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Radiative and precipitation controls on root zone soil moisture spectra
Author(s) -
Nakai Taro,
Katul Gabriel G.,
Kotani Ayumi,
Igarashi Yasunori,
Ohta Takeshi,
Suzuki Masakazu,
Kumagai Tomo'omi
Publication year - 2014
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 - 10.1002/2014gl061745
Subject(s) - evapotranspiration , precipitation , environmental science , context (archaeology) , radiative transfer , atmospheric sciences , water content , climatology , geology , meteorology , physics , ecology , paleontology , geotechnical engineering , quantum mechanics , biology
Temporal variability in root zone soil moisture content ( w ) exhibits a Lorentzian spectrum with memory dictated by a damping term when forced with white‐noise precipitation. In the context of regional dimming, radiation and precipitation variability are needed to reproduce w trends prompting interest in how the w memory is altered by radiative forcing. A hierarchy of models that sequentially introduce the spectrum of precipitation, net radiation, and the effect of w on evaporative and drainage losses was used to analyze the spectrum of w at subtropical and temperate forested sites. Reproducing the w spectra at long time scales necessitated simultaneous precipitation and net radiation measurements depending on site conditions. The w memory inferred from observed w spectra was 25–38 days, larger than that determined from maximum wet evapotranspiration and field capacity. The w memory can be reasonably inferred from the Lorentzian spectrum when precipitation and evapotranspiration are in phase.