Simulated Sensitivity of Ozone Generation to Precursors in Beijing during a High O_(3) Episode

This study uses the WRF-Chem model combined with the empirical kinetic modeling method(EKMA curve)to study the compound pollution event in Beijing that happened in 13−23 May 2017.Sensitivity tests are conducted to analyze ozone sensitivity to its precursors,and to develop emission reduction measures.The results suggest that the model can accurately simulate the compound pollution process of photochemistry and haze.When VOCs and NOx were reduced by the same proportion,the effect of O_(3)reduction at peak time was more obvious,and the effect during daytime was more significant than at night.The degree of change in ozone was peak time>daytime average.When reducing or increasing the ratio of precursors by 25%at the same time,the effect of reducing 25%VOCs on the average ozone concentration reduction was most significant.The degree of change in ozone decreased with increasing altitude,the location of the ozone maximum change shifted westward,and its range narrowed.As the altitude increases,the VOCs-limited zone decreases,VOCs sensitivity decreases,NOx sensitivity increases.The controlled area changed from near-surface VOCs-limited to high-altitude NOx-limited.Upon examining the EKMA curve,we have found that suburban and urban are sensitive to VOCs.The sensitivity tests indicate that when VOCs in suburban are reduced about 60%,the O_(3)-1h concentration could reach the standard,and when VOCs of the urban decreased by about 50%,the O_(3)-1h concentration could reach the standard.Thus,these findings could provide references for the control of compound air pollution in Beijing.

Some reflections on researches of Future Earth changes in air quality and climate

Within the context of our current research and understanding of climate change,decisionmakers are particularly concerned with the extent of future climate change,its comprehensive impact,and the types of socioeconomic pathways available with respect to mitigation and adaptation.Among the factors contributing to these important issues,the role of air pollution in global and regional climate warming remains as one of the largest uncertainties.On the basis of understanding of the IPCC Fifth Assessment Report,specifically,in the role of air pollution in climate change,scenarios establishment,and relationship between the Shared Socioeconomic Pathways(SSPs) and Representative Concentration Pathways(RCPs).Weaknesses and reflections were discussed here especially in strengthening impact,adaptation and mitigation research that related with changes in air pollution and climate.In the future,there are needs to in-depth understand how and why the air pollution in China is so serious and changing; to understand the likely future changes in air pollution and climate; to strengthen comprehensive impact research and selective reduction strategies related to changes in air pollution and climate.Furthermore,this study outlines the needs to develop strategies to close the loop of differential impacts and costs; to establish co-benefits and sustainable development goals,to identify the crucial risks and options for synergies/trade-offs; to integrate sector-specific details with macro-economics,and to integrate the assessments of the various policy instruments.All these focus areas will help to facilitate the transition of economic development patterns towards green and low-carbon development.

Comparisons of cloud detection among four satellite sensors on severe haze days in eastern China

云在天气、气候和地球能量平衡中非常重要。雾霾地区不同卫星云探测精度如何的研究较少。本论文详细比较了中国东部地区2015–2016年冬季2次严重雾霾天气时,"A-Train"星群上四个遥感器的云探测。结果显示,在雾霾区域,MODIS/Aqua真彩色图和CALIOP/CALIPSO清楚地观测到气溶胶层时,AIRS/Aqua、CALIOP和CPR/CloudSat没有观测到云,而MODIS则观测到云顶高度接近地面的云,表明MODIS将气溶胶误判为云。更多雾霾天气个例结果显示,在雾霾区域,MODIS云量比AIRS云量高13%–49%,平均高36%.

Application of a Neural Network to Store and Compute the Optical Properties of Non-Spherical Particles

Radiative transfer simulations and remote sensing studies fundamentally require accurate and efficient computation of the optical properties of non-spherical particles.This paper proposes a deep learning(DL)scheme in conjunction with an optical property database to achieve this goal.Deep neural network(DNN)architectures were obtained from a dataset of the optical properties of super-spheroids with extensive shape parameters,size parameters,and refractive indices.The dataset was computed through the invariant imbedding T-matrix method.Four separate DNN architectures were created to compute the extinction efficiency factor,single-scattering albedo,asymmetry factor,and phase matrix.The criterion for designing these neural networks was the achievement of the highest prediction accuracy with minimal DNN parameters.The numerical results demonstrate that the determination coefficients are greater than 0.999 between the prediction values from the neural networks and the truth values from the database,which indicates that the DNN can reproduce the optical properties in the dataset with high accuracy.In addition,the DNN model can robustly predict the optical properties of particles with high accuracy for shape parameters or refractive indices that are unavailable in the database.Importantly,the ratio of the database size(~127 GB)to that of the DNN parameters(~20 MB)is approximately 6810,implying that the DNN model can be treated as a highly compressed database that can be used as an alternative to the original database for real-time computing of the optical properties of non-spherical particles in radiative transfer and atmospheric models.

