Vertical distribution of sand-dust aerosols and the relationships with atmospheric environment

The vertical distribution of aerosols in the troposphere is important for determining their effects on cli- mate. The vertical distribution of aerosols under different atmospheric conditions in the free troposphere was di- rectly observed using a surface micro-pulse LIDAR （MPL） and a TP/WVP-3000 microwave radiometer at the Semi-Arid Climate ＆ Environment Observatory of Lanzhou University （SACOL, 35.95~N, 104.10~E） in the western Loess Plateau, China, in the spring of 2008. The results showed two possible transportation paths of a sandstorm from May 1 to May 4 in 2008. In one path, sand-dust aerosols were transported toward the east from the Taklimakan Desert to the Badain Jaran Desert and the Tengger Desert by a westerly wind and then toward the southeast to Jingtai and Lanzhou. A weak aerosol index （AI） indicated another possible transport path toward the east from the Taklimakan Desert to the Qaidam Basin and through the Tibetan Plateau eastward to SACOL. The aerosol profile of sandstorm processes over the SACOL area displayed three patterns： a single peak distribution under stable at- mospheric conditions, indicating urban aerosol distribution; an exponential decrease under unstable atmospheric conditions in the presence of a sandstorm; and a slight change in the mixed layer during the first and last stages of the sandstorm, indicative of thorough mixing during lifting and deposition stages. Analyses of the aerosol layer height （ALH） showed that there are two types of ALH diurnal variation. The ALH during the first sandstorm stage was complex and disordered, and affected by atmospheric circulation. While the ALH had obvious diurnal variation in the other stage, the ALH and aerosol extinction coefficient （AEC） had a single peak, and was higher in the af- ternoon and lower in the morning. In the second case the ALH was in agreement with the atmospheric boundary layer height （BLH） variation. As a result of the development of the atmospheric boundary layer （ABL） during day and maintenance at night, ALH during sandstorm-free days showed obvious diurnal variations. Multiple vertical distribu- tion patterns of sand-dust aerosols will result in different climate effects; therefore, the vertical distribution patterns can be used to parameterize climate and aerosol models.

Simulation of the Ecosystem Productivity Responses to Aerosol Diffuse Radiation Fertilization Effects over the Pan-Arctic during 2001–19

The pan-Arctic is confronted with air pollution transported from lower latitudes.Observations have shown that aerosols help increase plant photosynthesis through the diffuse radiation fertilization effects(DRFEs).While such DRFEs have been explored at low to middle latitudes,the aerosol impacts on pan-Arctic ecosystems and the contributions by anthropogenic and natural emission sources remain less quantified.Here,we perform regional simulations at 0.2o×0.2ousing a well-validated vegetation model(Yale Interactive terrestrial Biosphere,YIBs)in combination with multi-source of observations to quantify the impacts of aerosol DRFEs on the net primary productivity(NPP)in the pan-Arctic during 2001-19.Results show that aerosol DRFEs increase pan-Arctic NPP by 2.19 Pg C(12.8%)yr^(-1)under clear-sky conditions,in which natural and anthropogenic sources contribute to 8.9% and 3.9%,respectively.Under all-sky conditions,such DRFEs are largely dampened by cloud to only 0.26 Pg C(1.24%)yr^(-1),with contributions of 0.65% by natural and 0.59% by anthropogenic species.Natural aerosols cause a positive NPP trend of 0.022% yr^(-1)following the increased fire activities in the pan-Arctic.In contrast,anthropogenic aerosols induce a negative trend of-0.01% yr^(-1)due to reduced emissions from the middle latitudes.Such trends in aerosol DRFEs show a turning point in the year of 2007 with more positive NPP trends by natural aerosols but negative NPP trends by anthropogenic aerosols thereafter.Though affected by modeling uncertainties,this study suggests a likely increasing impact of aerosols on terrestrial ecosystems in the pan-Arctic under global warming.

