Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Characteristics of Low-Level Jets over Northern Taiwan in Mei-Yu Season and Their Relationship to Heavy Rain Events

Characteristics of Low-Level Jets over Northern Taiwan in Mei-Yu Season and Their Relationship to... The present study investigates the characteristics of low-level jets (LLJs) (≥12.5 m s −1 ) below 600 hPa over northern Taiwan in the mei-yu season and their relationship to heavy rainfall events (≥50 mm in 24 h) through the use of 12-h sounding data, weather maps at 850 and 700 hPa, and hourly rainfall data at six surface stations during the period of May–June 1985–94. All LLJs are classified based on their height, appearance (single jet or double jet), and movement (migratory and nonmigratory). The frequency, vertical structure, and spatial and temporal distribution of LLJs relative to the onset of heavy precipitation are discussed. Results on the general characteristics of LLJs suggest that they occurred about 15% of the time in northern Taiwan, with a top speed below 40 m s −1 . The level of maximum wind appeared mostly between 850 and 700 hPa, with highest frequency at 825–850 hPa. A single jet was observed more often (76%) than a double jet (24%), while in the latter case a barrier jet usually existed at 900–925 hPa as the lower branch. Migratory and nonmigratory LLJs each constituted about half of all cases, and there existed no apparent relationship between their appearance and movement. Migratory LLJs tended to be larger in size, stronger over a thicker layer, more persistent, and were much more closely linked to heavy rainfall than nonmigratory jets. They often formed over southern China between 20° and 30°N and moved toward Taiwan presumably along with the mei-yu frontal system. Before and near the onset of the more severe heavy rain events (≥100 mm in 24 h) in northern Taiwan, there was a 94% chance that an LLJ would be present over an adjacent region at 850 hPa, and 88% at 700 hPa, in agreement with earlier studies. Occurrence frequencies of LLJs for less severe events (50–100 mm in 24 h) were considerably lower, and the difference in accumulative rainfall amount was seemingly also affected by the morphology of the LLJs, including their strength, depth, elevation of maximum wind, persistence, proximity to northern Taiwan, source region of moisture, and their relative timing of arrival before rainfall. During the data period, about 40% of all migratory LLJs at 850 or 700 hPa passing over northern Taiwan were associated with heavy rainfall within the next 24 h. The figure, however, was much lower compared to earlier studies, and some possible reasons are offered to account for this deficit. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Monthly Weather Review American Meteorological Society

Characteristics of Low-Level Jets over Northern Taiwan in Mei-Yu Season and Their Relationship to Heavy Rain Events

Download PDF
24 pages

Loading next page...
 
/lp/american-meteorological-society/characteristics-of-low-level-jets-over-northern-taiwan-in-mei-yu-BoESQbxWed

References

References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.

Publisher
American Meteorological Society
Copyright
Copyright © 2003 American Meteorological Society
ISSN
1520-0493
DOI
10.1175/MWR-2813.1
Publisher site
See Article on Publisher Site

Abstract

The present study investigates the characteristics of low-level jets (LLJs) (≥12.5 m s −1 ) below 600 hPa over northern Taiwan in the mei-yu season and their relationship to heavy rainfall events (≥50 mm in 24 h) through the use of 12-h sounding data, weather maps at 850 and 700 hPa, and hourly rainfall data at six surface stations during the period of May–June 1985–94. All LLJs are classified based on their height, appearance (single jet or double jet), and movement (migratory and nonmigratory). The frequency, vertical structure, and spatial and temporal distribution of LLJs relative to the onset of heavy precipitation are discussed. Results on the general characteristics of LLJs suggest that they occurred about 15% of the time in northern Taiwan, with a top speed below 40 m s −1 . The level of maximum wind appeared mostly between 850 and 700 hPa, with highest frequency at 825–850 hPa. A single jet was observed more often (76%) than a double jet (24%), while in the latter case a barrier jet usually existed at 900–925 hPa as the lower branch. Migratory and nonmigratory LLJs each constituted about half of all cases, and there existed no apparent relationship between their appearance and movement. Migratory LLJs tended to be larger in size, stronger over a thicker layer, more persistent, and were much more closely linked to heavy rainfall than nonmigratory jets. They often formed over southern China between 20° and 30°N and moved toward Taiwan presumably along with the mei-yu frontal system. Before and near the onset of the more severe heavy rain events (≥100 mm in 24 h) in northern Taiwan, there was a 94% chance that an LLJ would be present over an adjacent region at 850 hPa, and 88% at 700 hPa, in agreement with earlier studies. Occurrence frequencies of LLJs for less severe events (50–100 mm in 24 h) were considerably lower, and the difference in accumulative rainfall amount was seemingly also affected by the morphology of the LLJs, including their strength, depth, elevation of maximum wind, persistence, proximity to northern Taiwan, source region of moisture, and their relative timing of arrival before rainfall. During the data period, about 40% of all migratory LLJs at 850 or 700 hPa passing over northern Taiwan were associated with heavy rainfall within the next 24 h. The figure, however, was much lower compared to earlier studies, and some possible reasons are offered to account for this deficit.

