Title Page
ABSTRACT
Contents
Chapter 1. Introduction 20
1.1. Background 20
1.1.1. Precipitation climatology in South Korea 20
1.1.2. East Asian summer monsoon (EASM) 21
1.1.3. Large-scale modulation of EASM 22
1.1.4. Changma 23
1.1.5. Synoptic features of HREs 24
1.1.6. Mesoscale features of HREs 25
1.1.7. Thermodynamic characteristics of HREs 26
1.1.8. Tropical cyclones (TCs) 26
1.2. Aims of dissertation 28
Chapter 2. Climatological features of HREs and TC-HREs 29
2.1. Motivation 29
2.2. Data and methods 30
2.2.1. Data 30
2.2.2. Definition of HRE and TC-HRE 30
2.3. Composited synoptic conditions 33
2.3.1. HREs 33
2.3.2. TC-HREs 37
2.4. Spatiotemporal occurrence distributions 41
Chapter 3. Quasi-geostrophic diagnosis of HREs 43
3.1. Motivation 43
3.2. Data and methods 46
3.2.1. Dataset 46
3.2.2. QG diagnosis of vertical motion 46
3.2.3. Transverse and shearwise components of Q vector 47
3.3. QG forcing: Dynamic versus diabatic forcings 48
3.4. QG dynamic forcing: Transverse versus shearwise Q-vector forcings 54
3.5. Discussion 62
Chapter 4. Diverse synoptic weather patterns of HREs 64
4.1. Motivation 64
4.2. Data and methods 65
4.2.1. Dataset 65
4.2.2. Classification of HREs 65
4.3. Overview of the SOM clustering results 66
4.4. Synoptic patterns of the six HRE clusters 70
4.4.1. Quasi-stationary frontal boundary between low and high (C1 and C3) 70
4.4.2. ETC from eastern China (C2 and C5) 73
4.4.3. Local disturbance at the edge of the NPH (C4) 76
4.4.4. Moisture pathway between continental and oceanic highs (C6) 78
4.5. Discussion 83
Chapter 5. Role of midlatitude condition in TC-HREs 84
5.1. Motivation 84
5.2. Literature review of ET 85
5.2.1. Structure changes of TC 85
5.2.2. Impacts on midlatitude flow 86
5.3. Data and methods 88
5.3.1. Data 88
5.3.2. Definition of TC-HREs 89
5.3.3. Classification of TC-HREs 90
5.3.4. PV tendency equation 93
5.3.5. QG omega equation 93
5.4. Overview of the SOM clustering results 94
5.5. Synoptic evolutions under different tropopause patterns 98
5.5.1. Upper-and low-level evolutions 98
5.5.2. Vertical cross sections 105
5.6. Quantitative assessments 109
5.6.1. TC influence on the tropopause circulation 109
5.6.2. QG diagnosis of vertical motion 114
5.7. Discussion 121
Chapter 6. Record-breaking rainfall in the summer of 2020 123
6.1. Motivation 123
6.2. Data and methods 124
6.3. Overview of the 2020 summer rainfall 126
6.3.1. Record-breaking rainfall amount 126
6.3.2. Weather patterns of the HREs 128
6.4. Subseasonal variation of HREs and background flow 132
6.4.1. Synoptic characteristics of HREs in P1 and P2 132
6.4.2. Background monsoon flows in P1 and P2 136
6.5. Possible mechanisms of the monsoon circulation change 141
6.5.1. Meridional wave train by the SCS convection 141
6.5.2. Zonal wave train by the SNAO 144
6.5.3. Combined effect of the SCS convection and SNAO 145
6.6. Discussion 149
6.6.1. IPOC effect 149
6.6.2. BSISO 152
6.6.3. Other possible factors 153
Chapter 7. Conclusions and final remarks 154
7.1. Overall 154
7.2. Summary of dissertation 156
7.2.1. Chapter 2 "Climatological features of HREs and TC-HREs" 156
7.2.2. Chapter 3 "Quasi-geostrophic diagnosis of HREs" 157
7.2.3. Chapter 4 "Diverse synoptic weather patterns of HREs" 157
7.2.4. Chapter 5 "Role of midlatitude condition in TC-HREs" 159
