scholarly journals Investigations of Temporal and Spatial Distribution of Precursors SO<sub>2</sub> and NO<sub>2</sub> Vertical Columns in North China Plain by Mobile DOAS

2017 ◽  
Author(s):  
Fengcheng Wu ◽  
Pinhua Xie ◽  
Ang Li ◽  
Fusheng Mou ◽  
Hao Chen ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Air Quality ◽  
North China Plain ◽  
North China ◽  
Emission Sources ◽  
Pollution Transport ◽  
Temporal And Spatial Distribution ◽  
Near Surface ◽  
Air Mass ◽  
Temporal And Spatial

Abstract. Recently, Chinese cities have suffered severe events of haze air pollution, particularly in the North China Plain (NCP). Investigating the temporal and spatial distribution of pollutants, emissions, and pollution transport is necessary to better understand the effect of various sources on air quality. We report on mobile differential optical absorption spectroscopy (mobile DOAS) observations of precursors SO2 and NO2 vertical columns in NCP in summer of 2013 (from 11 June to 7 July) in this study. The different temporal and spatial distributions of SO2 and NO2 vertical column density (VCD) over this area are characterized under various wind fields. The results show that the transport from southern NCP strongly affects the air quality in Beijing, and the transport route, particularly SO2 transport of Shijiazhuang–Baoding–Beijing is identified. In addition, the major contributors to SO2 along the route of Shijiazhuang–Baoding–Beijing are elevated sources and low area sources for the route of Dezhou–Cangzhou–Tianjin–Beijing are found using the interrelated analysis between in situ and mobile DOAS observations during the measurement periods. Furthermore, the discussion of hot spot near Ji’nan City shows that the average observed width of polluted air mass is 11.83 km and 17.23 km associated with air mass diffusion, which is approximately 60 km away from emission sources based on geometrical estimation. Finally, a reasonable agreement exists between OMI and mobile DOAS observations with correlation coefficient (R2) of 0.65 for NO2 VCDs. Both datasets also have similar spatial pattern. The fitted slop of 0.55 is significantly less than unity can reflect the contamination of local sources and OMI observations need to improve the sensitivities to the near-surface emission sources through the improvements of retrieval algorithm or resolution of satellites.

scholarly journals Investigations of temporal and spatial distribution of precursors SO<sub>2</sub> and NO<sub>2</sub> vertical columns in the North China Plain using mobile DOAS

2018 ◽  
Vol 18 (3) ◽  
pp. 1535-1554 ◽  
Author(s):  
Fengcheng Wu ◽  
Pinhua Xie ◽  
Ang Li ◽  
Fusheng Mou ◽  
Hao Chen ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Air Quality ◽  
North China Plain ◽  
North China ◽  
Emission Sources ◽  
Temporal And Spatial Distribution ◽  
Air Mass ◽  
The North ◽  
The North China Plain ◽  
Temporal And Spatial

Abstract. Recently, Chinese cities have suffered severe events of haze air pollution, particularly in the North China Plain (NCP). Investigating the temporal and spatial distribution of pollutants, emissions, and pollution transport is necessary to better understand the effect of various sources on air quality. We report on mobile differential optical absorption spectroscopy (mobile DOAS) observations of precursors SO2 and NO2 vertical columns in the NCP in the summer of 2013 (from 11 June to 7 July) in this study. The different temporal and spatial distributions of SO2 and NO2 vertical column density (VCD) over this area are characterized under various wind fields. The results show that transport from the southern NCP strongly affects air quality in Beijing, and the transport route, particularly SO2 transport on the route of Shijiazhuang–Baoding–Beijing, is identified. In addition, the major contributors to SO2 along the route of Shijiazhuang–Baoding–Beijing are elevated sources compared to low area sources for the route of Dezhou–Cangzhou–Tianjin–Beijing; this is found using the interrelated analysis between in situ and mobile DOAS observations during the measurement periods. Furthermore, the discussions on hot spots near the city of JiNan show that average observed width of polluted air mass is 11.83 and 17.23 km associated with air mass diffusion, which is approximately 60 km away from emission sources based on geometrical estimation. Finally, a reasonable agreement exists between the Ozone Monitoring Instrument (OMI) and mobile DOAS observations, with a correlation coefficient (R2) of 0.65 for NO2 VCDs. Both datasets also have a similar spatial pattern. The fitted slope of 0.55 is significantly less than unity, which can reflect the contamination of local sources, and OMI observations are needed to improve the sensitivities to the near-surface emission sources through improvements of the retrieval algorithm or the resolution of satellites.

