Different trends in extreme and median surface aerosol extinction coefficients over China inferred from quality-controlled visibility data

Li, Jing; Li, Chengcai; Zhao, Chunsheng

doi:10.5194/acp-18-3289-2018

Cited by 18 publications

(20 citation statements)

References 36 publications

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“…8 and S7), the decadal trends of MERRA-2 agreed better with the trend results from MODIS and MISR. This implies that the trends can change relatively quickly with time (Li et al, 2018). Sup- Figure 9.…”

Section: Regional Aod Trendsmentioning

confidence: 99%

“…Finally, to better quantify the relative contributions of each independent explanatory variable, which were obtained from the stepwise MLR model, to AOD variability, the LMG method (Bi, 2012;Grömping, 2006;Lindeman et al, 2014) was applied. This approach is one of the most advanced methods for determining the relative importance of explanatory variables in a linear model and provides a decomposition of the fraction of model-explained contributions (i.e., R 2 ) into nonnegative contributions using semi-partial R values.…”

Section: Trend Analysis and Stepwise Mlr Modelmentioning

confidence: 99%

“…Furthermore, considering that aerosol concentration and composition usually have strong seasonal cycles (Li et al, 2018), the trends for each season were also calculated separately and compared with the MODIS and MISR trends in the period of overlap (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016). Note that Fig.…”

Section: Regional Aod Trendsmentioning

confidence: 99%

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Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

et al. 2019

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Abstract. Aerosol optical depth (AOD) has become a crucial metric for assessing global climate change. Although global and regional AOD trends have been studied extensively, it remains unclear what factors are driving the inter-decadal variations in regional AOD and how to quantify the relative contribution of each dominant factor. This study used a long-term (1980–2016) aerosol dataset from the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis, along with two satellite-based AOD datasets (MODIS/Terra and MISR) from 2001 to 2016, to investigate the long-term trends in global and regional aerosol loading. Statistical models based on emission factors and meteorological parameters were developed to identify the main factors driving the inter-decadal changes of regional AOD and to quantify their contribution. Evaluation of the MERRA-2 AOD with the ground-based measurements of AERONET indicated significant spatial agreement on the global scale (r= 0.85, root-mean-square error = 0.12, mean fractional error = 38.7 %, fractional gross error = 9.86 % and index of agreement = 0.94). However, when AOD observations from the China Aerosol Remote Sensing Network (CARSNET) were employed for independent verification, the results showed that MERRA-2 AODs generally underestimated CARSNET AODs in China (relative mean bias = 0.72 and fractional gross error =-34.3 %). In general, MERRA-2 was able to quantitatively reproduce the annual and seasonal AOD trends on both regional and global scales, as observed by MODIS/Terra, although some differences were found when compared to MISR. Over the 37-year period in this study, significant decreasing trends were observed over Europe and the eastern United States. In contrast, eastern China and southern Asia showed AOD increases, but the increasing trend of the former reversed sharply in the most recent decade. The statistical analyses suggested that the meteorological parameters explained a larger proportion of the AOD variability (20.4 %–72.8 %) over almost all regions of interest (ROIs) during 1980–2014 when compared with emission factors (0 %–56 %). Further analysis also showed that SO2 was the dominant emission factor, explaining 12.7 %–32.6 % of the variation in AOD over anthropogenic-aerosol-dominant regions, while black carbon or organic carbon was the leading factor over the biomass-burning-dominant (BBD) regions, contributing 24.0 %–27.7 % of the variation. Additionally, wind speed was found to be the leading meteorological parameter, explaining 11.8 %–30.3 % of the variance over the mineral-dust-dominant regions, while ambient humidity (including soil moisture and relative humidity) was the top meteorological parameter over the BBD regions, accounting for 11.7 %–35.5 % of the variation. The results of this study indicate that the variation in meteorological parameters is a key factor in determining the inter-decadal change in regional AOD.

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Section: Regional Aod Trendsmentioning

confidence: 99%

Section: Trend Analysis and Stepwise Mlr Modelmentioning

confidence: 99%

Section: Regional Aod Trendsmentioning

confidence: 99%

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Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

et al. 2019

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“…The Beijing-Tianjin-Hebei (BTH) region, which is one of the most densely populated economic zones in China, has considerably high levels of PM 2.5 (Jiang et al, 2015;Chen and Wang, 2015). During severe winter haze days (SWHDs), the detected daily mean PM 2.5 concentrations reached 300-600 µg m −3 in BTH (Wang et al, 2014a;Li et al, 2018b). Exposure to these fine particulate matters detrimentally affects human health, causing problems from respiratory illnesses to cardiovascular diseases and premature death (Lelieveld et al, 2015;Zhang et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Severe winter haze days in the Beijing–Tianjin–Hebei region from 1985 to 2017 and the roles of anthropogenic emissions and meteorology