7.2.5. Chapter 6 "Record-breaking rainfall in the summer of 2020" 160
7.3. Future directions 162
Appendices 163
Appendix A 163
A1. Integrated water vapor transport 163
A2. 2D frontogenesis 163
A3. Curvature and shear components of geostrophic relative vorticity 163
A4. Wave activity flux by stationary Rossby wave 164
Appendix B 166
B1. Q-vector-form QG omega equation 166
B2. Numerical details of the QG omega equation inversion 169
B3. Transverse and shearwise Q vectors 171
Appendix C 175
C1. SOM algorithm 175
Appendix D 179
D1. PV tendency equation 179
REFERENCES
국문초록
Table 2.1. Summary ofthe HREs and TC-HREs. The first three rows are synoptic description, and preferred occurrence period and region. The fourth and fifth rows are averages of the... 32
Table 3.1. Fractional contributions (%) of vertical motion by diabatic, transverse Q-vector and shearwise Q-vector forcings to ωQG at 250 hPa, 500 hPa and 850 hPa averaged over the...[이미지참조] 61
Table 4.1. SOM parameters specified in this chapter. 66
Table 4.2. Summary of the six HRE clusters. The first nine rows are in compliance with those in Table 2.1. 67
Table 5.1. SOM parameters specified in this chapter. 91
Table 5.2. List of TC-HREs in C1 and C2. The reference time is in UTC. 92
Table 6.1. List of the HREs (including TC-HREs) in JJAS 2020. HRE ID (third column) follows the temporal order of occurrence. The TC name is indicated in the rightmost column.... 125
Figure 1.1. The number of all HREs in 10-day bins over the period of 1979-2018 (colored bars) overlaid with rainfall climatology (black line, mm day-1). The HREs are defined as 12-...[이미지참조] 21
Figure 1.2. Schematic representation of the five warm-season air masses around the Korean Peninsula and quasi-stationary monsoon front. 24
Figure 1.3. Schematic illustration of vertical coupling of ULJ and LLJ via a thermally-direct secondary circulation at the entrance region of the ULJ streak. 25
Figure 2.1. Tracks of TCs involved in TC-HREs for 1979-2018 with different colors depending on months. For clarity, the tracks for the grades of TD and ETCare not expressed.... 31
Figure 2.2. Hourly time series of 12-h accumulated rainfall for individual HREs and TC-HREs (thin lines) at the station of maximum accumulated 12-h rainfall, and their means (bold... 32
Figure 2.3. Time evolution (-36 h, -18 h and 0 h) of synoptic circulation patterns of HREs: a SLP (hPa, black contours), SLP anomalies (hPa, shading), IVT (〉300 kg m-1 s-1, vectors)...[이미지참조] 34
Figure 2.4. Thermodynamic and dynamic structures of the mature HREs (0 h): a 850-hPa Ɵe (K, shading) and the Petterssen frontogenesis function applied to the 850-hPa Ɵe [blue...[이미지참조] 36
Figure 2.5. As in Fig. 2.3, but for TC-HREs. In a, the 850-hPa T42 relative vorticity is contoured in white with a two times larger interval than in Fig. 2.3a (2-CVU interval). The... 38
Figure 2.6. As in Fig. 2.4, but for TC-HREs. Note that the shading range in c is two times larger than that in Fig. 2.4c. 40
Figure 2.7. The left panels are the number of a HREs and b TC-HREs in 10-day bins in JJAS (colored bars) overlaid with rainfall climatology (mm day-1, black line). The right panels are...[이미지참조] 42
Figure 3.1. Composites of the 250-hPa GPH (gpm, black contours), 500-hPa ω (blue contours with a 0.04-Pa s-1 interval), 250-hPa horizontal wind speed (shading) and IVT...[이미지참조] 43
