The Surface Energy Budget of a Wheat Crop: Estimates of Storage

The residual found by Garratt and Pearman (2020, Boundary-Layer Meteorology 177: 613–641) in the surface energy budget of a winter wheat crop is the result of combining seven separately measured or estimated individual fluxes, each with its own uncertainty. We show that the mean hourly residual as it varies through the day is closely correlated with the rate-of-change of radiative surface temperature. Using the latter as a basis for estimating the hourly storage closes the budget to within 5% of the incident broadband shortwave irradiance, down from 10% when storage is excluded. The storage so calculated both agrees with estimates for a maize crop (Hicks et al. 2020, Agricultural and Forest Meteorology 290: 108035) and with theoretical considerations. However, for storage calculations in the field, soil and canopy temperatures are preferable to surface temperature.