2021 Volume 77 Issue 2 Pages I_1303-I_1308
The objective of this study is to observe and analyze the Doppler lidar signature before and during the first echo from Ka-band radar. In addition, two time-lapse cameras are also utilized to capture the visual evolution of the cloud. Radiosonde from the nearest launch site is also used in this study for meteorological data. The observation data used in this study is a case study of an isolated convective cumulus cloud on August 18, 2019. Ka-band radar captures the first echo at 14:34 JST during this period, confirmed by the cloud image from a two time-lapse camera. Updraft exists at the bottom of the first echo. This presence is strengthened by convergence value, doppler velocity variance during the first echo and quantitative result between this divergence-convergence and variance in 30 minutes before the first echo. The Doppler lidar also detects pairs of vorticity before and during the first echo. This pair of vorticity is lifted vertically, known as the vortex tube, and is moved towards the northwest due to the environment wind in the lower levels. A potential reason why vortex tubes exist is the condition of vertical shear added with the updraft presence. This small vortex tube is located at the bottom of the baby-rain cell cumulus cloud and could only be detected using the sensitive Doppler lidar.
PROCEEDINGS OF HYDRAULIC ENGINEERING
