The moving of high emission for biomass burning in China: View from multi-year emission estimation and human-driven forces

Chen

et al. 2021

Atmos. Chem. Phys.

Abstract. Accurate lidar ratio (LR) and better understanding of its variation characteristics can not only improve the retrieval accuracy of parameters from elastic lidar, but also play an important role in assessing the impacts of aerosols on climate. Using the observational data of a Raman lidar in Shanghai from 2017 to 2019, LRs at 355 nm were retrieved and their variations and influence factors were analyzed. Within the height range of 0.5–5 km, about 90 % of the LRs were distributed in 10–80 sr with an average value of 41.0 ± 22.5 sr, and the LR decreased with the increase in height. The volume depolarization ratio (δ) was positively correlated with LR, and it also decreased with the increase in height, indicating that the vertical distribution of particle shape was one of the influence factors of the variations in LR with height. LR had a strong dependence on the original source of air masses. Affected by the aerosols transported from the northwest, the average LR was the largest, 44.2 ± 24.7 sr, accompanied by the most irregular particle shape. The vertical distribution of LR was affected by atmospheric turbidity, with the greater gradient of LR under clean conditions. The LR above 1 km could be more than 80 sr, when Shanghai was affected by biomass burning aerosols.

Section: Era5mentioning

confidence: 72%

Long-term variation in aerosol lidar ratio in Shanghai based on Raman lidar measurements

Chen

et al. 2021

Atmos. Chem. Phys.

“…It should be noted that the average  affected by aerosols brought by air mass 4 was small, which was comparable to that of air mass 1, indicating a high contribution of spherical aerosol particles, but LR was larger. By observing the trajectory of air mass 4, we found that it passed through Hubei Province with high industrial level (Wang et al, 2016) and Anhui Province with heavy pollution of biomass burning (Wu et al, 2020). The accompanying industrial and smoke aerosols, which are approximately spherical (Giannakaki et al, 2016;Müller et al, 2007) could be responsible for the smaller  .…”

Section: Influences Of Aerosol Sources On Lrmentioning

confidence: 92%

“…Biomass burning is one of the important sources of PM, organic carbon (OC) and black carbon (BC) in the atmosphere (Wu et al, 2020). It also emits pollutant gases such as CO, SO2, NOx and HCN (Andreae and Merlet, 2001;Kalluri et al, 2020;Randel et al, 2010).…”

Section: The Main Aerosol Types Causing the Abnormal Variation Of Lrmentioning

confidence: 99%

Study on variations in lidar ratios for Shanghai based on Raman lidar

Chen

et al. 2020

Preprint

Abstract. Accurate Lidar ratios (LR) and better understanding of their variation characteristics can not only improve the retrieval accuracy of parameters from elastic lidar, but also play an important role in assessing the impacts of aerosols on the climate. Using the observational data of Raman lidar in Shanghai from 2017 to 2019, the LR at 355 nm were retrieved and their variations and influencing factors were analyzed. Within the height range of 0.5 km–5 km, about 90 % of the LR were distributed in 10 sr–80 sr with an average value of 41.0 ± 22.5 sr, and the LR decreased with the increase of height. The volume depolarization ratios (δ) were positively correlated with LR, and they also decreased with the increase of height, indicating that the vertical distribution of particle shape was one of the influencing factors of the variations of LR with height. LR had a strong dependence on the original source of the air masses. Affected by the aerosol transported from northwest of Shanghai, the average LR was the largest, 44.2 ± 24.7 sr, accompanied by the most irregular particle shape. The vertical distributions of LR were affected by the atmospheric turbidity, with the greater gradient of LR under the clean conditions. The LR above 1 km could be more than 80 sr, when Shanghai was affected by the biomass burning aerosols.

“…Both the simulation and observations revealed near-surface extinctions as high as 0.4 km −1 during the winter, when aerosol pollution was frequent over eastern China, but the observed high extinctions of 0.2-0.4 km −1 at near-surface altitudes during summer and fall were underestimated by the model. Because biomass burning activities are predominantly concentrated in the summer and fall in eastern China and are critical determinants of aerosol pollution (Chen et al, 2017;Wu et al, 2017), the low biases of aerosol extinction profiles could partially stem from the model's use of biomass burning emissions that were derived from the GFED4 database. That emission inventory has been considered to be a lower estimate on a global scale compared to other commonly used databases constrained by satellite observations (Pan et al, 2020).…”

Section: Changes In Aerosol Optical Propertiesmentioning

confidence: 99%

Aerosol radiative forcings induced by substantial changes in anthropogenic emissions in China from 2008 to 2016

Matsui

2021

Atmos. Chem. Phys.

Abstract. Anthropogenic emissions in China play an important role in altering the global radiation budget. Over the past decade, the strong clean-air policies in China have resulted in substantial reductions of anthropogenic emissions of sulfur dioxide (SO2) and primary particulate matter, and air quality in China has consequently improved. However, the resultant aerosol radiative forcings have been poorly understood. In this study, we used an advanced global climate model integrated with the latest localized emission inventory to quantify the aerosol radiative forcings by the changes of anthropogenic emissions in China between 2008 and 2016. By comparing with multiple observation datasets, our simulations reproduced the considerable reductions of sulfate and black carbon (BC) mass loadings reasonably well over eastern China (the key region subject to stringent emission controls) during the period and accordingly showed a clear decline in both aerosol optical depth and absorption aerosol optical depth. The results revealed a regional annual mean positive direct radiative forcing (DRF) of +0.29 W m−2 at the top of the atmosphere (TOA) due to the reduction of SO2 emissions. This positive aerosol radiative forcing was comprised of diminished sulfate scattering (+0.58 W m−2), enhanced nitrate radiative effects (−0.29 W m−2), and could be completely offset by the concurrent reduction of BC emissions that induced a negative BC DRF of −0.33 W m−2. Despite the small net aerosol DRF (−0.05 W m−2) at the TOA, aerosol–radiation interactions could explain the surface brightening in China over the past decade. The overall reductions in aerosol burdens and associated optical effects mainly from BC and sulfate enhanced the regional annual mean downward solar radiation flux at the surface by +1.0 W m−2 between 2008 and 2016. The enhancement was in general agreement with a long-term observational record of surface energy fluxes in China. We also estimated that aerosol effects on cloud radiative forcings may have played a dominant role in the net aerosol radiative forcings at the TOA in China and over the northern Pacific Ocean during the study period. This study will facilitate more informed assessment of climate responses to projected emissions in the future as well as to sudden changes in human activities (e.g., the COVID-19 lockdown).