Atmospheric oxidizing capacity in autumn Beijing:Analysis of the O_(3) and PM_(2.5) episodes based on observation-based model

Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AOC still remains uncertainty.In this study,a comprehensive field campaign was conducted during autumn 2019 in downtown of Beijing,where O_(3) and PM_(2.5) episodes had been experienced successively.The observation-based model(OBM)is used to quantify the AOC at O_(3) and PM_(2.5) episodes.The strong intensity of AOC is found at O_(3) and PM2.5 episodes,and hydroxyl radical(OH)is the dominating daytime oxidant for both episodes.The photolysis of O_(3) is main source of OH at O_(3) episode;the photolysis of nitrous acid(HONO)and formaldehyde(HCHO)plays important role in OH formation at PM_(2.5) episode.The radicals loss routines vary according to precursor pollutants,resulting in different types of air pollution.O_(3) budgets and sensitivity analysis indicates that O_(3) production is transition regime(both VOC and NOx-limited)at O3 episode.The heterogeneous reaction of hydroperoxy radicals(HO_(2))on aerosol surfaces has significant influence on OH and O_(3) production rates.The HO_(2) uptake coefficient(γHO_(2))is the determining factor and required accurate measurement in real atmospheric environment.Our findings could provide the important bases for coordinated control of PM_(2.5) and O_(3) pollution.

Simulation of CO_2 variations at Chinese background atmospheric monitoring stations between 2000 and 2009: Applying a CarbonTracker model

We carried out a downscaling treatment over China using the CarbonTracker numerical model,which was applied using double grid nesting technology(3°×2°over the whole globe,1°×1°over China),simulating and analyzing atmospheric CO2concentrations over 10 recent years(2000–2009).The simulation results agreed very well with observed data from four background atmospheric monitoring stations in China(The periods for which the simulation results and observed values be compared were January2000 to December 2009 for the WLG station and June 2006 to December 2009 for the SDZ,LFS,and LAN stations),giving correlation coefficients of>0.7.The high-resolution simulation data correlated slightly better than the low resolution simulation data with the observed data for three of the regions’atmospheric background stations.Further analysis of the annual,seasonal CO2concentration variations at the background stations showed that the CO2concentration increased each year over the study period,with an average annual increase of more than 5%,and annual increases of more than 7%at the Shangdianzi and Lin’an stations.Seasonal CO2variations were greater at the Longfengshan station than at the Shangdianzi or Lin’an stations.However,the CO2concentrations were higher at the Shangdianzi and Lin’an stations because they are greatly affected by human activities in the Jingjinji and Changjiang Delta economic zones.Spatial distribution in CO2concentrations and fluxes were higher in eastern than in western China.

A New Statistic Approach towards Landslide Hazard Risk Assessment

To quantitatively assess the landslide hazard in Khelvachauri, Georgia, the statistic method of hazard index was applied. A spatial database was constructed in Geographic Information System (GIS) including topographic data, geologic maps, land-use, and active landslide events (extracted from the landslide inventory). After that, causal factors of landslides (such as slope, aspect, lithology, geomorphology, land-use and soil depth) were produced to calculate the corresponding weights, and thereby we defined a relevant set of spatial criteria for the latter landslide hazard assessment. On top of that, susceptibility assessment was performed in order to classify the area to low, moderate and high susceptible regions. Results showed that NW aspect, mountain geomorphology, private land-use, laterite loam and clay, slope between 19 to 24 degrees, and soil depth between 10 - 20 cm were found to have the largest contribution to high landslide susceptibility. The high success rate (72.35%) was obtained using area under the curve from the landslide susceptibility map. Meanwhile, effect analysis was carried out to assess the accuracy of the landslide susceptibility, indicating that the factor of slope played the most important role in determining the occurring probability of landslide although it did not deviate as much as other factors. Finally, the vulnerability analyses were carried out by means of the Spatial Multi-Criteria Estimation model, which in turn, led to the risk assessment. It turned out that not so much of the number of buildings (~ 34.13%) was associated with high-risk zone and that governmental and private land-use almost accounted for the same risk (39.9% and 40.9%, respectively).

