scholarly journals Modeling precipitation δ<sup>18</sup>O pariability in East Asia since the Last Glacial Maximum: temperature and amount effects across different time scales

2016 ◽  
Author(s):  
Xinyu Wen ◽  
Zhengyu Liu ◽  
Zhongxiao Chen ◽  
Esther Brady ◽  
David Noone ◽  
...  
Keyword(s):  
East Asia ◽  
Temperature Effect ◽  
Southern China ◽  
Northern China ◽  
Point Of View ◽  
Central China ◽  
Maximum Temperature ◽  
Past Climate ◽  
Amount Effect ◽  
Significant Temperature

Abstract. Water isotope in precipitation has played a key role in the reconstruction of past climate on millennial and longer timescales. However, for mid-latitude regions like East Asia with complex terrain, the reliability behind the basic assumptions of the temperature effect and amount effect are based on modern observational data and still remains unclear for past climate. In the present work, we re-examine the two basic effects on seasonal, interannual, and millennial timescales in a set of time slice experiments for the period 22 ka thru 00 ka using an isotope-enable AGCM. Our study confirms the robustness of the temperature and amount effects on the seasonal cycle over China, with the temperature effect dominating in northern China, and the amount effect dominating in deep southern China, but no one distinct in the transition region of central China. However, our analysis does not show significant temperature and amount effects over China on millennial and interannual timescales, which is a challenge to those classic assumptions in past climate reconstruction. Our work helps shed light on the interpretation of the proxy record of δ18O from modeling point of view.

scholarly journals Modeling precipitation <i>δ</i><sup>18</sup>O variability in East Asia since the Last Glacial Maximum: temperature and amount effects across different timescales

2016 ◽  
Vol 12 (11) ◽  
pp. 2077-2085 ◽  
Author(s):  
Xinyu Wen ◽  
Zhengyu Liu ◽  
Zhongxiao Chen ◽  
Esther Brady ◽  
David Noone ◽  
...  
Keyword(s):  
East Asia ◽  
Temperature Effect ◽  
General Circulation ◽  
Circulation Model ◽  
Northern China ◽  
Climatic Conditions ◽  
Central China ◽  
Maximum Temperature ◽  
Past Climate ◽  
Amount Effect

Abstract. Water isotopes in precipitation have played a key role in the reconstruction of past climate on millennial timescales and longer. However, for midlatitude regions like East Asia with complex terrain, the reliability behind the basic assumptions of the temperature effect and amount effect is based on modern observational data and still remains unclear for past climate. In the present work, we reexamine the two basic effects on seasonal, interannual, and millennial timescales in a set of time slice experiments for the period 22–0 ka using an isotope-enabled atmospheric general circulation model (AGCM). Our study confirms the robustness of the temperature and amount effects on the seasonal cycle over China in the present climatic conditions, with the temperature effect dominating in northern China and the amount effect dominating in the far south of China but no distinct effect in the transition region of central China. However, our analysis shows that neither temperature nor amount effect is significantly dominant over China on millennial and interannual timescales, which is a challenge to those classic assumptions in past climate reconstruction. Our work helps shed light on the interpretation of the proxy record of δ18O from a modeling point of view.

Observed and Projected Frontal Activities in East Asia

2021 ◽  
pp. 1-46
Author(s):  
Chia-Chi Wang ◽  
Huang-Hsiung Hsu ◽  
Ying-Ting Chen
Keyword(s):  
East Asia ◽  
Climate Model ◽  
Southern China ◽  
Model Performance ◽  
Moisture Flux ◽  
Central China ◽  
Cmip5 Models ◽  
The South ◽  
Front Detection ◽  
Local Moisture

