双月刊

ISSN 1006-9895

CN 11-1768/O4

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
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中国气象科学研究院

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(41875036)和国家重点研发计划(2018YFC1507400)资助


Air vertical motion and raindrop size distribution retrieval with Ka/Ku dual-wavelength cloud radar and its preliminary application
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    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数据(SZ)和最优估计技术的云内空气垂直运动速度(Vair)、雨滴谱分布(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0-30dBZ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2km 高度层到达最大,粒子数密度(Nw)、LWC和R在2km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 8.9mm and 2.2cm, respectively) cloud radar (DWCR) upgraded form the Ka band cloud radar was used to observe the vertical structures of cloud and precipitation in Southeaster China to improve the observational ability of air vertical motion and microphysical parameters. Aiming at researching the dynamic and microphysical parameters of precipitation in Southeaster China by the DWCR, a retrieval algorithm (DWSZ) for air vertical motion (Vair), raindrop size distribution (DSD), liquid water content (LWC) and rain rate (R) and radar wave attenuation correction in rain area with the DWCR’s reflectivity spectral density data (SZ) were presented in this paper. A precipitation case in Longmen, Guangdong Province, was used to analyze the vertical air motions with DWSZ and single Ka and Ku band CR. The DSD data from disdrometer were used to examine the retrieved Vair and microphysical parameters by the DWSZ. The results showed that the retrieval algorithm gave a reasonable Vair,microphysical parameters and their vertical distributions. The attenuation correction for Ka and Ku band reflectivity data reduced the bias between both bands of reflectivity. The DWCR could be used to observe cloud and precipitation with reflectivity of 0-30dBZ. In the mixed cloud observed by the DWCR, the updraft and downdraft were found in front and back of the convective cells. From the averaged profiles, Vair and mass-weighted mean diameter (Dm) reached their maximum at 2 km, drop number concentration (Nw), LWC and R increased below this level. Water vapor condensation, rain drop collection cloud drop are possibly main process. This work revealed the relationships between microphysical and dynamic processes in this precipitation case, verified the DWCR observational ability and provided the base for development of Ka/Ku band dual wavelength cloud radar, future improvement of single wavelength cloud radar retrieval algorithm and observation of more fine and accurate structures of the microphysical and dynamic parameters.

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  • 收稿日期:2020-09-14
  • 最后修改日期:2021-04-13
  • 录用日期:2021-05-06
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