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Zengxin Pan
State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China

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Journal article
Published: 05 July 2018 in Remote Sensing of Environment
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Changes in aerosol loading affect cloud albedo and emission and Earth's radiative balance with a low level of scientific understanding. In this study, we investigate the vertical response of ice clouds to aerosols within the Indian subcontinent during monsoon season (2006–2010) based on multiple satellite observations. As a function of aerosol loading, we find that the cloud optical depth, cloud geometrical depth and ice water path decrease by 0.23 (from 0.39 to 0.16), 0.8 km (from 2.6 to 1.8 km), 5.1 g/m2 (from 7.9 to 2.8 g/m2), respectively, and that ice particles possibly decrease in size and become more spherical in shape as aerosol optical depth (AOD) increases from 0.1 to 1; these changes tend to plateau as AOD increases beyond 1. The absolute negative response between ice clouds and aerosols under moist and unstable atmospheric conditions is stronger than that under drier and stable atmospheric conditions, and vice versa. Moreover, the negative impact of smoke on ice clouds is stronger than dust and polluted dust, which is likely related to the strong absorption properties and poor ice nucleation efficiency of smoke. Aerosol impacts on ice clouds lead to a decrease in the net cloud radiative effect of 7.3 W/m2 (from 18.5 to 11.2 W/m2) as AOD increases from 0.1 to 1. This change in ice cloud properties mainly results in the decrease in downwelling LW radiation to the surface and consequently weakened radiative forcing of ice clouds during the Indian summer monsoon season.

ACS Style

Feiyue Mao; Zengxin Pan; David S. Henderson; Wei Wang; Wei Gong. Vertically resolved physical and radiative response of ice clouds to aerosols during the Indian summer monsoon season. Remote Sensing of Environment 2018, 216, 171 -182.

AMA Style

Feiyue Mao, Zengxin Pan, David S. Henderson, Wei Wang, Wei Gong. Vertically resolved physical and radiative response of ice clouds to aerosols during the Indian summer monsoon season. Remote Sensing of Environment. 2018; 216 ():171-182.

Chicago/Turabian Style

Feiyue Mao; Zengxin Pan; David S. Henderson; Wei Wang; Wei Gong. 2018. "Vertically resolved physical and radiative response of ice clouds to aerosols during the Indian summer monsoon season." Remote Sensing of Environment 216, no. : 171-182.

Journal article
Published: 23 April 2018 in Remote Sensing
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South Asia is experiencing a levelling-off trend in solar radiation and even a transition from dimming to brightening. Any change in incident solar radiation, which is the only significant energy source of the global ecosystem, profoundly affects our habitats. Here, we use multiple observations of the A-Train constellation to evaluate the impacts of three-dimensional (3D) aerosol, cloud, and water vapor variations on the changes in surface solar radiation during the monsoon season (June–September) in South Asia from 2006 to 2015. Results show that surface shortwave radiation (SSR) has possibly increased by 16.2 W m−2 during this period. However, an increase in aerosol loading is inconsistent with the SSR variations. Instead, clouds are generally reduced and thinned by approximately 8.8% and 280 m, respectively, with a decrease in both cloud water path (by 34.7 g m−2) and particle number concentration under cloudy conditions. Consequently, the shortwave cloud radiative effect decreases by approximately 45.5 W m−2 at the surface. Moreover, precipitable water in clear-sky conditions decreases by 2.8 mm (mainly below 2 km), and related solar brightening increases by 2.5 W m−2. Overall, the decreases in 3D water vapor and clouds distinctly result in increased absorption of SSR and subsequent surface brightening.

ACS Style

Zengxin Pan; Feiyue Mao; Wei Wang; Bo Zhu; Xin Lu; Wei Gong. Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season. Remote Sensing 2018, 10, 651 .

AMA Style

Zengxin Pan, Feiyue Mao, Wei Wang, Bo Zhu, Xin Lu, Wei Gong. Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season. Remote Sensing. 2018; 10 (4):651.

Chicago/Turabian Style

Zengxin Pan; Feiyue Mao; Wei Wang; Bo Zhu; Xin Lu; Wei Gong. 2018. "Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season." Remote Sensing 10, no. 4: 651.