AbstractAn objective front detection method is applied to ERA5, CMIP5 historical, and RCP8.5 simulations to evaluate climate model performance in simulating front frequency and understand future projections of seasonal front activities. The study area is East Asia for two natural seasons, defined as winter (December 2nd –February 14th) and spring (February 15th –May 15th), in accordance with regional circulation and precipitation patterns. Seasonal means of atmospheric circulation and thermal structures are analyzed to understand possible factors responsible for future front changes.The front location and frequency in CMIP5 historical simulations are captured reasonably. Frontal precipitation accounts for more than 30% of total precipitation over subtropical regions. Projections suggest that winter fronts will decrease over East Asia, especially over southern China. Frontal precipitation is projected to decrease for 10-30%. Front frequency increases in the South China Sea and tropical western Pacific because of more tropical moisture supply, which enhances local moisture contrasts. During spring, southern China and Taiwan will experience fewer fronts and less frontal precipitation while central China, Korea, and Japan may experience more fronts and more frontal precipitation due to moisture flux from the south that enhances 𝜽𝒘 gradients.Consensus among CMIP5 models in front frequency tendency is evaluated. The models exhibit relatively high consensus in the decreasing trend over polar and subtropical frontal zone in winter and over southern China and Taiwan in spring that may prolong the dry season. Spring front activities are crucial for water resource and risk management in the southern China and Taiwan.

scholarly journals Occurrence and source apportionment of perfluoroalkyl acids (PFAAs) in the atmosphere in China

2019 ◽  
Vol 19 (22) ◽  
pp. 14107-14117 ◽  
Author(s):  
Deming Han ◽  
Yingge Ma ◽  
Cheng Huang ◽  
Xufeng Zhang ◽  
Hao Xu ◽  
...  
Keyword(s):  
Degradation Products ◽  
Southern China ◽  
Eastern China ◽  
Northern China ◽  
Central China ◽  
Western China ◽  
Perfluoroalkyl Acids ◽  
Average Value ◽  
Pmf Model ◽  
Air Sampler

Abstract. Perfluoroalkyl acids (PFAAs) are a form of toxic pollutant that can be transported across the globe and accumulated in the bodies of wildlife and humans. A nationwide geographical investigation considering atmospheric PFAAs via a passive air sampler (PAS) based on XAD (a styrene–divinylbenzene copolymer) was conducted in 23 different provinces/municipalities/autonomous regions in China, which provides an excellent chance to investigate their occurrences, spatial trends, and potential sources. The total atmospheric concentrations of 13 PFAAs (n=268) were 6.19–292.57 pg m−3, with an average value of 39.84±28.08 pg m−3, which were higher than other urban levels but lower than point source measurements. Perfluorooctanoic acid (PFOA) was the dominant PFAA (20.6 %), followed by perfluorohexanoic acid (PFHxA), perfluorooctane sulfonate (PFOS), and perfluoroheptanoic acid (PFPeA). An increasing seasonal trend of PFAA concentrations was shown as summer < autumn < spring < winter, which may be initiated by stagnant meteorological conditions. Spatially, the content of PFAAs displayed a declining gradient trend of central China > northern China > eastern China > north-eastern China > south-western China > north-western China > southern China, and Henan contributed the largest proportion of PFAAs. Four sources of PFAAs were identified using a positive matrix factorization (PMF) model, including PFOS-based products (26.1 %), products based on PFOA and perfluorononanoic acid (PFNA; 36.6 %), degradation products of fluorotelomer-based products (15.5 %), and an unknown source (21.8 %).

scholarly journals Imbalance and breakout in the post-epidemic era: Research into the spatial patterns of freight demand network in six provinces of central China

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250375
Author(s):  
Yin Huang ◽  
Runda Liu ◽  
Shumin Huang ◽  
Gege Yang ◽  
Xiaofan Zhang ◽  
...  
Keyword(s):  
Big Data ◽  
Spatial Patterns ◽  
Southern China ◽  
Northern China ◽  
Central China ◽  
Chain Reaction ◽  
Information Platform ◽  
Tail Distribution ◽  
Demand Information ◽  
A Chain

This study aims to explore the freight demand network spatial patterns in six provinces of central China from the perspective of the spread of the epidemic and the freight imbalance and breakout. To achieve this purpose, the big data of “cart search” demand information provided by small and medium freight enterprises on the freight information platform are analyzed. 343,690 pieces of freight demand big data on the freight information platform and Python, ArcGIS, UCINET, and Gephi software are used. The results show that: (1) The choke-point of unbalanced freight demand network is Wuhan, and the secondary choke-points are Hefei and Zhengzhou. (2) In southern China, a chain reaction circle of freight imbalance is formed with Wuhan, Hefei, and Nanchang as the centers. In northern China, a chain reaction circle of freight imbalance is formed with Zhengzhou and Taiyuan as the centers. (3) The freight demand of the six provinces in central China exhibits typical characteristics of long tail distribution with large span and unbalanced distribution. (4) The import and export of freight in different cities vary greatly, and the distribution is unbalanced. This study indicates the imbalance difference, chain reaction, keys and hidden troubles posed by the freight demand network. From the perspectives of freight transfer breakout, freight balance breakout, freight strength breakout, and breakout of freight periphery cities, we propose solutions to breakouts in the freight market in six provinces of central China in the post-epidemic era.

