22 results
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2. Evaluation of the Added Value of Probabilistic Nowcasting Ensemble Forecasts on Regional Ensemble Forecasts.
- Author
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Yang, Lu, Cheng, Cong-Lan, Xia, Yu, Chen, Min, Chen, Ming-Xuan, Zhang, Han-Bin, and Huang, Xiang-Yu
- Subjects
METEOROLOGICAL services ,FORECASTING - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2023
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3. Assessment of FY-4A and Himawari-8 Cloud Top Height Retrieval through Comparison with Ground-Based Millimeter Radar at Sites in Tibet and Beijing.
- Author
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Liu, Bo, Huo, Juan, Lyu, Daren, and Wang, Xin
- Subjects
ATMOSPHERIC physics ,SURFACE temperature - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
- Full Text
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4. A Model Output Machine Learning Method for Grid Temperature Forecasts in the Beijing Area.
- Author
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Li, Haochen, Yu, Chen, Xia, Jiangjiang, Wang, Yingchun, Zhu, Jiang, and Zhang, Pingwen
- Subjects
MACHINE learning ,RANDOM forest algorithms ,ATMOSPHERIC temperature ,FORECASTING ,WEATHER forecasting - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
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5. Evaluation of the tropical variability from the Beijing Climate Center's real-time operational global Ocean Data Assimilation System.
- Author
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Zhou, Wei, Wu, Tongwen, Chen, Mengyan, Zhuang, Wei, Wang, Xin, Xu, Fanghua, and Zheng, Fei
- Subjects
OCEANOGRAPHIC observations ,RELATIVE sea level change ,EL Nino ,RADAR altimetry ,MATHEMATICAL models ,DATA acquisition systems ,GLOBAL Ocean Observing System ,MODES of variability (Climatology) ,SCIENTIFIC communication - Abstract
The second-generation Global Ocean Data Assimilation System of the Beijing Climate Center (BCC GODAS2.0) has been run daily in a pre-operational mode. It spans the period 1990 to the present day. The goal of this paper is to introduce the main components and to evaluate BCC GODAS2.0 for the user community. BCC GODAS2.0 consists of an observational data preprocess, ocean data quality control system, a three-dimensional variational (3DVAR) data assimilation, and global ocean circulation model [Modular Ocean Model 4 (MOM4)]. MOM4 is driven by six-hourly fluxes from the National Centers for Environmental Prediction. Satellite altimetry data, SST, and in-situ temperature and salinity data are assimilated in real time. The monthly results from the BCC GODAS2.0 reanalysis are compared and assessed with observations for 1990-2011. The climatology of the mixed layer depth of BCC GODAS2.0 is generally in agreement with that ofWorld Ocean Atlas 2001. The modeled sea level variations in the tropical Pacific are consistent with observations from satellite altimetry on interannual to decadal time scales. Performances in predicting variations in the SST using BCC GODAS2.0 are evaluated. The standard deviation of the SST in BCC GODAS2.0 agrees well with observations in the tropical Pacific. BCC GODAS2.0 is able to capture the main features of El Ni˜no Modoki I and Modoki II, which have different impacts on rainfall in southern China. In addition, the relationships between the Indian Ocean and the two types of El Ni˜no Modoki are also reproduced. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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6. Meshless Surface Wind Speed Field Reconstruction Based on Machine Learning.
- Author
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Liu, Nian, Yan, Zhongwei, Tong, Xuan, Jiang, Jiang, Li, Haochen, Xia, Jiangjiang, Lou, Xiao, Ren, Rui, and Fang, Yi
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WIND speed ,MACHINE learning ,STANDARD deviations ,MACHINE theory ,RANDOM forest algorithms ,AERONAUTICAL safety measures - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2022
- Full Text
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7. Characterization of Regional Combustion Efficiency using ΔXCO: ΔXCO2 Observed by a Portable Fourier-Transform Spectrometer at an Urban Site in Beijing.
- Author
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Che, Ke, Liu, Yi, Cai, Zhaonan, Yang, Dongxu, Wang, Haibo, Ji, Denghui, Yang, Yang, and Wang, Pucai
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COMBUSTION efficiency ,FOURIER transform spectrometers ,EMISSION inventories ,METEOROLOGICAL research ,CARBON monoxide ,EXHAUST gas recirculation - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2022
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8. Evaluation and Evolution of MAX-DOAS-observed Vertical NO2 Profiles in Urban Beijing.
