scholarly journals Influence of Decadal Ocean Signals on Meteorological Conditions Associated With the Winter Haze Over Eastern China

2021 ◽  
Vol 9 ◽  
Author(s):  
Wen Zhang ◽  
Xiao Dong ◽  
Zhenxin Liu ◽  
Renping Lin ◽  
Hao Luo
Keyword(s):  
Time Scale ◽  
Wave Train ◽  
Eastern China ◽  
Meteorological Conditions ◽  
Positive Phase ◽  
Decadal Time Scale ◽  
Near Surface ◽  
The Pacific ◽  
Decadal Scale ◽  
Central Eastern

The possible influence of the Atlantic multidecadal oscillation (AMO) and the Pacific decadal oscillation (PDO) on the meteorological conditions associated with haze over central eastern China at decadal time scale was investigated using reanalysis and observational dataset for 1979–2018. Four indices, including Siberian high (SH) strength and position indices (SHI/SHPI), a normalized near-surface wind-speed index (WSI) and a potential air temperature gradient index (ATGI), are adopted to denote the meteorological conditions associated with haze. Results shown that the AMO and PDO are both highly correlated with the fluctuation of meteorological factors associated with haze on decadal scale. Although AMO and PDO were in opposite phases during the whole period, since 1997, they both changed phases (AMO shifted to a positive phase and PDO changed to negative) and became favorable for an anomalous dipole-type SLP pattern in the middle-high latitudes of East Asia. The AMO has played a leading role in decadal variation of the large-scale circulation system, while the PDO has had a closer relationship with the lower ventilation condition in eastern China. On the decadal time scale, the AMO stimulates a zonal teleconnection wave train (the AMO northern Hemisphere pattern, ANH) that originates from the North Atlantic Ocean and passes through central Europe, the northern Ural Mountains, Lake Balkhash-Baikal, and central eastern China. During the positive phase of AMO, the ANH induces a stronger and westward shifted SH, with the central eastern China controlled by the anomalous high pressure. In addition, affected by the cyclone (anticyclone) anomaly over Hetao region and North China (the Sea of Japan), southerly wind anomalies dominate over central eastern China. Compared with the AMO, the wave train generated by the negative (positive) PDO phase mainly propagates in the Pacific region, and there is a strong anticyclonic (cyclonic) anomaly over the Northeast Pacific, guiding the air flow southward (northward) along the East Asian coast and thus suppressing (encouraging) the dispersion of pollutants and resulting in above (below)-normal haze episodes.

scholarly journals Meridionally Extending Anomalous Wave Train over Asia During Breaks in the Indian Summer Monsoon

2019 ◽  
Vol 3 (3) ◽  
pp. 353-366 ◽  
Author(s):  
Uppara Umakanth ◽  
Ramesh K. Vellore ◽  
R. Krishnan ◽  
Ayantika Dey Choudhury ◽  
Jagat S. H. Bisht ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
General Circulation ◽  
Wave Train ◽  
Eastern China ◽  
Circulation Model ◽  
Cyclonic Circulation ◽  
The Arctic ◽  
Indian Landmass ◽  
Central Eastern