Figure 3.2. Schematic illustration of the typical QG vertical motion by a the transverse Q vector and b shearwise Q vector around the jet streak, and c by theshearwise Q vector around... 45
Figure 3.3. Lagged composites of a 250-hPa GPH (gpm, contours) and its anomalies (gpm, shading), and b 850-hPa GPH (gpm, contours), its anomalies (gpm, shading) and IVT... 48
Figure 3.4. a Lagged composites of ω (contours with a 0.04-Pa s-1 interval), dynamic forcing (10-18 m kg-1 s-1, shading) and Q vector (10-12 ㎡ kg-1 s-1 , vectors) at 500 hPa at -36,...[이미지참조] 50
Figure 3.5. a Lagged composites (-36, -18 and 0 h) of the latitude-pressure cross section of ωDyn (blue contours with a 0.02-Pa s-1 interval), horizontal wind speed (〉12 m s-1, black...[이미지참조] 51
Figure 3.6. Vertical profiles of (black solid), ωQG (black dashed), ωDyn (blue dashed), ωBEta (green dashed) and ωDia (red dashed) averaged over the boxed regions in Fig. 3.4 in...[이미지참조] 53
Figure 3.7. Composites of a horizontal wind speed (〉12 m s-1, contours with a 2-m s-1 interval),Qnn forcing (10-18 m kg-1 s-1, shading) and Qnn (10-12 ㎡ kg-1 s-1, vectors), and b...[이미지참조] 55
Figure 3.8. Composites of a ωn and b ωs at 500 hPa at 0 h. Unit is Pa s-1.[이미지참조] 56
Figure 3.9. Composites of a thickness between 700 hPa and 300 hPa (gpm, contours), and geostrophic shear vorticity (CVU, shading) at 500 hPa at 0 h. b As in a, but for geostrophic... 57
Figure 3.10. As in Fig. 3.5a, but the blue contours and shading are replaced by a ωn (0.01- Pa s-1 interval) and Qnn forcing (10-18 m kg-1 s-1), and b ωs (0.01-Pa s-1 interval) and Qss...[이미지참조] 58
Figure 3.11. Vertical profiles of vertical motion (Pa s-1) averaged over the boxed regions in Fig. 3.4. The left panels show ωDyn (blue dashed), ωn (green dashed) and ωs (sky-blue...[이미지참조] 60
Figure 3.12. An updated conceptual model of HREs, which describes the typical 3D structure of warm-season HREs in South Korea. 62
Figure 4.1. The results of the 1x6 SOM clustering applied to HREs. The plotted variable is the composited -6-h SLP fields for the six clusters (C1-C6) over the clustering domain (27°-... 66
Figure 4.2. As in Fig. 2.7, but for the six HRE clusters: athe number of HREs in 10-day bins in JJAS (colored bars), and b the spatial distributions of the probability of occurrence (%,... 68
Figure 4.3. As in Fig. 2.3, but for C1 HREs. The 850-hPa T42 relative vorticity in a is contoured in white. Note that the shading range in a is 3 times larger than that in Fig. 2.3a. 72
Figure 4.4. As in Fig. 2.3, but for C3 HREs. Note that the shading range in a is 3 times larger than that in Fig. 2.3a. 72
Figure 4.5. As in Fig. 2.3, but for C2 HREs. Note that the shading range in a is 3 times larger than that in Fig. 2.3a. 75
Figure 4.6. As in Fig. 2.3, but for C5 HREs. Note that the shading range in a is 3 times larger than that in Fig. 2.3a. 75
Figure 4.7. As in Fig. 2.3, but for C4 HREs. Note that the shading range in a is 3 times larger than that in Fig. 2.3a. 77
Figure 4.8. As in Fig. 2.3, but for C6 HREs. Note that the shading range in a is 3 times larger than that in Fig. 2.3a. 79
Figure 4.9. As in Fig. 2.4a, but for the six HRE clusters: 850-hPa Ɵe (K, shading) and the Petterssen frontogenesis function applied to the 850-hPa Ɵe [blue contours for positive...[이미지참조] 80
