Dynamical and Microphysical Interactions in a Coastal Bow-Echo Producing Extreme Rainfall

Jeong, Jong-Hoon; Kim, Seung Hee; Oh, Su-Bin; Lee, Jeong-Eun; Tasi, Chia-Lun; Lee, Gyuwon

doi:10.5194/egusphere-2026-1878

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https://doi.org/10.5194/egusphere-2026-1878

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26 Jun 2026

| 26 Jun 2026

Dynamical and Microphysical Interactions in a Coastal Bow-Echo Producing Extreme Rainfall

Jong-Hoon Jeong, Seung Hee Kim, Su-Bin Oh, Jeong-Eun Lee, Chia-Lun Tasi, and Gyuwon Lee

Abstract. On 2 August 2020, a coastal bow-echo mesoscale convective system (MCS) produced severe rainfall and damaging winds over South Korea, resulting in casualties and property losses. Forecasting rapidly developing coastal bow echoes remains challenging due to limited understanding of the interactions between mesoscale dynamics and microphysical processes. Here, we analyze these interactions using improved multi-Doppler wind retrievals and polarimetric radar observations. The system evolved into a leading convective–trailing stratiform structure, reinforced by a rear-inflow jet (RIJ) that enhanced low-level convergence and shaped bowing segments. Feedbacks between RIJ-driven downdrafts, convective updrafts, and hydrometeor recycling sustained precipitation and prolonged the system’s lifetime after landfall. In particular, mixed-phase hydrometeors in stratiform clouds were advected into the leading convective line, where they enhanced and maintained deep convection. These dynamic–microphysical interactions governed storm organization and rainfall efficiency, explaining the persistence of heavy precipitation in the coastal zone. Beyond advancing process understanding, our results highlight the role of land–sea contrasts in shaping mesoscale circulations that intensify convection and provide observational benchmarks for improving forecasts and hazard resilience in coastal regions.

Received: 01 Apr 2026 – Discussion started: 26 Jun 2026

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Jong-Hoon Jeong, Seung Hee Kim, Su-Bin Oh, Jeong-Eun Lee, Chia-Lun Tasi, and Gyuwon Lee

Status: final response (author comments only)

RC1: 'Comment on egusphere-2026-1878', Anonymous Referee #1, 12 Jul 2026

General comments
Mesoscale Convective Systems are one of the convective modes most associated with adverse weather around the World. The high organisation of this type of structure causes MCS to last for a longer time than other structures. The particularity of the bow echoes structures is still more complex and requires more research, like that provided here. In general, the manuscript is well-conducted, but I miss some important comments regarding the data provided, the definition of the phenomena, the figures' description, and, what is one of the main issues, the references are outdated in general. Most of them are prior to 2010, and many updated references can give more relevance to some of the affirmations.

Specific comments
L27-28: The references are outdated. I can understand that the Authors use some of the classical ones, but there are more updated works that can be perfectly referenced. Same in L30 and the following paragraphs of the Introduction.
I suggest briefly defining the main concepts: RIJs, bow echoes, pressure gradients, cold pool, etc.
Figure 1: Include a larger map of Eastern Asia to show the location of the area of study to external readers.
About the use of different weather radar networks and bands: (1) provide more information about each system (e.g. time and spatial resolution, number of elevations, maximum range, minimum and maximum height); (2) Are all double-polarisation systems? (3) How difficult is it to combine the three technologies? I need more information about integrating different data types.
Before Figure 4, I suggest adding a new figure showing the life cycle of the bow-echo system at low levels.
Figure 4: continue the vertical red dashed line in the bottom panel. It seems that the development and part of the system maturity are not included. Why?
L232: “At 2 km altitude, system-relative southwesterly RIJ winds reached about 13 m s-1. Although this magnitude is slightly weaker than the >15 m s-1 values reported …” Could this issue be caused by some radar limitation? (e.g. distance to the echo, strong reflectivity prior to the area of interest, etc)
Which is the cause of the absence of low reflectivity echoes leading to the more intense area in the southern part of the System, observed in panels (a) to (c) of Figure 5?
Figure 6: add in any part of the graph where the field is reflectivity. Besides, to provide support to Figures 7 and 8, it would be interesting to mark the convective and stratiform regions.
Figure 7: How do you estimate the melting level?

Citation: https://doi.org/10.5194/egusphere-2026-1878-RC1
RC2:
'Comment on egusphere-2026-1878', Anonymous Referee #2, 17 Aug 2026
Journal: Natural Hazards and Earth System Sciences (NHESS)
Manuscript ID: egusphere-2026-1878
Title: Dynamical and Microphysical Interactions in a Coastal Bow-Echo Producing Extreme Rainfall
Authors: Jong-Hoon Jeong, Seung Hee Kim, Su-Bin Oh, Jeong-Eun Lee, Chia-Lun Tsai, and Gyuwon Lee
Recommendation: Minor Revision