Abstract Anomalous interactions between the Indian summer monsoon (ISM) circulation and subtropical westerlies are known to trigger breaks in the ISM on subseasonal time-scales, characterised by a pattern of suppressed rainfall over central-north India, and enhanced rainfall over the foothills of the central–eastern Himalayas (CEH). An intriguing feature during ISM breaks is the formation of a mid-tropospheric cyclonic circulation anomaly extending over the subtropical and mid-latitude areas of the Asian continent. This study investigates the mechanism of the aforesaid Asian continental mid-tropospheric cyclonic circulation (ACMCC) anomaly using observations and simplified model experiments. The results of our study indicate that the ACMCC during ISM breaks is part of a larger meridional wave train comprising of alternating anticyclonic and cyclonic anomalies that extend poleward from the monsoon region to the Arctic. A lead–lag analysis of mid-tropospheric circulation anomalies suggests that the meridional wave-train generation is linked to latent heating (LH) anomalies over the CEH foothills, Indo-China, and the Indian landmass during ISM breaks. By conducting sensitivity experiments using a simplified global atmospheric general circulation model forced with satellite-derived three-dimensional LH, it is demonstrated that the combined effects of the enhanced LH over the CEH foothills and Indo-China and decreased LH over the Indian landmass during ISM breaks are pivotal for generating the poleward extending meridional wave train and the ACMCC anomaly. At the same time, the spatial extent of the mid-latitude cyclonic anomaly over Far-East Asia is also influenced by the anomalous LH over central–eastern China. While the present findings provide interesting insights into the role of LH anomalies during ISM breaks on the poleward extending meridional wave train, the ACMCC anomaly is found to have important ramifications on the daily rainfall extremes over the Indo-China region. It is revealed from the present analysis that the frequency of extreme rainfall occurrences over Indo-China shows a twofold increase during ISM break periods as compared to active ISM conditions.

scholarly journals Impacts of meteorology and emissions on surface ozone increases over Central Eastern China between 2003 and 2015

2018 ◽  
Author(s):  
Lei Sun ◽  
Likun Xue ◽  
Yuhang Wang ◽  
Longlei Li ◽  
Jintai Lin ◽  
...  
Keyword(s):  
Urban Areas ◽  
Control Strategies ◽  
Process Analysis ◽  
Surface Ozone ◽  
Eastern China ◽  
Meteorological Conditions ◽  
Transboundary Transport ◽  
Anthropogenic Nitrogen ◽  
Central Eastern ◽  
Emission Changes

Abstract. Recent studies have shown that surface ozone (O3) concentrations over Central Eastern China (CEC) have increased significantly during the past decade. We quantified the effects of changes in meteorological conditions and O3 precursor emissions on surface O3 levels over CEC between July 2003 and July 2015 using the GEOS-Chem model. The simulated monthly mean maximum daily 8-h average O3 concentration (MDA8 O3) in July increased by approximately 13.6 %, from 65.5 ± 7.9 ppbv (2003) to 74.4 ± 8.7 ppbv (2015), comparable to the observed results. The change in meteorology led to an increase of MDA8 O3 of 5.8 ± 3.9 ppbv over the central part of CEC, in contrast to a decrease of about −0.8 ± 3.5 ppbv over the eastern part of the region. In comparison, the MDA8 O3 over the central and eastern parts of CEC increased by 3.5 ± 1.4 ppbv and 5.6 ± 1.8 ppbv due to the increased emissions. The increase in regional averaged O3 resulting from the emission increase (4.0 ± 1.9 ppbv) was higher than that caused by meteorological changes (3.1 ± 4.9 ppbv) relative to the 2003 standard simulation, while the regions with larger O3 increases showed a higher sensitivity to meteorological conditions than to emission changes. Sensitivity tests indicate that increased levels of anthropogenic non-methane volatile organic compounds (NMVOCs) dominate the O3 increase over the eastern part of CEC, and anthropogenic nitrogen oxides (NOx) mainly increase O3 concentrations over the central and western parts, while decrease O3 in a few urban areas in the eastern part. Process analysis showed that net photochemical production and meteorological conditions (transport in particular) are two important factors that influence O3 levels over the CEC. The results of this study suggest a need to further assess the effectiveness of control strategies for O3 pollution in the context of regional meteorology, transboundary transport, and anthropogenic emission changes.