Figure 4.10. As in Fig. 2.4c, but for the six HRE clusters: longitude-pressure cross section of GPH anomalies (gpm, shading) and vertical velocity (contours with a 0.04 Pa s-1 interval)....[이미지참조] 81
Figure 4.11. a ω (solid line), ωQG (dashed line), ωDyn (blue bars) and ωDia (red bars) at 500 hPa in the mature stage (0 h) of the six HRE clusters estimated over the boxed region...[이미지참조] 82
Figure 5.1. Infrared imagery of transitioning typhoons Ginger at a 0332 UTC 28, b 0032 UTC 29, and c 1232 UTC 29 September 1997, and Stella at d 0032 UTC 15, e 1232 UTC 15,... 86
Figure 5.2. Overview of modification of upper-level midlatitude flow by transitioning TCs. The dark red line denotes the meandering tropopause waveguide separating stratospheric... 87
Figure 5.3. Schematic representation of midlatitude flow amplification by the divergent outflow of a TC. The black contours, shadings and vectors denote the PV, horizontal wind... 88
Figure 5.4. Tracks of TCs involved in TC-HREs in South Korea in JJAS 1979-2020 with different colors depending on the status (e.g., TD: orange, TC: purple, ETC: blue). The... 90
Figure 5.5. a,b The 1x2 SOM clustering results. The plotted variable is the composited 2-PVUsurface height (km) at 0 h for C1 and C2, respectively, over the clustering domain (30°-... 95
Figure 5.6. a,b As in Fig. 5.4, but for C1 and C2, respectively, in a narrower domain. 96
Figure 5.7. a,b Time series of 12-h accumulated rainfall amount at the station where the maximum 12-h accumulated rainfall is recorded at 0 h for C1 and C2, respectively. c,d... 97
Figure 5.8. Lagged composites (-48, -24, 0 and +24 h) of 2-PVU surface height (km, black contours) and its anomaly (km, shading), and horizontal wind speed at 2-PVU surface (green... 100
Figure 5.9. Lagged composites (-48, -24, 0 and +24 h) of GPH (gpm, contours) and its anomaly (gpm, shading) at 700 hPa, and IVT (〉300 kg m-1 s-1, vectors) for a-d C1TC-HREs...[이미지참조] 102
Figure 5.10. Lagged composites (-48, -24, 0 and +24 h) of 700-hPa GPH (gpm, contours) and its anomaly (gpm, shading) in the TC-relative frame for a-d C1 TC-HREs and e-h C2 TC-HREs. 104
Figure 5.11. Lagged composites (-48, -24, 0 and +24 h) of longitude-pressure cross section of GPH anomaly (gpm, shading) and PV anomaly (contours with a 0.1-PVU interval)... 106
Figure 5.12. Lagged composites (-48, -24, 0 and +24 h) of latitude-pressure cross section of PV (PVU, shading), ω (contours with a 0.04-Pa s-1 interval), horizontal wind speed...[이미지참조] 108
Figure 5.13. Composites of PV tendency budget for C1 TC-HREs at 0 h: arate of local PV change (∂p/∂t;shaing), b rotational wind (m s-1, vectors) and its resulting PV advection (-VΨ·...[이미지참조] 111
Figure 5.14. Time series of the 250-150-hPa layer-averaged PV advections by rotational (−VΨ·∇P; dotted lines) and divergent winds (−VX·∇P; solid lines), and rate of local PV...[이미지참조] 113
Figure 5.15. Vertical profiles of ω from ERA5, and ,ωQG,ωDyn, ωBEta, ωDia and ωbf obtained from omega equation inversion, which are averaged around South Korea (33°-39°N...[이미지참조] 115
Figure 5.16. Composites of a ωs (Pa s-1, shading), Qss (10-12 ㎡ kg s-1, vectors) and GPH (gpm, contours), and b ωn (Pa s-1, shading), Qnn (10 -12 ㎡ kg s-1 , vectors) and horizontal...[이미지참조] 117
Figure 5.17. As in Fig. 5.16, but for C2 TC-HREs. 118
