| 摘要(英) |
3-D wind and DSD can be retrieved using dual polarization Doppler radar data. In addition to warm-rain microphysical processes such as nucleation, condensation, evaporation, coalescence and breakup, advection and sedimentation also lead to variation of DSD. The DSD at two time steps and the 3-D wind between allow a budget analysis of the drop number concentration, separating microphysical and kinematic effects.
This article analyzes a convective cell observed by NCAR’s SPOL radar when it performed intensive sector scans toward its south during IOP-8 of SoWMEX/TiMREX. The data processing steps include interpolating radar data, calculating the average system speed, correcting the observation time lag, retrieving 3-D wind, retrieving DSD and calculating the budget equation at different stages of the convective cell. The 3-D wind is recovered by the single-Doppler velocity retrieval method of Liou (2007). The DSD is retrieved by the constrained gamma method of Brandes et al. (2003).
The evolution of the convective cell is divided into 3 stages, during which the budget analysis of rain water content in the reflectivity core is as follows. During the intensifying stage, the total derivative of rain water content is positive for all drop sizes, which infers coalescence and condensation are the dominant microphysical processes. During mature stage I, the total derivative is negative for small and big drops but positive for median ones, which infers, besides condensation, coalescence and breakup dominate for small and big drops respectively. During mature stage II, the total derivative is nearly zero for all sizes, which infers opposite microphysical processes are well-matched. During the dissipating stage, the total derivative is negative for all sizes, which results, in doubt, from evaporation due to entrainment of drier air.
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