المؤلفون: Xutao Zhang, Ke Gui, Zhaoliang Zeng, Ye Fei, Lei Li, Yu Zheng, Yue Peng, Yurun Liu, Nanxuan Shang, Hengheng Zhao, Wenrui Yao, Hong Wang, Zhili Wang, Yaqiang Wang, Huizheng Che, Xiaoye Zhang

المصدر: npj Climate and Atmospheric Science, Vol 7, Iss 1, Pp 1-12 (2024)

مصطلحات موضوعية: Environmental sciences, GE1-350, Meteorology. Climatology, QC851-999

الوصف: Abstract Surface visibility (SV), a key indicator of atmospheric transparency, is used widely in the fields of environmental monitoring, transportation, and aviation. However, the sparse distribution and limited number of SV monitoring sites make it difficult to fulfill the urgent need for spatiotemporally seamless fine-scale monitoring. Here, we developed the operational real-time SV retrieval (RT-SVR) framework for China that incorporates information from multiple data sources, including Chinese Land Data Assimilation System meteorological data, in situ observations, and other ancillary data. Seamless hourly SV data with 6.25-km spatial resolution are available in real time via the operational RT-SVR model, which was built using a two-layer stacked ensemble approach that combines multiple machine learning algorithms and a deep learning module. Sample-based cross-validation of the RT-SVR model on approximately 41.3 million data pairs revealed strong robustness and high accuracy, with a Pearson correlation coefficient (R) value of 0.95 and a root mean square error (RMSE) of 3.17 km. An additional hindcast-validation experiment, performed with continuous observations obtained over one year (approximately 20.8 million data pairs), demonstrated the powerful generalization capabilities of the RT-SVR model, albeit with slight degradation in performance (R = 0.85, RMSE = 5.28 km). The seamless hourly SV data with real-time update capability enable tracking of the generation, development, and dissipation of various low-SV events (e.g., fog, haze, and dust storms) in China. The developed framework might also prove useful for quantitative retrieval of aerosol-related parameters (e.g., PM2.5, PM10, and aerosol optical depth).

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2397-3722Test

الوصول الحر: https://doaj.org/article/f87e242c0699450d918057214ea98f22Test

المؤلفون: Zhengqing Zhou, Dianjie Li, Ziheng Zhao, Shuyu Shi, Jianghua Wu, Jianwei Li, Jingpeng Zhang, Ke Gui, Yu Zhang, Qi Ouyang, Heng Mei, Yu Hu, Fangting Li

المصدر: PLoS Computational Biology, Vol 19, Iss 9, p e1011383 (2023)

مصطلحات موضوعية: Biology (General), QH301-705.5

الوصف: Once challenged by the SARS-CoV-2 virus, the human host immune system triggers a dynamic process against infection. We constructed a mathematical model to describe host innate and adaptive immune response to viral challenge. Based on the dynamic properties of viral load and immune response, we classified the resulting dynamics into four modes, reflecting increasing severity of COVID-19 disease. We found the numerical product of immune system's ability to clear the virus and to kill the infected cells, namely immune efficacy, to be predictive of disease severity. We also investigated vaccine-induced protection against SARS-CoV-2 infection. Results suggested that immune efficacy based on memory T cells and neutralizing antibody titers could be used to predict population vaccine protection rates. Finally, we analyzed infection dynamics of SARS-CoV-2 variants within the construct of our mathematical model. Overall, our results provide a systematic framework for understanding the dynamics of host response upon challenge by SARS-CoV-2 infection, and this framework can be used to predict vaccine protection and perform clinical diagnosis.

