Abstract

Abstract. Information about the raindrop size distribution (RSD) is vital for comprehending the precipitation microphysics, improving the rainfall estimation algorithms, and appraising the rainfall erosivity. Previous research has revealed that the RSD exhibits diversity with geographical location and weather type, which leads to the assessment of the region and weather-specific RSDs. Based on long-term (2004 to 2016) disdrometer measurements in northern Taiwan, this study attempts to demonstrate the RSD aspects of summer seasons that were bifurcated into two weather conditions, namely typhoon (TY) and non-typhoon (NTY) rainfall. The results show a higher concentration of small drops and a lower concentration of large-sized drops in TY compared to NTY rainfall, and this behavior persisted even after characterizing the RSDs into different rainfall rate classes. RSDs expressed in gamma parameters show higher mass-weighted mean diameter (Dm) and lower normalized intercept parameter (Nw) values in NTY than TY rainfall. Moreover, sorting these two weather conditions (TY and NTY rainfall) into stratiform and convective regimes revealed a larger Dm in NTY than in TY rainfall. The RSD empirical relations used in the valuation of rainfall rate (Z–R, Dm–R, and Nw–R) and rainfall kinetic energy (KE–R and KE–Dm) were enumerated for TY and NTY rainfall, and they exhibited profound diversity between these two weather conditions. Attributions of RSD variability between the TY and NTY rainfall to the thermodynamical and microphysical processes are elucidated with the aid of reanalysis, remote sensing, and ground-based data sets.

Highlights

  • Taiwan, an island in the northwestern Pacific, has complex topography that extends from south to north, with an average elevation of about 2 km and peaks of ∼ 4 km

  • The data points in each rainfall rate category should be sufficiently large in TY and NTY rainfall, and for each category, the mean values of rainfall rates should be nearly equal between these two weather conditions (TY and NTY rainfall; Jayalakshmi and Reddy, 2014; Deo and Walsh, 2016; Seela et al, 2017)

  • Ample literature showed a distinction between the raindrop size distribution (RSD) with the precipitation type, and numerous methods were documented for the segregation of the precipitation into stratiform and convective types (Ma et al, 2019; Jayalakshmi and Reddy, 2014; Ulbrich and Atlas, 2007)

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Summary

Introduction

An island in the northwestern Pacific, has complex topography that extends from south to north, with an average elevation of about 2 km and peaks of ∼ 4 km. This study sought to address the following objectives: (1) to investigate alike or unalike individualities of RSDs between the typhoon and non-typhoon rainfall, (2) to identify the comparable or unrelated features of typhoon and non-typhoon rainfall to the previous studies, (3) to quantify the rainfall rate and rainfall kinetic energy relations, and (4) to discern a conceivable rationale for peculiarities in the RSDs between typhoon and non-typhoon rainfall events In this context, to address the aforementioned objectives for the typhoon and non-typhoon rainfall, long-term disdrometer, radar, remote sensing, and reanalysis data sets were used

Data sets used
Observational results
Contribution of raindrop diameters to Nt and R
Segregation of RSDs based on rainfall rates
RSDs in precipitation types
Rainfall estimation relations
The rainfall rate relationships with Dm and Nw
KE–R and KE–Dm relations
Discussion
Summary and conclusions
Full Text
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