# How to convert ERA5 cloud liquid water content from kg kg^-1 to kg m^3?

**URL:** <https://forum.ecmwf.int/t/how-to-convert-era5-cloud-liquid-water-content-from-kg-kg-1-to-kg-m-3/1215>\
**Category:** C3S - Datasets and Usage\
**Tags:** c3s, conversion, era5\
**Created:** [7 January 2021 12:58 UTC](https://forum.ecmwf.int/t/how-to-convert-era5-cloud-liquid-water-content-from-kg-kg-1-to-kg-m-3/1215 "2021-01-07T12:58:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Kevin\_Marsh](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/kevin_marsh/32/368_2.png) [@Kevin\_Marsh](https://forum.ecmwf.int/u/Kevin_Marsh)\
**Post date:** [7 January 2021 12:58 UTC](https://forum.ecmwf.int/t/how-to-convert-era5-cloud-liquid-water-content-from-kg-kg-1-to-kg-m-3/1215/1 "2021-01-07T12:58:01Z")

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For cloud liquid water in ERA5 there are 2 variables:

1. Specific cloud liquid water content (code 246) on pressure (and model) levels. This parameter has units of kg kg-1, see Table 9 in the [ERA5 data documentation](https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation#ERA5Land:datadocumentation-parameterlistingParameterlistings). You can convert the units of this parameter to kg m-3 by multiplying by the density (=P/RT, where P is pressure, T is the absolute temperature and R is the specific gas constant).
2. Total column cloud liquid water (code 78) on surface and single levels. This parameter has units of kg m-2, see Table 6&nbsp;in the [ERA5 data documentation](https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation#ERA5Land:datadocumentation-parameterlistingParameterlistings). These units occur because a vertical integral has been performed.

Thanks,

Kevin

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**Author:** ![Philipp\_Richter](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/p/a5b964/32.png) [@Philipp\_Richter](https://forum.ecmwf.int/u/Philipp_Richter)\
**Post date:** [17 January 2021 18:31 UTC](https://forum.ecmwf.int/t/how-to-convert-era5-cloud-liquid-water-content-from-kg-kg-1-to-kg-m-3/1215/2 "2021-01-17T18:31:09Z")

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Is there a difference between these two datasets? Should the integrated Specific cloud liquid water content (after converting to kg m-3 ) be the same as Total column cloud liquid water?

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**Author:** ![Marie-Laure\_Frery](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/8baadc/32.png) [@Marie-Laure\_Frery](https://forum.ecmwf.int/u/Marie-Laure_Frery)\
**Post date:** [20 May 2021 14:44 UTC](https://forum.ecmwf.int/t/how-to-convert-era5-cloud-liquid-water-content-from-kg-kg-1-to-kg-m-3/1215/3 "2021-05-20T14:44:06Z")

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Coud you explicit which density/ which specific gas constant you use for the conversion ?&nbsp; is it dry air or wet constant ?