2:15 PM - 2:30 PM
[AAS08-03] Characteristics of Baiu Frontal Depressions that Cause Linear Stationary Heavy Rainfall in Japan
★Invited Papers
Keywords:Linear-stationary precipitation band, cyclone, depression, Baiu
This study investigates the characteristics of low-pressure systems associated with the development of linear-stationary precipitation bands (LS-BFD) and those not associated (NLS-BFD) over Kyushu, often caused by the occurrence and development of low-pressure systems along the Baiu front. Understanding the features of low-pressure systems that lead to linear-stationary precipitation bands is crucial for understanding the mechanisms and environmental conditions for their occurrence. However, not all low-pressure systems along the Baiu season front generate linear precipitation bands, and there is insufficient understanding of the differences in characteristics between those that do and those that do not.
Using long-term reanalysis data (1989-2020), this study extracts LS-BFD and NLS-BFD over Kyushu and examines the differences in their characteristics through composite analysis. The results of the composite analysis show that, just before the occurrence of linear precipitation bands, both LS-BFD and NLS-BFD exhibit strong lower-tropospheric water vapor flux to the southwest of Kyushu. While LS-BFD tends to have a stronger trend, no statistically significant difference was observed. However, focusing on lower-level water vapor flux convergence, a significant difference was observed in the lower troposphere approximately 12 hours before the occurrence of linear precipitation bands and for several hours afterward.
Additionally, the study investigates convective available potential energy (CAPE) and entrainment-CAPE (E-CAPE) composite fields to compare atmospheric instability. The results show significant differences in both CAPE and E-CAPE to the west of Kyushu between LS-BFD and NLS-BFD. However, E-CAPE is more distinct, with high values limited to the vicinity of Kyushu where linear precipitation bands occurred, showing a more pronounced difference. On the other hand, the composite of storm-relative helicity, one of the conditions for the occurrence of linear-stationary precipitation bands, did not show significant differences between LS-BFD and NLS-BFD.
Using long-term reanalysis data (1989-2020), this study extracts LS-BFD and NLS-BFD over Kyushu and examines the differences in their characteristics through composite analysis. The results of the composite analysis show that, just before the occurrence of linear precipitation bands, both LS-BFD and NLS-BFD exhibit strong lower-tropospheric water vapor flux to the southwest of Kyushu. While LS-BFD tends to have a stronger trend, no statistically significant difference was observed. However, focusing on lower-level water vapor flux convergence, a significant difference was observed in the lower troposphere approximately 12 hours before the occurrence of linear precipitation bands and for several hours afterward.
Additionally, the study investigates convective available potential energy (CAPE) and entrainment-CAPE (E-CAPE) composite fields to compare atmospheric instability. The results show significant differences in both CAPE and E-CAPE to the west of Kyushu between LS-BFD and NLS-BFD. However, E-CAPE is more distinct, with high values limited to the vicinity of Kyushu where linear precipitation bands occurred, showing a more pronounced difference. On the other hand, the composite of storm-relative helicity, one of the conditions for the occurrence of linear-stationary precipitation bands, did not show significant differences between LS-BFD and NLS-BFD.