General Assessment
This manuscript provides a high-quality observational investigation of a landfalling bow-echo mesoscale convective system (MCS) over the western coast of South Korea on 2 August 2020. By integrating high-resolution 3D multi-Doppler wind retrievals from the WISSDOM synthesis system with S-band polarimetric radar microphysical retrievals, the authors systematically document the kinematic evolution (rear-inflow jet, low-level convergence, and asymmetric mesovortices) alongside vertical microphysical distributions (LWC, IWC, D_m, and N_t). The proposed feedback between the trailing stratiform ice-phase reservoir and the leading convective line via a hydrometeor-recycling pathway offers valuable insight into how coastal MCSs sustain high precipitation efficiency after landfall.
The paper is well-written, logically organized, and suitable for publication in Natural Hazards and Earth System Sciences. I recommend a Minor Revision to address a few methodological clarifications, presentation enhancements, and minor technical corrections outlined below.
Specific Comments & Suggestions
1. Conceptual Schematic for Dynamic–Microphysical Coupling
The proposed hydrometeor-recycling mechanism—where ice particles generated in the leading convective line are advected into the trailing stratiform region and partially re-ingested into the convective updraft via the upper branch of the rear-inflow jet (RIJ)—is physically sound and well supported by the CFADs and vertical profiles (Figs. 7 and 8). However, because observational radar data cannot track individual trajectories directly, this conceptual model would be much more impactful if summarized visually.
Suggestion: Consider adding a conceptual schematic diagram (or incorporating schematic arrows into an expanded panel of Fig. 6) that explicitly illustrates the 2D/3D airflow streams (front-to-rear flow, RIJ, recirculation), hydrometeor phase zones (graupel/large drops in convective core vs. aggregated ice aloft in stratiform), and the recycling pathway. Providing a clear conceptual schematic (similar in purpose to Fig. 15 of Park et al., 2021) would help synthesize these dynamic–microphysical interactions into an easily digestible visual summary for readers.

Reference for context: Park, C., S.-W. Son, and J.-H. Kim, 2021: Role of baroclinic trough in triggering vertical motion during summertime heavy rainfall events in Korea. Journal of Atmospheric Sciences, 78(6), 1801–1817, https://doi.org/10.1175/JAS-D-20-0216.1.

2. Surface Cold Pool Characterization & Coastal AWS Observations
The manuscript highlights the role of the descending RIJ and low-level convergence in shaping the bowing line and maintaining deep convection near the coast. In classical bow-echo dynamics (e.g., RKW theory), the balance between cold pool-induced circulation and environmental low-level shear plays a central governing role.
Suggestion: While 850 hPa shear and LLJ structures are presented (Fig. 3b), the surface thermodynamic footprint (Delta T, dewpoint drop, or surface pressure perturbations) of the cold pool during landfall (13:30–15:00 LST) is not explicitly shown. Including surface station time series or spatial mesonet/AWS analysis along the coastline would provide valuable observational grounding for how the cold pool interacted with onshore flow to slow system propagation (28 m s^-1) while sustaining coastal convergence. In particular, further analyzing cold pool evolution and its interaction/intensification with the descending RIJ using coastal AWS observations (e.g., drawing on the observational/mesoscale analysis framework in Byeon et al., 2024) would add substantial physical clarity to the manuscript.

Reference for context: Byeon, K., J.-H. Kim, and Y.-J. Park, 2024: Synoptic and mesoscale mechanisms of reported tornado-like gust wind event in Korea using high-resolution numerical simulation. Atmosphere-Korea, 34(4), 397–415, https://doi.org/10.14191/ATMOS.2024.34.4.397.

3. Uncertainty and Resolution Constraints of Retrieved Vertical Velocity (w)
In Figure 6, vertical velocity (w) reaches values exceeding 5m s^-1, successfully capturing convective updrafts and bounded weak echo regions (BWER).
Suggestion: Since vertical velocity derived from multi-Doppler variational synthesis is highly sensitive to mass continuity integration, lower boundary conditions, radar spatial sampling, and terrain-induced flow distortion (even when employing the Immersed Boundary Method), please add a brief discussion in Section 2.1 addressing the vertical resolution limits, smoothing constraints, and uncertainty bounds associated with the retrieved w field. Citing foundational variational multi-Doppler and WISSDOM error analysis literature (e.g., Gao et al., 1999; Liou and Chang, 2009; Liou et al., 2012; Potvin et al., 2012) would provide helpful context regarding how boundary layer errors and divergence integration weightings affect vertical motion magnitudes.

Minor / Technical Corrections
Section Outlining and Numbering Sequence:

In Section 3 (Results), the manuscript transitions from Section 3.1 (Synoptic environment, p. 8, line 168) directly to Section 3.3 (Kinematic structure of the bow-echo MCS, p. 10, line 203), followed by Section 3.2 (Microphysical properties of the bow-echo MCS, p. 13, line 291). Please correct the subsection numbering sequence to follow numerical order (3.1 - 3.2 - 3.3).

Table 1 Platform Formatting:

In Table 1 (p. 20), please verify that radar station identifiers (e.g., KWK, BRI, KSN, GDK vs. SKWK, SBRI, SKSN, SGDK used in Section 2.1 line 100) are fully consistent across the text and table.

Figure 3 Caption Formatting Error:

In the caption of Figure 3 (p. 9–10, line 200), there appears to be a minor formatting artifact in the units for relative vorticity (10-5 s-1 200 , shading). Please clean up the text formatting in the figure caption.
Citation: https://doi.org/10.5194/egusphere-2026-1878-RC2

Jong-Hoon Jeong, Seung Hee Kim, Su-Bin Oh, Jeong-Eun Lee, Chia-Lun Tasi, and Gyuwon Lee

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https://doi.org/10.5194/egusphere-2026-1878-supplement

Jong-Hoon Jeong, Seung Hee Kim, Su-Bin Oh, Jeong-Eun Lee, Chia-Lun Tasi, and Gyuwon Lee

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Short summary

This study examines why extreme rainfall can persist near coastal regions by analyzing a severe storm over western South Korea. Using advanced radar observations, we identify how interactions between airflow, precipitation processes, and coastal land–sea contrasts enhance storm organization. Our results show that these coupled processes play a critical role in sustaining heavy rainfall and support efforts to mitigate hazards in densely populated coastal areas.


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