The role of warm clouds in monsoon rainfall and the warm rain onset process are investigated using high-resolution cloud-sensitive radar measurements. Quality controlled data from Ka-band radar consisting of 1.8 million profiles during July–August 2015, have been explored. A method is devised using the Z_e profiles, for identifying warm clouds whose cloud tops are confined below 5.3 km. Warm rain microphysical parameters are examined utilizing the complemented measurements from Disdrometer, rain gauge, and CloudSat data. The strong temperature inversion of 2 to 4 K km⁻¹ at 3 km explained the generation of shallow warm clouds. Strong low-level updraft and subsidence above the warm clouds are also evident. Contoured frequency by altitude diagram infers that 75% of Z_e (velocity) dominates at −20 dBZ_e (−1 m s⁻¹). Simultaneous Disdrometer measurements revealed 78% of cases with zero-drop count and zero rain rates. The dominating non-precipitating characteristics of warm clouds are also confirmed from the CloudSat inferred cloud droplet effective radius below 10 μm. During the rainy episodes, peak at 0.91 mm in the drop size distribution suggests prominence of drizzle-sized drops. The precipitation caused by warm clouds accounts for a small fraction (28%) of the total rainfall. The warm rain onset process involving the transformation of smaller cloud droplets into big raindrops is investigated using the radar's three lower-order moments. Before cloud droplet to raindrop transition an intense spike in the spectral width (SW) is observed for a brief period in 98% of the cases. Therefore, SW, which infers turbulence, triggers the collision-coalescence of cloud droplets to form raindrops. This study provides a multi-observation-based perspective on the macro- and micro-physical characteristics of monsoon warm clouds and the onset of warm rain for a better representation in the global climate models.

使用高分辨率云敏感雷达测量研究了暖云在季风降雨中的作用和暖雨开始过程。对 2015 年 7 月至 8 月期间由 180 万个剖面组成的 Ka 波段雷达的质量控制数据进行了探索。_{使用 Z e}剖面设计了一种方法，用于识别云顶限制在 5.3 公里以下的暖云。利用来自 Disdrometer、雨量计和 CloudSat 数据的补充测量来检查暖雨微物理参数。^{3 km 处 2 到 4 K km -1}的强烈逆温解释了浅层暖云的产生。暖云层上方的强烈低层上升气流和沉降也很明显。高度图的轮廓频率推断 Z _{e的 75%}（速度）在 -20 dBZ _e (-1 m s ^-1）。同步测量仪测量结果显示，78% 的案例具有零滴计数和零降雨率。CloudSat 推断的 10 μm 以下的云滴有效半径也证实了暖云的主要非降水特征。在雨季期间，水滴大小分布的峰值为 0.91 毫米，这表明毛毛雨大小的水滴很突出。由暖云引起的降水只占总降雨量的一小部分（28%）。使用雷达的三个低阶矩研究了涉及较小云滴转变为大雨滴的暖雨开始过程。在云滴转变为雨滴之前，在 98% 的情况下会在短时间内观察到光谱宽度 (SW) 的强烈尖峰。因此，推断湍流的 SW，触发云滴碰撞合并形成雨滴。本研究为季风暖云的宏观和微观物理特征和暖雨的开始提供了基于多观测的视角，以便更好地在全球气候模型中表示。