Causes of extreme rainfall in May 2013 over Henan Province: the role of the southwest vortex and low-level jet

Abstract This study continues the investigation of airstreams in idealized moist baroclinic waves and addresses the formation of the cold conveyor belt (CCB), its linkage to the warm conveyor belt (WCB), and their impact on the development of a midlatitude cyclone. The CCB is identified as a coherent bundle of trajectories, characterized by weak ascent and a strong increase of potential vorticity (PV) along the flow, in contrast to the WCB, defined as the trajectories with maximum ascent. The authors illuminate the role of the two conveyor belts in the formation of two strong PV anomalies that form in the upper (WCB, negative PV anomaly) and lower troposphere (CCB, positive PV anomaly), respectively, and thereby establish a link between these airstreams and relevant aspects of the dynamics of extratropical cyclones. The CCB moves close to the surface along the colder side of the bent-back front and experiences a PV increase as it passes below a region of maximum latent heat release at midtropospheric levels. Accordingly, it arrives with high PV values at the tail of the bent-back front where the most intense low-level winds occur. The WCB, which rises above the bent-back front, causes the formation of the midtropospheric heating rate maximum and thereby not only influences the upper-level downstream development, but also drives the increase of PV along the CCB and, in consequence, indirectly drives the formation of the low-level jet at the tail of the bent-back front.

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The role of the US Great Plains low-level jet in nocturnal migrant behavior

International Journal of Biometeorology ◽

10.1007/s00484-016-1144-9 ◽

2016 ◽

Vol 60 (10) ◽

pp. 1531-1542 ◽

Cited By ~ 16

Author(s):

Charlotte E. Wainwright ◽

Phillip M. Stepanian ◽

Kyle G. Horton

Keyword(s):

Great Plains ◽

Low Level ◽

The Us ◽

Low Level Jet ◽

Us Great Plains ◽

Migrant Behavior

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An Observational Analysis of Three Extreme Rainfall Episodes of 19–20 July 2016 along the Taihang Mountains in North China

Monthly Weather Review ◽

10.1175/mwr-d-18-0402.1 ◽

2019 ◽

Vol 147 (11) ◽

pp. 4199-4220 ◽

Cited By ~ 2

Author(s):

Rudi Xia ◽

Da-Lin Zhang

Keyword(s):

North China ◽

Extreme Rainfall ◽

Northern Region ◽

Convective System ◽

Target Region ◽

Local Topography ◽

Southwest Vortex ◽

Low Level Jet ◽

The Stability ◽

Mesoscale Processes

Abstract This study examines the synoptic- and mesoscale processes leading to the generation of three extreme rainfall episodes with hourly rates of greater than 100 mm h−1 over the southern, middle, and northern portions of the eastern foothills of Mt. Taihang in North China on 19–20 July 2016. The extreme rainfall episodes took place over the 200–600-m elevation zones in the southern and northern portions but also over the lower elevations in the middle portion of the target region, sequentially during late morning, early evening, and midnight hours. Echo training accounted for the development of a linear convective system in the southern region after the warm and moist air carried by a southeasterly low-level jet (LLJ) was lifted to condensation as moving across Mt. Yuntai. In contrast, two isolated circular-shaped convective clusters, with more robust convective cores in its leading segment, developed in the northern region through steep topographical lifting of moist northeasterly airflow, albeit conditionally less unstable. Extreme rainfall in the middle region developed from the convergence of a moist easterly LLJ with a northerly colder airflow associated with an extratropical cyclogenesis. Results reveal that the LLJs and associated moisture transport, the intensifying cyclone interacting with a southwest vortex and its subsequent northeastward movement, and the slope and orientation of local topography with respect to and the stability of the approaching airflows played different roles in determining the timing and location, the extreme rainfall rates, and convective organizations along the eastern foothills of Mt. Taihang.

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