- Author
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Kang, Yanyu, Tang, Guiqian, Li, Qihua, Liu, Baoxian, Cao, Jianfeng, Hu, Qihou, and Wang, Yuesi
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BOUNDARY layer (Aerodynamics) ,TROPOSPHERIC ozone ,NITROGEN dioxide ,CITIES & towns ,STATISTICAL correlation ,OZONE - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
- Full Text
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9. Simulated Sensitivity of Ozone Generation to Precursors in Beijing during a High O3 Episode.
- Author
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Cui, Meng, An, Xingqin, Xing, Li, Li, Guohui, Tang, Guiqian, He, Jianjun, Long, Xin, and Zhao, Shuman
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TROPOSPHERIC ozone ,OZONE ,AIR pollution control ,OXYGEN carriers ,ALTITUDES - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
- Full Text
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10. Increases in Anthropogenic Heat Release from Energy Consumption Lead to More Frequent Extreme Heat Events in Urban Cities.
- Author
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Liu, Bin, Xie, Zhenghui, Qin, Peihua, Liu, Shuang, Li, Ruichao, Wang, Longhuan, Wang, Yan, Jia, Binghao, Chen, Si, Xie, Jinbo, and Shi, Chunxiang
- Subjects
ENERGY consumption ,WEATHER forecasting ,ATMOSPHERIC boundary layer ,HEAT ,METEOROLOGICAL research ,ECONOMIES of agglomeration ,SURFACE energy - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
- Full Text
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11. Investigating Lightning Characteristics through a Supercell Storm by Comprehensive Coordinated Observations over North China.
- Author
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Liu, Dongxia, Qie, Xiushu, Chen, Yichen, Sun, Zhuling, and Yuan, Shanfeng
- Subjects
LIGHTNING ,SNOWFLAKES ,ICE crystals ,RADIATION sources ,HAIL - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2020
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12. Investigating the Transport Mechanism of PM2.5 Pollution during January 2014 in Wuhan, Central China.
- Author
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Lu, Miaomiao, Tang, Xiao, Wang, Zifa, Wu, Lin, Chen, Xueshun, Liang, Shengwen, Zhou, Hui, Wu, Huangjian, Hu, Ke, Shen, Longjiao, Yu, Jia, and Zhu, Jiang
- Subjects
HAZE ,POLLUTION ,AIR pollutants ,AIR masses ,WEATHER ,MEGALOPOLIS - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
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13. Cloud Classification and Distribution of Cloud Types in Beijing Using Ka-Band Radar Data.
- Author
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Huo, Juan, Bi, Yongheng, Lü, Daren, and Duan, Shu
- Subjects
STRATOCUMULUS clouds ,CLASSIFICATION algorithms ,RADAR ,K-means clustering ,FUZZY logic ,CUMULONIMBUS - Abstract
Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
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14. Comparison of Beijing MST radar and radiosonde horizontal wind measurements.
- Author
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Tian, Yufang and Lü, Daren
- Subjects
RADAR interference ,RADIOSONDE observations of the upper atmosphere ,WIND measurement ,SPATIOTEMPORAL processes ,CITIES & towns & the environment - Abstract
To determine the performance and data accuracy of the 50 MHz Beijing Mesosphere-Stratosphere-Troposphere (MST) radar, comparisons of radar measured horizontal winds in the height range 3-25 km with radiosonde observations were made during 2012. A total of 427 profiles and 15 210 data pairs were compared. There was very good agreement between the two types of measurement. Standard deviations of difference (mean difference) for wind direction, wind speed, zonal wind and meridional wind were 24.86◦ (0.77◦), 3.37 (−0.44), 3.33 (−0.32) and 3.58 (−0.25) m s, respectively. The annual standard deviations of differences for wind speed were within 2.5-3 m s at all heights apart from 10-15 km, the area of strong winds, where the values were 3-4 m s. The relatively larger differences were mainly due to wind field variations in height regions with larger wind speeds, stronger wind shear and the quasi-zero wind layer. A lower MST radar SNR and a lower percentage of data pairs compared will also result in larger inconsistencies. Importantly, this study found that differences between the MST radar and radiosonde observations did not simply increase when balloon drift resulted in an increase in the real-time distance between the two instruments, but also depended on spatiotemporal structures and their respective positions in the contemporary synoptic systems. In this sense, the MST radar was shown to be a unique observation facility for atmospheric dynamics studies, as well as an operational meteorological observation system with a high temporal and vertical resolution. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
15. Changes of precipitation and extremes and the possible effect of urbanization in the Beijing metropolitan region during 1960-2012 based on homogenized observations.
