Urban Climate Research Group

Arizona State University



Urban Canopy Model

Sensor Network

Subsurface Transport

Turbulent Dispersion


Subsurface Transport


An integrated earth system modeling must be able to physically resolve the transfer of the thermal energy, water, and tracer fluxes across the land-atmosphere interface, coupled through terrestrial evapotranspiration and turbulent dispersion processes. Coupled transport of heat, moisture and tracers underneath the Earth¡¯s surface are critical in regulating the subsurface and surface physical processes, where the coupling is through two major processes, viz. the subsurface advection-diffusion and the atmospheric evaporation. In particular, as all major surface energy budgets (net radiative, sensible, latent and ground heat fluxes) are strong functions of the surface temperature, the subsurface heat transport largely dictates the partitioning of the available energy on the land surface (net radiation) into the dissipative heat budgets (sensible, latent and ground heat).


As a very first step, we investigate the thermal diffusion process isolated from convection of soil waster flux. Though it is well-known that evolutions of the soil temperature and heat flux are two physically inseparable processes in the heat conduction, the possibility has long been overlooked that the complete thermal field information can be encrypted into a time series of a single thermal quantity (temperature or soil flux). We derived a set of numerical algorithms that reconstruct the entire thermal field from a single-depth measurement, based on the Green¡¯s function approach and Duhamel¡¯s principle. The algorithms are robust and preserve numerical accuracy with other numerical methods in the literature and therefore provide a unified framework for soil thermal field estimation.



The next step will be to investigate the coupled heat and moisture transport governed by the diffusion-advection equation. The physical process can be linearize by assuming that heat conduction dominates over convective transfer, thus thermal homogeneity exists between the liquid and the porous medium. The subsurface physics of couple heat and moisture transport contains the signature of surface energy dissipation and is capable of providing insight to more complex phenomena such as the surface energy imbalance enigma land-atmospheric interactions.