Most studies of land-atmosphere coupling have focused on bivariate
linear statistics like correlation. However, more complex dependencies
exist, including nonlinear relationships between components of
land-atmosphere coupling and the transmutability of relationships
between soil moisture and surface heat fluxes under different
environmental conditions. In this study, a technique called multivariate
mutual information, based on information theory, is used to quantify how
surface heat fluxes depend on both surface energy and wetness
conditions, i.e. net radiation and soil moisture, across the globe by
season using reanalysis data. Such interdependency is then decomposed
into linear and nonlinear contributions, which are further decomposed as
different components explainable as the unique contribution from
individual land surface conditions, redundant contributions shared by
both land surface conditions, and the synergistic contribution from the
coaction of net radiation and soil moisture. The dependency linearly
contributed from soil moisture bears a similar global pattern to
previously identified hot spots of coupling. The linear unique
contributions of net radiation and soil moisture are mainly
nonoverlapping, which suggests two separate regimes are governed by
either energy or water limitations. These patterns persist when the
nonlinearity is superimposed, thus reinforcing the validity of the
land-atmospheric coupling hot spot paradigm and the spatial division of
energy-limited as well as water-limited regions. Nevertheless, strong
nonlinear relationships are detected, particularly over subtropical
regions. Synergistic components are found across the globe, implying
widespread multidimensional physical relationships among net radiation,
soil moisture, and surface heat fluxes that previously had only been
inferred locally.