وصف الملف: electronic resource

العلاقة: https://journals.plos.org/ploscompbiol/article/file?id=10.1371/journal.pcbi.1011383&type=printableTest; https://doaj.org/toc/1553-734XTest; https://doaj.org/toc/1553-7358Test

الوصول الحر: https://doaj.org/article/9ddd92010ee04d528de88d0a1016d6d4Test

المؤلفون: Fei Xie, Xuan Ma, Yanjie Li, Jianping Li, Xiaosong Chen, Wenshou Tian, Cheng Sun, Mian Xu, Jiankai Zhang, Ke Gui, Ruiqiang Ding, Yan Xia, Yingli Niu

المصدر: Environmental Research Letters, Vol 19, Iss 4, p 044053 (2024)

مصطلحات موضوعية: Arctic stratospheric polar vortex (APV), Southern Hemispheric jet, planetary waves, precipitation, Environmental technology. Sanitary engineering, TD1-1066, Environmental sciences, GE1-350, Science, Physics, QC1-999

الوصف: Our study reframes our understanding of stratosphere–troposphere interactions, traditionally thought to be confined within individual hemispheres, by introducing a novel cross-hemispheric link. We demonstrate that strong boreal winter Arctic stratospheric polar vortex (APV) boosts the transmission of upper tropospheric waves from Northern Hemisphere’s mid-high latitudes to the equator. Facilitated by the tropical central and eastern Pacific’s ‘westerly bridge’, these waves reach Southern Hemisphere’s mid-high latitudes. The entire process shows a ‘semicircular road’. Waves reaching the Southern Hemisphere affect the circulation through wave-flow interaction, causing a southward swing of the Southern Hemispheric westerly jet center. This displacement weakens the subtropical jet and strengthens the polar jet, resulting in increased subtropical precipitation and decreased mid-latitude precipitation in the Southern Hemisphere during austral summer. Correspondingly, a weak APV may lead to the opposite result. Our findings underscore APV’s broader impact on the tropospheric atmosphere, extending beyond prior knowledge.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1748-9326Test

الوصول الحر: https://doaj.org/article/de0a361e3cc842c1827e60f056448424Test

المؤلفون: Lei Zhang, Xiaomei Guo, Tianliang Zhao, Xiangde Xu, Xiaobo Zheng, Yueqing Li, Lei Luo, Ke Gui, Yu Zheng, Zhuozhi Shu

المصدر: Frontiers in Earth Science, Vol 10 (2022)

مصطلحات موضوعية: Sichuan Basin, atmospheric environment, visibility, climate, topographic effects, Science

الوصف: Using 51 years (1960–2010) of observations from meteorological stations in the Sichuan-Chongqing region, including atmospheric visibility as a proxy for aerosol concentration, relative humidity, air temperature, wind speed and FNL reanalysis data (1°×1°) of air temperature, pressure and wind, and the altitude of each station, a linear trend and multivariate fitting approach was used to explore the effects of the large topography on the atmospheric environment in the Sichuan-Chongqing region. The region mainly consists of two areas: Sichuan Basin (SCB) and Western Sichuan Plateau (WSP; eastern part of the Tibetan Plateau). Visibility was relatively low in the SCB and high in the WSP, indicating the high and low levels of aerosols respectively in the SCB and the WSP. Additionally, visibility and wind speed were positively correlated within the basin (altitude below 750 m), while negatively correlated at stations above 1,500 m, such as on the WSP, indicating that the topography had an influence on the atmospheric environment of the basin. On the one hand, the vertical structures of the wind fields and the vertical profiles of latitudinal deviations in wind speed and air temperature in the basin show that the unique large topography causes a “harbour” effect on the leeward-slope of the WSP, with the SCB being a weak wind region, while the descending air currents in the upper westerlies of the basin form a huge “vault” of air. On the other hand, topographic effects can make the basin more susceptible to the formation of inversion structures near the surface and at high altitudes, thus stabilising the atmosphere. The topographic effects, which is not conducive to horizontal diffusion and convective transport of pollutants, were the most significant in winter, followed by autumn and spring.