Electric field and force characteristic of dust aerosol particles on the surface of high-voltage transmission line

High-voltage transmission lines play a crucial role in facilitating the utilization of renewable energy in regions prone to desertification. The accumulation of atmospheric particles on the surface of these lines can significantly impact corona discharge and wind-induced conductor displacement. Accurately quantifying the force exerted by particles adhering to conductor surfaces is essential for evaluating fouling conditions and making informed decisions. Therefore, this study investigates the changes in electric field intensity along branched conductors caused by various fouling layers and their resulting influence on the adhesion of dust particles. The findings indicate that as individual particle size increases, the field strength at the top of the particle gradually decreases and eventually stabilizes at approximately 49.22 k V/cm, which corresponds to a field strength approximately 1.96 times higher than that of an unpolluted transmission line. Furthermore,when particle spacing exceeds 15 times the particle size, the field strength around the transmission line gradually decreases and approaches the level observed on non-adhering surface. The electric field remains relatively stable. In a triangular arrangement of three particles, the maximum field strength at the tip of the fouling layer is approximately 1.44 times higher than that of double particles and 1.5 times higher compared to single particles. These results suggest that particles adhering to the transmission line have a greater affinity for adsorbing charged particles. Additionally, relevant numerical calculations demonstrate that in dry environments, the primary adhesion forces between particles and transmission lines follow an order of electrostatic force and van der Waals force. Specifically, at the minimum field strength, these forces are approximately74.73 times and 19.43 times stronger than the gravitational force acting on the particles.

Applying the Dark Target Aerosol Algorithm to MERSI-Ⅱ:Retrieval and Validation of Aerosol Optical Depth over the Ocean

The Medium-Resolution Spectral Imager-Ⅱ(MERSI-Ⅱ)instrument aboard China’s Fengyun-3D satellite shares similarities with NASA’s Moderate Resolution Imaging Spectroradiometer(MODIS)sensor,enabling the retrieval of global aerosol optical depth(AOD).However,no officially released operational MERSI-Ⅱ aerosol products currently exist over the ocean.This study focuses on adapting the MODIS dark target(DT)ocean algorithm to the MERSI-Ⅱ sensor.A retrieval test is conducted on the 2019 MERSI-Ⅱ data over the global ocean,and the retrieved AODs are validated against ground-based measurements from the automatic Aerosol Robotic Network(AERONET)and the shipborne Maritime Aerosol Network(MAN).The operational MODIS DT aerosol products are also used for comparison purposes.The results show that MERSI-Ⅱ AOD granule retrievals are in good agreement with MODIS products,boasting high correlation coefficients(R)of up to 0.96 and consistent spatial distribution trends.Furthermore,the MERSI-Ⅱ retrievals perform well in comparison to AERONET and MAN measurements,with high R-values(>0.86).However,the low-value retrievals from MERSI-Ⅱ tend to be slightly overestimated compared to MODIS,despite both AODs displaying a positive bias.Notably,the monthly gridded AODs over the high latitudes of the northern and southern hemispheres suggest that MERSI-Ⅱ exhibits greater stability in space and time,effectively reducing unrealistically high-value noise in the MODIS products.These results illustrate that the MERSI-Ⅱ retrievals meet specific accuracy requirements by maintaining the algorithmic framework and most of the algorithmic assumptions,providing a crucial data supplement for aerosol studies and climate change.

Composition optimization and performance prediction for ultra-stable water-based aerosol based on thermodynamic entropy theory

Water-based aerosol is widely used as an effective strategy in electro-optical countermeasure on the battlefield used to the preponderance of high efficiency,low cost and eco-friendly.Unfortunately,the stability of the water-based aerosol is always unsatisfactory due to the rapid evaporation and sedimentation of the aerosol droplets.Great efforts have been devoted to improve the stability of water-based aerosol by using additives with different composition and proportion.However,the lack of the criterion and principle for screening the effective additives results in excessive experimental time consumption and cost.And the stabilization time of the aerosol is still only 30 min,which could not meet the requirements of the perdurable interference.Herein,to improve the stability of water-based aerosol and optimize the complex formulation efficiently,a theoretical calculation method based on thermodynamic entropy theory is proposed.All the factors that influence the shielding effect,including polyol,stabilizer,propellant,water and cosolvent,are considered within calculation.An ultra-stable water-based aerosol with long duration over 120 min is obtained with the optimal fogging agent composition,providing enough time for fighting the electro-optic weapon.Theoretical design guideline for choosing the additives with high phase transition temperature and low phase transition enthalpy is also proposed,which greatly improves the total entropy change and reduce the absolute entropy change of the aerosol cooling process,and gives rise to an enhanced stability of the water-based aerosol.The theoretical calculation methodology contributes to an abstemious time and space for sieving the water-based aerosol with desirable performance and stability,and provides the powerful guarantee to the homeland security.