Journal article
Published: 18 February 2018 in Remote Sensing
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Aerosols greatly influence global and regional atmospheric systems, and human life. However, a comprehensive understanding of the source regions and three-dimensional (3D) characteristics of aerosol transport over central China is yet to be achieved. Thus, we investigate the 3D macroscopic, optical, physical, and transport properties of the aerosols over central China based on the March 2007 to February 2016 data obtained from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission and the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model. Our results showed that approximately 60% of the aerosols distributed over central China originated from local areas, whereas non-locally produced aerosols constituted approximately 40%. Anthropogenic aerosols constituted the majority of the aerosol pollutants (69%) that mainly distributed less than 2.0 km above mean sea level. Natural aerosols, which are mainly composed of dust, accounted for 31% of the total aerosols, and usually existed at an altitude higher than that of anthropogenic aerosols. Aerosol particles distributed in the near surface were smaller and more spherical than those distributed above 2.0 km. Aerosol optical depth (AOD) and the particulate depolarization ratio displayed decreasing trends, with a total decrease of 0.11 and 0.016 from March 2007 to February 2016, respectively. These phenomena indicate that during the study period, the extinction properties of aerosols decreased, and the degree of sphericity in aerosol particles increased. Moreover, the annual anthropogenic and natural AOD demonstrated decreasing trends, with a total decrease of 0.07 and 0.04, respectively. This study may benefit the evaluation of the effects of the 3D properties of aerosols on regional climates.

ACS Style

Xin Lu; Feiyue Mao; Zengxin Pan; Wei Gong; Wei Wang; Liqiao Tian; Shenghui Fang. Three-Dimensional Physical and Optical Characteristics of Aerosols over Central China from Long-Term CALIPSO and HYSPLIT Data. Remote Sensing 2018, 10, 314 .

AMA Style

Xin Lu, Feiyue Mao, Zengxin Pan, Wei Gong, Wei Wang, Liqiao Tian, Shenghui Fang. Three-Dimensional Physical and Optical Characteristics of Aerosols over Central China from Long-Term CALIPSO and HYSPLIT Data. Remote Sensing. 2018; 10 (2):314.

Chicago/Turabian Style

Xin Lu; Feiyue Mao; Zengxin Pan; Wei Gong; Wei Wang; Liqiao Tian; Shenghui Fang. 2018. "Three-Dimensional Physical and Optical Characteristics of Aerosols over Central China from Long-Term CALIPSO and HYSPLIT Data." Remote Sensing 10, no. 2: 314.

Comparative study
Published: 05 September 2017 in International Journal of Environmental Research and Public Health
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The Visible Infrared Imaging Radiometer Suite (VIIRS) is a next-generation polar-orbiting operational environmental sensor with a capability for global aerosol observations. Identifying land aerosol types is important because aerosol types are a basic input in retrieving aerosol optical properties for VIIRS. The VIIRS algorithm can automatically select the optimal land aerosol model by minimizing the residual between the derived and expected spectral surface reflectance. In this study, these selected VIIRS aerosol types are evaluated using collocated aerosol types obtained from the Aerosol Robotic Network (AERONET) level 1.5 from 23 January 2013 to 28 February 2017. The spatial distribution of VIIRS aerosol types and the aerosol optical depth bias (VIIRS minus AERONET) demonstrate that misidentifying VIIRS aerosol types may lead to VIIRS retrieval being overestimated over the Eastern United States and the developed regions of East Asia, as well as underestimated over Southern Africa, India, and Northeastern China. Approximately 22.33% of VIIRS aerosol types are coincident with that of AERONET. The agreements between VIIRS and AERONET for fine non-absorbing and absorbing aerosol types are approximately 36% and 57%, respectively. However, the agreement between VIIRS and AERONET is extremely low (only 3.51%). The low agreement for coarse absorbing dust may contribute to the poor performance of VIIRS retrieval under the aerosol model (R = 0.61). Results also show that an appropriate aerosol model can improve the retrieval performance of VIIRS over land, particularly for dust type (R increases from 0.61 to 0.72).

ACS Style

Wei Wang; Zengxin Pan; Feiyue Mao; Wei Gong; Longjiao Shen. Evaluation of VIIRS Land Aerosol Model Selection with AERONET Measurements. International Journal of Environmental Research and Public Health 2017, 14, 1016 .

AMA Style

Wei Wang, Zengxin Pan, Feiyue Mao, Wei Gong, Longjiao Shen. Evaluation of VIIRS Land Aerosol Model Selection with AERONET Measurements. International Journal of Environmental Research and Public Health. 2017; 14 (9):1016.

Chicago/Turabian Style

Wei Wang; Zengxin Pan; Feiyue Mao; Wei Gong; Longjiao Shen. 2017. "Evaluation of VIIRS Land Aerosol Model Selection with AERONET Measurements." International Journal of Environmental Research and Public Health 14, no. 9: 1016.

