Comments on “The Intensification of the Low-Level Jet during the Development of Mesoscale Convective Systems on a Mei-Yu Front”

Chen, Yi-Leng; Tseng, Shu-Fen

doi:10.1175/1520-0493(2000)128<0495:cotiot>2.0.co;2

Cited by 11 publications

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“…Chen et al (1998) suggest that the LLJ was generated by Coriolis force acting on the mesoinflow associated with mesoscale convective systems in the Mei-Yu frontal zone. Nevertheless, observational studies (Chen et al 1994;Tseng 2000) show that the LLJ defined by Chen and Yu (1988) is a subsynoptic-scale feature in the warm sector of the Mei-Yu trough. These studies also show that the LLJ is close to geostrophic balance.…”

Section: Introductionmentioning

confidence: 99%

“…As a result, the upper-level westerly flow along the southern China coast was replaced by a northeasterly flow after the seasonal change. Chen and Li (1995) show that during the TAMEX IOP (Intensive Observing Period) 3 (May 21-23), the coupling between the upperlevel troughs, and low-level baroclinic forcing, is important for the development of the heavy precipitation along the southeastern China coast.…”

Section: Introductionmentioning

confidence: 99%

“…The LLJ transports warm, moist air from the southwest to generate convective instability (Chen 1983;Chen et al 1994;Li et al 1997). Numerical studies of the LLJ have focused on the massmomentum adjustment process driven by convective heating (Chen and Dell'Osso 1984;Chou et al 1990;Hsu and Sun 1994;Chen et al 1998).…”

Section: Introductionmentioning

confidence: 99%

“…The northwesterly flow behind the midlatitude trough brings in colder, drier air to the rear of the Mei-Yu trough from higher latitudes (Ma and Bosart 1987;Chen and Hui 1990. Based on the diagnosis of the MeiYu system during the TAMEX IOP 5 (1-2 June), Chen et al (1994) show that the transverse secondary circulation across the jet-front system is characterized by a thermally direct circulation across the baroclinic zone. The upper-level frontal zone and tropopause folding are also evident.…”

Section: Introductionmentioning

confidence: 99%

“…The upper-level frontal zone and tropopause folding are also evident. Chen et al (1997) simulated the cyclone-jet event during the TAMEX IOP 5 (1-2 June), with the Pennsylvania State University (PSU)/ National Center for Atmospheric Research (NCAR) mesoscale model version 4 (hereafter referred to as MM4). It was shown that in their control experiment, the model successfully reproduces most principal features of this event including cyclone path, intensification of the LLJ, upper-level short-wave trough and the associated ULJ, distribution of precipitation, and the secondary circulation across the jet-front system.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic Energy Budgets of the Low-Level Jet during TAMEX IOP 5.

Chen

2002

Journal of the Meteorological Society of Japan

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Using results from numerical experiments, budgets of divergent kinetic energy (k D ) and nondivergent kinetic energy (k ND ), are examined for the subsynoptic-scale low-level jet (LLJ) event that occurred during 1-2 June 1987 (TAMEX IOP 5) to diagnose the energy conversion process leading to the LLJ development.Nondivergent kinetic energy (k ND ) dominates the total kinetic energy. The intensification of the LLJ, and the subsynoptic-scale upper-level jet (ULJ) is due to the increase in k ND . Divergent kinetic energy (k D ) is rather small. In the area encompassing the LLJ, the most important energy source of k ND is k D generated from the potential energy (PE) through the cross-contour divergent winds, and then converted into k ND via a conversion process through the transverse secondary circulation across the jet-front system. In the upper troposphere, the cross-contour flow across the ULJ is dominated by the nondivergent winds. The major source for the increase of k ND associated with the intensification of ULJ is the conversion from the potential energy to k ND via cross-contour nondivergent winds. This conversion rate is independent of the strength of the secondary circulation. The upper-level divergence ahead of the upperlevel trough is mainly contributed by the along-stream agesotrophic winds along the ULJ axis, and it provides the upper-level support needed for the LLJ development in the lower troposphere. This mechanism is at variance with the CISK (Condtional Instability of the Second Kind) process in the traditional view.Without the feedback effects from convective heating (NOLH), low-level frontal cyclone fails to fully develop. The secondary circulation is weaker with a much slower energy conversion process from PE to k D , and then to k ND in the lower troposphere. As a result, the simulated LLJ in the NOLH experiment is much weaker. Nevertheless, the intensity of the simulated ULJ without latent heating is about the same as that with latent heating. This is because the conversion from the potential energy to k ND via crosscontour nondivergence winds, is independent of the strength of the transverse secondary circulation across the jet-front system.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinetic Energy Budgets of the Low-Level Jet during TAMEX IOP 5.

Chen

2002

Journal of the Meteorological Society of Japan

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Spatial and temporal characteristics of warm season convection over Pearl River Delta region, China, based on 3 years of operational radar data

2014

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This study examines the temporal and spatial characteristics and distributions of convection over the Pearl River Delta region of Guangzhou, China, during the May-September warm season, using, for the first time for such a purpose, 3 years of operational Doppler radar data in the region. Results show that convective features occur most frequently along the southern coast and the windward slope of the eastern mountainous area of Pearl River Delta, with the highest frequency occurring in June and the lowest in September among the 5 months. The spatial frequency distribution pattern also roughly matches the accumulated precipitation pattern. The occurrence of convection in this region also exhibits strong diurnal cycles. During May and June, the diurnal distribution is bimodal, with the maximum frequency occurring in the early afternoon and a secondary peak occurring between midnight and early morning. The secondary peak is much weaker in July, August, and September. Convection near the coast is found to occur preferentially on days when a southerly low-level jet (LLJ) exists, especially during the Meiyu season. Warm, moist, and unstable air is transported from the ocean to land by LLJs on these days, and the lifting along the coast by convergence induced by differential surface friction between the land and ocean is believed to be the primary cause for the high frequency along the coast. In contrast, the high frequency over mountainous area is believed to be due to orographic lifting of generally southerly flows during the warm season.

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The Mei-Yu Season Over the Taiwan Area

Chen,

2024

Reference Module in Earth Systems and Environmental Sciences

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Comments on “The Intensification of the Low-Level Jet during the Development of Mesoscale Convective Systems on a Mei-Yu Front”

Cited by 11 publications

References 0 publications

Kinetic Energy Budgets of the Low-Level Jet during TAMEX IOP 5.

Kinetic Energy Budgets of the Low-Level Jet during TAMEX IOP 5.

Spatial and temporal characteristics of warm season convection over Pearl River Delta region, China, based on 3 years of operational radar data

The Mei-Yu Season Over the Taiwan Area

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