Optical Modeling of Sea Salt Aerosols Using in situ Measured Size Distributions and the Impact of Larger Size Particles

Sea salt aerosols play a critical role in regulating the global climate through their interactions with solar radiation.The size distribution of these particles is crucial in determining their bulk optical properties.In this study,we analyzed in situ measured size distributions of sea salt aerosols from four field campaigns and used multi-mode lognormal size distributions to fit the data.We employed super-spheroids and coated super-spheroids to account for the particles’non-sphericity,inhomogeneity,and hysteresis effect during the deliquescence and crystallization processes.To compute the singlescattering properties of sea salt aerosols,we used the state-of-the-art invariant imbedding T-matrix method,which allows us to obtain accurate optical properties for sea salt aerosols with a maximum volume-equivalent diameter of 12μm at a wavelength of 532 nm.Our results demonstrated that the particle models developed in this study were successful in replicating both the measured depolarization and lidar ratios at various relative humidity(RH)levels.Importantly,we observed that large-size particles with diameters larger than 4μm had a substantial impact on the optical properties of sea salt aerosols,which has not been accounted for in previous studies.Specifically,excluding particles with diameters larger than 4μm led to underestimating the scattering and backscattering coefficients by 27%−38%and 43%−60%,respectively,for the ACE-Asia field campaign.Additionally,the depolarization ratios were underestimated by 0.15 within the 50%−70%RH range.These findings emphasize the necessity of considering large particle sizes for optical modeling of sea salt aerosols.

Contrast in Secondary Organic Aerosols between the Present Day and the Preindustrial Period:The Importance of Nontraditional Sources and the Changed Atmospheric Oxidation Capability

Quantifying differences in secondary organic aerosols(SOAs)between the preindustrial period and the present day is crucial to assess climate forcing and environmental effects resulting from anthropogenic activities.The lack of vegetation information for the preindustrial period and the uncertainties in describing SOA formation are two leading factors preventing simulation of SOA.This study calculated the online emissions of biogenic volatile organic compounds(VOCs)in the Aerosol and Atmospheric Chemistry Model of the Institute of Atmospheric Physics(IAP-AACM)by coupling the Model of Emissions of Gases and Aerosols from Nature(MEGAN),where the input vegetation parameters were simulated by the IAP Dynamic Global Vegetation Model(IAP-DGVM).The volatility basis set(VBS)approach was adopted to simulate SOA formation from the nontraditional pathways,i.e.,the oxidation of intermediate VOCs and aging of primary organic aerosol.Although biogenic SOAs(BSOAs)were dominant in SOAs globally in the preindustrial period,the contribution of nontraditional anthropogenic SOAs(ASOAs)to the total SOAs was up to 35.7%.In the present day,the contribution of ASOAs was 2.8 times larger than that in the preindustrial period.The contribution of nontraditional sources of SOAs to SOA was as high as 53.1%.The influence of increased anthropogenic emissions in the present day on BSOA concentrations was greater than that of increased biogenic emission changes.The response of BSOA concentrations to anthropogenic emission changes in the present day was more sensitive than that in the preindustrial period.The nontraditional sources and the atmospheric oxidation capability greatly affect the global SOA change.

Experimental investigation on effective aerosol scavenging using different spray configurations with pre-injection of water mist for Fukushima Daiichi decommissioning

During the decommissioning of the Fukushima Daiichi nuclear power plant,it is important to consider the retrieval of resolidified debris both in air and underwater configurations.For the subsequent retrieval of debris from the reactor building,the resolidified debris must be cut into smaller pieces using various cutting methods.During the cutting process,aerosol particles are expected to be generated at the submicron scale.It has been noted that such aerosols sizing within the Greenfield gap(0.1-1μm)are difficult to remove effectively using traditional spraying methods.Therefore,to improve the aerosol removal efficiency of the spray system,a new aerosol agglomeration method was recently proposed,which involves injecting water mist to enlarge the sizes of the aerosol particles before removing them using water sprays.In this study,a series of experiments were performed to clarify the proper spray configurations for effective aerosol scavenging and to improve the performance of the water mist.The experimental results showed that the spray flow rate and droplet characteristics are important factors for the aerosol-scavenging efficiency and performance of the water mist.The results obtained from this study will be helpful for the optimization of the spray system design for effective aerosol scavenging during the decommissioning of the Fukushima Daiichi plant.