scholarly journals A Comprehensive Study of Spatiotemporal Variations in Temperature Extremes across China during 1960–2018

2021 ◽  
Vol 13 (7) ◽  
pp. 3807
Author(s):  
Na Zhao ◽  
Mingxing Chen
Keyword(s):  
Spatial Heterogeneity ◽  
Mainland China ◽  
Kendall Test ◽  
Northern China ◽  
Central China ◽  
Maximum Temperature ◽  
Temperature Extremes ◽  
Northwestern Part ◽  
Spatiotemporal Variations ◽  
Increasing Trends

Understanding the changing patterns of extreme temperatures is important for taking measures to reduce their associated negative impacts. Based on daily temperature data derived from 2272 meteorological stations in China, the spatiotemporal variations in temperature extremes were examined with respect to covariates by means of the Mann–Kendall test and a spatiotemporal model during 1960–2018. The results indicated that the temporal changes in cold extremes showed decreasing trends and warm extremes experienced increasing trends across almost all of China, with mean change rates of −3.9 days, −1.8 days, 3.7 days and 2.3 days per decade for TN10p, TX10p, TN90p and TX90p, respectively. Nighttime warming/cooling was higher than daytime warming/cooling, which indicated that trends in minimum temperature extremes are more rapid than trends in maximum temperature extremes. In addition, the temporal effect on the temperature extremes varied throughout the year, with significant increasing trends in the temporal heterogeneity of warm extremes occurring during 1992–2018. The areas with strong spatial heterogeneity of cool nights mainly included northeastern and central China, and the spatial variation on cool days was more prominent in northern China. For warm nights, the areas showing high spatial heterogeneity were mainly located in the northwestern part of China, while areas for warm days were distributed in northern China. Our results provide meaningful information for a deeper understanding of the spatiotemporal variations in temperature extremes across mainland China.

scholarly journals Diurnal Cycle of a Heavy Rainfall Corridor over East Asia

2017 ◽  
Vol 145 (8) ◽  
pp. 3365-3389 ◽  
Author(s):  
Guixing Chen ◽  
Weiming Sha ◽  
Toshiki Iwasaki ◽  
Zhiping Wen
Keyword(s):  
East Asia ◽  
Heavy Rainfall ◽  
Southern China ◽  
Central China ◽  
Moist Convection ◽  
Low Level ◽  
Effective Discharge ◽  
Upward Transport ◽  
Convection Initiation ◽  
The Impact

Moist convection occurred repeatedly in the midnight-to-morning hours of 11–16 June 1998 and yielded excessive rainfall in a narrow latitudinal corridor over East Asia, causing severe flood. Numerical experiments and composite analyses of a 5-day period are performed to examine the mechanisms governing nocturnal convection. Both simulations and observations show that a train of MCSs concurrently developed along a quasi-stationary mei-yu front and coincided with the impact of a monsoon surge on a frontogenetic zone at night. This process was regulated primarily by a nocturnal low-level jet (NLLJ) in the southwesterly monsoon that formed over southern China and extended to central China. In particular, the NLLJ acted as a mechanism of moisture transport over the plains. At its northern terminus, the NLLJ led to a zonal band of elevated conditionally unstable air where strong low-level ascent overcame small convective inhibition, triggering new convection in three preferred plains. An analysis of convective instability shows that the low-tropospheric intrusion of moist monsoon air generated CAPE of ~1000 J kg−1 prior to convection initiation, whereas free-atmospheric forcing was much weaker. The NLLJ-related horizontal advection accounted for most of the instability precondition at 100–175 J kg−1 h−1. At the convective stage, instability generation by the upward transport of moisture increased to ~100 J kg−1 h−1, suggesting that ascending inflow caused feedback in convection growth. The convection dissipated in late morning with decaying NLLJ and moisture at elevated layers. It is concluded that the diurnally varying summer monsoon acted as an effective discharge of available moist energy from southern to central China, generating the morning-peak heavy rainfall corridor.

