Land surface energy balance is central to characterizing land surface ecological, hydrological, and biogeochemical processes. The land surface energy balance equation can be written as

Rn = G + H + λET (5.1)

where Rn is the all-wave net radiation, G is the soil heat flux, H is the sensible heat flux, and λET is the latent heat flux in which λ is the latent heat of evaporation of water and ET is the rate of evaporation of water.