A Deep-Learning and Transfer-Learning Hybrid Aerosol Retrieval Algorithm for FY4-AGRI:Development and Verification over Asia

The Advanced Geosynchronous Radiation Imager(AGRI)is a mission-critical instrument for the Fengyun series of satellites.AGRI acquires full-disk images every 15 min and views East Asia every 5 min through 14 spectral bands,enabling the detection of highly variable aerosol optical depth(AOD).Quantitative retrieval of AOD has hitherto been challenging,especially over land.In this study,an AOD retrieval algorithm is proposed that combines deep learning and transfer learning.The algorithm uses core concepts from both the Dark Target(DT)and Deep Blue(DB)algorithms to select features for the machinelearning(ML)algorithm,allowing for AOD retrieval at 550 nm over both dark and bright surfaces.The algorithm consists of two steps:①A baseline deep neural network(DNN)with skip connections is developed using 10 min Advanced Himawari Imager(AHI)AODs as the target variable,and②sunphotometer AODs from 89 ground-based stations are used to fine-tune the DNN parameters.Out-of-station validation shows that the retrieved AOD attains high accuracy,characterized by a coefficient of determination(R2)of 0.70,a mean bias error(MBE)of 0.03,and a percentage of data within the expected error(EE)of 70.7%.A sensitivity study reveals that the top-of-atmosphere reflectance at 650 and 470 nm,as well as the surface reflectance at 650 nm,are the two largest sources of uncertainty impacting the retrieval.In a case study of monitoring an extreme aerosol event,the AGRI AOD is found to be able to capture the detailed temporal evolution of the event.This work demonstrates the superiority of the transfer-learning technique in satellite AOD retrievals and the applicability of the retrieved AGRI AOD in monitoring extreme pollution events.

Aerosol deposition technology and its applications in batteries

Aerosol deposition(AD)method is a kind of additive manufacturing technology for fabricating dense films such as metals and ceramics at room temperature.It resolves the challenge of integrating ceramic films onto temperaturesensitive substrates,including metals,glasses,and polymers.It should be emphasized that the AD is a spray coating technology that uses powder without thermal assistance to generate films with high density.Compared to the traditional sputter-based approach,the AD shows several advantages in efficiency,convenience,better interfacial bonding and so on.Therefore,it opens some possibilities to the field of batteries,especially all-solidstate batteries(ASSBs)and draws much attention not only for research but also for large scale applications.The purpose of this work is to provide a critical review on the science and technology of AD as well as its applications in the field of batteries.The process,mechanism and effective parameters of AD,and recent developments in AD applications in the field of batteries will be systematically reviewed so that a trend for AD will be finally provided.

Contribution of Satellite Observations in the Optical and Microphysical Characterization of Aerosols in Burkina Faso, West Africa

In this work, we proceed to an optical and microphysical analysis of the observations reversed by the MODIS, SeaWiFS, MISR and OMI sensors with the aim of proposing the best-adapted airborne sensor for better monitoring of aerosols in Burkina Faso. To this end, a comparison of AOD between satellite observations and in situ measurements at the Ouagadougou site reveals an underestimation of AERONET AOD except for OMI which overestimates them. Also, an inter-comparison done based on the linear regression line representation shows the correlation between the aerosol models incorporated in the airborne sensor inversion algorithms and the aerosol population probed. This can be seen through the correlation coefficients R which are 0.84, 0.64, 0.55 and 0.054 for MODIS, SeaWiFS, MISR and OMI respectively. Furthermore, an optical analysis of aerosols in Burkina Faso by the MODIS sensor from 2001 to 2016 indicates a large spatial and temporal variability of particles strongly dominated by desert dust. This is corroborated by the annual and seasonal cycles of the AOD at 550 nm and the Angström coefficient measured in the spectral range between 412 nm and 470 nm. A zoom on a few sites chosen according to the three climatic zones confirms the majority presence of mineral aerosols in Burkina Faso, whose maxima are observed in spring and summer.