- Author
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Li, Zhen, Yan, Zhongwei, Tu, Kai, and Wu, Hongyi
- Subjects
METEOROLOGICAL precipitation ,CLIMATE extremes ,URBANIZATION ,METROPOLITAN areas -- Environmental conditions - Abstract
Daily precipitation series at 15 stations in the Beijing metropolitan region (BMR) during 1960-2012 were homogenized using the multiple analysis of series for homogenization method, with additional adjustments based on analysis of empirical cumulative density function (ECDF) regarding climate extremes. The cumulative density functions of daily precipitation series, the trends of annual and seasonal precipitation, and summer extreme events during 1960-2012 in the original and final adjusted series at Beijing station were comparatively analyzed to show the necessity and efficiency of the new method. Results indicate that the ECDF adjustments can improve the homogeneity of high-order moments of daily series and the estimation of climate trends in extremes. The linear trends of the regional-mean annual and seasonal (spring, summer, autumn, and winter) precipitation series are −10.16, 4.97, −20.04, 5.02, and −0.11 mm (10 yr), respectively. The trends over the BMR increase consistently for spring/autumn and decrease for the whole year/summer; however, the trends for winter decrease in southern parts and increase in northern parts. Urbanization affects local trends of precipitation amount, frequency, and intensity and their geographical patterns. For the urban-influenced sites, urbanization tends to slow down the magnitude of decrease in the precipitation and extreme amount series by approximately −10.4% and −6.0%, respectively; enhance the magnitude of decrease in precipitation frequency series by approximately 5.7%; reduce that of extremes by approximately −8.9%; and promote the decreasing trends in the summer intensity series of both precipitation and extremes by approximately 6.8% and 51.5%, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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- View/download PDF
16. Contrasting characteristics of the surface energy balance between the urban and rural areas of Beijing.
- Author
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Wang, Linlin, Gao, Zhiqiu, Miao, Shiguang, Guo, Xiaofeng, Sun, Ting, Liu, Maofeng, and Li, Dan
- Subjects
SURFACE energy ,METROPOLITAN areas ,RURAL geography ,TERRESTRIAL radiation ,ATMOSPHERIC aerosols ,GREENHOUSE gases & the environment ,EVAPOTRANSPIRATION - Abstract
A direct comparison of urban and rural surface energy balances, as well as a variety of other variables including incoming shortwave/longwave radiation and aerosol optical depth, is conducted for the Beijing metropolitan area. The results indicate that, overall, the urban area receives a smaller amount of incoming shortwave radiation but a larger amount of incoming longwave radiation. However, comparisons in the aerosol optical depth and cloud fraction at the two locations suggest that neither aerosol optical depth nor cloud fraction alone can explain the difference in the incoming shortwave radiation. The urban-rural differences in the incoming longwave radiation are unlikely to be caused by the presence of more abundant greenhouse gases over the urban area, as suggested by some previous studies, given that water vapor is the most dominant greenhouse gas and precipitable water is found to be less in urban areas. The higher incoming longwave radiation observed over the urban area is mostly likely due to the higher temperatures of the ambient air. The urban area is also found to always produce higher sensible heat fluxes and lower latent heat fluxes in the growing season. Furthermore, the urban area is associated with a larger amount of available energy (the sum of sensible and latent heat fluxes) than the rural area, except in May and October when evapotranspiration in the rural area significantly exceeds that in the urban area. This study provides observational evidence of urban-rural contrasts in relevant energy-balance components that plausibly arise from urban-rural differences in atmospheric and land-surface conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
