Abstract The objective of this study is to investigate cloud attenuation at 30 GHz frequency using ground-based microwave radiometric observations at a tropical location, Kolkata. At higher frequencies and lower elevation angles, cloud attenuation is of major concern at a tropical location. The location experiences high value of liquid water path (LWP), which is responsible for cloud attenuation, during the Indian summer monsoon (ISM) and pre-monsoon season. Significant amount of cloud attenuation has been observed during monsoon season at 30 GHz. Two years observations of exceedance probability of cloud attenuation and worst month statistics are presented. The variation of cloud attenuation with frequencies for different elevation angles has also been investigated. The seasonal and diurnal patterns of cloud attenuation are examined. Cloud attenuation, inferred from radiometric measurements before rain commencement, has been compared to rain attenuation at Ku-band. Exceedance probabilities of cloud and rain attenuation have been compared.

中文翻译：

---

来自印度加尔各答热带地区辐射测量的云衰减统计

摘要 本研究的目的是在加尔各答热带地区使用地基微波辐射测量研究 30 GHz 频率下的云衰减。在较高频率和较低仰角下，云衰减是热带地区的主要问题。在印度夏季风 (ISM) 和季风前季节，该位置经历了导致云层衰减的液态水路径 (LWP) 的高价值。在 30 GHz 的季风季节期间观察到大量云衰减。提供了两年的云衰减超标概率观测值和最差月份统计数据。还研究了不同仰角下云衰减随频率的变化。检查了云衰减的季节性和昼夜模式。从降雨开始前的辐射测量推断出的云衰减与 Ku 波段的雨衰减进行了比较。已经比较了云衰减和雨衰减的超出概率。