Abstract
The microphysical characteristics of a mesoscale convective system (MCS) during a summer monsoon of South Korea are investigated using the generalized drop size distributions (DSD) that are derived from S-band dual-polarization radar data. The characteristics parameters of generalized DSDs (generalized number concentration, N0′ and generalized mean diameter, Dm) are directly calculated from DSD’s two moments without any assumption on the DSD model. Relationships between ZDR and generalized DSD parameters normalized by ZH are derived in the form of the polynomial equation. Verification of the retrieved DSD parameters is conducted with the 2-D video disdrometer (2DVD) located about 23 km from the radar. The standard deviations (SD) of retrieved DSD parameters are about 0.26 for log N0′, and about 0.11 for Dm because of the variability of DSDs. The SD of the retrieved log N0′ from the dual-polarimetric measurement reaches to about 0.46 (almost double) for 11 rain events while the accuracy of retrieved Dm is quite higher (~0.19). This higher error in retrieved log N0′ is likely attributed to the larger discrepancy in radar-observed and DSD-calculated ZDR when ZH is low. This retrieval technique is applied to a mesoscale convective system (MCS) case to investigate the Lagrangian characteristics of the microphysical process. The MCS is classified into the leading edge and trailing stratiform region by using the storm classification algorithm. The leading edge dominated by strong updraft showed the broad DSD spectra with a steady temporal increase of Dm throughout the event, likely because of the dominant drop growth by the collision-coalescence process. On the other hand, the drop growth is less significant in the trailing stratiform region as shown by the nearly constant Dm for the entire period. The DSD variation is also controlled by the new generation of drops in the leading edge and less extent in the trailing stratiform during the early period when precipitation systems grow. When the system weakens, the characteristic number concentration decreases with time, indicating the new generation of drops becomes less significant in both regions.
Highlights
Drop size distribution (DSD) is an outcome of the complex microphysical processes of precipitation particles
Mesoscale convective systems (MCSs) that include mesoscale convective complexes (MCCs), tropical cyclones, and squall lines are the complex of thunderstorms that involves a well-organized convective region [31,32,33,34]
We derived the relationships between differential reflectivity and generalized DSD parameters normalized by radar reflectivity derived from DSDs
Summary
Drop size distribution (DSD) is an outcome of the complex microphysical processes of precipitation particles (e.g., collision-coalescence, break-up, evaporation, etc.). We have selected a squall line case to investigate the different microphysical processes within a precipitation system in the Lagrangian framework without any assumption on the shape of DSDs. In this study, we retrieved the generalized characteristic DSD parameters, Dm and N0 , [3] of double-moments scaling normalized DSD function. The DSDs collected from a 2DVD at Jinchun Weather Observatory operated by Korea Meteorological Administration (KMA) are used to derive the empirical relationship between polarimetric radar variables and microphysical parameters (Figure 1). The 12,945 of 1-min DSDs during 2012 observed in KNU are used to verify retrieved characteristic DSD parameters from the dWuaeli-gphot larimetric radar (blue lines in FigurAep2p)r.oTxh. e80mkagximum rainfall intensity is similar to the Jinchun data set that is used to derive the relationship. Ref. [25] suggested the following setup: the axis ratio of [17] for Deq > 1.5 mm, and [26] for drops smaller than 1.5 mm
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