Ten-year emission characteristics of atmospheric pollutants from incineration of sacrificial offerings in China

The incineration of sacrificial offerings is a significant widely practiced custom that is also a kind of neglected air pollution source in China.Our results showed that the emission factors of particulate matter,SO_(2),CO,NO_(x),and VOCs emitted from the incineration of sacrificial offerings with purification systems were reduced by 95%,19%,9%,82%,and 42%,respectively,compared with those without a purification system,revealing a significant effect of the flue gas purification system on reducing particulate matter and gaseous pollutants.The emission level of air pollutants from the incineration of sacrificial offerings remained stable before 2013 and then showed a remarkable decrease after the implementation of China′s Air Pollution Prevention Action Plan in 2013.The emissions of TSP(total suspended particulate),PM_(10),PM_(2.5),and NO_(x)in 2009 were 8222,6106,5656 and 15,878 ton,respectively,obviously higher than 3434,2551,2305 and 8579 ton in 2019.Such trend was affected by both the quantity of incineration and the installation rate of purification systems after the Emission Standard of Air Pollutants for Crematory(GB 13801-2015)issued in China.Distinct spatial distribution of atmospheric pollutants from incineration of sacrificial offerings was found with higher in the east and south of China than the west and north of China,which is proportional to the regional economy and population.The maximum ground-level concentration typically occurred at 0.12-0.2 km from the pollution source,posing potential health risks to people entering and exiting funeral and burial sites and nearby residents.

Progress in quantitative research on the relationship between atmospheric oxidation and air quality

Atmospheric oxidizing capacity(AOC)is an essential driving force of troposphere chemistry and self-cleaning,but the definition of AOC and its quantitative representation remain uncertain.Driven by national demand for air pollution control in recent years,Chinese scholars have carried out studies on theories of atmospheric chemistry and have made considerable progress in AOC research.This paper will give a brief review of these developments.First,AOC indexes were established that represent apparent atmospheric oxidizing ability(AOIe)and potential atmospheric oxidizing ability(AOIp)based on aspects of macrothermodynamics and microdynamics,respectively.A closed study refined the quantitative contributions of heterogeneous chemistry to AOC in Beijing,and these AOC methods were further applied in Beijing-Tianjin-Hebei and key areas across the country.In addition,the detection of ground or vertical profiles for atmospheric OH·,HO_(2)·,NO_(3)·radicals and reservoir molecules can now be obtained with domestic instruments in diverse environments.Moreover,laboratory smoke chamber simulations revealed heterogeneous processes involving reactions of O_(3)and NO_(2),which are typical oxidants in the surface/interface atmosphere,and the evolutionary and budgetary implications of atmospheric oxidants reacting under multispecies,multiphase and multi-interface conditions were obtained.Finally,based on the GRAPES-CUACE adjoint model improved by Chinese scholars,simulations of key substances affecting atmospheric oxidation and secondary organic and inorganic aerosol formation have been optimized.Normalized numerical simulations of AOIe and AOIp were performed,and regional coordination of AOC was adjusted.An optimized plan for controlling O_(3)and PM2.5was analyzed by scenario simulation.

Estimation and inter-comparison of dust aerosols based on MODIS, MISR and AERONET retrievals over Asian desert regions

This study presents detailed analysis of spatiotemporal variations and trend of dust optical properties i.e., Aerosol Optical Depth(AOD) and Angstrom component over Asian desert regions using thirteen years of data(i.e., 2001–2013) retrieved from Aerosol Robotic Network(AERONET), Moderate Resolution Imaging Spectroradiometer(MODIS) and Multi-angle Imaging Spectroradiometer(MISR). These regions include Solar Village, Dunhuang and Dalangzadgad and are considered as origin of desert aerosols in Asia. Mann–Kendall trend test was used to show the trend of AOD. The relationship of AOD with weather parameters and general AOD trend over different wavelengths has also been shown. AOD's trend has been observed significant throughout the year in Solar Village, while in Dunhuang and Dalanzadgad the significant trend has been found only in peak period(March–June).Analysis show high values of AOD and low values of angstrom in Solar Village during peak period. In Chinese desert regions, high values of AOD have been found during peak period and low values in pre-peak period. Significant relationship has been observed between AOD and average temperature in Solar Village and Dalanzadgad whereas rainfall and wind speed showed no significant impact on AOD in all desert regions.