وصف الملف: electronic resource

العلاقة: https://www.frontiersin.org/articles/10.3389/feart.2022.997586/fullTest; https://doaj.org/toc/2296-6463Test

الوصول الحر: https://doaj.org/article/02cb6ee0f3fd4abca550b85f2fa87e71Test

المؤلفون: Hujia Zhao, Ke Gui, Yanjun Ma, Yangfeng Wang, Yaqiang Wang, Hong Wang, Yuanyuan Dou, Yu Zheng, Lei Li, Lei Zhang, Yuqi Zhang, Huizheng Che, Xiaoye Zhang

المصدر: Frontiers in Environmental Science, Vol 10 (2022)

مصطلحات موضوعية: Pm, meteorological parameters, aerosol, aerosol optical depth, North China plain, Environmental sciences, GE1-350

الوصف: Located in East Asia, the North China Plain (NCP) has a severe air pollution problem. In this study, variations in visibility, particulate matter (PM), gaseous pollutants, vertical meteorological parameters, and different types of aerosols and their optical properties were evaluated during an air pollution episode that occurred from 10 to 15 January 2019 in Tianjin over the NCP. The visibility was

وصف الملف: electronic resource

العلاقة: https://www.frontiersin.org/articles/10.3389/fenvs.2022.814736/fullTest; https://doaj.org/toc/2296-665XTest

الوصول الحر: https://doaj.org/article/59565b9a859a464595e93f61860f41eaTest

المؤلفون: Zhili Wang, Lei Lin, Yangyang Xu, Huizheng Che, Xiaoye Zhang, Hua Zhang, Wenjie Dong, Chense Wang, Ke Gui, Bing Xie

المصدر: npj Climate and Atmospheric Science, Vol 4, Iss 1, Pp 1-8 (2021)

مصطلحات موضوعية: Environmental sciences, GE1-350, Meteorology. Climatology, QC851-999

الوصف: Abstract Anthropogenic aerosol (AA) forcing has been shown as a critical driver of climate change over Asia since the mid-20th century. Here we show that almost all Coupled Model Intercomparison Project Phase 6 (CMIP6) models fail to capture the observed dipole pattern of aerosol optical depth (AOD) trends over Asia during 2006–2014, last decade of CMIP6 historical simulation, due to an opposite trend over eastern China compared with observations. The incorrect AOD trend over China is attributed to problematic AA emissions adopted by CMIP6. There are obvious differences in simulated regional aerosol radiative forcing and temperature responses over Asia when using two different emissions inventories (one adopted by CMIP6; the other from Peking university, a more trustworthy inventory) to driving a global aerosol-climate model separately. We further show that some widely adopted CMIP6 pathways (after 2015) also significantly underestimate the more recent decline in AA emissions over China. These flaws may bring about errors to the CMIP6-based regional climate attribution over Asia for the last two decades and projection for the next few decades, previously anticipated to inform a wide range of impact analysis.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/2397-3722Test

الوصول الحر: https://doaj.org/article/9e9b71576bb84d058a7c61db6be73672Test

المؤلفون: Xinglu Zhang, Yu Zheng, Huizheng Che, Ke Gui, Lei Li, Hujia Zhao, Yuanxin Liang, Wenrui Yao, Xindan Zhang, Hengheng Zhao, Yanting Lu, Xiaoye Zhang

المصدر: Remote Sensing, Vol 15, Iss 2, p 475 (2023)

مصطلحات موضوعية: aerosol vertical distribution, aerosol optical properties, haze, Beijing, Science

الوصف: Seasonal and diurnal characteristics of the vertical profiles of aerosol properties are essential for detecting the regional transport and the climatic radiative effects of aerosol particles. We have studied the seasonal and diurnal characteristics of the vertical distribution of aerosols in urban Beijing from 2017 to 2021 based on long-term Raman–Mie LiDAR observations. The influence of the vertical distribution of aerosols, the meteorological conditions within the boundary layer, the optical–radiometric properties of aerosols, and their interconnections, were investigated during a heavy haze pollution event in Beijing from 8 to 15 February 2020 using both meteorological and sun photometer data. The aerosol extinction coefficient was highest in summer (0.4 km−1), followed by winter (0.35 km−1), and roughly equal in spring and autumn (0.3 km−1). The aerosol extinction coefficient showed clear daily variations and was different in different seasons as a result of the variation in the height of the boundary layer. During the haze pollution event, the particulate matter mainly consisted of scattered spherical fine particles and the accumulation time of pollutants measured via the AOD440nm and PM2.5 mass concentration was different as a result of the hygroscopic growth of the aerosol particles. This growth increased scattering and led to an increase in the aerosol optical depth. The vertical transport of particulate matter also contributed to the increase in the aerosol optical depth.

