Organized Warm-Sector Rainfall in the Coastal Region of South China in an Anticyclone Synoptic Situation: Observational Analysis

The characteristics of the synoptic situation and the evolution of the organized warm-sector rainfalls (OWSRs) in the coastal region of South China in the pre-summer rainy season were investigated, using a period (2011–2016) of high-resolution observational data and European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-Interim) data. The results show that a strong southwesterly low-level jet (LLJ) ahead of a trough over southwestern China with a marked boundary-layer jet (BLJ) over the northern South China Sea (synoptic situation SWLLJ) or a prominent, low-level anticyclone over the Yangtze River Basin (synoptic situation ACR) is present when the OWSRs occur in the coastal region of South China. The OWSRs are prone to initiate on the windward side of the coastal mountains, owing to the convergence enhanced by the colliding of the BLJ with the mountains and the coupling of double LLJs near the coast (for SWLLJ), or due to the convergence between northerly and southeasterly winds near the coastal mountains (for ACR). The OWSRs present a long extension when the LLJ axis is nearby. The translation of the LLJ itself also promotes the long extension of the OWSRs. In contrast, the OWSRs show a short extension when the LLJ axis is farther away or ACR occurs. Meanwhile, the OWSRs are directed northeastward in Guangxi Province and more eastward in Guangdong Province, probably owing to the orientation difference of the LLJ in these two provinces. The rainfall systems in the ACR situation tend to move eastward, whereas those in the SWLLJ situation are prone to move eastward when equivalently strong or much-stronger upper-level winds overlay the LLJ, but move northeastward when much weaker upper-level winds couple with the LLJ.

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A Case Study of the Effects of a Synoptic Situation on the Motion and Development of Warm-Sector Mesoscale Convective Systems over South China

Asia-Pacific Journal of Atmospheric Sciences ◽

10.1007/s13143-018-0063-6 ◽

2018 ◽

Vol 55 (2) ◽

pp. 255-268 ◽

Cited By ~ 2

Author(s):

Zhaoming Liang ◽

Ying Liu ◽

Jinfang Yin ◽

Chongjian Liu

Keyword(s):

South China ◽

Mesoscale Convective Systems ◽

Synoptic Situation ◽

Convective Systems ◽

Warm Sector ◽

Mesoscale Convective

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Budgets of rotational and divergent kinetic energy in the warm-sector torrential rains over South China: a case study

Meteorology and Atmospheric Physics ◽

10.1007/s00703-021-00778-1 ◽

2021 ◽

Author(s):

Shui-Xin Zhong ◽

Wei-Guang Meng ◽

Fu-You Tian

Keyword(s):

Kinetic Energy ◽

Energy Budget ◽

South China ◽

Extreme Precipitation ◽

Flux Divergence ◽

Low Level ◽

Warm Sector ◽

Kinetic Energy Budget ◽

Rotational Components ◽

The Pearl River

AbstractThe contributions of divergent and rotational wind components to the kinetic energy budget during a record-breaking rainstorm on 7 May 2017 over South China are examined. This warm-sector extreme precipitation caused historical maximum of 382.6 mm accumulated rainfall in 3 h over the Pearl River Delta (PRD) regions in South China. Results show that there was a high low-level southerly wind-speed tongue stretching into the PRD regions from the northeast of the South China Sea (SCS) during this extreme precipitation. The velocity potential exhibited a low-value center as well as a low-level divergence-center over the SCS. The rotational components of the kinetic energy (KR)-related terms were the main contribution-terms of the kinetic energy budget. The main contribution-terms of KR and the divergent component of kinetic energy (KD) were the barotropical and baroclinic processes-related terms due to cross-contour flow and the vertical flux divergence.

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Distribution and Exposure Risk Assessment of Perfluorinated Alkyl Substances in Aquatic Products along the Coastal Region of the South China Sea

Exposure and Health ◽

10.1007/s12403-021-00399-4 ◽

2021 ◽

Author(s):

Xu-Feng Wang ◽

Meng-Song Mo ◽

Hai-Gang Chen ◽

Qiang Wang ◽

Jin-Lan Yang ◽

...

Keyword(s):

Risk Assessment ◽

South China Sea ◽

South China ◽

Coastal Region ◽

The South China Sea ◽

Exposure Risk ◽

China Sea ◽

Aquatic Products ◽

Perfluorinated Alkyl Substances ◽

Exposure Risk Assessment

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A 7-Year Climatology of Warm-Sector Heavy Rainfall over South China during the Pre-Summer Months

Atmosphere ◽

10.3390/atmos12070914 ◽

2021 ◽

Vol 12 (7) ◽

pp. 914

Author(s):

Tao Chen ◽

Da-Lin Zhang

Keyword(s):

