Relative Humidity
DATASET DESCRIPTION
Daily UK relative humidity grids are available for 2003–2024 as GeoTIFF rasters. The provider identifies ERA5 hourly data on single levels as their source. Relative humidity is expressed as a percentage: the ratio of actual water vapour pressure to saturation vapour pressure at the same temperature.
ERA5 is produced by ECMWF and distributed through the Copernicus Climate Change Service. The source atmospheric grid is 0.25° × 0.25°; the UK daily data were resampled to 1 km. ECMWF documents how near-surface relative humidity can be derived from temperature and dewpoint, since it is not archived directly. The provider’s specific derivation formula, measurement height and daily aggregation method are not documented.
The annual maps show the arithmetic mean of available daily humidity percentages at each grid cell, calculated in R with missing values omitted. Humidity was not recalculated from annual temperature. All panels share a 70–90% colour scale. Spatial detail is limited by the original ERA5 resolution despite the finer output grid.
Hersbach, H., Bell, B., Berrisford, P., Biavati, G., Horányi, A., Muñoz Sabater, J., Nicolas, J., Peubey, C., Radu, R., Rozum, I., Schepers, D., Simmons, A., Soci, C., Dee, D., Thépaut, J-N. (2023): ERA5 hourly data on single levels from 1940 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS), DOI: 10.24381/cds.adbb2d47.
DATA SOURCE
| Data Sources: ERA5 single levels, ECMWF / Copernicus C3S |
| Geographic Coverage: United Kingdom |
| Coordinate System: OSGB36 / British National Grid (inspected UK sample) |
| Source Spatial Resolution: 0.25° × 0.25°; project grid: 1 km (resampled) |
| Data Preparation Date: September 2026 |
| Data Format: GeoTIFF |
| Sampling Frequency of Data: Daily (source: hourly) |
| Years Available: 2003–2024 |
VARIABLES
- Daily relative humidity and the annual mean of supplied daily values (%)
CONTACT
- UK Dataset Prepared By: Bocheng Zhu
- Email: bocheng.zhu@mail.utoronto.ca
- Affiliated Organization: Ge-iSEE Lab, University of Toronto, Ontario, Canada
