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刘黎平, 张扬, 丁晗. 2021. Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用[J]. 大气科学, 45(5): 1099−1113. doi: 10.3878/j.issn.1006-9895.2104.20200
引用本文: 刘黎平, 张扬, 丁晗. 2021. Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用[J]. 大气科学, 45(5): 1099−1113. doi: 10.3878/j.issn.1006-9895.2104.20200
LIU Liping, ZHANG Yang, DING han. 2021. Vertical Air Motion and Raindrop Size Distribution Retrieval Using a Ka/Ku Dual-Wavelength Cloud Radar and Its Preliminary Application [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 45(5): 1099−1113. doi: 10.3878/j.issn.1006-9895.2104.20200
Citation: LIU Liping, ZHANG Yang, DING han. 2021. Vertical Air Motion and Raindrop Size Distribution Retrieval Using a Ka/Ku Dual-Wavelength Cloud Radar and Its Preliminary Application [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 45(5): 1099−1113. doi: 10.3878/j.issn.1006-9895.2104.20200

Ka/Ku双波段云雷达反演空气垂直运动速度和雨滴谱方法研究及初步应用

Vertical Air Motion and Raindrop Size Distribution Retrieval Using a Ka/Ku Dual-Wavelength Cloud Radar and Its Preliminary Application

  • 摘要: 在Ka波段云雷达上升级改造建成的Ka/Ku(Ka和Ku波段波长分别为8.9 mm和2.2 cm)双波段云雷达2019年用于华南云降水垂直结构观测,以改进云内动力和微物理参数探测能力。为了利用该双波段云雷达研究华南降水微物理和动力结构,本文提出了基于双波段云雷达回波强度谱密度(SZ)数据和最优估计技术的云内空气垂直运动速度(Vair)、雨滴谱(DSD)、含水量(LWC)、雨强(R)的反演方法(DWSZ),雨区衰减的订正方法。利用2019年在广东龙门观测的一次降水过程数据,对比分析了云雷达反演的微物理参数与雨滴谱直接观测量,并检验了云雷达反演的低层空气垂直运动速度,利用反演结果分析了一次混合云过程的Vair与这些微物理参数的垂直结构和相互关系。结果表明:Ka/Ku双波段云雷达合理反演了微降水微物理和动力参数及其垂直分布,经过衰减订正的Ka和Ku波段回波强度偏差明显减小。该双波段云雷达数据可以用于分析0~30 dBZ回波强度的云降水垂直结构。本次过程为混合云降水,对流单体前部存在明显的上升气流,后部存在下沉气流;从平均垂直结构来看:Vair和粒子平均直径(Dm)在2 km高度层到达最大,粒子数密度(Nw)、LWC和R在2 km以下明显增强,粒子直径却减小,水汽凝结过程、雨滴碰并云滴是本次过程的主要机制。这一工作验证了Ka和Ku波段组合的双波段云雷达的可行性,为Ka/Ku波段云雷达技术的推广,单波段云雷达反演算法进一步改进,云降水精细结构分析等提供了基础。

     

    Abstract: A new Ka/Ku dual-wavelength (Ka- and Ku-band wavelengths are 8.9 mm and 2.2 cm, respectively) cloud radar (DWCR), an upgraded from the Ka-band CR (cloud radar), was used to observe the vertical structures of cloud and precipitation in South China to improve the observational ability of vertical velocity for air motion (Vair) and microphysical parameters. Based on the study of the dynamic and microphysical parameters of precipitation in South China using the DWCR, this paper presents a retrieval algorithm (DWSZ) for the Vair, raindrop size distribution (DSD), liquid water content (LWC), rain rate (R), and radar wave attenuation correction in rain areas with the reflectivity spectral density (SZ) data of the DWCR. The Vair was studied using the DWSZ and single Ka- and Ku-band CR in a precipitation case in Longmen, Guangdong Province. The Vair and microphysical parameters retrieved by the DWSZ were examined using the DSD data from a disdrometer. The results revealed that the DWSZ provided acceptable Vair, microphysical parameters, and vertical distributions. The attenuation correction for the Ka- and Ku-band reflectivity data minimized the bias between the two reflectivity bands. The DWCR can detect cloud and precipitation with a reflectivity of 0–30 dBZ. In the mixed cloud detected by the DWCR, the updraft and downdraft were found in front of and behind the convective cells. According to the averaged profiles, the Vair and mass-weighted mean diameter (Dm) reached their maximum at 2 km, and the drop number concentration (Nw), LWC, and R increased below this level. Water vapor condensation, raindrop collection of cloud drops are possibly the main processes. This work revealed the relationships between the microphysical and dynamic processes in this precipitation case, verified the DWCR observational ability, and provided the basis for the development of Ka/Ku-band DWCR, future improvement of single-wavelength CR observation ability, and observation of finer and more accurate structures of the microphysical and dynamic parameters.

     

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