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In 2022, Guangxi experienced the strongest Dragon Boat Precipitation since the founding of the People's Republic of China. The persistent rainstorm process from 17 June to 22 June 2022 had large accumulations and overlapping falling areas, leading to floods, torrential floods, landslides, and other disasters. The impacts of the low-level jet and its characteristics during this process were analyzed based on multi-source observation data and ERA5 reanalysis data. The results show that: (1) The low-level jet enhanced significantly during the night, and the convective system developed on the north side of the jet core. During the daytime, the low-level jet weakened and the convective system gradually disappeared, resulting in the heavy precipitation being mainly concentrated during the night. (2) During the night, the positive vorticity zone on the left of the 850 hPa low-level jet coincided with the exit zone of the 925 hPa boundary-level jet in the northeast of Guangxi, which combined with the mountain terrain barrier, and caused deep low-level convergence. The low-level convergence was conducive to the enhancement of the upward movement in northeast Guangxi and favored the continuous development of the convective system. At the same time, the convective instability in the lower atmosphere also increased rapidly, which provided a favorable unstable stratification environment for heavy precipitation. (3) The variation of the low-level jet can be well explained by the inertial oscillation mechanism. During the day, the surface heating in the central and southern regions of Guangxi led to the gradual enhancement of turbulent friction, resulting in jet deceleration with the characteristics of sub-geostrophic. During the night, the turbulent friction was weakened, and the jet accelerated, which gradually presented the characteristics of super-geostrophic. The Coriolis force acting on ageostrophic wind was the main contributor to the momentum of the jet, while friction dissipation and vertical transport were the momentum sinks.

Different from other upper‐tropospheric jet stream that owns the single jet axis, the tropical easterly jet (TEJ) generally splits into two branches over the tropical western Pacific where the TEJ inflows from June to September, with the north branch locating near 20°N and the south branch appearing near the equator. However, how these double easterly jets change from year to year and whether they have effects on the tropical cyclones (TCs) over the tropical western Pacific are still unknown. Observational evidence has demonstrated that the double easterly jets in the TEJ's inflow region exhibit an out‐of‐phase relationship in the interannual time scale and is significantly related to the TCs genesis. Corresponding to a stronger south branch and a weaker north branch, the accelerated (decelerated) easterly wind for the south (north) branch would induce a northerly (southerly) ageostrophic wind, thus triggering an upper‐tropospheric divergence between the double easterly jets. This divergence can further lead to anomalous ascending flows over the western North Pacific, which turns out to be the primary cause that increases the TCs number over there. The results highlight that the out‐of‐phase variation of the double easterly jets could dynamically modulate the occurrence of the TCs over the western North Pacific by inducing the secondary vertical circulation. [ABSTRACT FROM AUTHOR]

The third precipitation episode of China's great snowstorms of 2008 was analyzed using station observations and ECMWF six-hourly data. The variation of the shape of the upper-level subtropical jet played an important role in the rainfall over southern China. With the eastward movement of the trough, the jet shape changed from two straight jets to a tilting jet over China and then it moved southward. With these variations, the south-north movement of ascending flow and precipitation area over southern China occurred. [ABSTRACT FROM AUTHOR]