Radiative and precipitation controls on root zone soil moisture spectra
Journal
Geophysical Research Letters
Date Issued
2014
Author(s)
Katul, Gabriel G.
Kotani, Ayumi
Igarashi, Yasunori
Ohta, Takeshi
Suzuki, Masakazu
Kumagai, Tomo'omi
Abstract
©2014. American Geophysical Union. All Rights Reserved. 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. Key PointsClimate models predict Lorentzian temporal spectra for root zone soil moisture wLong-term site measurements deviate from Lorentzian and report shorter w memoryPrecipitation and net radiation impact w spectra and its memory at long scales
Publisher
AMER GEOPHYSICAL UNION
Type
journal article