Does Relative Size of Sensible vs. Latent Heat Fluxes Affect Energy Balance Closure?

We have run eddy covariance systems for several years over irrigated agriculture in the Upper Colorado River Basin to quantify the water and energy balance during the growing season. Preliminary analyses suggest that the ability to close the energy balance generally increases as the site conditions become drier, compared to situations with large latent heat fluxes.

This has led to the hypothesis that ability to close the energy balance is related how “wet” or “dry” is the surface. Or more precisely, the relative size of sensible and latent heat fluxes. We seek to formally test this hypothesis using a large dataset collected throughout the upper Colorado river basin over growing seasons from 2018-2021. Although all the sites are irrigated, there were a range of conditions of the ratio of sensible to latent heat fluxes due to differences in irrigation type and amounts, as well as variations in weather.

The relationship between the daytime energy balance closure vs. the relative importance of sensible (H) and latent heat (LE) fluxes will be examined, including cases where advection of sensible heat from the surroundings causes H to be negative. Comparisons will be made year to year for individual sites as well as through cross comparisons between multiple sites during growing seasons. Other atmospheric variables and soil moisture measurements will also be examined in order to reveal if other environmental factors appear to connect with the ability to close the energy balance.