Spatial variation of East Asian winter monsoon evolution between northern and southern China since the last glacial maximum

2021 ◽  
pp. 1-14
Author(s):  
Qin Li ◽  
Haibin Wu ◽  
Jun Cheng ◽  
Shuya Zhu ◽  
Chunxia Zhang ◽  
...  
Keyword(s):  
East Asian Winter Monsoon ◽  
Southern China ◽  
Ice Sheets ◽  
Northern China ◽  
Winter Monsoon ◽  
Asian Winter Monsoon ◽  
Spatial Differences ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract The East Asian winter monsoon (EAWM) is one of the most dynamic components of the global climate system. Although poorly understood, knowledge of long-term spatial differences in EAWM variability during the glacial–interglacial cycles is important for understanding the dynamic processes of the EAWM. We reconstructed the spatiotemporal characteristics of the EAWM since the last glacial maximum (LGM) using a comparison of proxy records and long-term transient simulations. A loess grain-size record from northern China (a sensitive EAWM proxy) and the sea surface temperature gradient of an EAWM index in sediments of the southern South China Sea were compared. The data–model comparison indicates pronounced spatial differences in EAWM evolution, with a weakened EAWM since the LGM in northern China but a strengthened EAWM from the LGM to the early Holocene, followed by a weakening trend, in southern China. The model results suggest that variations in the EAWM in northern China were driven mainly by changes in atmospheric carbon dioxide (CO2) concentration and Northern Hemisphere ice sheets, whereas orbital insolation and ice sheets were important drivers in southern China. We propose that the relative importance of insolation, ice sheets, and atmospheric CO2 for EAWM evolution varied spatially within East Asia.

scholarly journals Development of revised diagnostic criteria for Fuchs’ uveitis syndrome in a Chinese population

2021 ◽  
pp. bjophthalmol-2021-319343
Author(s):  
Peizeng Yang ◽  
Wanyun Zhang ◽  
Zhijun Chen ◽  
Han Zhang ◽  
Guannan Su ◽  
...  
Keyword(s):  
Diagnostic Criteria ◽  
Clinical Symptoms ◽  
Southern China ◽  
High Sensitivity ◽  
Northern China ◽  
Chinese Patients ◽  
Tertiary Referral Centre ◽  
Tree Algorithms ◽  
Vitreous Opacities ◽  
Fuchs Uveitis Syndrome

Background/aimsFuchs’ uveitis syndrome (FUS) is one of the frequently misdiagnosed uveitis entities, which is partly due to the absence of internationally recognised diagnostic criteria. This study was performed to develop and evaluate a set of revised diagnostic criteria for FUS.MethodsThe clinical data of Chinese patients with FUS and patients with non-FUS were collected and analysed from a tertiary referral centre between April 2008 and December 2020. A total of 593 patients with FUS and 625 patients with non-FUS from northern China were enrolled for the development of diagnostic criteria for FUS. Three hundred and seventy-seven patients with FUS and 503 patients with non-FUS from southern China were used to validate the criteria. Clinical symptoms and ocular signs were collected from all patients with FUS and patients with non-FUS. Multivariate two-step cluster analysis, logistic regression and decision tree algorithms in combination with the clinical judgement of uveitis experts were used to revise diagnostic criteria for FUS.ResultsThree essential findings including diffuse iris depigmentation, absence of posterior synechiae, mild inflammation in the anterior chamber at presentation and five associated findings including mostly unilateral involvement, cataract, vitreous opacities, absence of acute symptoms and characteristic iris nodules were used in the development of FUS diagnostic criteria. All essential findings were required for the diagnosis of FUS, and the diagnosis was further strengthened by the presence of associated findings.ConclusionRevised diagnostic criteria for FUS were developed and validated by analysing data from Chinese patients and showed a high sensitivity (96.55%) and specificity (97.42%).

Sign in / Sign up

Export Citation Format

Share Document