Low-frequency divergence of tree-ring d18O variations on both sides of climatic boundary mountain of eastern China since 1980s

2020 ◽  
Author(s):  
Qiang Li ◽  
Yu Liu ◽  
Huiming Song
Keyword(s):  
Relative Humidity ◽  
Tree Ring ◽  
Time Scale ◽  
Eastern China ◽  
Sampling Site ◽  
Low Frequency ◽  
Mountain Range ◽  
Decadal Time Scale ◽  
Qinling Mountain ◽  
Significant Divergence

<p>The Qinling Mountain is the most important mountain range in eastern China, and is the geographical boundary and the climatic boundary. We investigated tree-ring d18O variations in South and North Slope of the Qinling Mountain, and found that the variations of tree-ring  d18O were significantly correlated over the past two and a half centuries (r=0.641, n=247, p<0.001). And they are negatively correlated with relative humidity and precipitation, and positively correlated with temperature. Compared with the various hydroclimate-related time series in the surrounding area, it is found that both can represent the region's long-term hydroclimate change. The consistent changes in the interannual time scale may be due to the common modulation of ENSO. However, on the decadal time scale, there have been significant divergence between the two tree-ring  d18O series since 1981 and the divergence may be caused by changes in relative humidity at the sampling site, suggesting that in the context of global warming, although the warming range is the same, but the triggered relative humidity changes are not consistent. In addition, changes in PDO may be another cause of low-frequency difference.</p>

scholarly journals Influence of Asian-Pacific Oscillation on Precipitation in Central Eastern China during Autumn (1960–2016)

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Zouxing Lin ◽  
Jiajin Zhu ◽  
Wei Hua ◽  
Guangzhou Fan
Keyword(s):  
Close Association ◽  
Eastern China ◽  
Walker Circulation ◽  
Reanalysis Data ◽  
Teleconnection Pattern ◽  
Upward Movement ◽  
Tropical Eastern Pacific ◽  
The Pacific ◽  
Central Eastern ◽  
Asian Pacific

The Asian-Pacific Oscillation (APO) plays an important role in precipitation in Central Eastern China (CEC). This study analyzed observational and reanalysis data to investigate CEC precipitation during autumn (1960–2016) and its association with the APO. The APO index (APOI) was redefined, and an autumn CEC precipitation index (CECPI) was calculated to elucidate the relationship between the APO and CEC precipitation. Significant positive correlation (correlation coefficient: 0.60) was found between the APOI and CECPI. Further analysis revealed anomalous southerly winds at 850 hPa over CEC when the APO was strong, which corresponded to anomalous strengthened (weakened) sea level pressure and increased 500-hPa geopotential height over Asia (the Pacific), together with strong meridional shear of the East Asian jet. This configuration is conducive to transportation of warm moist air to CEC during strong APOI years (SAY), but the effect is much diminished during weak APOI years. Moreover, strengthening of both the Walker Circulation of the tropical Pacific and the anomalous upward movement (and convergence) over the Western Pacific (WP) observed during SAY is also conducive to the formation of precipitation in CEC. A possible physical explanation for the close association of the APO with tropical circulation changes is that decreased (increased) sea surface temperature in the tropical eastern Pacific (WP and extratropical Pacific) is beneficial for stimulating a strong APO teleconnection pattern, which further affects precipitation in CEC by strengthening the connection between tropical and subtropical regions.

Impact of atmospheric quasi-biweekly oscillation on the persistent heavy PM2.5 pollution over Beijing-Tianjin-Hebei region, China during winter

2020 ◽  
Author(s):  
Libo Gao ◽  
Tijian Wang ◽  
Xuejuan Ren ◽  
Bingliang Zhuang ◽  
Shu Li ◽  
...  
Keyword(s):  
Time Scale ◽  
Wave Train ◽  
Fine Particulate Matter ◽  
East Asian ◽  
Eastern China ◽  
Lower Troposphere ◽  
Stable Stratification ◽  
East Asian Trough ◽  
Asian Winter Monsoon ◽  
Bth Region

