Towards the connection between snow microphysics and melting layer: Insights from multi-frequency and dual-polarization radar observations during BAECC
Towards the connection between snow microphysics and melting layer: Insights from multi-frequency and dual-polarization radar observations during BAECC
复制标题
DOI：
10.5194/acp-2020-16
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Haoran Li;Jussi Tiira;A. von Lerber;D. Moisseev
中科院分区：
文献类型：
--
作者：
Haoran Li;Jussi Tiira;A. von Lerber;D. Moisseev
在层状降雨中，融化层 (ML) 在雷达观测中通常可见为增强反射率带，即所谓的亮带。尽管关于 ML 中发生的确切微物理过程以及它们如何转化为雷达测量结果的争论仍在继续，但模型模拟和观测都表明，雷达测量的 ML 特性受到其上方发生的雪微物理过程的影响。然而，仍然缺乏将两者联系起来的全面观察。为了增进我们对冰云中降水形成的了解，并为雪生长过程的雷达特征提供新的见解，我们研究了这一联系。本研究分为两部分。首先，使用基于地表的降雪测量来开发一种新方法，用于根据 X 和 Ka 波段多普勒雷达观测来识别有框雪和无框雪。其次，该分类与2014年生物气溶胶——对云和气候的影响（BAECC）实验期间收集的多频和双偏振雷达观测数据相结合，研究降水强度、聚集、雾化和树突生长对ML特性的影响。结果表明，雷达观测的ML特性与降水强度高度相关。此前报道的亮带“下垂”主要与降水强度的增加有关。冰粒边缘起次要作用。在中到大雨中，雾化可能会导致额外的亮带下垂，而在小雨中，下垂与未雾化的雪有关。上面雪区的 ML 属性和双偏振雷达特征之间的相关性似乎是通过雷达特征和 ML 属性与降水强度的联系而产生的。除了增进我们对 ML 属性和降雪过程之间联系的了解之外，所提出的分析还演示了如何使用多频多普勒雷达观测来更详细地了解云过程并建立与降水形成的联系。
In stratiform rainfall, the melting layer (ML) is often visible in radar observations as an enhanced reflectivity band, the so-called bright band. Despite the ongoing debate on the exact microphysical processes taking place in the ML and on how they translate into radar measurements, both model simulations and observations indicate that the radarmeasured ML properties are influenced by snow microphysical processes that take place above it. There is still, however, a lack of comprehensive observations to link the two. To advance our knowledge of precipitation formation in ice clouds and provide new insights into radar signatures of snow growth processes, we have investigated this link. This study is divided into two parts. Firstly, surface-based snowfall measurements are used to develop a new method for identifying rimed and unrimed snow from Xand Ka-band Doppler radar observations. Secondly, this classification is used in combination with multifrequency and dual-polarization radar observations collected during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) experiment in 2014 to investigate the impact of precipitation intensity, aggregation, riming and dendritic growth on the ML properties. The results show that the radar-observed ML properties are highly related to the precipitation intensity. The previously reported bright band “sagging” is mainly connected to the increase in precipitation intensity. Ice particle riming plays a secondary role. In moderate to heavy rainfall, riming may cause additional bright band sagging, while in light precipitation the sagging is associated with unrimed snow. The correlation between ML properties and dual-polarization radar signatures in the snow region above appears to be arising through the connection of the radar signatures and ML properties to the precipitation intensity. In addition to advancing our knowledge of the link between ML properties and snow processes, the presented analysis demonstrates how multifrequency Doppler radar observations can be used to get a more detailed view of cloud processes and establish a link to precipitation formation.