Distinct Convection Initiation Near and Far ahead of an Idealized Squall Line.
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| Title: | Distinct Convection Initiation Near and Far ahead of an Idealized Squall Line. |
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| Authors: | Yang, Hongpei1 (AUTHOR), Du, Yu1,2,3 (AUTHOR) duyu7@mail.sysu.edu.cn |
| Source: | Journal of the Atmospheric Sciences. Jan2026, Vol. 83 Issue 1, p151-168. 18p. |
| Subjects: | Gravity waves, Thunderstorms, Meteorology, Atmospheric physics, Fronts (Meteorology), Natural heat convection, Numerical weather forecasting |
| Abstract: | Convection initiation (CI) ahead of convective systems, such as squall lines, is a widely observed phenomenon. Based on multiple CI events simulated ahead of an idealized squall line, this study investigates their spatiotemporal characteristics and their intrinsic connection to squall-line evolution. Over an 8-h simulation, CI events exhibit periodic episodes, primarily as distant events (≥5 km from the gust front) that progressively form farther ahead (extending beyond 100 km), while adjacent events (<5 km) maintain a stable frequency. Distant events are predominantly driven by cyclically generated low-amplitude n = 2 gravity waves and significantly correlate with locally stronger cold pools and higher radar reflectivity. These n = 2 waves, characterized by lower-tropospheric updrafts and upper-tropospheric downdrafts, promote CI by moistening the environment, enhancing instability, and lifting low-level parcels. Repeated wave generation and long-distance propagation (>300 km) further amplify their impact, expanding the spatial coverage of CI. Since these waves are generated through intense diabatic cooling, which simultaneously intensifies cold pools, the delayed wave propagation explains the higher frequency of distant CI linked to stronger cold pools. In contrast, adjacent events additionally rely on cold pools' mechanical lifting of nearby clouds, forming upright updrafts above the gust front, distinct from the squall line's tilted updraft. These near-vertical updrafts then prevent hydrometeor fallout, producing pendant-shaped echoes in the forward stratiform region. Both types of CI subsequently contribute to squall-line intensification and morphology modification through mergers and system reorganization, demonstrating the intricate feedback between CI and squall-line evolution. Significance Statement: Convection initiation often occurs ahead of thunderstorms, where new cells may either organize independently into new thunderstorms, or may merge with ongoing storms, significantly influencing their evolution. However, current understanding of convection initiation focuses on synoptic and mesoscale forcings, with limited understanding of its connections to nearby storms. Through high-resolution simulations, this work reveals how thunderstorm-generated gravity waves and cold pools collectively govern the formation of preline convective cells. These cells exhibit distinct temporal and spatial patterns, depending on local storm intensity. Furthermore, these newly initiated cells could, in turn, strengthen the storm, highlighting a self-reinforcing cycle driven by waves–cold pool interactions. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Convection initiation (CI) ahead of convective systems, such as squall lines, is a widely observed phenomenon. Based on multiple CI events simulated ahead of an idealized squall line, this study investigates their spatiotemporal characteristics and their intrinsic connection to squall-line evolution. Over an 8-h simulation, CI events exhibit periodic episodes, primarily as distant events (≥5 km from the gust front) that progressively form farther ahead (extending beyond 100 km), while adjacent events (<5 km) maintain a stable frequency. Distant events are predominantly driven by cyclically generated low-amplitude n = 2 gravity waves and significantly correlate with locally stronger cold pools and higher radar reflectivity. These n = 2 waves, characterized by lower-tropospheric updrafts and upper-tropospheric downdrafts, promote CI by moistening the environment, enhancing instability, and lifting low-level parcels. Repeated wave generation and long-distance propagation (>300 km) further amplify their impact, expanding the spatial coverage of CI. Since these waves are generated through intense diabatic cooling, which simultaneously intensifies cold pools, the delayed wave propagation explains the higher frequency of distant CI linked to stronger cold pools. In contrast, adjacent events additionally rely on cold pools' mechanical lifting of nearby clouds, forming upright updrafts above the gust front, distinct from the squall line's tilted updraft. These near-vertical updrafts then prevent hydrometeor fallout, producing pendant-shaped echoes in the forward stratiform region. Both types of CI subsequently contribute to squall-line intensification and morphology modification through mergers and system reorganization, demonstrating the intricate feedback between CI and squall-line evolution. Significance Statement: Convection initiation often occurs ahead of thunderstorms, where new cells may either organize independently into new thunderstorms, or may merge with ongoing storms, significantly influencing their evolution. However, current understanding of convection initiation focuses on synoptic and mesoscale forcings, with limited understanding of its connections to nearby storms. Through high-resolution simulations, this work reveals how thunderstorm-generated gravity waves and cold pools collectively govern the formation of preline convective cells. These cells exhibit distinct temporal and spatial patterns, depending on local storm intensity. Furthermore, these newly initiated cells could, in turn, strengthen the storm, highlighting a self-reinforcing cycle driven by waves–cold pool interactions. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00224928 |
| DOI: | 10.1175/JAS-D-25-0073.1 |