Case study of longwave contribution to dust radiative effects over East Asia

In order to evaluate the impacts of LW contribution to aerosol radiative effects over East Asia,a dust longwave radiative parameterization scheme is integrated into the online mesoscale dust forecasting model GRAPES_CUACE/dust.A case modeling study shows that about half at surface and one third at TOA of the dust negative shortwave radiative forcing are cancelled by its positive longwave forcing over the dust affected area.In the dust layer,longwave radiation emitting by dust cools the atmosphere,which counteracts about 17%of shortwave heating of atmosphere during daytime and results in cooling of atmosphere simply during nighttime.At the same time,the atmosphere beyond the dust layer is warmed because of absorbing the LW radiation emitted by dust layer.Dust longwave contribution exerts more evident impact on the air temperature in lower atmosphere and surface.The surface air temperature cooling rate resulting from the dust solar radiation is cancelled about 40%by dust longwave warming at daytime.At nighttime,dust longwave contribution warms land and sea surface.The online calculation of dust LW radiation reduces about 15%relative errors of predicted AOD based on the dust model with only SW radiative feedback.This case study result suggests that dust longwave contribution has important impacts on the earth-atmosphere energy process,especially on the surface and in the lower atmosphere and should not be neglected in the study of dust radiation effects.

Comparison of Two Air Pollution Episodes over Northeast China in Winter 2016/17 Using Ground-Based Lidar

This study analyzes and compares aerosol properties and meteorological conditions during two air pollution episodes in 19–22（E1） and 25–26（E2） December 2016 in Northeast China. The visibility, particulate matter（PM） mass concentration, and surface meteorological observations were examined, together with the planetary boundary layer（PBL） properties and vertical profiles of aerosol extinction coefficient and volume depolarization ratio that were measured by a ground-based lidar in Shenyang of Liaoning Province, China during December 2016–January 2017.Results suggest that the low PBL height led to poor pollution dilution in E1, while the high PBL accompanied by low visibility in E2 might have been due to cross-regional and vertical air transmission. The PM mass concentration decreased as the PBL height increased in E1 while these two variables were positively correlated in E2. The enhanced winds in E2 diffused the pollutants and contributed largely to the aerosol transport. Strong temperature inversion in E1 resulted in increased PM2.5 and PM10 concentrations, and the winds in E2 favoured the southwesterly transport of aerosols from the North China Plain into the region surrounding Shenyang. The large extinction coefficient was partially attributed to the local pollution under the low PBL with high ground-surface PM mass concentrations in E1,whereas the cross-regional transport of aerosols within a high PBL and the low PM mass concentration near the ground in E2 were associated with severe aerosol extinction at high altitudes. These results may facilitate better understanding of the vertical distribution of aerosol properties during winter pollution events in Northeast China.

Wintertime peroxyacetyl nitrate(PAN) in the megacity Beijing: Role of photochemical and meteorological processes

Previous measurements of peroxyacetyl nitrate （PAN） in Asian megacities were scarce and mainly conducted for relative short periods in summer. Here, we present and analyze the measurements of PAN, O3, NOx, etc., made at an urban site （CMA） in Beijing from 25 January to 22 March 2010. The hourly concentration of PAN averaged 0.70 × 10^-9 mol/mol （0.23 × 10^9-3.51 × 10^9 mol/mol） and was well correlated with that of NOa but not O3, indicating that the variations of the winter concentrations of PAN and O3 in urban Beijing are decoupled with each other. Wind conditions and transport of air masses exert very significant impacts on O3, PAN, and other species. Air masses arriving at the site originated either from the boundary layer over the highly polluted N-S-W sector or from the free troposphere over the W-N sector. The descending free-tropospheric air was rich in O3, with an average PAN/O3 ratio smaller than 0.O31, while the boundary layer air over the polluted sector contained higher levels of PAN and primary pollutants, with an average PAN/O3 ratio of 0.11. These facts related with transport conditions can well explain the observed PAN-O3 decoupling. Photochemical production is important to PAN in the winter over Beijing. The concentration of the peroxyacetyl （PA） radicai was estimated to be in the range of 0.0014 × 10^-12～0.0042 × 10^-12 mol/mol. The contributions of the formation reaction and thermal decomposition to PAN＇s variation were calculated and found to be significant even in the colder period in air over Beijing, with the production exceeding the decomposition.