<p>In recent years, persistent heavy air pollution (PHP) events occurred frequently over the Beijing-Tianjin-Hebei (BTH) region in China, which posed a great threat to human health. The pollution was characterized by fine particulate matter smaller than 2.5 μm in diameter (PM<sub>2.5</sub>). This study investigates the evolution of PHP over the BTH region and its relation to the atmospheric quasi-biweekly oscillation in winters of 2013–2017. A PHP event is defined as three or more consecutive days with daily mean PM<sub>2.5</sub> concentration exceeding 150 μg m<sup>-3</sup>. We observed a significant periodicity of 10–16 days of the PM<sub>2.5</sub> concentration, which notably contributes to the occurrence of PHP. According to the quasi-biweekly variation of PM<sub>2.5</sub>, the life cycle of PHP events are divided into eight phases. The phase composites of circulation anomalies show that the atmospheric quasi-biweekly oscillation provides favorable conditions for the persistence of wintertime PM<sub>2.5</sub> pollution. During the PHP events, the quasi-biweekly southerly anomalies prevail persistently over eastern China. The East Asian winter monsoon is weakened and more moisture is transported to the BTH region continuously. The anomalous warming in the lower troposphere indicates a stable stratification on the quasi-biweekly time scale. In the mid-troposphere, the oscillation of East Asian trough’s intensity is significantly correlated with the PHP events. Further lead-lag correlation analysis suggested that the quasi-biweekly oscillation of East Asian trough can be traced back to a precursor signal over northwestern Eurasia about 11 days earlier, through a southeastward wave train propagation. Therefore, the meteorological conditions conducive to PHP over the BTH region can be predicted on the quasi-biweekly time scale.</p>

scholarly journals Impacts of meteorology and emissions on summertime surface ozone increases over central eastern China between 2003 and 2015

2019 ◽  
Vol 19 (3) ◽  
pp. 1455-1469 ◽  
Author(s):  
Lei Sun ◽  
Likun Xue ◽  
Yuhang Wang ◽  
Longlei Li ◽  
Jintai Lin ◽  
...  
Keyword(s):  
Urban Areas ◽  
Control Strategies ◽  
Surface Ozone ◽  
Eastern China ◽  
Meteorological Conditions ◽  
Budget Analysis ◽  
Sensitivity Tests ◽  
Anthropogenic Nitrogen ◽  
Central Eastern ◽  
Emission Changes

Abstract. Recent studies have shown that surface ozone (O3) concentrations over central eastern China (CEC) have increased significantly during the past decade. We quantified the effects of changes in meteorological conditions and O3 precursor emissions on surface O3 levels over CEC between July 2003 and July 2015 using the GEOS-Chem model. The simulated monthly mean maximum daily 8 h average O3 concentration (MDA8 O3) in July increased by approximately 13.6 %, from 65.5±7.9 ppbv (2003) to 74.4±8.7 ppbv (2015), comparable to the observed results. The change in meteorology led to an increase in MDA8 O3 of 5.8±3.9 ppbv over the central part of CEC, in contrast to a decrease of about -0.8±3.5 ppbv over the eastern part of the region. In comparison, the MDA8 O3 over the central and eastern parts of CEC increased by 3.5±1.4 and 5.6±1.8 ppbv due to the increased emissions. The increase in averaged O3 in the CEC region resulting from the emission increase (4.0±1.9 ppbv) was higher than that caused by meteorological changes (3.1±4.9 ppbv) relative to the 2003 standard simulation, while the regions with larger O3 increases showed a higher sensitivity to meteorological conditions than to emission changes. Sensitivity tests indicate that increased levels of anthropogenic non-methane volatile organic compounds (NMVOCs) dominate the O3 increase over the eastern part of CEC, and anthropogenic nitrogen oxides (NOx) mainly increase MDA8 O3 over the central and western parts and decrease O3 in a few urban areas in the eastern part. Budget analysis showed that net photochemical production and meteorological conditions (transport in particular) are two important factors that influence O3 levels over the CEC. The results of this study suggest a need to further assess the effectiveness of control strategies for O3 pollution in the context of regional meteorology and anthropogenic emission changes.

scholarly journals Heavy air pollution with the unique “non-stagnant” atmospheric boundary layer in the Yangtze River Middle Basin aggravated by regional transport of PM<sub>2.5</sub> over China

