scholarly journals Summer Regional Pentad Extreme Precipitation in Eastern China and Their Possible Causes

2021 ◽  
Vol 8 ◽  
Author(s):  
Yaqin Ji ◽  
Xuguang Sun ◽  
Yiming Xu ◽  
Jingxin Yao ◽  
Xiu-Qun Yang
Keyword(s):  
Extreme Precipitation ◽  
Yangtze River ◽  
North China ◽  
Eastern China ◽  
Lower Troposphere ◽  
Western Pacific Subtropical High ◽  
Low Pressure ◽  
Large Area ◽  
Reanalysis Dataset ◽  
The North

Persistent extreme precipitation covering a large area usually causes severe flooding disasters in China, but how to depict it and what are the possible causes are still open questions. With Climate Prediction Center global unified gauge-based analysis of daily precipitation and NCEP/NCAR daily reanalysis dataset from 1979 to 2019, summer regional pentad extreme precipitation (RPEP) is defined according to the threshold of the 95th percentile of pentad precipitation with more than 5% land grids coverage in eastern China. While the definition of RPEP highlights the climate features of both the persistence and the regionality of extreme precipitation, it is distinctly different from the previous definitions that mainly reflect the synoptic aspects with daily data and have strictly temporal-spatial constraints. Four categories of RPEPs are objectively identified by K-means cluster analysis, i.e., South China (SC), South of Yangtze River (SYR), Jianghuai River (JHR), and North China (NC). Along the Yangtze River (SYR and JHR), intensity and area of RPEP are positively correlated with each other, and with the increase of RPEP intensity, its center of gravity tends to move eastward in all the four cluster regions and southward in Jianghuai River and North China, respectively, and vice versa. The RPEPs mostly persist for one pentad but can reach up to two to three pentads at most, and along with the duration of RPEP, its intensity and area are both enhanced accordingly. Furthermore, the frequency of RPEP increased significantly since the late 1990s in SYR, JHR, and SC. Associated with RPEP, strong pentad-mean convergence and ascending motion occur in the middle-lower troposphere, and except for SC that is dominated by the local low-pressure and cyclone anomalies, the other three cluster regions are all forced by the western Pacific subtropical high to the southeast and weak low-pressure trough to the north, and the low-level anticyclone anomaly to the southeast transports abundant water vapors to the RPEP regions accordingly. Besides, all the RPEPs are closely in accordance with obvious subseasonal oscillations, especially the 10–30-day and 30–60-day oscillations, which can be regarded as the potential sources of RPEP predictability in eastern China.

scholarly journals Dynamic Processes Dominating Ozone Variability in Warm Seasons of 2014–2018 over the Yangtze River Delta Region, China

2020 ◽  
Author(s):  
Da Gao ◽  
Min Xie ◽  
Jane Liu ◽  
Tijian Wang ◽  
Chaoqun Ma ◽  
...  
Keyword(s):  
Time Series ◽  
Yangtze River ◽  
North China ◽  
Western Pacific Subtropical High ◽  
Yangtze River Delta ◽  
Western Pacific ◽  
The Yangtze River ◽  
The North ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. Ozone (O3) pollution is of great concern in the Yangtze River Delta (YRD) region of China, and the regional O3 pollution is closely associated with dominant weather systems. With a focus on the warm seasons (April–September) from 2014 to 2018, we quantitatively analyze the characteristics of O3 variations over the YRD, the impacts of large-scale and synoptic-scale circulations on the variations and the associated meteorological controlling factors, based on observed ground-level O3 and meteorological data. Our analysis suggests an increasing trend of the regional mean O3 concentration in the YRD at 1.81 ppb per year over 2014–2018. Spatially, the empirical orthogonal function (EOF) analysis suggests the dominant mode accounting for 65.70 % variation in O3, implying that an increase in O3 is the dominant tendency in the entire YRD. Meteorology is estimated to increase the regional mean O3 concentration by 2.81 ppb at most from 2014 to 2018. Relative humidity is found to be the most influential meteorological factor impacting O3 concentration. As the atmospheric circulation can affect local meteorological factors and O3 levels, we identify five dominant synoptic weather patterns (SWPs) in the warm seasons in the YRD using the t-mode principal component analysis (PTT) classification. The typical weather systems of SWPs include western Pacific Subtropical High (WPSH) under SWP1, a continental high under SWP2, an extratropical cyclone under SWP3, a southern low pressure and WPSH under SWP4 and the north China anticyclone under SWP5. The annual variations of all five SWPs are favorable to the increase in O3 concentrations over 2014–2018. Moreover, the change in SWP intensity contributes more to the O3 inter-annual variation than the SWP frequency change. The SWP intensity change includes the weakening and northward-extending of the western Pacific subtropical high (WPSH) under SWP1, the weakening of the continental high under SWP2, an extratropical cyclone strengthening under SWP3, the southern low pressure weakening and WPSH weakening under SWP4, and the north China anticyclone weakening under SWP5. All these changes prevent the water vapor in the southern sea from being transported to the YRD, and increase air temperature in the YRD. In addition, the descending motions strengthen in the YRD located behind the trough and in front of the ridge due to the strengthening of the ridge and trough in the westerlies. Then, the strengthened descending motion leads to less cloud cover and strong solar radiation, which are favorable to O3 formation and accumulation. Finally, we reconstruct an EOF mode 1 time series that shows high correlation with the original O3 time series, and the reconstructed time series performs well in defining the change in SWP intensity according to the unique feature under each of the SWPs.