Journal article
Published: 19 August 2017 in Remote Sensing
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Monitoring fine particulate matter with diameters of less than 2.5 μm (PM2.5) is a critical endeavor in the Beijing–Tianjin–Hebei (BTH) region, which is one of the most polluted areas in China. Polar orbit satellites are limited by observation frequency, which is insufficient for understanding PM2.5 evolution. As a geostationary satellite, Himawari-8 can obtain hourly optical depths (AODs) and overcome the estimated PM2.5 concentrations with low time resolution. In this study, the evaluation of Himawari-8 AODs by comparing with Aerosol Robotic Network (AERONET) measurements showed Himawari-8 retrievals (Level 3) with a mild underestimate of about −0.06 and approximately 57% of AODs falling within the expected error established by the Moderate-resolution Imaging Spectroradiometer (MODIS) (±(0.05 + 0.15AOD)). Furthermore, the improved linear mixed-effect model was proposed to derive the surface hourly PM2.5 from Himawari-8 AODs from July 2015 to March 2017. The estimated hourly PM2.5 concentrations agreed well with the surface PM2.5 measurements with high R2 (0.86) and low RMSE (24.5 μg/m3). The average estimated PM2.5 in the BTH region during the study time range was about 55 μg/m3. The estimated hourly PM2.5 concentrations ranged extensively from 35.2 ± 26.9 μg/m3 (1600 local time) to 65.5 ± 54.6 μg/m3 (1100 local time) at different hours.

ACS Style

Wei Wang; Feiyue Mao; Lin Du; Zengxin Pan; Wei Gong; Shenghui Fang. Deriving Hourly PM2.5 Concentrations from Himawari-8 AODs over Beijing–Tianjin–Hebei in China. Remote Sensing 2017, 9, 858 .

AMA Style

Wei Wang, Feiyue Mao, Lin Du, Zengxin Pan, Wei Gong, Shenghui Fang. Deriving Hourly PM2.5 Concentrations from Himawari-8 AODs over Beijing–Tianjin–Hebei in China. Remote Sensing. 2017; 9 (8):858.

Chicago/Turabian Style

Wei Wang; Feiyue Mao; Lin Du; Zengxin Pan; Wei Gong; Shenghui Fang. 2017. "Deriving Hourly PM2.5 Concentrations from Himawari-8 AODs over Beijing–Tianjin–Hebei in China." Remote Sensing 9, no. 8: 858.

Journal article
Published: 25 April 2017 in Remote Sensing
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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 R2 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.

ACS Style

Wei Wang; Feiyue Mao; Zengxin Pan; Lin Du; Wei Gong. Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan. Remote Sensing 2017, 9, 403 .

AMA Style

Wei Wang, Feiyue Mao, Zengxin Pan, Lin Du, Wei Gong. Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan. Remote Sensing. 2017; 9 (5):403.

Chicago/Turabian Style

Wei Wang; Feiyue Mao; Zengxin Pan; Lin Du; Wei Gong. 2017. "Validation of VIIRS AOD through a Comparison with a Sun Photometer and MODIS AODs over Wuhan." Remote Sensing 9, no. 5: 403.

Journal article
Published: 01 November 2016 in International Journal of Environmental Research and Public Health
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The atmospheric boundary layer (ABL), an atmospheric region near the Earth’s surface, is affected by surface forcing and is important for studying air quality, climate, and weather forecasts. In this study, long-term urban nocturnal boundary layers (NBLs) were estimated by an elastic backscatter light detection and ranging (LiDAR) with various methods in Wuhan (30.5° N, 114.4° E), a city in Central China. This study aims to explore two ABL research topics: (1) the relationship between NBL height (NBLH) and near-surface parameters (e.g., sensible heat flux, temperature, wind speed, and relative humidity) to elucidate meteorological processes governing NBL variability; and (2) the influence of NBLH variations in surface particulate matter (PM) in Wuhan. We analyzed the nocturnal ABL-dilution/ABL-accumulation effect on surface particle concentration by using a typical case. A long-term analysis was then performed from 5 December 2012–17 June 2016. Results reveal that the seasonal averages of nocturnal (from 20:00 to 05:00 next day, Chinese standard time) NBLHs are 386 ± 161 m in spring, 473 ± 154 m in summer, 383 ± 137 m in autumn, and 309 ± 94 m in winter. The seasonal variations in NBLH, AOD, and PM2.5 display a deep (shallow) seasonal mean NBL, consistent with a small (larger) seasonal mean PM2.5 near the surface. Seasonal variability of NBLH is partly linearly correlated with sensible heat flux at the surface (R = 0.72). Linear regression analyses between NBLH and other parameters show the following: (1) the positive correlation (R = 0.68) between NBLH and surface temperature indicates high (low) NBLH corresponding to warm (cool) conditions; (2) the slight positive correlation (R = 0.52) between NBLH and surface relative humidity in Wuhan; and (3) the weak positive correlation (R = 0.38) between NBLH and wind speed inside the NBL may imply that the latter is not an important direct driver that governs the seasonal variability of NBLH.

