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首页> 外文会议>Remote sensing for agriculture, ecosystems, and hydrology XI >Critical analysis of empirical ground heat flux equations on a cereal Held using micrometeorological data
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Critical analysis of empirical ground heat flux equations on a cereal Held using micrometeorological data

机译：使用微气象数据对谷物实地热通量方程的临界分析

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The rate at which the net radiation is transferred to the soil as ground heat flux varies with surface characteristics. Surface energy balance algorithms use empirical relationships taking into account the effects of the canopy cover to insulate the soil through vegetation indexes, the soil capacity to absorb incoming net radiation via the albedo, and the surface temperature promoting the energy transfer. However empirical relationships are often dependent on local conditions, such as the soil humidity and vegetation type. Ground heat flux assumes a minimum value in case of full canopy cover and a maximum value for dry bare soil. Aim of the present research is the critical analysis of some ground heat flux equations on a homogeneous field of cereal using measured data acquired between February and May 2008. The study period covers almost a full phenological cycle, including phases characterised by a significant change in both reflected radiation and vegetation cover. The dataset begins with the emergence phase, in November, within which shoots emerge from the ground and finishes with the flowering phase, in May, when tiny white stems begin to come-out; moreover the dataset includes a bare soil period (from September up to November). The daily evapotranspiration is calculated in energy balance models under the hypotheses of negligible daily ground heat flux and constant daily evaporative fraction. Actually micrometeorological data show that daily average ground heat flux is not null but characterised by an increasing or decreasing transient. As a consequence, it is particular important to assess the effects of neglecting the daily ground heat flux on daily evapotranspiration estimation.
机译：随着地面热通量，净辐射传递到土壤的速率随表面特性而变化。表面能平衡算法使用经验关系式，其中考虑了冠层覆盖的作用以通过植被指标使土壤隔热，土壤吸收通过反照率吸收的净辐射的能力以及促进能量传递的表面温度。但是，经验关系通常取决于当地条件，例如土壤湿度和植被类型。地热通量在树冠完全覆盖的情况下取最小值，而在干燥的裸露土壤中取最大值。本研究的目的是使用在2008年2月至2008年5月之间获得的实测数据，对谷物均匀地上的一些地面热通量方程进行关键分析。研究期几乎涵盖了整个物候周期，包括两个特征均发生显着变化的阶段。反射的辐射和植被覆盖。数据集从11月的萌芽阶段开始，在那一刻，芽从地面萌芽，到5月开花，最后是细小的白色茎开始出芽。此外，数据集包括一个裸土时期（从9月到11月）。每天的蒸散量是在能量平衡模型中根据每日地面热通量可以忽略不计和每日蒸发分数恒定的假设来计算的。实际上，微气象学数据表明，每日平均地面热通量不是零，而是以瞬态增加或减少为特征。因此，评估忽略每日地面热通量对每日蒸散估算的影响尤为重要。

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