scholarly journals Aerosol transport pathways and source attribution in China during the COVID-19 outbreak

2021 ◽  
Vol 21 (20) ◽  
pp. 15431-15445
Author(s):  
Lili Ren ◽  
Yang Yang ◽  
Hailong Wang ◽  
Pinya Wang ◽  
Lei Chen ◽  
...  
Keyword(s):  
Air Quality ◽  
North China Plain ◽  
North China ◽  
Eastern China ◽  
Lower Troposphere ◽  
Aerosol Transport ◽  
Transport Pathways ◽  
The North ◽  
The North China Plain ◽  
Local Emissions

Abstract. Due to the coronavirus disease 2019 (COVID-19) pandemic, human activities and industrial productions were strictly restricted during January–March 2020 in China. Despite the fact that anthropogenic aerosol emissions largely decreased, haze events still occurred. Characterization of aerosol transport pathways and attribution of aerosol sources from specific regions are beneficial to air quality and pandemic control strategies. This study establishes source–receptor relationships in various regions covering all of China during the COVID-19 outbreak based on the Community Atmosphere Model version 5 with Explicit Aerosol Source Tagging (CAM5-EAST). Our analysis shows that PM2.5 burden over the North China Plain between 30 January and 19 February is mostly contributed by local emissions (40 %–66 %). For other regions in China, PM2.5 burden is largely contributed from nonlocal sources. During the most polluted days of the COVID-19 outbreak, local emissions within the North China Plain and eastern China contributed 66 % and 87 % to the increase in surface PM2.5 concentrations, respectively. This is associated with the anomalous mid-tropospheric high pressure at the location of the climatological East Asia trough and the consequently weakened winds in the lower troposphere, leading to the local aerosol accumulation. The emissions outside China, especially those from South Asia and Southeast Asia, contribute over 50 % to the increase in PM2.5 concentration in southwestern China through transboundary transport during the most polluted day. As the reduction in emissions in the near future is desirable, aerosols from long-range transport and unfavorable meteorological conditions are increasingly important to regional air quality and need to be taken into account in clean-air plans.

scholarly journals Springtime daily variations in lower-tropospheric ozone over east Asia: the role of cyclonic activity and pollution as observed from space with IASI

2015 ◽  
Vol 15 (18) ◽  
pp. 10839-10856 ◽  
Author(s):  
G. Dufour ◽  
M. Eremenko ◽  
J. Cuesta ◽  
C. Doche ◽  
G. Foret ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
East Asia ◽  
Tropospheric Ozone ◽  
North China Plain ◽  
North China ◽  
Low Pressure ◽  
The North ◽  
The North China Plain ◽  
Co Observations ◽  
Low Pressure Systems