Figure 5.18. Time series of a ω,ωQG, ωDyn, and ωDia, and b ωDyn by the upper (400-100 hPa; subscript u) and lower layers (1000-400 hPa; subscript l), and their transverse and...[이미지참조] 120
Figure 5.19. The box-whisker plots of lifetime minimum center pressure a for all TCs in C1 and C2, and b for the resampled TCs in C1 and C2. The TCs are resampled by constraining... 122
Figure 6.1. a Yearly time series of JJAS accumulated rainfall (black line) and its anomaly (colored bars) for the period of 1971-2020. Here, the anomaly is defined as a deviation from... 127
Figure 6.2. The 850-hPa GPH (contours, gpm) and relative vorticity (shading, CVU) truncated at T42 spatial resolution for all HREs (including TC-HREs) listed in Table 6.1. A... 129
Figure 6.3. As in Fig. 6.2, but for satellite images (10.5-mm infrared channel). 130
Figure 6.4. Tracks of TCs mentioned in Table 6.1. The stages of TD or ETC are indicated by dashed lines. 131
Figure 6.5. Composited synoptic structures of the four HREs in P1 (HREs 2-5 in Table 6.1). a GPH (gpm, contours) at 850 hPa, IVT anomaly (kg m-1 s-1 , shading) and IVT anomaly...[이미지참조] 133
Figure 6.6. As in Fig. 6.5 but for the six HREs in P2 (HREs 6-8 and HREs 10-12 in Table 6.1). 135
Figure 6.7. Hovmöller diagram (time-latitude) of IVT anomaly (kg m-1 s-1, shading), 5,840- and 5,880-gpm GPHs at 500 hPa (thick black line), and their climatologies (thick green line)...[이미지참조] 136
Figure 6.8. a,c The GPH at 500 hPa (gpm, black contours), Ɵe anomaly at 850 hPa (K, shading) and IVT anomaly (〉100 kg m-1 s-1 , vectors) in a P1 and c P2. The 5,840 and 5,880...[이미지참조] 138
Figure 6.9. Hovmöller diagram (longitude-time) of the T42-filtered relative vorticity at 850 hPa (shading, CVU) averaged over a 30°-40°N and b 42°-52°N during the period of 29... 139
Figure 6.10. Ψ anomaly at 500 hPa (contours with a 0.1x10-7 ㎡ s-1 ), horizontal wind anomaly at 500 hPa (〉3 m s-1 , vectors) and OLR anomaly (W m-2, shading) in a P1 and b P2.[이미지참조] 143
Figure 6.11. The 500-hPa Ψ anomaly (10-7 ㎡ s-1, contours and shading) and ITV anomaly (kg m-1 s-1, vectors) when the SCS OLR index is a above +1.0σ and b below -1.0σ for the...[이미지참조] 147
Figure 6.12. Daily time series of the SCS OLR index and SNAO index normalized by their one standard deviation during the period of 29 June-15 August 2020 (P1+P2). A 9-day... 148
Figure 6.13. a Monthly time series of SST anomaly (K) over the Niño 3.4 region (5°S-5°N, 190°-240°E) from January 2018 to October 2020. b Daily time series of SST anomaly (K)... 151
Figure 6.14. Phase diagram of BSISO mode 1 during the period of 29 June-15 August 2020(P1+P2). 152
Figure 7.1. Structure of this dissertation. 155
Figure A4.1. Ψ anomaly (contours), GPH anomaly (shading) and WAF for stationary Rossby waves (vectors) at (top) 250 hPa, (middle) 500 hPa and (bottom) 850 hPa in a 29... 165
Figure B1.1. Vertical profile of σo averaged for 318 non-TC HREs in chapter 3.[이미지참조] 168
Figure B3.1. Composites of 318 non-TC HREs considered in chapter 3: a Ɵ (K, contours), Qnn (10-12 ㎡ kg-1 s-1 , vectors) and Qnn forcing (10-18 m kg-1 s-1, shading) at 500 hPa in the...[이미지참조] 172
Figure C1.1. a Rectangular nodes and b hexagonal nodes in 3 x 6 array. 176
Figure C1.2. Examples of a sheep map, b cylinder map and c toroid map with rectangular nodes. 176