Abstract. Recently, a C-band dual-polarization Doppler weather radar (C-DWR) was installed at Thumba (8.537°N, 76.865°E), a coastal station in the southern peninsula of India known as “Gateway of Indian Summer Monsoon.” The C-DWR operates in the frequency range of 5.6 to 5.65 GHz with a peak transmitting power of 250 kW at 0.004 duty ratio and employs the state-of-the-art technology for both transmitting and receiving subsystems. Apart from providing regular base products such as reflectivity (Z), radial velocity (V), and spectral width (σ), the DWR being equipped with dual-polarization capability provides differential reflectivity (Zdr), differential phase shift (ϕdp), and correlation coefficient (ρhv). This is the first DWR with polarimetric capability developed indigenously in India. The C-DWR was operated during North-East as well as South-West monsoon period to evaluate its performance with special emphasis on the reflectivity and rainfall intensity measurements. Before the commencement of the campaign, the C-DWR was calibrated using a metallic sphere and the appropriate corrections were made to the radar constant. The preliminary results show that the radar products are consistent with present understanding of precipitating cloud systems. The simultaneous observations of precipitating clouds by C-DWR and Global Precipitation Measurement mission are used to evaluate the former. The comparison of spatial pattern of reflectivity from space-based radars and C-DWR shows very good agreement, qualitatively. The C-DWR-derived rainfall observations also show very good agreement with ground-based laser precipitating monitor measurements. The regression analysis between the C-DWR and laser precipitation monitor-derived rainfall shows a correlation coefficient of 0.89. The C-DWR observations during the passage of tropical cyclone Ockhi are also discussed. The significance of this study lies in describing the first indigenously developed C-band dual-polarization radar and its validation using the space- and ground-based observations.

中文翻译：

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Thumba (8.537°N, 76.865°E) 的 C 波段双极化多普勒天气雷达：初步结果和验证

摘要。近日，位于印度南部半岛的沿海站 Thumba（北纬 8.537°，东经 76.865°）安装了 C 波段双极化多普勒天气雷达（C-DWR），被称为“印度夏季风的门户”。C-DWR 在 5.6 至 5.65 GHz 的频率范围内运行，在 0.004 占空比下的峰值发射功率为 250 kW，并为发射和接收子系统采用了最先进的技术。除了提供反射率 (Z)、径向速度 (V) 和谱宽 (σ) 等常规基础产品外，配备双极化能力的 DWR 还提供差分反射率 (Zdr)、差分相移 (ϕdp) 和相关系数（ρhv）。这是第一个在印度本土开发的具有极化能力的 DWR。C-DWR 在东北和西南季风期间运行，以评估其性能，特别强调反射率和降雨强度测量。在战役开始之前，C-DWR 使用金属球进行校准，并对雷达常数进行了适当的修正。初步结果表明，雷达产品与目前对降水云系统的认识是一致的。C-DWR 和全球降水测量任务对降水云的同时观测用于评估前者。天基雷达和 C-DWR 反射率空间模式的比较在性质上显示出非常好的一致性。C-DWR 衍生的降雨观测也显示出与地面激光降水监测仪测量结果非常吻合。C-DWR 和激光降水监测仪得出的降雨之间的回归分析显示相关系数为 0.89。还讨论了热带气旋 Ockhi 通过期间的 C-DWR 观测。这项研究的意义在于描述了第一个自主开发的 C 波段双极化雷达及其使用空基和地基观测的验证。