The nocturnal boundary layer transition from weakly to very stable. Part I: Observations
The nocturnal boundary layer transition from weakly to very stable. Part I: Observations
复制标题
夜间边界层从弱过渡到非常稳定。
DOI：
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发表时间：
2019
影响因子：
8.9
通讯作者：
L. Mortarini
中科院分区：
文献类型：
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作者：
O. Acevedo;Rafael Maroneze;F. D. Costa;F. Puhales;G. Degrazia;L. G. Nogueira Martins;P. E. Soares de Oliveira;L. Mortarini
利用在巴西东南海岸附近140米微气象桅杆上进行的10级湍流观测，分析了夜间边界层从弱稳定（强风）到非常稳定（弱风）的转变。天气和局地气流的结合有利于系统地发生这种转变，通常发生在日落后5至7小时。状态转变的标志是温度、风速、湍流动能（TKE）和绝对热通量的降低。温度的下降往往是突然的，温度序列的拐点标志着状态的转变。绝对热通量在弱稳定期前达到峰值，而温度变化在弱稳定期附近达到峰值。采用36种冷却速率超过2℃/h的复合材料，描述了两种冷却速率下稳定边界层（SBL）的垂直结构。对于这些突变，将与流动的热学和力学特性相关的无量纲变量作为SBL状态的指标进行比较，发现梯度理查德森数更适合于此目的。只有在非常稳定状态的强风极限下，绝对热通量才与风速的立方成正比。第二部分描述了使用二阶模型模拟类似的过渡。
The nocturnal boundary‐layer regime transition from weakly stable (strong wind) to very stable (weak wind) is analyzed using 10 levels of turbulence observations made at a 140 m micrometeorological mast near the southeastern Brazilian coast. The combination of synoptic and local flow favors the systematic occurrence of such a transition, typically 5 to 7 h after sunset. The regime transition is marked by decreases in temperature, wind speed, turbulent kinetic energy (TKE) and absolute heat flux. The decrease in temperature is often abrupt and the inflection point in the temperature series marks the regime transition. Absolute heat flux peaks before the transition during the weakly stable period, while temperature variance peaks near the transition. Composites from 36 cases when the cooling rate exceeded 2 °C/h are used to describe the vertical structure of the stable boundary layer (SBL) in both regimes. For these abrupt transitions, dimensionless variables that relate thermal and mechanical properties of the flow are compared as indicators of the SBL regime, and the gradient Richardson number is found to be better for that purpose. The absolute heat flux is shown to be proportional to the cube of the wind speed only in the strong wind limit of the very stable regime. Simulations of similar transitions using a second‐order model are described in Part II.
影响因子：
8.9
作者：
Freire, Livia S.;Chamecki, Marcelo;Dias, Nelson L.
通讯作者：
Dias, Nelson L.