17. An improved method for correction of air temperature measured using different radiation shields.
- Author
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Cheng, Xinghong, Su, Debin, Li, Deping, Chen, Lu, Xu, Wenjing, Yang, Meilin, Li, Yongcheng, Yue, Zhizhong, and Wang, Zijing
- Subjects
ATMOSPHERIC temperature measurements ,RADIATION shielding ,MEASUREMENT errors ,METEOROLOGICAL stations ,ATMOSPHERIC radiation - Abstract
The variation of air temperature measurement errors using two different radiation shields (DTR502B Vaisala, Finland, and HYTFZ01, Huayun Tongda Satcom, China) was studied. Datasets were collected in the field at the Daxing weather station in Beijing from June 2011 to May 2012. Most air temperature values obtained with these two commonly used radiation shields were lower than the reference records obtained with the new Fiber Reinforced Polymers (FRP) Stevenson screen. In most cases, the air temperature errors when using the two devices were smaller on overcast and rainy days than on sunny days; and smaller when using the imported rather than the Chinese shield. The measured errors changed sharply at sunrise and sunset, and reached maxima at noon. Their diurnal variation characteristics were, naturally, related to changes in solar radiation. The relationships between the record errors, global radiation, and wind speed were nonlinear. An improved correction method was proposed based on the approach described by Nakamura and Mahrt (2005) (NM05), in which the impact of the solar zenith angle (SZA) on the temperature error is considered and extreme errors due to changes in SZA can be corrected effectively. Measurement errors were reduced significantly after correction by either method for both shields. The error reduction rate using the improved correction method for the Chinese and imported shields were 3.3% and 40.4% higher than those using the NM05 method, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
18. Effects of NO and VOCs from five emission sources on summer surface O over the Beijing-Tianjin-Hebei region.
- Author
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Qu, Yu, An, Junling, Li, Jian, Chen, Yong, Li, Ying, Liu, Xingang, and Hu, Min
- Subjects
VOLATILE organic compounds ,NITRIC oxide ,SUMMER ,EMISSION control ,OXYGEN reduction ,CLIMATE change - Abstract
The impacts of emissions from industry, power plant, transportation, residential, and biogenic sources on daily maximum surface ozone (O) over the Beijing-Tianjin-Hebei (BTH) region in North China in the summer of 2007 were examined in a modeling study. The modeling system consisted of the Weather Research and Forecasting (WRF) model and the photochemical dispersion model, CAMx. The factor separation technique (FST) was used to quantify the effect of individual emission source types and the synergistic interactions among two or more types. Additionally, the effectiveness of emission reduction scenarios was explored. The industry, power plant, and transportation emission source types were found to be the most important in terms of their individual effects on ODM. The key contributor to high surface O was power plant emissions, with a peak individual effect of 40 ppbv in the southwestern BTH area. The individual effect from the biogenic emission category was quite low. The synergistic effects from the combinations of each pair of anthropogenic emission types suppressed O formation, while the synergistic effects for combinations of three were favorable for O formation when the industrial and power plant emission source types coexisted. The quadruple synergistic effects were positive only with the combination of power plant, transportation, residential, and biogenic sources, while the quintuple synergistic effect showed only minor impacts on O concentrations. A 30% reduction in industrial and transportation sources produced the most effective impacts on O concentrations, with a maximum decrease of 20 ppbv. These results suggested that the synergistic impacts among emission source types should be considered when formulating emission control strategies for O reduction. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
19. Improvement of 6-15 day precipitation forecasts using a time-lagged ensemble method.
- Author
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Jie, Weihua, Wu, Tongwen, Wang, Jun, Li, Weijing, and Liu, Xiangwen
- Subjects
METEOROLOGICAL precipitation ,CLIMATOLOGY ,RAINFALL ,CIRCULATION models ,CITIES & towns & the environment - Abstract
A time-lagged ensemble method is used to improve 6-15 day precipitation forecasts from the Beijing Climate Center Atmospheric General Circulation Model, version 2.0.1. The approach averages the deterministic predictions of precipitation from the most recent model run and from earlier runs, all at the same forecast valid time. This lagged average forecast (LAF) method assigns equal weight to each ensemble member and produces a forecast by taking the ensemble mean. Our analyses of the Equitable Threat Score, the Hanssen and Kuipers Score, and the frequency bias indicate that the LAF using five members at time-lagged intervals of 6 h improves 6-15 day forecasts of precipitation frequency above 1 mm d and 5 mm d in many regions of China, and is more effective than the LAF method with selection of the time-lagged interval of 12 or 24 h between ensemble members. In particular, significant improvements are seen over regions where the frequencies of rainfall days are higher than about 40%-50% in the summer season; these regions include northeastern and central to southern China, and the southeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