Journal

Monthly Weather Review – American Meteorological Society

Published: Dec 15, 2003

References

  • Ageostrophic low level jet stream in the baiu season associated with heavy rainfalls over the sea area.
    Akiyama
  • The Great Plains low-level jet during the warm season of 1993.
    Arritt
  • Boundary layer wind maxima and their significance for the growth for the nocturnal inversions.
    Blackadar
  • Climatology of the low-level jet.
    Bonner
  • Satellite observations of the wind jets off the Pacific coast of Central America. Part I: Case studies and statistical characteristics.
    Chelton
  • An analysis of the relationship between the low-level jet stream and the heavy rainfall during the mei-yu season in Taiwan (in Chinese with English abstract).
    Chen
  • Observational aspects of mei-yu phenomena in subtropical China.
    Chen
  • On the heavy rainfall research in the Taiwan mei-yu season (in Chinese with English abstract).
    Chen
  • On the spatial and temporal patterns of heavy rainfall in Taiwan mei-yu season (in Chinese with English abstract).
    Chen
  • Study of low-level jet and extremely heavy rainfall over northern Taiwan in the mei-yu season.
    Chen
  • Composite structure of a low-level jet over southern China observed during the TAMEX period.
    Chen
  • Potential vorticity diagnostics of a mei-yu front case.
    Chen
  • A modeling case study of heavy rainstorms along the mei-yu front.
    Chen
  • Mesoscale convective systems along the Meiyu front in a numerical model.
    Chen
  • The synoptic-scale environment associated with the low-level jet of the Great Plains.
    Chen
  • Development of low-level jets during TAMEX.
    Chen
  • Some synoptic aspects of the surface fronts over southern China during TAMEX.
    Chen
  • Analysis of a relatively dry front during the Taiwan Area Mesoscale Experiment.
    Chen
  • Large-scale conditions favorable for the development of heavy rainfall during TAMEX IOP 3.
    Chen
  • A diagnostic study of the low-level jet during TAMEX IOP 5.
    Chen
  • A numerical study of the low-level jet during TAMEX IOP 5.
    Chen
  • A numerical simulation of the mei-yu front and the associated low level jet.
    Chou
  • Summer monsoon rainfalls in China.
    Ding
  • Diurnal variation and horizontal extent of the low-level jet over the northern Gulf of California.
    Douglas
  • Baroclinic instability in an environment of small stability to slantwise moist convection. Part I: Two-dimensional models.
    Emanuel
  • The effects of released latent heat in growing baroclinic waves.
    Gall
  • The impact of diurnal cycle on a low–Froude number flow observed during the PYREX experiment.
    Georgelin
  • A numerical study of a low-level jet and its accompanying secondary circulation in a mei-yu system.
    Hsu
  • Low-level jet development during a numerically simulated return flow event.
    Igau
  • The Taiwan Area Mesoscale Experiment (TAMEX): An overview.
    Kuo
  • Barrier jets during TAMEX.
    Li
  • Analysis of a heavy rainfall event during TAMEX.
    Li
  • Orographic effects on airflow and mesoscale weather systems over Taiwan.
    Lin
  • Lower tropospheric wind and precipitation activity.
    Matsumoto
  • A climatology of the warm season Great Plains low-level jet using wind profiler observations.
    Mitchell
  • A modeling case study of interaction between heavy precipitation and a low-level jet over Japan in the baiu season.
    Nagata
  • Band structure of mesoscale echo cluster associated with low-level jet stream.
    Ninomiya
  • The early summer rainy season (baiu) over Japan.
    Ninomiya
  • On the formation process of spring low-level jet over subtropical China (in Chinese with English abstract).
    Pu
  • Mesoscale Meteorology and Forecasting.
    Ray
  • Models of coastally trapped disturbances.
    Skamarock
  • Aerial observations of Hawaii's wake.
    Smith
  • The coupling of upper-level and low-level jet streaks during TAMEX period (in Chinese with English abstract).
    Tsay
  • On the role of upper tropospheric jet streaks and leeside cyclogenesis in the development of low-level jets in the Great Plains.
    Uccellini
  • The coupling of upper and lower tropospheric jet streaks and implication for the development of severe convective storms.
    Uccellini
  • Synergistic interactions between an upper-level jet streak and diabatic processes that influence the development of a low-level jet and a secondary coastal cyclone.
    Uccellini
  • On the formation of leeside mesolows under different Froude number flow regime in TAMEX.
    Wang
  • A case study of the Great Plains low-level jet using wind profiler network data and a high-resolution mesoscale model.
    Zhong