A viscous sublayer was introduced into a PBL model in order to specify the lower boundary condition for temperature. The simulated results have been compared against available observations. However, for such a comparison, some of the variables and parameters that are necessary are not known but can be deduced from observed data. In this way, surface temperature and thermal diffusivity of the soil, representative for the four-day period studied here, have been estimated from measured data. An optimized relation for the thickness of the viscous sublayer δ$\delta$ was found that includes the diurnal variation of the properties of the air flow. Including this approach in the model, simulated temperatures in the ground at different levels as well as temperature in the atmosphere agree very well with the observations. The applicability for a wider range of wind speeds was demonstrated by calculating daily maximum temperatures Tmax$T_{\text{max}}$. An analysis of long-term observations for the summer season at different operational weather stations consistently show a distinct maximum of Tmax$T_{\text{max}}$ for a 10‑m wind between 2–3 m/s, which can be explained by the interaction between the molecular transport of heat within the viscous sublayer of thickness δ$\delta$ and the turbulent heat flux.

中文翻译：

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关于粘性表面层描述温度下边界条件的重要性

粘性子层被引入到 PBL 模型中，以指定温度的下边界条件。已将模拟结果与可用观察结果进行比较。然而，对于这样的比较，一些必要的变量和参数是未知的，但可以从观察到的数据中推导出来。通过这种方式，代表了此处研究的四天时间的土壤表面温度和热扩散率已从测量数据中估算出来。发现了粘性亚层厚度δ$\delta$ 的优化关系，其中包括气流特性的昼夜变化。在模型中包括这种方法，模拟的不同水平的地面温度以及大气温度与观测结果非常吻合。通过计算每日最高温度 Tmax$T_{\text{max}}$ 证明了对更广泛风速的适用性。对不同运营气象站夏季长期观测的分析一致表明，对于 2-3 m/s 之间的 10 米风，Tmax$T_{\text{max}}$ 的最大值明显不同，这可以是由厚度为 δ$\delta$ 的粘性子层内的分子热传递与湍流热通量之间的相互作用来解释。