Optical and Radiative Properties of Aerosols during a Severe Haze Episode over the North China Plain in December 2016

The optical and radiative properties of aerosols during a severe haze episode from 15 to 22 December 2016 over Beijing, Shijiazhuang, and Jiaozuo in the North China Plain were analyzed based on the ground-based and satellite data, meteorological observations, and atmospheric environmental monitoring data. The aerosol optical depth at 500 nm was 〈 0.30 and increased to 〉 1.4 as the haze pollution developed. The Angstr6m exponent was 〉 0.80 for most of the study period. The daily single-scattering albedo was 〉 0.85 over all of the North China Plain on the most polluted days and was 〉 0.97 on some particular days. The volumes of fine and coarse mode particles during the haze event were approximately 0.05-0.21 and 0.01-0.43 μm^3, respectively-that is, larger than those in the time without haze. The daily absorption aerosol optical depth was about 0.01-0.11 in Beijing, 0.01-0.13 in Shijiazhuang, and 0.01-0.04 in Jiaozuo, and the average absorption Angstrom exponent varied between 0.6 and 2.0. The aerosol radiative forcing at the bottom of the atmosphere varied from -23 to -227, -34 to -199, and -29 to -191 W m^-2 for the whole haze period, while the aerosol radiative forcing at the top of the atmosphere varied from -4 to -98, -10 to -51, and -21 to -143 W m^-2 in Beijing, Shijiazhuang, and Jiaozuo, respectively. Satellite observations showed that smoke, polluted dust, and polluted continental components of aerosols may aggravate air pollution during haze episodes. The analysis of the potential source contribution function and concentration-weighted trajectory showed that the contribu- tion from local emissions and pollutants transport from upstream areas were 190-450 and 100-410 btg m-3, respectively.

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. There was a good correlation between the AERONET and the MODIS. The spatial and temporal distribution and trends in the COD over China were then analyzed using MODIS satellite data from 2003 to 2016. The seasonal changes in the AERONET data and the time sequence variation of the satellite data suggest that the seasonal variations in the COD are significant. The result shows that the COD first decreases and then increases with the season in northern China, and reaches the maximum in summer and minimum in winter.However, the spatial distribution change is just the opposite in southern China. The spatial variation trend shows the COD in China decreases first with time and gradually increases after 2014. And the trend of COD in the western and central China is consistent with that in China. While the trend of COD shows a continuously increasing over time in northeast China and the Pearl River Delta.

Assessment of Soil Erosion Susceptibility Using Empirical Modeling

Soil erosion is one of the most serious land degradation problems all over the world, causing irreversible land quality reduction. In this paper, we modify the Revised Universal Soil Loss Equation （RUSLE） model by replacing the factors of slope length and gradient with Sediment Transport Index （STI）. The Digital Elevation Model, terrain parameters, Normalized Difference Vegetation Index （NDVI）, and rainfall data are used as inputs to the model. Along with the application of remote sensing techniques and ground survey measurements, erosion susceptibility maps are produced. The revised models are then used to obtain the optimal estimate of soil erosion susceptibility at Alianello of southern Italy, which is prone to soil erosion. The soil loss estimated from the modified RUSLE model shows a large spatial variance, ranging from 10 to as much as 7000 ton ha^-1 yr^-1. The high erosion susceptible area constitutes about 46.8% of the total erosion area, and when classified by land cover type, 33% is ＂mixed bare with shrubs and grass＂, followed by 5.29% of ＂mixture of shrubs and trees＂, with ＂shrubs＂ having the lowest percentage of 0.06%. In terms of slope types, very steep slope accounts for a total of 40.90% and belongs to high susceptibility, whereas flat slope accounts for only 0.12%, indicating that flat topography has little effect on the erosion hazard. As far as the geomorphologic types are concerned, the type of ＂moderate steep-steep slopes with moderate to severe erosion＂ is most favorable to high soil erosion, which comprises about 9.34%. Finally, we validate the soil erosion map from the adapted RUSLE model against the visual interpretation map, and find a similarity degree of 71.9%, reflecting the efficiency of the adapted RUSLE model in mapping the soil erosion in this study area.

