth_550nm",
        "total_column_sulphur_dioxide",
        "vertically_integrated_mass_of_sulphur_dioxide"
    ],
    "year": ["2025"],
    "month": [
        "01", "02", "03",
        "04", "05", "06",
        "07", "08", "09",
        "10", "11", "12"
    ],
    "product_type": ["monthly_mean"],
    "data_format": "netcdf",
    "download_format": "unarchived"

}

Regards,
Andreas

```

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**Author:** ![Andreas\_Sterl1](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/a/49beb7/32.png) [@Andreas\_Sterl1](https://forum.ecmwf.int/u/Andreas_Sterl1)\
**Post date:** [18 August 2026 10:29 UTC](https://forum.ecmwf.int/t/differences-between-so2-and-tcso2/1350/6 "2026-08-18T10:29:22Z")

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Additional info:

I used [CAMS global reanalysis (EAC4) monthly averaged fields](https://ads.atmosphere.copernicus.eu/datasets/cams-global-reanalysis-eac4-monthly?tab=download) to generate the API