Long-term observations of aerosol optical properties at Wuhan, an urban site in Central China

Wang, Lunche; Gong, Wei; Xia, Xiangao; Zhu, Jun; Li, Jun; Zhu, Zhenfeng

doi:10.1016/j.atmosenv.2014.11.021

Cited by 111 publications

(79 citation statements)

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“…2017, 9, 403 7 of 13 AE > 1.3 influenced most of the systematic underestimation of VIIRS IP AODs (Figure 2a), and the underestimation is explained in the next subsection analyses about monthly variations. The fine mode aerosols with strong absorption and large AE over Wuhan often have a dominant function due to automobile exhaust and the use of coal for domestic cooking, heating, and industrial processes [25]. Moreover, most matchups over a broad range of particle sizes (0.6-1.3 of AE), show smaller retrieval bias but larger uncertainty than MODIS.…”

Section: Comparison and Verification Of Methodsmentioning

confidence: 99%

“…Wuhan is the largest city in central China, with a dense population and heavy industrialization on the Yangtze River Basin (indicated by the white point in Figure 1). Wuhan experiences a typical north subtropical humid monsoon climate, with an annual average temperature of 15.8 °C to 17.5 °C and an annual average rainfall of 1050 mm to 2000 mm [25,26]. Most areas in Wuhan are 50 m above sea level.…”

Section: Study Areamentioning

confidence: 99%

“…A large amount of straw is burned in farmlands from nearby provinces during the harvest seasons (summer and autumn), thereby leading to the frequent haze conditions in recent years [43]. Moreover, increasing industrial and human activities, such as cement processing, smelting, coal combustion, and automobile emissions, generally lead to severe air pollution [25]. Climatologically, Wuhan is located in the East Asian monsoon area.…”

Section: Monthly Variations In Viirs Modis and Sun Photometer Aod Omentioning

confidence: 99%

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Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan

et al. 2017

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Visible Infrared Imaging Radiometer Suite (VIIRS) is a next-generation polar-orbiting operational environmental sensor with a capability for global aerosol observations. A comprehensive validation of VIIRS products is significant for improving product quality, assessing environment quality for human life, and studying regional climate change. In this study, three-year (from 1 January 2014 to 31 December 2016) records of VIIRS Intermediate Product (IP) data and Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals on aerosol optical depth (AOD) at 550 nm were evaluated by comparing them to ground sun photometer measurements over Wuhan. Results indicated that VIIRS IP retrievals were underestimated by 5% for the city. A comparison of VIIRS IP retrievals and ground sun photometer measurements showed a lower R 2 of 0.55 (0.79 for Terra-MODIS and 0.76 for Aqua-MODIS), with only 52% of retrievals falling within the expected error range established by MODIS over land (i.e., ±(0.05 + 0.15AOD)). Bias analyses with different Ångström exponents (AE) demonstrated that land aerosol model selection of the VIIRS retrieval over Wuhan was appropriate. However, the larger standard deviations (i.e., uncertainty) of VIIRS AODs than MODIS AODs could be attributed to the less robust retrieval algorithm. Monthly variations displayed largely underestimated AODs of VIIRS in winter, which could be caused by a large positive bias in surface reflectance estimation due to the sparse vegetation and greater surface brightness of Wuhan in this season. The spatial distribution of VIIRS and MODIS AOD observations revealed that the VIIRS IP AODs over high-pollution areas (AOD > 0.8) with sparse vegetation were underestimated by more than 20% in Wuhan, and 40% in several regions. Analysis of several clear rural areas (AOD < 0.2) with native vegetation indicated an overestimation of about 20% in the northeastern region of the city. These findings showed that the VIIRS IP AOD at 550 nm can provide a solid dataset with a high resolution (750 m) for quantitative scientific investigations and environmental monitoring over Wuhan. However, the performance of dark target algorithms in VIIRS was associated with aerosol types and ground vegetation conditions.