Some Features of Black Carbon Aerosols Connected with Regional Climate Over Pristine Environment

The authors report the results of aethalometer black carbon(BC)aerosol measurements carried out over a rural(pristine)site,Panchgaon,Haryana State,India during the winter months of 2021-2022 and 2022-2023.They are compared with collocated and concurrent observations from the Air Quality Monitoring Station(AQMS),which provides synchronous air pollution and surface meteorological parameters.Secular variations in BC mass concentration are studied and explained with variations in local meteorological parameters.The biomass burning fire count retrievals from NASA-NOAA VIIRS satellite,and backward airmass trajectories from NOAA-ERL HYSPLIT Model analysis have also been utilized to explain the findings.They reveal that the north-west Indian region contributes maximum to the BC mass concentration over the study site during the study period.Moreover,the observed BC mass concentrations corroborate the synchronous fire count,primary and secondary pollutant concentrations.The results were found to aid the development of mitigation methods to achieve a sustainable climate system.

Analysis on the Distribution Characteristics of Atmospheric Aerosol Particles in Hebei Area in the Cloudy Day Condition

By using the probe data of two sorties airplane in the middle and southern parts of Hebei Province in 2007 spring,the characteristics of atmospheric aerosol particles concentration and size distribution in the area in the cloudy day situation were analyzed.The results showed that the overall trend of aerosol particles concentration in the weather systems which included the south branch trough and North China low vortex was the decrease as the height increased.However,if the cirrostratus was in the high altitude,it increased as the height increased.In the bottom of inversion layer,there existed the obvious accumulation of aerosol and cloud droplet.Affected by the complex weather systems,the aerosol particle size distribution presented the multi-peak type for the disturbance of updraft or turbulence.

A Smog Chamber Facility for Qualitative and Quantitative Study on Atmospheric Chemistry and Secondary Organic Aerosol

In order to investigate the atmospheric oxidation processes and the formation of secondary organic aerosol （SOA）, an indoor environmental reaction smog chamber are constructed and characterized. The system consists of the collapsible ～830 L FEP Teflon film main reactor, in which the atmospheric chemical reactions take place and the formation of SOA occurs under the simulated atmospheric conditions, and the diverse on-line gas- and particle-phase instrumentation, such as the proton transfer reaction mass spectrometer, the synchrotron radiation photoionization mass spectrometer, the aerosol laser time-of-flight mass spectrometer, and other traditional commercial instruments. The initial characterization experiments are described, concerning the temperature and ultraviolet light intensity, the reactivity of the pure air, the wall loss rates of gaseous compounds and particulate matter. And the initial evaluation experiments for SOA yields from the ozonolysis of α-pinene and for mass spectra of the products resulting from the photooxidation of OH initiated isoprene are also presented, which indicate the applicability of this facility on the studies of gas-phase chemical mechanisms as well as the formation of SOA expected in the atmosphere.

A Preliminary Investigation on Anti-inflammatory and Antibacterial Effect of Compound Sarcandra Aerosol

[Objective] This study aimed to reveal the therapeutic mechanism of compound sarcandra aerosol, which was exclusively owned by the Second Affiliated Hospital of Guiyang College of Traditional Chinese Medicine. [Method] An inflammation model was established by xylene-induced inflammation test and carrageenan- induced inflammation test to analyze the anti-inflammatory effect of compound sarcandra aerosol. By bacteriostasis test in vitro, the antibacterial effect of compound sarcandra aerosol against five common pathogens of pharyngitis was investigated. Blood samples were collected from Wistar rats in different compound sarcandra aerosol groups and control group to compare blood routine indicators and interleukin-1 （IL-1） levels. [Result] Three different concentrations of compound sarcandra aerosol could reduce degrees of xylene-induced ear edema in mice and carrageenan- induced paw edema in rats, but the anti-inflammatory effect of compound sarcandra aerosol was reduced as the concentration declined. In bacteriostasis test in vitro, the minimum inhibitory concentration of compound sarcandra aerosol against Streptococcus pneumoniae, Streptococcus hemolytis, Corynebacterium diphtheriae, Staphylococcus aureus and Salmonella typhimurium was 76, 105 38, 65 and 30 mg/ml, respectively. Compound sarcandra aerosol reduced white blood cell count, neutrophil count and lymphocyte percentage in pharyngitis model rats. Moreover, interleukin-1 level in watermelon frost lozenge group and different compound sarcandra aerosol groups was lower compared with control group. [Conclusion] Compound sarcandra aerosol can effectively treat pharyngitis by exerting anti-inflammatory and antibacterial effect and reducing interleukin-1 level. This study laid a solid foundation for clinical application of compound sarcandra aerosol.