وصف الملف: electronic resource

العلاقة: https://www.mdpi.com/2072-4292/15/2/475Test; https://doaj.org/toc/2072-4292Test

الوصول الحر: https://doaj.org/article/66ac80aa9e2849f1b1e4666de452c9feTest

المؤلفون: Lei Li, Huizheng Che, Xin Su, Xindan Zhang, Ke Gui, Yu Zheng, Hujia Zhao, Hengheng Zhao, Yuanxin Liang, Yadong Lei, Lei Zhang, Junting Zhong, Zhili Wang, Xiaoye Zhang

المصدر: Remote Sensing, Vol 15, Iss 2, p 388 (2023)

مصطلحات موضوعية: atmospheric aerosol, mineral dust, black carbon, MERRA-2, aerosol component retrievals, Science

الوصف: The aerosol optical property products of Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis dataset have been extensively investigated on a global or regional scale. However, the understanding of MERRA-2 aerosol component products on an extensive temporal and spatial scale is inadequate. Recently, the aerosol component products have been derived from the observations of Polarization and Directionality of the Earth’s Reflectances/Polarization and Anisotropy of Reflectance for Atmospheric Science coupled with observations from a Lidar (POLDER/PARASOL). This study presents a quantitative evaluation of the MERRA-2 reanalysis dust and black carbon (BC) column concentration using independent satellite-based aerosol component concentration retrievals. Both GRASP/Component and MERRA-2 reanalysis products can capture well the temporal variation in dust column concentration over the dust emission resource and downwind dust-dominated regions with the correlation coefficient (R) varying from 0.80 to 0.98. MERRA-2 reanalysis dust products present higher column concentration than GRASP/Component dust retrievals with relative differences of about 20~70%, except in the Taklamakan Desert and Bay of Bengal, where the relative differences can be negative. The differences in dust column concentration over the African dust regions are larger than that over the Asian dust regions. Similar temporal variations in BC column concentration are characterized by both GRASP/Component BC retrievals and MERRA-2 BC products with R of about 0.70~0.90, except in the North China Plain region. We should pay more caution with the regional applicability of MERRA-2 component products when large differences and high correlation coefficients are obtained simultaneously. The results are favorable for identifying the behavior of MERRA-2 reanalysis component estimation in a new view and demonstrate a practical application of the satellite-based component retrievals, which could make more contributions to the improvement of model estimation in the near future.

وصف الملف: electronic resource

العلاقة: https://www.mdpi.com/2072-4292/15/2/388Test; https://doaj.org/toc/2072-4292Test

الوصول الحر: https://doaj.org/article/4fde8bb142ba4411ba3ffef9e6f42bbaTest

المؤلفون: Yu Zheng, Huizheng Che, Ke Gui, Xiangao Xia, Hujia Zhao, Lei Li, Lei Zhang, Xinglu Zhang, Hengheng Zhao, Yuanxin Liang, Hong Wang, Yaqiang Wang, Xiaoye Zhang

المصدر: Remote Sensing, Vol 14, Iss 17, p 4321 (2022)

مصطلحات موضوعية: Sun photometer, Langley calibration, calibration assessment, aerosol optical depth verification, Mt. Foyeding Observatory, Beijing, Science