ACS Style

Wei Wang; Feiyue Mao; Wei Gong; Zengxin Pan; Lin Du. Evaluating the Governing Factors of Variability in Nocturnal Boundary Layer Height Based on Elastic Lidar in Wuhan. International Journal of Environmental Research and Public Health 2016, 13, 1071 .

AMA Style

Wei Wang, Feiyue Mao, Wei Gong, Zengxin Pan, Lin Du. Evaluating the Governing Factors of Variability in Nocturnal Boundary Layer Height Based on Elastic Lidar in Wuhan. International Journal of Environmental Research and Public Health. 2016; 13 (11):1071.

Chicago/Turabian Style

Wei Wang; Feiyue Mao; Wei Gong; Zengxin Pan; Lin Du. 2016. "Evaluating the Governing Factors of Variability in Nocturnal Boundary Layer Height Based on Elastic Lidar in Wuhan." International Journal of Environmental Research and Public Health 13, no. 11: 1071.

Journal article
Published: 17 August 2016 in Atmosphere
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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.

ACS Style

Wei Wang; Wei Gong; Feiyue Mao; Zengxin Pan. An Improved Iterative Fitting Method to Estimate Nocturnal Residual Layer Height. Atmosphere 2016, 7, 106 .

AMA Style

Wei Wang, Wei Gong, Feiyue Mao, Zengxin Pan. An Improved Iterative Fitting Method to Estimate Nocturnal Residual Layer Height. Atmosphere. 2016; 7 (8):106.

Chicago/Turabian Style

Wei Wang; Wei Gong; Feiyue Mao; Zengxin Pan. 2016. "An Improved Iterative Fitting Method to Estimate Nocturnal Residual Layer Height." Atmosphere 7, no. 8: 106.

Journal article
Published: 18 May 2016 in International Journal of Environmental Research and Public Health
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We comprehensively evaluated particle lidar ratios (i.e., particle extinction to backscatter ratio) at 532 nm over Wuhan in Central China by using a Raman lidar from July 2013 to May 2015. We utilized the Raman lidar data to obtain homogeneous aerosol lidar ratios near the surface through the Raman method during no-rain nights. The lidar ratios were approximately 57 ± 7 sr, 50 ± 5 sr, and 22 ± 4 sr under the three cases with obviously different pollution levels. The haze layer below 1.8 km has a large particle extinction coefficient (from 5.4e-4 m−1 to 1.6e-4 m−1) and particle backscatter coefficient (between 1.1e-05 m−1sr−1 and 1.7e-06 m−1sr−1) in the heavily polluted case. Furthermore, the particle lidar ratios varied according to season, especially between winter (57 ± 13 sr) and summer (33 ± 10 sr). The seasonal variation in lidar ratios at Wuhan suggests that the East Asian monsoon significantly affects the primary aerosol types and aerosol optical properties in this region. The relationships between particle lidar ratios and wind indicate that large lidar ratio values correspond well with weak winds and strong northerly winds, whereas significantly low lidar ratio values are associated with prevailing southwesterly and southerly wind.

ACS Style

Wei Wang; Wei Gong; Feiyue Mao; Zengxin Pan; Boming Liu. Measurement and Study of Lidar Ratio by Using a Raman Lidar in Central China. International Journal of Environmental Research and Public Health 2016, 13, 508 .

AMA Style

Wei Wang, Wei Gong, Feiyue Mao, Zengxin Pan, Boming Liu. Measurement and Study of Lidar Ratio by Using a Raman Lidar in Central China. International Journal of Environmental Research and Public Health. 2016; 13 (5):508.

Chicago/Turabian Style

Wei Wang; Wei Gong; Feiyue Mao; Zengxin Pan; Boming Liu. 2016. "Measurement and Study of Lidar Ratio by Using a Raman Lidar in Central China." International Journal of Environmental Research and Public Health 13, no. 5: 508.