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Vegetation controls on surface heat flux partitioning, and land‐atmosphere coupling
Author(s) -
Williams Ian N.,
Torn Margaret S.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066305
Subject(s) - latent heat , sensible heat , environmental science , atmosphere (unit) , vegetation (pathology) , flux (metallurgy) , water content , atmospheric sciences , forcing (mathematics) , transpiration , moisture , climatology , geology , meteorology , chemistry , geography , medicine , biochemistry , photosynthesis , geotechnical engineering , organic chemistry , pathology
We provide observational evidence that land‐atmosphere coupling is underestimated by a conventional metric defined by the correlation between soil moisture and surface evaporative fraction (latent heat flux normalized by the sum of sensible and latent heat flux). Land‐atmosphere coupling is 3 times stronger when using leaf area index as a correlate of evaporative fraction instead of soil moisture, in the Southern Great Plains. The role of vegetation was confirmed using adjacent flux measurement sites having identical atmospheric forcing but different vegetation phenology. Transpiration makes the relationship between evaporative fraction and soil moisture nonlinear and gives the appearance of weak coupling when using linear soil moisture metrics. Regions of substantial coupling extend to semiarid and humid continental climates across the United States, in terms of correlations between vegetation metrics and evaporative fraction. The hydrological cycle is more tightly constrained by the land surface than previously inferred from soil moisture.