Abstract. We use satellite observations from IASI (Infrared Atmospheric Sounding Interferometer) on board the MetOp-A satellite to evaluate the springtime daily variations in lower-tropospheric ozone over east Asia. The availability of semi-independent columns of ozone from the surface up to 12 km simultaneously with CO columns provides a powerful observational data set to diagnose the processes controlling tropospheric ozone enhancement on synoptic scales. By combining IASI observations with meteorological reanalyses from ERA-Interim, we develop an analysis method based only on IASI ozone and CO observations to identify the respective roles of the stratospheric source and the photochemical source in ozone distribution and variations over east Asia. The succession of low- and high-pressure systems drives the day-to-day variations in lower-tropospheric ozone. A case study analysis of one frontal system and one cut-off low system in May 2008 shows that reversible subsiding and ascending ozone transfers in the upper-troposphere–lower-stratosphere (UTLS) region, due to the tropopause perturbations occurring in the vicinity of low-pressure systems, impact free and lower-tropospheric ozone over large regions, especially north of 40° N, and largely explain the ozone enhancement observed with IASI for these latitudes. Irreversible stratosphere–troposphere exchanges of ozone-rich air masses occur more locally in the southern and southeastern flanks of the trough. The contribution to the lower-tropospheric ozone column is difficult to dissociate from the tropopause perturbations generated by weather systems. For regions south of 40° N, a significant correlation has been found between lower-tropospheric ozone and carbon monoxide (CO) observations from IASI, especially over the North China Plain (NCP). Considering carbon monoxide observations as a pollutant tracer, the O3–CO correlation indicates that the photochemical production of ozone from primary pollutants emitted over such large polluted regions significantly contributes to the ozone enhancements observed in the lower troposphere via IASI. When low-pressure systems circulate over the NCP, stratospheric and pollution sources play a concomitant role in the ozone enhancement. IASI's 3-D observational capability allows the areas in which each source dominates to be determined. Moreover, the studied cut-off low system has enough potential convective capacity to uplift pollutants (ozone and CO) and to transport them to Japan. The increase in the enhancement ratio of ozone to CO from 0.16 on 12 May over the North China Plain to 0.28 over the Sea of Japan on 14 May indicates photochemical processing during the plume transport.

scholarly journals Seasonal Evolution of Aleutian Low Pressure Systems: Implications for the North Pacific Subpolar Circulation*

2009 ◽  
Vol 39 (6) ◽  
pp. 1317-1339 ◽  
Author(s):  
Robert S. Pickart ◽  
Alison M. Macdonald ◽  
G. W. K. Moore ◽  
Ian A. Renfrew ◽  
John E. Walsh ◽  
...  
Keyword(s):  
North Pacific ◽  
Lower Troposphere ◽  
Gulf Of Alaska ◽  
Low Pressure ◽  
Aleutian Low ◽  
The North ◽  
Early Fall ◽  
The Impact ◽  
The North Pacific ◽  
Low Pressure Systems

Abstract The seasonal change in the development of Aleutian low pressure systems from early fall to early winter is analyzed using a combination of meteorological reanalysis fields, satellite sea surface temperature (SST) data, and satellite wind data. The time period of the study is September–December 2002, although results are shown to be representative of the long-term climatology. Characteristics of the storms were documented as they progressed across the North Pacific, including their path, central pressure, deepening rate, and speed of translation. Clear patterns emerged. Storms tended to deepen in two distinct geographical locations—the Gulf of Alaska in early fall and the western North Pacific in late fall. In the Gulf of Alaska, a quasi-permanent “notch” in the SST distribution is argued to be of significance. The signature of the notch is imprinted in the atmosphere, resulting in a region of enhanced cyclonic potential vorticity in the lower troposphere that is conducive for storm development. Later in the season, as winter approaches and the Sea of Okhotsk becomes partially ice covered and cold, the air emanating from the Asian continent leads to enhanced baroclinicity in the region south of Kamchatka. This corresponds to enhanced storm cyclogenesis in that region. Consequently, there is a seasonal westward migration of the dominant lobe of the Aleutian low. The impact of the wind stress curl pattern resulting from these two regions of storm development on the oceanic circulation is investigated using historical hydrography. It is argued that the seasonal bimodal input of cyclonic vorticity from the wind may be partly responsible for the two distinct North Pacific subarctic gyres.

scholarly journals Measuring the Vertical Profiles of Aerosol Extinction in the Lower Troposphere by MAX-DOAS at a Rural Site in the North China Plain

