基于Ka-MMCR和C-FMCW雷达资料的青藏高原对流云大气垂直速度反演方法研究

Air vertical motion is one of the important cloud dynamic factors and has a profound impact on the formation, evolution and maintenance of convective cloud system. In the summertime, the Tibetan Plateau (TP) is a huge heat source relative to surround atmosphere and the intense air vertical motion can cause frequent occurrence of convective clouds, often remove to the central and eastern China and cause severe disaster weather. Currently, quantitative measurements of air vertical velocity in convective cloud over TP are still unavailable with the lack of valid measuring instrument. Therefore, meteorologists know rarely about the kinetics features in TP’s convective clouds during their development and evolution processes. In order to intensify the observation of cloud and precipitation over TP, Chinese newest science experiment (i.e. the 3rd Tibetan Plateau Atmospheric Science Experiment, abbreviated as TIPEX-Ш) was carried out since 2013, a Ka-band millimeter-wave cloud radar (Ka-MMCR) and a C-band continuous-wave Doppler radar (C-FMCW) were deployed in Naqu of Tibet during summertime of 2014 and 2015. This is the first effort to obtain long-time profiling measurements of convective cloud and precipitation over TP by Chinese scientists using short-wavelength vertical-oriented radars. These two radars have better sensitivities and much higher temporal resolutions and spatial resolutions compared with other instruments used in former experiment. As a result, vertical measurements of these two radar have provide a good chance for the study of air vertical motion in TP’s convective clouds. So, this project bases on the TIPEX-Ш measurements of Ka-MMCR and C-FMCW, to research a reliable and adaptable air vertical velocity retrieval method for TP’s convective clouds. It will help us better understand the microphysical and dynamical processes of convective systems over TP and provide critical fundamental dataset for numerical model parameterization establishment.

大气垂直运动是云动力的重要参量，在对流云形成、发展和维持过程中都起到关键作用。青藏高原夏季是个巨大的热源，强烈的大气垂直运动是对流云频发的直接原因，但受探测手段限制和青藏高原特殊环境影响，目前高原对流云的大气垂直运动还没有定量测量方法，人们对高原对流云发展和演变过程的动力特征还了解甚少。我国最新第三次青藏高原大气科学试验(TIPEX-Ш)于2014~2015年在西藏布置了一部Ka波段毫米波测云雷达和一部C波段连续波测雨雷达，这是国内外首次利用垂直定向的短波长雷达对高原对流云进行长时间连续观测。这两部新型雷达具有以往设备无法达到的高灵敏度和高时空分辨率资料，为高原对流云动力研究提供了良好契机和支撑。本项目基于这两部雷达在高原上的精细化资料，研究可靠、适用于青藏高原对流云的大气垂直速度定量反演方法，将有利揭示高原对流云的动力特征，也可为数值模式在高原区域的参数化方案构建提供重要基础。

大气垂直运动是云动力的重要参量，在对流云形成、发展和维持过程中都起到关键作用，然而云内大气垂直速度一直是气象探测的难点。本项目利用2014-2016青藏高原那曲地区和华南龙门地区的Ka波段毫米波云雷达和C波段连续波雷达资料，研究了两部雷达数据处理和质量控制方法，并以之为基础提出了雷达功率谱反演大气垂直速度的方法。为验证方法的有效性和可靠性，利用雷达反射率因子、径向速度、谱宽和下落末速度等回波特征，对反演结果进行了分析和论证；进一步利用地面激光雨滴谱仪资料，间接对雷达反演结果进行了定量检验。最后，利用不同典型对流云个例和统计，研究了青藏高原那曲地区对流云内的动力和微物理特征。项目研究结果表明，提出的雷达数据处理和质量控制方法能够显著改善国产多模式-固态体制毫米波雷达和连续波体制雷达的数据质量，这对该型号雷达的发展和应用有重要实际价值。提出的大气垂直速度反演方法，能够较为可靠反演对对流云内的大气垂直速度，反演结果和理论推测的结果一致，与地面激光雨滴谱仪反推的结果也非常一致，其对对流云动力和微物理过程的研究和自动化探测都具有重要的科学意义和应用价值。