Abstract
Millimeter wave cloud radar (MMCR) is one of the primary instruments employed to observe cloud–precipitation. With appropriate data processing, measurements of the Doppler spectra, spectral moments, and retrievals can be used to study the physical processes of cloud–precipitation. This study mainly analyzed the vertical structures and microphysical characteristics of different kinds of convective cloud–precipitation in South China during the pre-flood season using a vertical pointing Ka-band MMCR. Four kinds of convection, namely, multi-cell, isolated-cell, convective–stratiform mixed, and warm-cell convection, are discussed herein. The results show that the multi-cell and convective–stratiform mixed convections had similar vertical structures, and experienced nearly the same microphysical processes in terms of particle phase change, particle size distribution, hydrometeor growth, and breaking. A forward pattern was proposed to specifically characterize the vertical structure and provide radar spectra models reflecting the different microphysical and dynamic features and variations in different parts of the cloud body. Vertical air motion played key roles in the microphysical processes of the isolated- and warm-cell convections, and deeply affected the ground rainfall properties. Stronger, thicker, and slanted updrafts caused heavier showers with stronger rain rates and groups of larger raindrops. The microphysical parameters for the warm-cell cloud–precipitation were retrieved from the radar data and further compared with the ground-measured results from a disdrometer. The comparisons indicated that the radar retrievals were basically reliable; however, the radar signal weakening caused biases to some extent, especially for the particle number concentration. Note that the differences in sensitivity and detectable height of the two instruments also contributed to the compared deviation.
Highlights
Cloud and precipitation always experience multiple changes during their life cycles in the atmosphere
millimeter wave cloud radar (MMCR) can be more sensitive to small cloud particles and the received signal is more remarkable with a larger signal-to-noise ratio (SNR), because the backscattered ability of a hydrometeor is inversely proportional to the fourth power of an electromagnetic wavelength
A Ka-band MMCR accompanied by a raindrop disdrometer was used to detect the cloud–precipitation profiles and the ground rain drop size distribution (DSD)
Summary
Cloud and precipitation always experience multiple changes during their life cycles in the atmosphere. The narrow beam width can avoid some other non-hydrometeor signals (e.g., clear air turbulence), thereby leading to a good radar return that consists only of cloud and precipitation particles [5,6,7]. MMCR has very high spatial and temporal resolution, with magnitudes of several decameters and a few seconds, respectively [8,9,10]. This kind of high spatiotemporal resolution is superb for multiple aspects of radar data application, ranging from cloud microphysical phenomena to dynamic processes
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