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Section: Comparison and Verification Of Methodsmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Monthly Variations In Viirs Modis and Sun Photometer Aod Omentioning

confidence: 99%

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Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan

et al. 2017

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“…The mean scattering Ångström exponent was 1.59 in Wuhan, indicating that aerosols were mainly fine particulate. In summer, due to increased rainfall, coarse particles were eliminated and aerosol hygroscopic growth due to relatively high atmospheric humidity can lead to higher SSA [44]. At the same time, summer is the crop-harvesting season in China, large amounts of biomass (such as straw) were combusted and a great deal of aerosol pollutant can be emitted into the atmosphere in Hubei and surrounding provinces.…”

Section: Seasonal Variation Of Aerosol Scattering and Absorption Propmentioning

confidence: 99%

An Investigation of Aerosol Scattering and Absorption Properties in Wuhan, Central China

et al. 2015

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, and 0.73, respectively. Both σ and σ showed obvious annual variability with large values in winter and small values in summer, principally caused by the annual characteristics of meteorological conditions, especially planetary boundary layer height (PBLH) and local emissions. The SSA showed a slight annual variation. High values of SSA were related to formation of secondary aerosols in winter hazes and aerosol hygroscopic growth in humid summer. The large SSA in June can be attributed to the biomass combustion in Hubei and surrounding provinces. Both σ and σ showed double peak phenomena in diurnal variation resulting from the shallow stable PBLH at night and automobile exhaust emission during morning OPEN ACCESSAtmosphere 2015, 6 504 rush hours. The SSA also exhibited a double peak phenomenon related to the proportional variation of black carbon (BC) and light scattering particulates in the day and night. The long-term exploration on quantified aerosol optical properties can help offer scientific basis of introducing timely environmental policies for local government.

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“…The elastic Lidar system operates at the top of a building in the State Key Laboratory of Information Engineering in Surveying, Mapping, and Remote Sensing (30 • 32 N, 114 • 21 E and 28 m above sea level) at Wuhan University, Wuhan City, Hubei Province, China [19,20]. The backscatter signals of the elastic Lidar are recorded every minute.…”

Section: Experimental Methodsmentioning

confidence: 99%

An Improved Iterative Fitting Method to Estimate Nocturnal Residual Layer Height

et al. 2016

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Abstract:The planetary boundary layer (PBL) is an atmospheric region near the Earth's surface. It is significant for weather forecasting and for the study of air quality and climate. In this study, the top of nocturnal residual layers-which are what remain of the daytime mixing layer-are estimated by an elastic backscatter Lidar in Wuhan (30.5 • N, 114.4 • E), a city in Central China. The ideal profile fitting method is widely applied to determine the nocturnal residual layer height (RLH) from Lidar data. However, the method is seriously affected by an optical thick layer. Thus, we propose an improved iterative fitting method to eliminate the optical thick layer effect on RLH detection using Lidar. Two typical case studies observed by elastic Lidar are presented to demonstrate the theory and advantage of the proposed method. Results of case analysis indicate that the improved method is more practical and precise than profile-fitting, gradient, and wavelet covariance transform method in terms of nocturnal RLH evaluation under low cloud conditions. Long-term observations of RLH performed with ideal profile fitting and improved methods were carried out in Wuhan from 28 May 2011 to 17 June 2016. Comparisons of Lidar-derived RLHs with the two types of methods verify that the improved solution is practical. Statistical analysis of a six-year Lidar signal was conducted to reveal the monthly average values of nocturnal RLH in Wuhan. A clear RLH monthly cycle with a maximum mean height of about 1.8 km above ground level was observed in August, and a minimum height of about 0.7 km was observed in January. The variation in monthly mean RLH displays an obvious quarterly dependence, which coincides with the annual variation in local surface temperature.

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Long-term observations of aerosol optical properties at Wuhan, an urban site in Central China

Cited by 111 publications

References 50 publications

Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan

Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan

An Investigation of Aerosol Scattering and Absorption Properties in Wuhan, Central China

An Improved Iterative Fitting Method to Estimate Nocturnal Residual Layer Height

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