Wavelet Analysis of Thermal Activity and Cloud Initiation based on Boundary Layer Radar and Time Lapse Camera Observation

Abstract

This study aims at observing cumulus clouds generated in the boundary layer and to investigate relationship between the cumulus clouds and local thermals. Individual cumulus clouds generated in the boundary layer were observed by a time-lapse camera. Vertical air velocity measured by a Boundary Layer Radar (BLR) was used to observe local thermals. The BLR was collocated with the time-lapse camera. Wavelet coherence was used to quantify the relationship between the two variables. We found that an upward air motion was observed ahead of a cumulus cloud development below 900 m height within 27 events of an individual cumulus cloud. The phase classification showed that 40.7 % of the local thermal event in the boundary layer region impacted the cumulus cloud development. The scale period of these local thermals varied from 0.5 until 8 min.