Establishment of a Collection and Detection Technology of Mycoplasma hyopneumoniae in Aerosol

ObjectiveThis study was to establish a simple method for collecting and detecting Mycoplasma hyopneumoniae （Mhp） in aerosol. MethodBased on the mechanisms of liquid impinger and filtration sampler, a double concentration aerosol sampler was designed for collecting Mhp aerosol. Firstly, the collection was performed in a closed environment full of artificial aerosol of Mhp. Secondly, collection efficiency was detected by real-time PCR. Thereafter, the clinical feasibility of the designed equipment was tested by collecting aerosol samples in different pig herds. In one assay, the samples were collected at different times from one pig house challenged with Mhp. In another assay, the samples was collected from the delivery room, nursery and fattenning house of a MPS outbreak farm as well as a Mhp infection positive pig farm without obvious clinical symptoms. All the aerosol samples were then detected by real-time PCR or nested PCR. ResultThe collection efficiency of the designed bioaerosol sampler was （37.04±6.43） %, Mhp could be detected 7 d after intratracheal challenge with pneumonic lung homogenate suspension. Aerosol samples of 11 pig houses from the two Mhp positive pig farms with or without clinical symptoms all showed a positive result of PCR, the positivity rate was 100%. ConclusionA high sensitive collecting and detecting technology of aerosol was successfully established, which can be applied to clinical detection of Mhp in aerosol.

Aerosol－22与锡石浮选作用机理

研究了Ａｅｒｏｓｏｌ－２２（烷基磺化琥珀酰胺酸盐）对锡石的浮选行为以及浮选调整剂如稻草纤维素、水玻璃对石英、方解石的抑制作用。还考察了金属阳离子和中性油对锡石浮选的影响。结果表明，Ａｅｒｏｓｏｌ－２２是锡石的良好捕收剂，具有捕收力强、用量低等特点。Ａｅｒｏｓｏｌ－２２与锡石作用机理研究指出，Ａｅｒｏｓｏｌ－２２在锡石表面是通过羧酸和磺酸基中的氧原子与锡石表面的活性质点Ｓｎ４＋键合，并且形成了０。

A Review of Atmospheric Chemistry Research in China:Photochemical Smog, Haze Pollution,and Gas-Aerosol Interactions

In this paper we present a review of atmospheric chemistry research in China over the period 2006-2010, focusing on tropospheric ozone, aerosol chemistry, and the interactions between trace gases and aerosols in the polluted areas of China. Over the past decade, China has suffered severe photochemical smog and haze pollution, especially in North China, the Yangtze River Delta, and the Pearl River Delta. Much scientific work on atmospheric chemistry and physics has been done to address this large-scale, complex environmental problem. Intensive field experiments, satellite data analyses, and model simulations have shown that air pollution is significantly changing the chemical and physical characters of the natural atmosphere over these parts of China. In addition to strong emissions of primary pollutants, photochemical and heterogeneous reactions play key roles in the formation of complex pollution. More in-depth research is recommended to reveal the formation mechanism of photochemical smog and haze pollution and their climatic effects at the urban, regional, and global scales.

Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene

Hydroxyl radical （.OH）-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols （SOA）. It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm^3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride〉sodium silicate and ammonium nitrate〉ammonium sulfate.

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.S., Western Europe, Brazil and so on. The primary reason is due to the improper aerosol model used in MODIS aerosol retrieval algorithm, so it is of significance to characterize aerosol properties properly according to long term ground-based remote sensing or other relevant in situ observations in order to improve MODIS retrievals in East Asia. Cloud contamination is proved to be one of large errors, which is demonstrated by the significant relation between MODIS aerosol retrievals versus cloud fraction, as well as notable improvement of linear relation between satellite and ground aerosol data after potential cloud contamination screened. Hence, it is suggested that more stringent clear sky condition be set in use of MODIS aerosol data. It should be pointed out that the improvement might be offset by other error sources in some cases because of complex relation between different errors. Large seasonal variation of surface reflection and uncertainties associated with it result in large intercepts and random error in MODIS aerosol retrievals in northern inland of East Asia. It remains to be a big problem to retrieve aerosols accurately in inland characterized by relatively larger surface reflection than the requirement in MODIS aerosol retrieval algorithm.