# ”ERA5 hourly data on single levels from 1940 to present“-”Cloud base height“

**URL:** <https://forum.ecmwf.int/t/era5-hourly-data-on-single-levels-from-1940-to-present-cloud-base-height/15485>\
**Category:** C3S - Datasets and Usage\
**Tags:** era5\
**Created:** [22 October 2026 12:44 UTC](https://forum.ecmwf.int/t/era5-hourly-data-on-single-levels-from-1940-to-present-cloud-base-height/15485 "2026-10-22T12:44:46Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![hongmei\_ji](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/h/ebca7d/32.png) [@hongmei\_ji](https://forum.ecmwf.int/u/hongmei_ji)\
**Post date:** [22 October 2026 12:44 UTC](https://forum.ecmwf.int/t/era5-hourly-data-on-single-levels-from-1940-to-present-cloud-base-height/15485/1 "2026-10-22T12:44:46Z")

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The ERA5 cloud base height product shows values ​​that are too low—in some cases, extremely low, such as 30m. I need to understand how the ERA5 cloud base height is derived and how this dataset is constructed, so that I can determine the reason for these low values.