Entrainment, Decoupling, and Vertical Transport in the Marine Stratocumulus Cloud Deck

海洋层积云覆盖了海洋的大部分区域，并通过反射入射的阳光来冷却地球。天气或气候模式不能很好地模拟这些低云背后的过程。这一奖项将允许研究人员分析在之前的野外活动中收集的数据，以便他们能够研究海洋层积云中空气和水分的运动。其结果将是更好地理解云，并提高对云的形成、消散和影响进行建模的能力。这项研究的一个主要影响将是天气预报，重点是低云和雾，这是航空业的危险。这项工作还将有助于改进气候模型。研究小组将对2008年瓦莫斯海洋云大气陆地研究(VOALL)的激光雷达、雷达和探测数据进行分析，以更好地了解控制层积云结构、过渡和辐射特性的过程。研究人员指出，在层积云顶部夹带、上升为层积云的积云上升气流和蒸发式下降气流中，垂直混合很少观察到。这些现象的概念模型和数值模型只能通过它们对外部现象的影响来评估，而不是根据模型本身对实际内部过程的描述程度来评估。确定的三个科学目标将有助于更好地描述和理解夹卷、不耦合以及相关的上升和下降气流通量：1)与层积云中湍流的强度有关的夹带，并记录由于云顶浮力通量的变化而引起的湍流及其输送的日变化；2)记录导致层积云和地面混合层之间不耦合的湍流的结构和演变，并分析太阳辐射周期驱动的周日不耦合，以及与暖海温上的大尺度冷平流有关的不耦合；以及3)量化由云和小雨、蒸发和蒸发产生的负浮力上升和下降气流所产生的质量输送。并将观测到的垂直速度分布归因于湍流强度、不耦合、积云和毛毛雨。

Marine stratocumulus clouds cover significant areas of the ocean and act to cool the planet by reflecting incoming sunlight. The processes behind these low clouds are not well simulated by weather or climate models. This award will allow researchers to analyze data that was collected in a prior field campaign so that they can study the movement of air and moisture within marine stratocumulus clouds. The result will be a better understanding of the clouds and an improved ability to model their formation, dissipation, and impacts. One main impact of the research will be on weather forecasting with a focus on low clouds and fog, which are hazards for the aviation industry. The work will also help to improve climate models. Training and diversity impacts will be provided through the incorporation of students into the research plan.The research team will conduct an analysis of lidar, radar and sounding data from the 2008 VAMOS Ocean Cloud Atmosphere Land Study (VOCALS) to better understand the processes that control the structure, transitions, and radiative properties of stratocumulus clouds. The researchers note that vertical mixing is poorly observed in stratocumulus cloud top entrainment, in cumulus updrafts rising into stratocumulus, and in evaporative downdrafts. Conceptual and numerical models of these phenomena have only been evaluated by their effects on external phenomena, rather than how well the models represent the actual internal processes themselves. Three scientific objectives are identified that will lead to a better description and understanding of entrainment, decoupling, and coherent updraft and downdraft fluxes: 1) Relating entrainment to the strength of turbulence in the stratocumulus cloud and documenting diurnal variations of turbulence and its transport due to variation of buoyancy flux at cloud top, 2) Documenting the structure and evolution of turbulence leading to decoupling between the stratocumulus cloud and surface mixed layer, and analyzing both diurnal decoupling driven by the cycle of solar radiation, and decoupling associated with large-scale cold advection over warm SST, and 3) quantifying mass transports due to cumulus updrafts and downdrafts generated by negative buoyancy from cloud and drizzle evaporation, and attributing the observed distributions of vertical velocity to turbulence strength, decoupling, cumulus clouds, and drizzle.