A Three-Dimensional Numerical Investigation Of a Carolina Coastal Low-Level Jet during GALE IOP 2

AbstractA climatological approach is developed to characterize the mesoscale environment in which heavily precipitating events (HPEs) grow over a mountainous Mediterranean area. This climatology that is based on three-dimensional variational data assimilation (3D-Var) mesoscale analyses is performed for a 5-yr period, considering cases with daily precipitation of >150 mm occurring over southern France during autumn. Different diagnostics are used to document the time evolution of mesoscale features associated with the HPEs for initiation, mature, and dissipation stages. To underline differences according to the location of precipitation, four subdomains are also considered: Languedoc-Roussillon, Cévennes-Vivarais, South Alps, and Corsica. Composite analyses show that these events are driven by some common features (slowly evolving trough–ridge pattern and diffluent midlevel flow). Instability and moisture are transported by the low-level jet (LLJ) toward the target area from their sources, which are located upstream over the Mediterranean Sea. Strong moisture convergence is located within the left exit of the LLJ. These parameters reach a maximum during the mature stage. During the life cycle of the HPEs, the low-level winds rotate clockwise. Composite analyses also show that the synoptic and mesoscale patterns can differ greatly as a function of the location of the precipitation. Indeed, the LLJ varies from southeasterly to southwesterly. The midlevel flow varies from southerly to southwesterly. The areas of high moisture and instability are stretched in different orientations. Long-lasting events are associated with a more pronounced quasi-stationary trough–ridge pattern, higher values of CAPE, a wetter troposphere, and faster LLJ. The most-heavily precipitating events are found to be in general associated with higher values of these parameters or with a low-level inflow that is closer to perpendicular to the relief.

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A Modeling Study of a Low-Level Jet along the Yun-Gui Plateau in South China

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-15-0067.1 ◽

2016 ◽

Vol 55 (1) ◽

pp. 41-60 ◽

Cited By ~ 11

Author(s):

Ming-Yang He ◽

Hong-Bo Liu ◽

Bin Wang ◽

Da-Lin Zhang

Keyword(s):

South China ◽

Large Scale ◽

Model Simulation ◽

Three Dimensional ◽

Radiative Heating ◽

Horizontal Wind ◽

Maximum Speed ◽

Pressure System ◽

Low Level ◽

Low Level Jet

AbstractIn this study, the three-dimensional structures and diurnal evolution of a typical low-level jet (LLJ) with a maximum speed of 24 m s−1 occurring in the 850–800-hPa layer are examined using both large-scale analysis and a high-resolution model simulation. The LLJ occurred on the eastern foothills of the Yun-Gui Plateau in south China from 1400 LST 29 June to 1400 LST 30 June 2003. The effects of surface radiative heating, topography, and latent heat release on the development of the LLJ case are also studied. Results show that a western Pacific Ocean subtropical high and a low pressure system on the respective southeast and northwest sides of the LLJ provide a favorable large-scale mean pressure pattern for the LLJ development. The LLJ reaches its peak intensity at 850 hPa near 0200 LST with wind directions veering from southerly before sunset to southwesterly at midnight. A hodograph at the LLJ core shows a complete diurnal cycle of the horizontal wind with a radius of 5.5 m s−1. It is found that in an LLJ coordinates system the along-LLJ geostrophic component regulates the distribution and 65% of the intensity of LLJ, whereas the ageostrophic component contributes to the clockwise rotation, thus leading to the formation and weakening of the LLJ during night- and daytime, respectively. Numerical sensitivity experiments confirm the surface radiative heating as the key factor in determining the formation of the nocturnal LLJ. The existence of the Yun-Gui Plateau, and the downstream condensational heating along the mei-yu front play secondary roles in the LLJ formation.

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A case study of a low level jet during OPALE

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-31091-2014 ◽

2014 ◽

Vol 14 (22) ◽

pp. 31091-31109 ◽

Cited By ~ 1

Author(s):

H. Gallée ◽

H. Barral ◽

E. Vignon ◽

C. Genthon

Keyword(s):

Three Dimensional ◽

East Antarctica ◽

Low Level ◽

Thermal Wind ◽

Flat Terrain ◽

Dimensional Version ◽

Low Level Jet ◽

Oxidant Production

Abstract. A case study of a low level jet during the OPALE (Oxidant Production over Antarctic Land and its Export) summer campaign is presented. It has been observed at Dome C (East Antarctica) and is simulated accurately by the three-dimensional version of the Modèle Atmosphérique Régional (MAR). It is found that this low level jet is not related to an episode of thermal wind, conforting that Dome C may be a~place where turbulence on flat terrain can be studied.

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A case study of a low-level jet during OPALE

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-6237-2015 ◽

2015 ◽

Vol 15 (11) ◽

pp. 6237-6246 ◽

Cited By ~ 6

Author(s):

H. Gallée ◽

H. Barral ◽

E. Vignon ◽

C. Genthon

Keyword(s):

Three Dimensional ◽

East Antarctica ◽

Low Level ◽

Thermal Wind ◽

Flat Terrain ◽

Dimensional Version ◽

Low Level Jet ◽

Oxidant Production

Abstract. A case study of a low-level jet (LLJ) during the OPALE (Oxidant Production over Antarctic Land and its Export) summer campaign is presented. It has been observed at Dome C (East Antarctica) and is simulated accurately by the three-dimensional version of the Modèle Atmosphérique Régional (MAR). It is found that this low-level jet is not related to an episode of thermal wind, suggesting that Dome C may be a place where turbulence on flat terrain can be studied.

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Influence of Boundary Layer Structure and Low-Level Jet on PM2.5 Pollution in Beijing: A Case Study

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16040616 ◽

2019 ◽

Vol 16 (4) ◽

pp. 616 ◽

Cited By ~ 4

Author(s):

Yucong Miao ◽

Shuhua Liu ◽

Li Sheng ◽

Shunxiang Huang ◽

Jian Li

Keyword(s):

Boundary Layer ◽

Large Scale ◽

Layer Structure ◽

Three Dimensional ◽

Near Surface ◽

Thermally Induced ◽

Low Level ◽

Relative Contribution ◽

Low Level Jet ◽

Meteorological Observations

Beijing experiences frequent PM2.5 pollution, which is influenced by the planetary boundary layer (PBL) structure/process. Partly due to a lack of appropriate observations, the impacts of PBL on PM2.5 pollution are not yet fully understood. Combining wind-profiler data, radiosonde measurements, near-surface meteorological observations, aerosol measurements, and three-dimensional simulations, this study investigated the influence of PBL structure and the low-level jet (LLJ) on the pollution in Beijing from 19 to 20 September 2015. The evolution of the LLJ was generally well simulated by the model, although the wind speed within the PBL was overestimated. Being influenced by the large-scale southerly prevailing winds, the aerosols emitted from the southern polluted regions could be easily transported to Beijing, contributing to ~68% of the PM2.5 measured in Beijing on 20 September. The relative contribution of external transport of PM2.5 to Beijing was high in the afternoon (≥80%), which was related to the strong southerly PBL winds and the presence of thermally-induced upslope winds. On 20 September, the LLJ in Beijing demonstrated a prominent diurnal variation, which was predominant in the morning and after sunset. The occurrence of the LLJ could enhance the dilution capacity in Beijing to some extent, which favors the dilution of pollutants at a local scale. This study has important implications for better understanding the complexity of PBL structure/process associated with PM2.5 pollution in Beijing.

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