Pierre Gentine
Applied Mathematics, Columbia University
"Understanding the spectral behavior of a simple coupled land-atmosphere model"
The main objective of this work is to obtain better understanding of the daily cycle of the energy coupling between the land and the atmosphere in response to a forcing of incoming radiation at their common boundary, the land surface. This is of fundamental importance as the initial/boundary conditions (I/BC) of the land-surface state variables (e.g. soil moisture, soil temperature) exert strong control at various temporal scales on hydrologic, climatic and weather related processes. Hence diagnosing these state variables is crucial for extreme hydrological forecasting (flood/drought), agronomic crop management as well as weather and climatic forecasts.
Consequently in this work, the daily behavior of a simple land-atmosphere model is examined. A conceptual and linearized land-atmosphere model is first introduced and its response to a daily input of incoming radiation at the land surface is investigated. The solution of the different state and fluxes in the Atmospheric Boundary Layer (ABL) and in the soil are expressed as temporal Fourier series with vertically dependent coefficients. These coefficients highlight the impact of both the surface parameters and the frequency of the radiation on the heat propagation in the ABL and in the soil. The simplified model was shown to compare well with field measurements thus accounting for the main emergent behaviors of the system. In addition this analytical model helps much better understand the daily coupling between the land and the atmosphere as well as the propagation of land-surface energy noise within the system.
In the conclusion, possible improvements of our work are discussed.
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