Formation mechanisms of nitrous acid(HONO) during the haze and non-haze periods in Beijing,China

As an important precursor of hydroxyl radical(OH),nitrous acid(HONO)plays a significant role in atmospheric chemistry.Here,an observation of HONO and relevant air pollutants in an urban site of Beijing from 14 to 28 April,2017 was performed.Two distinct peaks of HONO concentrations occurred during the observation.In contrast,the concentration of particulate matter in the first period(periodⅠ)was significantly higher than that in the second period(periodⅡ).Comparing to HONO sources in the two periods,we found that the direct vehicle emissionwas an essential source of the ambient HONO during both periods at night,especially in periodⅡ.The heterogeneous reaction of NO_(2)was the dominant source in periodⅠ,while the homogeneous reaction of NO with OH was more critical source at night in periodⅡ.In the daytime,the heterogeneous reaction of NO_(2)was a significant source andwas confirmed by the good correlation coefficients(R^(2))between the unknown sources(P_(unknown))with NO_(2),PM_(2.5),NO_(2)×PM_(2.5)in periodⅠ.Moreover,when solar radiation and OH radicals were considered to explore unknown sources in the daytime,the enhanced correlation of P_(unknown)with photolysis rate of NO_(2)and OH(J_(NO_(2))×OH)were 0.93 in periodⅠ,0.95 in periodⅡ.These excellent correlation coefficients suggested that the unknown sources released HONO highly related to the solar radiation and the variation of OH radicals.

Exploring HONO formation and its role in driving secondary pollutants formation during winter in the North China Plain

Daytime HONO photolysis is an important source of atmospheric hydroxyl radicals(OH).Knowledge of HONO formation chemistry under typical haze conditions,however,is still limited.In the Multiphase chemistry experiment in Fogs and Aerosols in the North China Plain in 2018,we investigated the wintertime HONO formation and its atmospheric implications at a rural site Gucheng.Three different episodes based on atmospheric aerosol loading levels were classified:clean periods(CPs),moderately polluted periods(MPPs)and severely polluted periods(SPPs).Correlation analysis revealed that HONO formation via heteroge.neous conversion of NO_(2)was more efficient on aerosol surfaces than on ground,highlighting the important role of aerosols in promoting HONO formation.Daytime HONO budget analysis indicated a large missing source(with an average production rate of 0.66±0.26,0.97±0.47 and 1.45±0.55 ppbV/hr for CPs,MPPs and SPPs,respectively),which strongly correlated with photo-enhanced reactions(NO_(2)heterogeneous reaction and particulate nitrate photolysis).Average OH formation derived from HONO photolysis reached up to(0.92±0.71),(1.75±1.26)and(1.82±1.47)ppbV/hr in CPs,MPPs and SPPs respectively,much higher than that from O3 photolysis(i.e.,(0.004±0.004),(0.006±0.007)and(0.0035±0.0034)ppbV/hr).Such high OH production rates could markedly regulate the atmospheric oxidation capacity and hence promote the formation of secondary aerosols and pollutants.

大气反演中国陆地生态系统碳收支:进展与挑战

The atmospheric inversion is an effective method for quantifying surface CO_(2) fluxes at global and regional scales using the gradient of CO_(2) measurements and has the advantage of inferring CO_(2) sources and sinks over large spatial scales.The“2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories”was adopted and accepted during the 49th Session of the Intergovernmental Panel on Climate Change(IPCC)in May 2019.

Applying the WRF Double-Moment Six-Class Microphysics Scheme in the GRAPES_Meso Model： A Case Study

This study incorporated the Weather Research and Forecasting（WRF） model double-moment 6-class（WDM6） microphysics scheme into the mesoscale version of the Global/Regional Assimilation and Pr Ediction System（GRAPES_Meso）. A rainfall event that occurred during 3–5 June 2015 around Beijing was simulated by using the WDM6, the WRF single-moment 6-class scheme（WSM6）, and the NCEP 5-class scheme, respectively. The results show that both the distribution and magnitude of the rainfall simulated with WDM6 were more consistent with the observation. Compared with WDM6, WSM6 simulated larger cloud liquid water content, which provided more water vapor for graupel growth, leading to increased precipitation in the cold-rain processes. For areas with the warmrain processes, the sensitivity experiments using WDM6 showed that an increase in cloud condensation nuclei（CCN）number concentration led to enhanced CCN activation ratio and larger cloud droplet number concentration（Nc） but decreased cloud droplet effective diameter. The formation of more small-size cloud droplets resulted in a decrease in raindrop number concentration（Nr）, inhibiting the warm-rain processes, thus gradually decreasing the amount of precipitation. For areas mainly with the cold-rain processes, the overall amount of precipitation increased; however, it gradually decreased when the CCN number concentration reached a certain magnitude. Hence, the effect of CCN number concentration on precipitation exhibits significant differences in different rainfall areas of the same precipitation event.