A study on the cloud formation and modification processes and numerical modeling of YAMASE clouds

“山濑”云是一种典型的海洋边界层云，目前天气预报模式和大气环流模式的性能还不足以对其进行正确的模拟。夏季，在鄂霍次克反气旋吹来的偏东冷风下，山日云经常出现在西北太平洋地区，三陆地区海岸以东。本研究的目的是通过船舶、飞机和卫星等平台的综合观测，阐明山濑云的形成和演化过程以及微物理和辐射特性。研究还旨在通过发展更好的云参数化来提高海洋边界层云数值模式的性能。通过船载实验，我们首次观测到了山濑事件从开始到结束的海上边界层的时变。利用观测资料验证了山濑事件的数值模拟结果。通过飞机观测，我们获得了NOAA卫星同步观测的几片低空云微物理特性的良好原位数据。我们将从NOAA/AVHRR数据中获取的云微物理特性与飞机观测数据进行了比较。对比表明，利用NOAA/AVHRR资料进行云参数卫星遥感可以得到合理的结果。利用卫星遥感技术，研究了西北太平洋地区大范围云的宏观和微观物理特性。利用这些观测资料，我们分析了山濑事件和非山濑事件的海面与大气之间的热交换。分析结果表明，在山濑事件和非山濑事件中，沿海面和大气的热交换具有明显的差异。分析表明，沿气团轨迹的热交换对山濑云的形成和演化起着重要的作用。我们通过修改云辐射和湍流方案以及云参数化改进了用于模拟Yamase事件的非流体静力模型的性能。我们还开发了几种非均匀云的三维辐射传递方程的有效格式。本研究结果可为包括山濑云在内的海洋边界层云的研究提供新的思路。少

'Yamase' clouds are one of typical marine boundary-layer clouds, for which the present state-of-the-art performance of weather prediction models and general circulation models is not good enough to properly simulate. Yamase clouds frequently appear over the northwest Pacific region, east off the coast of the Sanriku district, in summer season under easterly cool winds blown out from Okhotsk anti-cyclones. The purpose of the present study is to clarify the formation and evolution processes and the microphysical and radiative properties of Yamase clouds through synthetic observations from such platforms as ship, aircraft, and satellites. The study also aims to improve the performance of numerical models for marine boundary-layer clouds by developing better cloud-parameterization.From the shipboard experiment, we could, for the first time, observe time-variation of the maritime boundary layer in a Yamase event from its beginning to ending. The observational data were used to validate the … More numerical simulations of the Yamase event. From the aircraft observation, we could obtain good in-situ data of microphysical properties of several low-level clouds, for which NOAA satellites observed simultaneously. We compared the cloud microphysical properties retrieved from the NOAA/AVHRR data with those from the aircraft observation. From the comparison, it is shown that the satellite remote sensing of cloud parameters from NOAA/AVHRR data could yield reasonable results. By means of the satellite remote sensing, we studied cloud macro-and micro-physical properties over a wide area of North western-Pacific region. By using these observational data, we analyzed the heat exchange between the sea surface and the atmosphere for Yamase cases and non-Yamase cases. The analysis revealed that the heat exchange along the sea surface and the atmosphere for Yamase cases and non-Yamase cases. The analysis revealed that the heat exchange along the air-mass trajectory plays an important role in formation and evolution of Yamase clouds. We have improved performance of the non-hydrostatic model used to simulate Yamase events by modifying the cloud-radiation and turbulence schemes as well as cloud-parameterizations. We have also developed a few efficient schemes of the 3-dimensional radiative transfer equation for inhomogeneous clouds. The results of the present study may cast a new light on the studies of marine boundary-layer clouds including Yamase clouds. Less