20. Simulating urban flow and dispersion in Beijing by coupling a CFD model with the WRF model.
- Author
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Miao, Yucong, Liu, Shuhua, Chen, Bicheng, Zhang, Bihui, Wang, Shu, and Li, Shuyan
- Subjects
COMPUTATIONAL fluid dynamics ,DISPERSION (Chemistry) ,METEOROLOGICAL research ,POLLUTANTS ,WEATHER forecasting ,CITIES & towns & the environment - Abstract
The airflow and dispersion of a pollutant in a complex urban area of Beijing, China, were numerically examined by coupling a Computational Fluid Dynamics (CFD) model with a mesoscale weather model. The models used were Open Source Field Operation and Manipulation (OpenFOAM) software package and Weather Research and Forecasting (WRF) model. OpenFOAM was firstly validated against wind-tunnel experiment data. Then, the WRF model was integrated for 42 h starting from 0800 LST 08 September 2009, and the coupled model was used to compute the flow fields at 1000 LST and 1400 LST 09 September 2009. During the WRF-simulated period, a high pressure system was dominant over the Beijing area. The WRF-simulated local circulations were characterized by mountain valley winds, which matched well with observations. Results from the coupled model simulation demonstrated that the airflows around actual buildings were quite different from the ambient wind on the boundary provided by the WRF model, and the pollutant dispersion pattern was complicated under the influence of buildings. A higher concentration level of the pollutant near the surface was found in both the step-down and step-up notches, but the reason for this higher level in each configurations was different: in the former, it was caused by weaker vertical flow, while in the latter it was caused by a downward-shifted vortex. Overall, the results of this study suggest that the coupled WRF-OpenFOAM model is an important tool that can be used for studying and predicting urban flow and dispersions in densely built-up areas. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
21. Detecting urban warming signals in climate records.
- Author
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He, Yuting, Jia, Gensuo, Hu, Yonghong, and Zhou, Zijiang
- Subjects
ATMOSPHERIC temperature ,METEOROLOGICAL stations ,URBANIZATION - Abstract
Determining whether air temperatures recorded at meteorological stations have been contaminated by the urbanization process is still a controversial issue at the global scale. With support of historical remote sensing data, this study examined the impacts of urban expansion on the trends of air temperature at 69 meteorological stations in Beijing, Tianjin, and Hebei Province over the last three decades. There were significant positive relations between the two factors at all stations. Stronger warming was detected at the meteorological stations that experienced greater urbanization, i.e., those with a higher urbanization rate. While the total urban area affects the absolute temperature values, the change of the urban area (urbanization rate) likely affects the temperature trend. Increases of approximately 10% in urban area around the meteorological stations likely contributed to the 0.13°C rise in air temperature records in addition to regional climate warming. This study also provides a new approach to selecting reference stations based on remotely sensed urban fractions. Generally, the urbanization-induced warming contributed to approximately 44.1% of the overall warming trends in the plain region of study area during the past 30 years, and the regional climate warming was 0.30°C (10 yr) in the last three decades. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
22. Interannual variation of tropical night frequency in Beijing and associated large-scale circulation background.
- Author
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Park, Jong-Kil, Lu, Riyu, Li, Chaofan, and Kim, Eun
- Subjects
HUMIDITY research ,CYCLONES ,RAINFALL - Abstract
This study examined the variability in frequency of tropical night occurrence (i.e., minimum air temperature >25°C) in Beijing, using a homogenized daily temperature dataset during the period 1960-2008. Our results show that tropical nights occur most frequently in late July and early August, which is consistent with relatively high air humidity associated with the rainy season in Beijing. In addition, year-to-year variation of tropical night occurrence indicates that the tropical nights have appeared much more frequently since 1994, which can be illustrated by the yearly days of tropical nights averaged over two periods: 9.2 days of tropical nights per year during 1994-2008 versus 3.15 days during 1960-1993. These features of tropical night variations suggest a distinction between tropical nights and extreme heat in Beijing. We further investigated the large-scale circulations associated with the year-to-year variation of tropical night occurrence in July and August, when tropical nights appear most frequently and occupy 95% of the annual sum. After comparing the results in the two reanalysis datasets (NCEP/NCAR and ERA-40) and considering the possible effects of decadal change in the frequency of tropical nights that occurred around 1993/94, we conclude that on the interannual time scale, the cyclonic anomaly with a barotropic structure centered over Beijing is responsible for less frequent tropical nights, and the anticyclonic anomaly is responsible for more frequent occurrence of tropical nights over Beijing. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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