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毫米波测云仪探测的宜昌冬季云垂直结构特征

Winter clouds vertical structure of Yichang detected by millimeter-wave cloud radar

  • 摘要: 毫米波测云仪(以下简称测云仪)是地基垂直观测系统的重要组成部分,用于云垂直结构的观测,可获取云的宏微观物理量,了解新建成的设备特性对后续资料应用具有重要意义。利用2022年11月—2023年1月三峡国家气候观象台测云仪观测资料,结合风云四号(FY-4A)卫星和同址观测的气溶胶激光观测仪(以下简称激光观测仪)、DSG5型降水现象仪对该地区云的云顶高度、云底高度和雷达反射率因子进行分析,揭示宜昌地区冬季云的垂直分布规律,结果表明:(1) 非降水条件下,测云仪与激光观测仪探测高云和中云的云底高度一致性较高,相关系数分别为0.8和0.74,测云仪探测的云顶高度与FY-4A云顶高度产品的相关系数为0.57;弱降水条件下,雷达反射率因子与降水现象仪的反演结果的相关系数为0.66。(2) 宜昌地区冬季云出现率在垂直方向上均呈双峰分布,主峰位于3 km以下,云出现率在午后开始增大,非降水云出现率的最大值出现在晚上(21:00—22:00),降水云出现率最大值出现在傍晚(18:00—20:00)。(3) 云底高度和云顶高度在垂直方向上均呈双峰分布,主峰位于对流层中下层,夜晚到午夜降水云云底的抬高预示了降水的减弱。(4) 冬季非降水云的雷达反射率因子的大值区主要出现在午后,最大值可达20 dBz;降水云的雷达反射率因子的大值区主要集中在中午和傍晚,最大值超过30 dBz,雷达反射率因子大值区对应地面降水量大值区。

     

    Abstract: As an important part of the ground-based vertical observation systems, the millimeter-wave cloud radar (referred to as the cloud radar) can be used to observe cloud vertical structures and obtain cloud macro/micro-physical parameters. It is significant to analyze the detecting ability of the newly-built cloud radar for the data applications. In this study, the cloud radar observations at Three Gorges National Climatological Observatory from November 2022 to January 2023 are utilized. To reveal the vertical cloud structures in winter, the cloud base height (CBH), cloud top height (CTH), and radar reflectivity factor are compared with the measurements from the aerosol lidar observation instrument, FY-4A satellite, and the DSG5 precipitation phenomenon instrument, respectively. The results show that: (1) Under non-precipitation conditions, the cloud radar is well consistent with aerosol lidar observation instruments in detecting high and medium CBH, with correlation coefficients of 0.8 and 0.74, respectively. The correlation coefficient between the CTH detected by cloud radar and FY-4A is 0.57. Under weak-precipitation conditions, the reflectivity factor correlation coefficient between the cloud radar and precipitation phenomenon instrument is 0.66. (2) The occurrence frequency in winter shows a bimodal distribution in the Yichang region, with main peaks below 3 km. The cloud occurrence begins to increase in the afternoon, with the maximum values of non-precipitating clouds occurring in the evening (21:00—22:00) and the maximum values of precipitation clouds appearing at dusk (18:00—20:00). (3) Both the CBH and CTH exhibit bimodal distributions in the vertical distributions, with the main peak in the middle and lower layers of the troposphere. The elevation of the cloud base from evening to midnight indicates a decrease in precipitation. (4) The maximum radar reflectivity factor of non-precipitating clouds in winter is 20 dBz and mainly occurs in the afternoon. The maximum value of precipitating clouds exceeds 30 dBz and mainly occurs in the noon and dusk. Larger reflectivity factors in the low layers correspond to larger ground precipitation.

     

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