الوصف: An assessment and verification of the Langley calibration method of the Sun photometer at Mt Foyeding (MFYD) Observatory in Beijing was performed. We explored whether the Langley plot calibration is practicable for this mountainous site by analyzing the aerosol climatology and carrying out a case study. Then, the aerosol optical depth (AOD) results were verified under the reference of AERONET AOD. The results showed that satisfactory atmospheric conditions are present on winter mornings, characterized by a smaller average AOD (~0.09–0.14) and a lower range ratio (~36.97–63.38%) than in the afternoons and over a whole day. The six days selected as the case study all showed stable atmospheric conditions characterized by daily average triplets of V0λ at all wavelengths was V0λ value was derived from 31 days of observation and the deviations from the reference V0λ were about −1.69, −1.29, −0.81, −0.42, −0.34, −0.22, −0.63 and −0.36% at 340, 380, 440, 500, 675, 870, 1020 and 1640 nm, respectively. The regression analysis of the AOD validation showed a perfect AOD performance, with 100% of the retrievals lying within the expected error (0.05 ± 10%) from 380 to 1640 nm and 99.99% for the 340 nm band. Good AOD agreement (correlation coefficients > 0.998) and residual standard deviation values ranging from ~0.006 to 0.011 were observed, with the relative mean bias varying from 0.999 to 1.066. The mean biases were concentrated within ±0.02 for the ultraviolet bands and within ±0.01 for the other bands; therefore, the results of this preliminary assessment and verification indicated that the Langley plots method is suitable for photometer calibration at the MFYD Observatory.

وصف الملف: electronic resource

العلاقة: https://www.mdpi.com/2072-4292/14/17/4321Test; https://doaj.org/toc/2072-4292Test

الوصول الحر: https://doaj.org/article/760a66df34f043c799b059030a097939Test

المؤلفون: Ke Gui, Huizheng Che, Zhaoliang Zeng, Yaqiang Wang, Shixian Zhai, Zemin Wang, Ming Luo, Lei Zhang, Tingting Liao, Hujia Zhao, Lei Li, Yu Zheng, Xiaoye Zhang

المصدر: Environment International, Vol 141, Iss , Pp 105801- (2020)

مصطلحات موضوعية: Virtual PM2.5 observation network, Surface meteorological observations, Visibility, Extreme Gradient Boosting model, Environmental sciences, GE1-350

الوصف: With increasing public concerns on air pollution in China, there is a demand for long-term continuous PM2.5 datasets. However, it was not until the end of 2012 that China established a national PM2.5 observation network. Before that, satellite-retrieved aerosol optical depth (AOD) was frequently used as a primary predictor to estimate surface PM2.5. Nevertheless, satellite-retrieved AOD often encounter incomplete daily coverage due to its sampling frequency and interferences from cloud, which greatly affect the representation of these AOD-based PM2.5. Here, we constructed a virtual ground-based PM2.5 observation network at 1180 meteorological sites across China using the Extreme Gradient Boosting (XGBoost) model with high-density meteorological observations as major predictors. Cross-validation of the XGBoost model showed strong robustness and high accuracy in its estimation of the daily (monthly) PM2.5 across China in 2018, with R2, root-mean-square error (RMSE) and mean absolute error values of 0.79 (0.92), 15.75 μg/m3 (6.75 μg/m3) and 9.89 μg/m3 (4.53 μg/m3), respectively. Meanwhile, we find that surface visibility plays the dominant role in terms of the relative importance of variables in the XGBoost model, accounting for 39.3% of the overall importance.We then use meteorological and PM2.5 data in the year 2017 to assess the predictive capability of the model. Results showed that the XGBoost model is capable to accurately hindcast historical PM2.5 at monthly (R2 = 0.80, RMSE = 14.75 μg/m3), seasonal (R2 = 0.86, RMSE = 12.28 μg/m3), and annual (R2 = 0.81, RMSE = 10.10 μg/m3) mean levels. In general, the newly constructed virtual PM2.5 observation network based on high-density surface meteorological observations using the Extreme Gradient Boosting model shows great potential in reconstructing historical PM2.5 at ~1000 meteorological sites across China. It will be of benefit to filling gaps in AOD-based PM2.5 data, as well as to other environmental studies including epidemiology.

وصف الملف: electronic resource

العلاقة: http://www.sciencedirect.com/science/article/pii/S0160412020317566Test; https://doaj.org/toc/0160-4120Test

الوصول الحر: https://doaj.org/article/3aa0a315e7a544fcaf4e36c81b5f98ccTest