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1037
Author(s):  
Siyang Cheng ◽  
Junli Jin ◽  
Jianzhong Ma ◽  
Xiaobin Xu ◽  
Liang Ran ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Lower Troposphere ◽  
Temporal Variations ◽  
Rural Site ◽  
Optical Absorption Spectroscopy ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Near Surface ◽  
The North

Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements were performed during the summer (13 June–20 August) of 2014 at a rural site in North China Plain. The vertical profiles of aerosol extinction (AE) in the lower troposphere were retrieved to analyze the temporal variations of AE profiles, near-surface AE, and aerosol optical depth (AOD). The average AOD and near-surface AE over the period of study were 0.51 ± 0.26 and 0.33 ± 0.18 km−1 during the effective observation period, respectively. High AE events and elevated AE layers were identified based on the time series of hourly AE profiles, near-surface AEs and AODs. It is found that in addition to the planetary boundary layer height (PBLH) and relative humidity (RH), the variations in the wind field have large impacts on the near-surface AE, AOD, and AE profile. Among 16 wind sectors, higher AOD or AE occur mostly in the directions of the cities upstream. The diurnal variations of the AE profiles, AODs and near-surface AEs are significant and influenced mainly by the source emissions, PBLH, and RH. The AE profile shape from MAX-DOAS measurement is generally in agreement with that from light detection and ranging (lidar) observations, although the AE absolute levels are different. Overall, ground-based MAX-DOAS can serve as a supplement to measure the AE vertical profiles in the lower troposphere.

Hydrologic and Climatic Responses to Global Anthropogenic Groundwater Extraction

2017 ◽  
Vol 30 (1) ◽  
pp. 71-90 ◽  
Author(s):  
Yujin Zeng ◽  
Zhenghui Xie ◽  
Jing Zou
Keyword(s):  
North China Plain ◽  
North China ◽  
Supply And Demand ◽  
Northern China ◽  
Large Area ◽  
Deep Soil ◽  
Northern India ◽  
The North ◽  
The North China Plain ◽  
Climatic Responses

In this study, a groundwater (GW) extraction scheme was incorporated into the Community Earth System Model, version 1.2.0 (CESM1.2.0), to create a new version called CESM1.2_GW, which was used to investigate hydrologic and climatic responses to anthropogenic GW extraction on a global scale. An ensemble of 41-yr simulations with and without GW extraction (estimated based on local water supply and demand) was conducted and analyzed. The results revealed that GW extraction and water consumption caused drying in deep soil layers but wetting in upper layers, along with a rapidly declining GW table in areas with the most severe GW extraction, including the central United States, the north China plain, and northern India and Pakistan. The atmosphere also responded to GW extraction, with cooling at the 850-hPa level over northern India and Pakistan and a large area in northern China and central Russia. Increased precipitation occurred in the north China plain due to increased evapotranspiration from irrigation. Decreased precipitation occurred in northern India because the Indian monsoon and its transport of water vapor were weaker as a result of cooling induced by GW use. Additionally, the background climate change may complicate the precipitation responses to the GW use. Local terrestrial water storage was shown to be unsustainable at the current high GW extraction rate. Thus, a balance between reduced GW withdrawal and rapid economic development must be achieved in order to maintain a sustainable GW resource, especially in regions where GW is being overexploited.

Separating multiple episodes of partial melting in polyorogenic crust: An example from the Haiyangsuo complex, northern Sulu belt, eastern China

2019 ◽  
Vol 132 (5-6) ◽  
pp. 1235-1256
Author(s):  
Peng Feng ◽  
Lu Wang ◽  
Michael Brown ◽  
Songjie Wang ◽  
Xiawen Li
Keyword(s):  
Partial Melting ◽  
North China Craton ◽  
North China ◽  
Eastern China ◽  
Magma Ascent ◽  
Magmatic Zircon ◽  
Weighted Mean ◽  
Heavy Rare Earth Element ◽  
Orogenic Collapse ◽  
The North

