Nonlinearity and Regimes in global Soil Moisture-surface Heat Flux Coupling

Feedbacks on the atmosphere induced by soil moisture variability are recognized as an essential component of the Earth system. Coupling between SM and surface heat fluxes, especially the latent heat flux (LE), is the foundation of these feedbacks as it exchanges water and energy between the interface of land and atmosphere. Building upon that, this dissertation aims to understand land-atmosphere interactions by exploring the nonlinearity, multivariable dependency, and regime characteristics in the SM:LE coupling at a global scale. I show that LE is significantly affected by both SM and net radiation not only linearly but also nonlinearly and synergistically. Then, I determine active and inactive regimes in SM:LE sensitivity and confirm spatial patterns of SM:LE dependency during active regimes are consistent among observations and climate models. Nevertheless, the spatial patterns of the existence of local coupling regimes reflecting hydroclimate are diverse. I further find that, under global warming, the locally dominant regime may change, and projected SM variability tends to span more regimes. These changes in the dominant regime are decomposed into contributions from moisture processes and energy processes using a novel framework. Results show moisture processes result in a more moisture-limited world while the energy effect is also significant, but its impact is inconsistent among climate models. The global patterns computed in this research not only shed new light on aspects of land-atmosphere interactions but also raise several follow-up topics worthy of further study.

Author

• Hsu, Hsin

• Global Warming
• Land-atmosphere Interactions
• Nonlinearity
• Soil Moisture
• Soil Moisture Regime
• Surface Heat Flux

Identifier

hdl:1920/13905

OAI identifier oai:identifier

oai:MARS:1920/13905