The feedback effects of aerosols from different sources on the urban boundary layer in Beijing China.

The interaction of aerosols and the planetary boundary layer (PBL) plays an important role in deteriorating urban air quality. Aerosols from different sources may have different effects on regulating PBL structures owing to their distinctive dominant compositions and vertical distributions. To characterize the complex feedback of aerosols on PBL over the Beijing megacity, multiple approaches, including in situ observations in the autumn and winter of 2016-2019, backward trajectory clusters, and large-eddy simulations, were adopted.

Emission, transport, deposition, chemical and radiative impacts of mineral dust during severe dust storm periods in March 2021 over East Asia.

A Regional Air Quality Model System (named RAQMS) coupled with a developed dust model driven by WRF was applied to synthetically investigate the emission, transport, deposition, budget, and chemical and radiative effects of mineral dust during the severe dust storm periods of 10-31 March 2021. Model results were validated against a variety of ground, vertical and satellite observations, which demonstrated a generally good model ability in reproducing meteorological variables, particulate matter and compositions, and aerosol optical properties. The first dust storm (DS1), which was the severest one since 2010 was originated from the Gobi Desert in southern Mongolia on 14 March, with the dust emission flux reaching 2785 μg m s and the maximum dust concentration exceeding 18,000 μg m in the dust deflation region.

Model analysis of vertical exchange of boundary layer ozone and its impact on surface air quality over the North China Plain.

In addition to photochemical production and horizontal regional transport, surface O concentration can also likely be affected by vertical transport, which is not well known so far. The process analysis was conducted by using the Regional Atmospheric Modeling System Community Multiscale Air Quality (RAMS-CMAQ) model to investigate photochemical production and the vertical transport mechanism of boundary-layer O during a typical O pollution episode in the North China Plain (NCP), and further quantify the contribution of vertical transport to surface O. The diurnal variations of vertical budgets of O and NO in the boundary layer at multiple sites showed that there were substantial differences in the vertical distribution of O production and transport between urban and suburban/rural areas.

Aerosol optical properties and its type classification based on multiyear joint observation campaign in north China plain megalopolis.

Since haze and other air pollution are frequently seen in the North China Plain (NCP), detail information on aerosol optical and radiative properties and its type classification is demanded for the study of regional environmental pollution. Here, a multiyear ground-based synchronous sun photometer observation at seven sites on North China Plain megalopolis from 2013 to 2018 was conducted. First, the annual and seasonal variation of these characteristics as well as the intercomparsion were analyzed.

The influence of aerosols on the NO photolysis rate in a suburban site in North China.

The photolysis of NO is an important driving force of tropospheric ozone. The intensity of this photolysis reaction affects atmospheric oxidation and photochemical pollution process. Photolysis rate of nitrogen dioxide (JNO) is affected by aerosols, temperature, solar zenith angle (SZA), clouds, and so on.

Effect of source variation on the size and mixing state of black carbon aerosol in urban Beijing from 2013 to 2019: Implication on light absorption.

Black carbon (BC) is the most important aerosol light-absorbing component, and its effect on radiation forcing is determined by its microphysical properties. In this study, two microphysical parameters of refractory BC (rBC), namely, size distribution and mixing state, in urban Beijing from 2013 to 2019 were investigated to understand the effects of source changes over the past years. The mass equivalent diameter of rBC (D) exhibited bimodal lognormal distributions in all seasons, with the major modes accounting for most (>85%) of the rBC masses.

First in situ UV profile across the UTLS accompanied by ozone measurement over the Tibetan Plateau.

Ultraviolet radiation (UV) and ozone can greatly affect human health and the Earth's ecological environment. By deploying a UV radiometer aboard a stratospheric balloon released at Qaidam (QDM) during the Asian summer monsoon (ASM) period in 2019, we provided in situ measurement of the UV profiles from the surface to the upper troposphere and lower stratosphere over the Tibetan Plateau (TP), China, for the first time. Based on two in situ UV profiles accompanied by four ozonesonde measurements, this study exhibited detailed variations of downwelling UV and vertical ozone distributions over the TP during the ASM period.