Abstract The exotic Haiyangsuo complex is structurally part of the Sulu belt but its contact relationship with surrounding Sulu gneisses is unexposed and therefore unknown, making its affinity uncertain. It comprises gneisses with in-source leucosomes that host minor metabasite bodies; both are cut by leucogranite dikes. In this study, we determine the timing and petrogenesis of leucosomes and leucogranites and assess the tectonic affinity of the complex based on data from gneisses and metabasites. Most zircon from gneisses and leucosomes has oscillatory-zoned cores with CL-bright overgrowth rims, but some has CL-dark cores or mantles between cores and rims. CL-dark and bright zircon yield weighted mean ages of ca. 1817–1812 Ma. CL-dark zircon has flat heavy rare earth element (HREE) patterns and crystallization temperatures of 829–875 °C, suggesting metamorphic growth, whereas rims have steep HREE patterns but a similar range of crystallization temperatures, suggesting growth from anatectic melt; εHf (t = 1813 Ma) of –18.3 to –10.8 indicates a North China Craton source. Magmatic zircon from metabasites yields ages of ca. 825 Ma, similar to those of scattered metabasite occurrences in the North China Craton. Paleoproterozoic zircon cores were scavenged during magma ascent. By contrast, zircon cores from the leucogranites yield concordant dates of 776–701 Ma, consistent with protolith ages in the Sulu belt, whereas overgrowth mantles and rims yield weighted mean ages of ca. 220 Ma and 162 Ma, respectively. Both mantles and rims host multiphase solid inclusions, representing former melt, suggesting anatexis and crystallization of zircon first during initial decompression and then during orogenic collapse of the Sulu belt; whole-rock Nd and Sr isotope compositions implicate the Sulu belt gneisses as the source of these melts. Our interpretation of these data is that the Haiyangsuo complex has an early geologic history similar to the Jiaobei terrane from the southeastern part of the North China Craton and was incorporated into the Sulu belt during Triassic collision of the Yangtze and North China Cratons. The two stages of melting relate to Upper Triassic early exhumation and Upper Jurassic late-stage orogenic collapse, during which the leucogranite magma was derived from a source similar to one elsewhere in the Sulu belt such as the subducted Yangtze Craton and not the North China Craton. This shows that during continental collisions, crust from the upper plate may be dragged into the subduction channel, deformed, and subsequently exhumed in association with partial melting of the crust.

Early Cretaceous Xiuyan adakitic granitoids in the Liaodong Peninsula, eastern China: petrogenesis and implications for lithospheric thinning of the North China Craton

2021 ◽  
Vol 58 (1) ◽  
pp. 50-66
Author(s):  
Yang Dong ◽  
Jingdang Liu ◽  
Yanfei Zhang ◽  
Shiyong Dou ◽  
Yanbin Li ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
North China Craton ◽  
Lower Crust ◽  
North China ◽  
Eastern China ◽  
Lithospheric Thinning ◽  
The North ◽  
Magma Sources ◽  
Liaodong Peninsula ◽  
T Values

Mesozoic magmatic rocks are widely distributed in the North China Craton (NCC) and are crucial to understanding the timing, location, and geodynamic mechanisms of lithospheric thinning of the NCC. In this study, we report geochronological, petrogeochemical, and Lu–Hf isotopic data for adakitic granitoids from different parts of Xiuyan pluton in the Liaodong Peninsula, aiming to constrain their magma sources, petrogenesis, and tectonic implications. The adakites are metaluminous to weakly peraluminous and are classified as high-K calc-alkaline I-type granite with Early Cretaceous zircon U–Pb ages of 129–126 Ma. They exhibit adakite-like geochemical characteristics, such as high Sr content and low Yb and Y contents, coupled with high Sr/Y and no pronounced Eu anomalies. They are enriched in Rb, U, and light rare-earth elements and are depleted in Ta, Nb, P, and Ti. The adakites from the eastern part of the pluton have low εHf(t) values (–8.5 to –4.0) with old TDM2 ages (1.57–1.31 Ga), indicating they were derived from the lower crust containing juvenile mantle-derived materials. In contrast, adakites from the northern part of the pluton have lower εHf(t) values (–19.7 to –16.6) with older TDM2 ages (2.21–2.03 Ga), indicating that they were derived mainly from an ancient crust. Our results show that both adakitic magmas were derived from partial melting of delaminated lower crust. Their relatively high MgO and Ni contents and Mg# values indicate that the melts interacted with mantle peridotites. The lower crust delamination beneath the Liaodong Peninsula resulted from paleo-Pacific plate subduction during the Early Cretaceous, which resulted in thinning of Mesozoic crust in the Xiuyan area.

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