2019

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Abstract. We applied a global 3-D chemical transport model (GEOS-Chem) to examine the variations in the frequency and intensity in severe winter haze days (SWHDs) in Beijing–Tianjin–Hebei (BTH) from 1985 to 2017 and quantified the roles of changes in anthropogenic emissions and/or meteorological parameters. Observed SWHDs were defined as the days with daily mean PM2.5 concentration exceeding 150 µg m−3, and simulated SWHDs were identified by using the same threshold but with adjustment on the basis of simulation biases. Comparisons between the simulated SWHDs and those obtained from the observed PM2.5 concentrations and atmospheric visibility showed that the model can capture the spatial and temporal variations in SWHDs in China; the correlation coefficient between the simulated and observed SWHDs is 0.98 at 161 grids in China. From 1985 to 2017, with changes in both anthropogenic emissions and meteorological parameters, the simulated frequency (total severe haze days in winter) and intensity (PM2.5 concentration averaged over severe haze days in winter) of SWHDs in BTH showed increasing trends of 4.5 d per decade and 13.5 µg m−3 per decade, respectively. The simulated frequency exhibited fluctuations from 1985 to 2017, with a sudden decrease from 1992 to 2001 (29 to 10 d) and a rapid growth from 2003 to 2012 (16 to 47 d). The sensitivity simulations indicated that variations in meteorological parameters played a dominant role during 1992–2001, while variations in both emissions and meteorological parameters were important for the simulated frequency trend during 2003–2012 (simulated trends were 27.3 and 12.5 d per decade owing to changes in emissions alone and changes in meteorology alone, respectively). The simulated intensity showed a steady increase from 1985 to 2017, which was driven by changes in both emissions and meteorology. Process analysis on all SWHDs during 1985–2017 indicated that transport was the most important process for the formation of SWHDs in BTH with a relative contribution of 65.3 %, followed by chemistry (17.6 %), cloud processes (−7.5 %), dry deposition (−6.4 %), and planetary boundary layer (PBL) mixing (3.2 %). Further examination showed that SWHDs exhibited large interannual variations in frequency and intensity, which were mainly driven by changes in meteorology. The results of this study have important implications for the control of SWHDs in BTH.

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“…Fu et al (2013) defined an extremely poor visibility event as a case with atmospheric visibility of less than 5 km for at least 3 days and found that the annual frequency of such event averaged over large cites in China (142 cities with populations of more than one million) increased from 1960 to 2009 with a trend of 0.68 events decade -1 . Using the visibility-converted daily aerosol extinction coefficient (AEC) dataset, Li et al (2018a) examined the long-term trends in extremely high AEC (the 95 th percentile in a year) at 272 sites in China and compared these trends with the trends in median AEC (the 50 th percentile in a year). They showed that the extreme trends exceeded the median trends at most sites in the 1980s, the extreme trends were larger than the median trends in the south (south of 33° N) but smaller in the north (north of 33° N) in the 1990s, and then, most sites exhibited a faster increase in the median trends in the 2000s.…”

mentioning

confidence: 99%

Severe winter haze days in the Beijing-Tianjin-Hebei region from 1985–2017 and the roles of anthropogenic emissions and meteorological parameters

Dang

Liao

2019

Preprint

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Abstract. We applied a global 3-D chemical transport model (GEOS-Chem) to examine the variations in the frequency and intensity in severe winter haze days (SWHDs) in BTH from 1985&#8211;2017 and quantified the roles of changes in anthropogenic emissions and/or meteorological parameters. Comparisons between the simulated SWHDs and those obtained from the observed PM2.5 concentrations and atmospheric visibility showed that the model can capture the spatial and temporal variations of SWHDs in China; the correlation coefficient between the simulated and observed SWHDs is 0.98 at 161 grids in China. From 1985&#8211;2017, with changes in both anthropogenic emissions and meteorological parameters, the simulated frequency (total severe haze days in winter) and intensity (PM2.5 concentration averaged over severe haze days in winter) of SWHDs in BTH showed increasing trends of 4.5&#8201;days&#8201;decade&#8722;1 and 13.7&#8201;&#956;g&#8201;m&#8722;3&#8201;decade&#8722;1, respectively. The simulated frequency exhibited fluctuations from 1985&#8211;2017, with a sudden decrease from 1992&#8211;2001 (29 days to 10 days) and a rapid growth from 2003&#8211;2012 (16 days to 47 days). The sensitivity simulations indicated that variations in meteorological parameters played a dominant role during 1992&#8211;2001, while variations in both emissions and meteorological parameters were important for the simulated frequency trend during 2003&#8211;2012 (simulated trends were 27.3&#8201;days&#8201;decade&#8722;1 and 12.5&#8201;days&#8201;decade&#8722;1 owing to changes in emissions alone and changes in meteorology alone, respectively). The simulated intensity showed a steady increase from 1985&#8211;2017, which was driven by changes in both emissions and meteorology. The results of this study have important implications for the control of SWHDs in BTH.

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Different trends in extreme and median surface aerosol extinction coefficients over China inferred from quality-controlled visibility data

Cited by 18 publications

References 36 publications

Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

Severe winter haze days in the Beijing–Tianjin–Hebei region from 1985 to 2017 and the roles of anthropogenic emissions and meteorology

Severe winter haze days in the Beijing-Tianjin-Hebei region from 1985–2017 and the roles of anthropogenic emissions and meteorological parameters

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