Spectral absorption properties of organic carbon aerosol during a polluted winter in Beijing, China.

A fraction of organic carbon (OC) is found to exhibit the capability to absorb solar radiation. However, the absorption properties of OC remain poorly characterized partly due to uncertainties in determination methods. In this study, the absorption coefficient (b) of OC (b) in Beijing during a polluted winter was estimated on the basis of the combined measurements of black carbon (BC) size distribution and total aerosol b (b).

Advances in sunphotometer-measured aerosol optical properties and related topics in China: Impetus and perspectives.

Aerosol is a critical trace component of the atmosphere. Many processes in the Earth's climate system are intimately related to aerosols via their direct and indirect radiative effects. Aerosol effects are not limited to these climatic aspects, however.

Variation in black carbon concentration and aerosol optical properties in Beijing: Role of emission control and meteorological transport variability.

Black carbon (BC), which is a by-product with incomplete combustion of carbonaceous materials, can be used as an indicator of combustion emissions and is an important climate forcer. In this study, a spatial-temporal synthesis of BC aerosols and the affecting factors was conducted in urban Beijing. As observed, BC showed a spatial pattern with high concentration in south and low in north.

Long-term validation of MODIS C6 and C6.1 Dark Target aerosol products over China using CARSNET and AERONET.

This study provided a comprehensive evaluation of the Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 006 (C6) and 061 (C6.1) Dark Target (DT) 10 km aerosol optical depth (AOD) over China during 2002-2014. Considering that sparse Aerosol Robotic Network (AERONET) sites are available in China, 18 sites from China Aerosol Remote Sensing Network (CARSNET) were also used to conduct this validation.

Five-year observation of aerosol optical properties and its radiative effects to planetary boundary layer during air pollution episodes in North China: Intercomparison of a plain site and a mountainous site in Beijing.

The aerosol microphysical, optical and radiative properties of the whole column and upper planetary boundary layer (PBL) were investigated during 2013 to 2018 based on long-term sun-photometer observations at a surface site (~106 m a.s.l.

Spatial and temporal distribution of the cloud optical depth over China based on MODIS satellite data during 2003-2016.

The cloud optical depth (COD) is one of the important parameters used to characterize atmospheric clouds. We analyzed the seasonal variations in the COD over East Asia in 2011 using cloud mode data from the AERONET (Aerosol Robotic Network) ground-based observational network. The applicability of the MODIS (Moderate Resolution Imaging Spectroradiometer) COD product was verified and compared with the AERONET cloud mode dataset.

Characterization of vertical distribution and radiative forcing of ambient aerosol over the Yangtze River Delta during 2013-2015.

As the central part of eastern China, the Yangtze River Delta (YRD) region, with its rapid economic growth and industrial expansion, has experienced severe air quality issues. In this study, the monthly variation and interaction between aerosol direct radiative forcing (ADRF) and aerosol vertical structure during 2013-2015 over the YRD were investigated using ground-based observations from a Micro Pulse Lidar (MPL) and a CE-318 sun-photometer. Combining satellite products from MODIS and CALIPSO, and reanalysis wind fields, an integrated discussion of a biomass burning episode in Hangzhou during August 2015 was conducted by applying analysis of optical properties, planetary boundary layer (PBL), spatial-temporal and vertical distributions, backward trajectories, Potential Source Contribution Function (PSCF), and Concentration Weighted Trajectory (CWT).

Analysis of water vapor effects on aerosol properties and direct radiative forcing in China.

The effects of column water vapor (CWV) on aerosol optical properties, radiative effects and classification are studied by using aerosol and CWV data from eight Aerosol Robotic Network (AERONET) sites in China: Beijing, XiangHe, Shouxian, Taihu, Hong_Kong, Zhongshan_Univ, SACOL, and Mt_WLG, which represents 5 distinct aerosol climatologies in China. Contrast in correlations between aerosol optical depth (AOD) and CWV is found. High correlation coefficient (R) ranging from 0.

Synergy of AERONET and MODIS AOD products in the estimation of PM concentrations in Beijing.

