Potential evapotranspiration (PET)

A representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile. It is a reflection of the energy available to evaporate water, and of the wind available to transport the water vapour from the ground up into the lower atmosphere.

In detail

• Potential evapotranspiration is one of the UKCP09 Weather Generator variables, measured in height of water per unit time (e.g. millimetres per day). 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.

• Probabilistic projections of potential evapotranspiration are not available from UKCP09, but projections are instead available from the 11-member RCM output. The 11-member RCM data is described in the Reports & guidance section and in Chapter 5 of the UKCP09 Climate change projections report. See this FAQ for details of how PET was generated for the 11-member RCM.