scholarly journals Estimation of Surface and Near-Surface Air Temperatures in Arid Northwest China Using Landsat Satellite Images

2021 ◽  
Vol 9 ◽  
Author(s):  
Yi Liu ◽  
Samuel Ortega-Farías ◽  
Fei Tian ◽  
Sufen Wang ◽  
Sien Li
Keyword(s):  
Spatial Distribution ◽  
Land Surface ◽  
Vegetation Index ◽  
Meteorological Data ◽  
Northwest China ◽  
Landsat 8 ◽  
Linear Regression Models ◽  
Temporal And Spatial Distribution ◽  
Near Surface ◽  
Temporal And Spatial

Near-surface air (Ta) and land surface (Ts) temperatures are essential parameters for research in the fields of agriculture, hydrology, and ecological changes, which require accurate datasets with different temporal and spatial resolutions. However, the sparse spatial distribution of meteorological stations in Northwest China may not effectively provide high-precision Ta data. And it is not clear whether it is necessary to improve the accuracy of Ts which has the most influence on Ta. In response to this situation, the main objective of this study is to estimate Ta for Northwest China using multiple linear regression models (MLR) and random forest (RF) algorithms, based on Landsat 8 images and auxiliary data collected from 2014 to 2019. Ts, NDVI (Normalized Difference Vegetation Index), surface albedo, elevation, wind speed, and Julian day were variables to be selected, then used to estimate the daily average Ta after analysis and adjustment. Also, the Radiative Transfer Equation (RTE) method for calculating Ts would be corrected by NDVI (RTE-NDVI). The results show that: 1) The accuracy of the surface temperature (Ts) was improved by using RTE-NDVI; 2) Both MLR and RF models are suitable for estimating Ta in areas with few meteorological stations; 3) Analyzing the temporal and spatial distribution of errors, it is found that the MLR model performs well in spring and summer, and is lower in autumn, and the accuracy is higher in plain areas away from mountains than in mountainous areas and nearby areas. This study shows that through appropriate selection and combination of variables, the accuracy of estimating the pixel-scale Ta from satellite remote sensing data can be improved in the area that has less meteorological data.

scholarly journals Modeling study of impacts on surface ozone of regional transport and emission reductions over North China Plain in summer 2015

2018 ◽  
Author(s):  
Xiao Han ◽  
Lingyun Zhu ◽  
Shulan Wang ◽  
Xiaoyan Meng ◽  
Meigen Zhang ◽  
...  
Keyword(s):  
Air Quality ◽  
Emission Reduction ◽  
North China Plain ◽  
North China ◽  
Emission Control ◽  
Effective Control ◽  
Emission Sources ◽  
Regional Transport ◽  
Reduction Percentage ◽  
Sensitive Conditions

Abstract. Tropospheric ozone (O3) has replaced PM2.5 or PM10 as the premier pollution in the North China Plain (NCP) during summer in recent years. A comprehensive understanding of the O3 production in responding to the reduction of precursor emission over NCP is demanded urgently for the effective control policy design. In this study, the air quality modeling system RAMS-CMAQ (regional atmospheric modeling system-community multiscale air quality), coupled with the ISAM (integrated source apportionment method) module is applied to investigate the O3 regional transport and source contribution features during a heavy O3 pollution episode in June 2015 over NCP. The results show that the emission sources in Shandong and Hebei were the major contributors to O3 production in the NCP. Not only more than 50 % O3 mass burden in local regions, but also about 20–30 % and 25–40 % O3 mass burdens in Beijing and Tianjin were contributed by the emission sources in these two provinces, respectively. On the other hand, the urban areas and most O3 pollution regions of NCP were mainly dominated by the VOC-sensitive conditions, while "both control" and NOx-sensitive conditions dominated the suburban and remote areas, respectively. Then, based on the sensitivity tests, the effects of several hypothetical scenarios of emission control on reducing the O3 pollution were compared and discussed. The results indicated that the emission control of industry and residential sectors was the most efficient way if the emission reduction percentage was higher than 40 %. However, when the emission reduction percentage dropped below 30 %, the power plant sector could make significant contributions to the decrease in O3. The control strategies should be promptly adjusted based on the emission reduction, and the modeling system can provide valuable information for precisely choosing the emission sector combination to achieve better efficiency.

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