Assessing the Diurnal Cycle of Surface Energy and Water Fluxes in an Irrigated Agricultural field using an Hydrological Model
Abstract
The diurnal variation of water and energy fluxes at the land surface is important
to
understand the diurnal cycle of photosynthesis, moisture and temperature at surface
and
deeper soil layers, especially during the growing season. The objective of the paper
is to
characterize the diurnal cycle of surface water and energy fluxes during the growing
season of
a corn in an irrigated agricultural field. The paper aims to study the response of
the landsurface
to observed atmospheric forcing at Citra, Florida, using a 1D column implementation
of an existing land surface hydrology model.
The observational data are analyzed first, including a careful analysis of physical
consistency and measurement error. Particular emphasis is placed on the steps taken
to
evaluate and improve the quality of the two key physical forcing for the model: observed
precipitation and radiation forcing. Simulations of energy fluxes, soil moisture and
soil
temperature from the model are compared against observations at fifteen minute time
scales.
The model is able to reproduce diurnal variability of the soil moisture and temperature
in
response to applied forcing. Root mean square error for soil moisture is calculated
to be 0.033
m^3/m^3, 0.04 m^3/m^3, and 0.005 m^3/m^3 for superficial, middle and deeper layers
respectively. A
sensitivity study is conducted to investigate model behavior by changing thermal diffusivity
and hydraulic diffusivity (not specified in the observation data), while keeping all
other
boundary conditions and physical forcing constant in the model. As opposed to previous
applications with the model (at larger field scales and not for agricultural fields),
it was found
that thermal diffusivity and hydraulic diffusivity have a strong impact on the partitioning
of
the surface energy fluxes, especially in the case of thermal diffusivity with regard
to diurnal
variation of deep soil temperature.
Type
Master's projectPermalink
https://hdl.handle.net/10161/335Citation
Manandhar, Rojina (2007). Assessing the Diurnal Cycle of Surface Energy and Water Fluxes in an Irrigated Agricultural
field using an Hydrological Model. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/335.Collections
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