Abstract
Carbon, water, and energy cycles are key processes controlling
land-atmosphere interactions. Carbon and energy fluxes are both coupled
with soil moisture (SM), leading to water-limited and energy-limited
regimes. Functional relationships between carbon, water, and energy are
key to understanding feedbacks between the land surface and atmosphere
and give an estimate of the land-atmosphere coupling strength. Current
carbon, water, and energy coupling relationships are commonly estimated
at the point or satellite scale. These coupling relationships are
expected to vary across scales. We investigated the carbon, water, and
energy coupling relationships and the limiting thresholds from the field
to satellite scale. We also investigated the effect of weather, seasons,
and land cover on carbon-water-energy coupling strength. Carbon (carbon
dioxide: CO2), energy (evapotranspiration: ET), and water (SM) were
estimated using Eddy covariance and soil moisture monitoring systems at
various FLUXNET sites in the Continental United States. These field
measurements were used together with LANDSAT, MODIS, SMAP remote sensing
satellites estimates of ET, CO2, and SM, respectively. Weather variables
were obtained from Daymet (a gridded daily surface weather data product)
and weather monitoring systems at the FLUXNET sites. This analysis
provided insights to the spatial and temporal variations of the carbon,
energy, and SM at different scales.