2019 ◽  
Author(s):  
Chao Yu ◽  
Tianliang Zhao ◽  
Yongqing Bai ◽  
Lei Zhang ◽  
Xingna Yu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Air Pollutants ◽  
Yangtze River ◽  
Eastern China ◽  
Temperature Inversion ◽  
Meteorological Conditions ◽  
Air Pollutant ◽  
Regional Transport ◽  
Central Eastern

Abstract. Regional transport of air pollutants controlled by both emission sources and meteorological factors results in a complex source-receptor relationship of air pollution change. Wuhan, a metropolis in the Yangtze River Middle Basin (YRMB) of central China experienced heavy air pollution characterized by excessive PM2.5 concentrations reaching 471.1 μg m−3 in January 2016. In order to investigate the regional transport of PM2.5 over China and the meteorological impact on wintertime air pollution in the YRMB area, observational meteorological and other relevant environmental data from January 2016 were analyzed. Our analysis presented the noteworthy cases of heavy PM2.5 pollution in the YRMB area with the unique “non-stagnant” meteorological conditions of strong northerly winds, no temperature inversion and additional unstable structures in the atmospheric boundary layer. This unique set of conditions differed from the stagnant meteorological conditions characterized by near-surface weak winds, air temperature inversion, and stable structure in the boundary layer observed in heavy air pollution over most regions in China. The regional transport of PM2.5 over central-eastern China aggravated PM2.5 levels present in the YRMB area, thus demonstrating the source-receptor relationship between the originating air pollution regions in central-eastern China and the receiving YRMB regions. Furthermore, a backward trajectory simulation using FLEXPART-WRF to integrate the air pollutant emission inventory over China was used to explore the patterns of regional transport of PM2.5 governed by the strong northerly winds in the cold air activity of the East Asian winter monsoon over central-eastern China, which contributes markedly to the heavy PM2.5 pollution in the YRMB area. It was estimated that the regional transport of PM2.5 of non-local air pollutant emissions could contribute more than 65 % of the PM2.5 concentrations to the heavy air pollution in the YRMB region during the study period, revealing the importance of the regional transport of air pollutants over central-eastern China in the formation of heavy air pollution over the YRMB region.

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

scholarly journals Variation Characteristics and Transportation of Aerosol, NO2, SO2, and HCHO in Coastal Cities of Eastern China: Dalian, Qingdao, and Shanghai

2021 ◽  
Vol 13 (5) ◽  
pp. 892
Author(s):  
Xiaomei Li ◽  
Pinhua Xie ◽  
Ang Li ◽  
Jin Xu ◽  
Zhaokun Hu ◽  
...  
Keyword(s):  
Eastern China ◽  
Temporal Distribution ◽  
Correlation Coefficients ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Mixing Ratios ◽  
Variation Characteristics ◽  
Spatio Temporal ◽  
Gas Volume ◽  
Transport Flux

This paper studied the method for converting the aerosol extinction to the mass concentration of particulate matter (PM) and obtained the spatio-temporal distribution and transportation of aerosol, nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) based on multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations in Dalian (38.85°N, 121.36°E), Qingdao (36.35°N, 120.69°E), and Shanghai (31.60°N, 121.80°E) from 2019 to 2020. The PM2.5 measured by the in situ instrument and the PM2.5 simulated by the conversion formula showed a good correlation. The correlation coefficients R were 0.93 (Dalian), 0.90 (Qingdao), and 0.88 (Shanghai). A regular seasonality of the three trace gases is found, but not for aerosols. Considerable amplitudes in the weekly cycles were determined for NO2 and aerosols, but not for SO2 and HCHO. The aerosol profiles were nearly Gaussian, and the shapes of the trace gas profiles were nearly exponential, except for SO2 in Shanghai and HCHO in Qingdao. PM2.5 presented the largest transport flux, followed by NO2 and SO2. The main transport flux was the output flux from inland to sea in spring and winter. The MAX-DOAS and the Copernicus Atmosphere Monitoring Service (CAMS) models’ results were compared. The overestimation of NO2 and SO2 by CAMS is due to its overestimation of near-surface gas volume mixing ratios.

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