South China ◽

Heavy Rainfall ◽

Large Scale ◽

Convective Available Potential Energy ◽

Potential Temperature ◽

Vertical Wind Shear ◽

Precipitable Water ◽

Atmospheric Parameter ◽

Low Level ◽

Warm Sector

In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., far ahead of the surface cold front), referred to as WSHR events, over South China during the months of April to June 2008~2014 is performed in terms of precipitation, large-scale circulations, pre-storm environmental conditions, and MCS types. Results show that the large-scale circulations of the WSHR events can be categorized into pre-frontal, southwesterly warm and moist ascending airflow, and low-level vortex types, with higher frequency occurrences of the former two types. Their pre-storm environments are characterized by a deep moist layer with >50 mm column-integrated precipitable water, high convective available potential energy with the equivalent potential temperature of ≥340 K at 850 hPa, weak vertical wind shear below 400 hPa, and a low-level jet near 925 hPa with weak warm advection, based on atmospheric parameter composite. Three classes of the corresponding MCSs, exhibiting peak convective activity in the afternoon and the early morning hours, can be identified as linear-shaped, a leading convective line adjoined with trailing stratiform rainfall, and comma-shaped, respectively. It is found that many linear-shaped MCSs in coastal regions are triggered by local topography, enhanced by sea breezes, whereas the latter two classes of MCSs experience isentropic lifting in the southwesterly warm and moist flows. They all develop in large-scale environments with favorable quasi-geostrophic forcing, albeit weak. Conceptual models are finally developed to facilitate our understanding and prediction of the WSHR events over South China.

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Oxygenated volatile organic carbon in the western Pacific convective center: ocean cycling, air–sea gas exchange and atmospheric transport

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-10837-2017 ◽

2017 ◽

Vol 17 (17) ◽

pp. 10837-10854 ◽

Cited By ~ 14

Author(s):

Cathleen Schlundt ◽

Susann Tegtmeier ◽

Sinikka T. Lennartz ◽

Astrid Bracher ◽

Wee Cheah ◽

...

Keyword(s):

South China ◽

Atmospheric Transport ◽

Coastal Region ◽

Western Pacific ◽

Northern Coast ◽

The South ◽

Model Calculations ◽

Surface Ocean ◽

Volatile Organic ◽

The Western Pacific

Abstract. A suite of oxygenated volatile organic compounds (OVOCs – acetaldehyde, acetone, propanal, butanal and butanone) were measured concurrently in the surface water and atmosphere of the South China Sea and Sulu Sea in November 2011. A strong correlation was observed between all OVOC concentrations in the surface seawater along the entire cruise track, except for acetaldehyde, suggesting similar sources and sinks in the surface ocean. Additionally, several phytoplankton groups, such as haptophytes or pelagophytes, were also correlated to all OVOCs, indicating that phytoplankton may be an important source of marine OVOCs in the South China and Sulu seas. Humic- and protein-like fluorescent dissolved organic matter (FDOM) components seemed to be additional precursors for butanone and acetaldehyde. The measurement-inferred OVOC fluxes generally showed an uptake of atmospheric OVOCs by the ocean for all gases, except for butanal. A few important exceptions were found along the Borneo coast, where OVOC fluxes from the ocean to the atmosphere were inferred. The atmospheric OVOC mixing ratios over the northern coast of Borneo were relatively high compared with literature values, suggesting that this coastal region is a local hotspot for atmospheric OVOCs. The calculated amount of OVOCs entrained into the ocean seemed to be an important source of OVOCs to the surface ocean. When the fluxes were out of the ocean, marine OVOCs were found to be enough to control the locally measured OVOC distribution in the atmosphere. Based on our model calculations, at least 0.4 ppb of marine-derived acetone and butanone can reach the upper troposphere, where they may have an important influence on hydrogen oxide radical formation over the western Pacific Ocean.

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Ozone pollution around a coastal region of South China Sea: Interaction between marine and continental air

10.5194/acp-2017-988 ◽

2017 ◽

Author(s):

Hao Wang ◽

Xiaopu Lyu ◽

Hai Guo ◽

Yu Wang ◽

Shichun Zou ◽

...

Keyword(s):

South China Sea ◽

South China ◽

Air Pollutants ◽

Coastal Region ◽

Oxidative Capacity ◽

Atmospheric Composition ◽

Marine Atmosphere ◽

Ozone Pollution ◽

China Sea ◽

Coastal Cities

Abstract. Marine atmosphere is usually considered to be a clean environment, while this study indicates that the near-coast waters of South China Sea (SCS) suffered from even worse air quality than coastal cities. The analyses were based on concurrent field measurements of target air pollutants and meteorological parameters conducted at a suburban site (TC) and a nearby marine site (WS) from August to November 2013. The observations showed that the levels of primary air pollutants were significantly lower at WS than those at TC, while ozone (O3) value was greater at WS. Higher O3 levels at WS were attributed to the weaker NO titration and higher O3 production rate because of stronger oxidative capacity of the atmosphere. However, O3 episodes were concurrently observed at both sites under certain meteorological conditions, such as tropical cyclones, continental anticyclones and sea-land breezes (SLBs). Driven by these synoptic systems and mesoscale recirculations, the interaction between continental and marine air masses had profoundly changed the atmospheric composition and subsequently influenced the formation and redistribution of O3 in the coastal areas. When continental air intruded into marine atmosphere, the O3 pollution was magnified over SCS, and the elevated O3 (> 100 ppbv) could overspread the sea boundary layer ~ 8 times the area of Hong Kong. In some cases, the exaggerated O3 pollution over the SCS was re-circulated to the coastal inshore by sea breeze, leading to even aggravating O3 pollution in coastal cities. The findings are applicable to similar mesoscale environments around the world where the maritime atmosphere is potentially influenced by severe continental air pollution.

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