Investigating the Impacts of Daytime Boundary Layer Clouds on Surface Energy Fluxes and Boundary Layer Structure During CHEESEHEAD19
Investigating the Impacts of Daytime Boundary Layer Clouds on Surface Energy Fluxes and Boundary Layer Structure During CHEESEHEAD19
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DOI：
10.1029/2021jd036060
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发表时间：
2022-02
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通讯作者：
J. Sedlar;L. Riihimaki;D. Turner;J. Duncan;B. Adler;L. Bianco;K. Lantz;J. Wilczak;E. Hall;Christian Herrera;G. Hodges
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作者：
J. Sedlar;L. Riihimaki;D. Turner;J. Duncan;B. Adler;L. Bianco;K. Lantz;J. Wilczak;E. Hall;Christian Herrera;G. Hodges
在晴朗的天空和低积云条件下研究陆-气相互作用是常见的长期观测站，如在南部大平原。如何以及从这些调查确定的地表辐射和湍流热通量的关系和响应举行更多的异质表面在其他气候制度，但是，是不确定的。在这项研究中，使用2019年7月至10月由高密度广泛阵列探测器2019年（CHEESEHEAD 19）实地活动实现的Chequamegon异质生态系统能量平衡研究的测量结果分析了表面能量预算和白天边界层特性的详细观测，该研究跨越了北方威斯康星州的异质森林景观。一个云系框架被用来将连续的晴空时段与低层大气层状云和积云进行分类。从低积云到低层云的季节性过渡，以及多云或晴朗天空时期占主导地位的日变化模式。辐射强迫高度依赖于天空条件，导致地面湍流热通量对辐射能量的再分配效率发生变化。在CHEESEHEAD 19期间，小Bowen比占主导地位，白天潜热通量是所有天空条件下感热通量的三倍;因此，森林地区福尔斯能量有限的区域。白天混合层的深度取决于天空条件和热力学设置;较深的混合层发生在低积云和不晴朗的天空期间。垂直速度的配置文件被发现有增强的变化，在低积云相比，晴朗的天空时期，这表明云反馈的边界层结构和表面能量通量的潜力。
Studies of land‐atmosphere interactions under a clear sky and low cumulus cloud conditions are common from long‐term observatories like at the southern great plains. How well the relationships and responses of surface radiative and turbulent heat fluxes determined from these investigations hold for more heterogeneous surfaces in other climate regimes, however, is uncertain. In this study, detailed observations of the surface energy budget and daytime boundary layer properties are analyzed using measurements from the Chequamegon Heterogenous Ecosystem Energy‐Balance Study Enabled by a High‐Density Extensive Array of Detectors 2019 (CHEESEHEAD19) field campaign, July‐October 2019, across a heterogeneous forested landscape of northern Wisconsin. A cloud regime framework is employed to classify consecutive periods of clear skies from lower atmosphere stratiform and cumulus clouds. A seasonal transition from low cumulus to low stratiform periods occurred, together with a diurnal pattern in cloudy or clear sky period dominance. Radiative forcing was highly dependent on sky conditions, leading to changes in the redistribution efficiency of radiative energy by the surface turbulent heat fluxes. During CHEESEHEAD19, small Bowen ratios dominated with daytime latent heat fluxes three times as large as sensible heat fluxes for all sky conditions studied; the forested region, therefore, falls within an energy‐limited regime. The depth of the daytime mixed layer depended upon the sky condition and thermodynamic setting; deeper mixed layers occurred during periods of low cumulus and not clear skies. Profiles of vertical velocity were found to have enhanced variance under low cumulus compared to clear sky periods, suggesting potential for cloud feedbacks on boundary layer structure and surface energy fluxes.