Abstract The thermodynamic characteristics of the atmosphere during the pre-monsoon thunderstorm period and the transition phase from pre-monsoon to monsoon period over the gateway of Indian summer monsoon is investigated in this study. The study utilizes Stratosphere-Troposphere (ST) wind profiling Radar, Microwave Radiometer, and GPS radiosonde observations. A sharp increase in the boundary-layer and middle-layer moisture content, abrupt changes in the mixing height, lifting condensation level (LCL), convective available potential energy (CAPE), and other thermodynamic variables are noted. The pre-monsoon period is characterized by intermittent deep convection that moistens the middle layers, while stratiform clouds are observed in the monsoon period and deep moist layer is observed. The dry middle-layers observed before the monsoon onset got moistened consistently as the low-level jet strengthened. The LCL height was lower than the mixing height after the onset of monsoon. The wet-bulb zero level (WBZ) height was reduced to 2 km during the pre-monsoon and shifted gradually to higher altitudes as the onset of monsoon occurs. Variations in WBZ height may help in the predictability of monsoon onset. The study has also investigated the characteristics of a thunderstorm event before the onset and suitable indices for early indication of the storm.

中文翻译：

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印度喀拉拉邦西南季风爆发的季风前对流事件和热力学特征——案例研究

摘要 本研究研究了季风前雷暴期和印度夏季风门户上空季风前向季风期过渡阶段大气的热力学特征。该研究利用平流层-对流层 (ST) 风廓线雷达、微波辐射计和 GPS 无线电探空仪观测。注意到边界层和中间层水分含量的急剧增加、混合高度的突然变化、提升凝结水平 (LCL)、对流可用势能 (CAPE) 和其他热力学变量。季风前期以间歇性深层对流为特征，湿润中层，而在季风期观测到层状云，观测到深层湿润层。随着低空急流的加强，季风爆发前观察到的干燥中层持续湿润。季风来临后，拼箱高度低于混合高度。湿球零高度 (WBZ) 高度在季风前期降低到 2 公里，并随着季风的到来逐渐转移到更高的高度。WBZ 高度的变化可能有助于季风爆发的可预测性。该研究还调查了雷暴事件发生前的特征以及风暴早期迹象的合适指标。WBZ 高度的变化可能有助于季风爆发的可预测性。该研究还调查了雷暴事件发生前的特征以及风暴早期迹象的合适指标。WBZ 高度的变化可能有助于季风爆发的可预测性。该研究还调查了雷暴事件发生前的特征以及风暴早期迹象的合适指标。