Humidity, relative

The ratio of the amount of water vapour in the air to that which would be needed to saturate it at the same temperature. It is usually expressed as a percentage, so saturated air has a relative humidity of 100%. The UKCP09 projections provide information on the 30-year average of monthly, seasonal and annual mean relative humidity. 

In detail

Relative humidity is one of the climate variables provided by UKCP09 over land areas, measured in per cent (%). Projected changes in seasonal relative humidity for the UK as a whole are available on the UKCP09 website in the form of maps and graphs.

• A complete list of climate variables for which probabilistic projections are available is given in Table 1.1 of the UKCP09 Climate change projections report. Some additional information about relative humidity is given in Box 1.2 of the UKCP09 Climate change projections report.

• Relative humidity is one of the UKCP09 Weather Generator variables, measured in per cent. An overview of the outputs from the UKCP09 Weather Generator is provided in Section 1.4 of the Climate change projections report. Further details are available in Section 1.3 and Annex 2 of the Weather Generator report.

• Information is also available on observed relative humidity. The UKCP09 Observed trends report provides details of recent trends in relative humidity in the UK.