Satellite aerosol optical depth (AOD) is widely used to estimate particulate matter with aerodynamic diameter ≤2.5 µm (PM) mass concentrations. Polar orbiting satellite retrieval 1-2 times each day is frequently affected by cloud, snow cover or misclassification of heavy pollution.

Roles of regional transport and heterogeneous reactions in the PM increase during winter haze episodes in Beijing.

Regional transport and chemical conversions are two major processes that lead to the severe haze pollution in China. Our observations during five haze episodes in Beijing between February 19 and March 12 of 2014 show that the two processes played different roles as PM increased from the clean (<75μgm) to the light-medium pollution level (75-150μg m-3) and to levels of heavy (150-250μgm) and severe (>250μgm) pollution. In the initial twelve hours of each episode, the PM reached the light-medium level with an increase of approximately 120μgm.

Quantification of the impact of aerosol on broadband solar radiation in North China.

PM2.5 plays a key role in the solar radiation budget and air quality assessments, but observations and historical data are relatively rare for Beijing. Based on the synchronous monitoring of PM2.

Evaluation of aerosol optical depth and aerosol models from VIIRS retrieval algorithms over North China Plain.

The first Visible Infrared Imaging Radiometer Suite (VIIRS) was launched on Suomi National Polar-orbiting Partnership (S-NPP) satellite in late 2011. Similar to the Moderate resolution Imaging Spectroradiometer (MODIS), VIIRS observes top-of-atmosphere spectral reflectance and is potentially suitable for retrieval of the aerosol optical depth (AOD). The VIIRS Environmental Data Record data (VIIRS_EDR) is produced operationally by NOAA, and is based on the MODIS atmospheric correction algorithm.

Parameterization of clear-sky surface irradiance and its implications for estimation of aerosol direct radiative effect and aerosol optical depth.

Aerosols impact clear-sky surface irradiance () through the effects of scattering and absorption. Linear or nonlinear relationships between aerosol optical depth (τa) and have been established to describe the aerosol direct radiative effect on (ADRE). However, considerable uncertainties remain associated with ADRE due to the incorrect estimation of (τa in the absence of aerosols).

[Observation study on aerosol optical properties and radiative forcing using the ground-based and satellite remote sensing at background station during the regional pollution episodes].

The significant effect of anthropogenic pollutants transportation on the physical and optical properties of regional background atmospheric aerosol was studied by using ground-based and satellite remote sensing data obtained at the atmospheric background station (Shangdianzi, Beijing) of North China during October 1 to 15 in 2011. The aerosol mass concentration and reactive gases concentration increased obviously during periods of October 4-5, October 7-9, and October 11-12. Comparing with the background period of October 1-3, volume concentration increased by a factor of 3-6 for reactive gases such as NO(x), and CO, and a factor of 10-20 for SO2.

Aerosol optical properties under the condition of heavy haze over an urban site of Beijing, China.

In January 2013, several serious haze pollution events happened in North China. Cimel sunphotometer measurements at an urban site of Beijing (Chinese Academy of Meteorological Sciences-CAMS) from 1 to 30 January 2013 were used to investigate the detailed variation of aerosol optical properties. It was found that Angstrom exponents were mostly larger than 0.

An examination of boundary layer structure under the influence of the gap winds in Urumqi, China, during air pollution episode in winter.

Tethered-sonde measurements of atmospheric profiles were performed at Urumuqi, capital of the Xinjiang Uyghur Autonomous Region of China, from 29 December 2008 to 14 January 2009. The data were used to examine the boundary layer structure during this severe air pollution period. Diurnal evolution of local wind flow near Urumqi was simulated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5).

Validation of MODIS aerosol retrievals and evaluation of potential cloud contamination in East Asia.

MODIS aerosol retrievals onboard Terra/Aqua and ground truth data obtained from AERONET (Aerosol Robtic Network) solar direct radiance measurements are collocated to evaluate the quality of the former in East Asia. AERONET stations in East Asia are separated into two groups according to their locations and the preliminary validation results for each station. The validation results showed that the accuracy of MODIS aerosol retrievals in East Asia is a little worse than that obtained in other regions such as Eastern U.