Abstract:Biogenic and anthropogenic organic gases undergo oxidation in the atmosphere,resulting in the formation of secondary organic aerosols (SOA).SOA plays a crucial role in climate change and human health.While considerable advancements have been made in understanding SOA production and its precursors,the intricate interactions among organic gases and the complex mechanisms governing SOA formation still presents challenges.Currently,knowledge gaps persist regarding SOA formation arising from the oxidation of different organic gases present within complex systems.This review aims to provide insights into the evolving research landscape concerning the oxidation of organic gases in complex systems leading to SOA formation.The review encompasses two primary aspects.Firstly,it summarizes the variations in mass concentration,yield,composition,volatility,and optical properties of SOA resulting from the oxidation of organic gases within complex systems.This section explores the different effects of organic gas oxidation within complex systems on SOA formation.Additionally,it delves into the evolving constituent elements and molecular composition of SOA.Furthermore,this review collates current laboratory-based simulation studies on generating SOA from composite systems and evaluating model accuracy.Secondly,it investigates the effects of environmental factors,including relative humidity (RH),temperature (T),and inorganic gases such as nitrogen oxides (NO_x),sulfur dioxide (SO₂),and ammonia (NH₃),on the interaction with organic gases within complex systems,ultimately leading to SOA formation.This exploration provides valuable insights into the interplay of environmental variables in shaping SOA characteristics.Therefore,this review contributes to a deeper understanding of the chemical evolution of organic gases in the real atmosphere.It highlights the necessity of studying the multi-source and complex interactions of organic gases and mapping the intricate atmospheric oxidation mechanisms,leading to SOA formation,and outlines avenues for future research,aiming to enhance the interpretation of laboratory simulation results within complex systems.

Abstract:To investigate the temporal and spatial variation characteristics of VOCs during fog and haze events,a comprehensive 58-day field observation experiment was conducted at the Donghai National Meteorological Observing Station in Jiangsu Province from November 19,2020,to January 15,2021.This study utilized a self-developed multi-rotor UAV observation system to observe two radiation fog events and two haze events,resulting in over 100 atmospheric boundary layer profiles,including air temperature,pressure,relative humidity (RH),wind direction,wind speed,VOCs,and O₃.The results show the following:In terms of time,the volume concentration of VOCs during nighttime in the haze process (0.225-0.253 ppm) (parts per million,ppm;1 ppm=10^-6) was significantly higher than during the daytime (0.191-0.205 ppm).Moreover,the volume concentration before fog formation (0.121-0.239 ppm) was significantly higher than during the fog process (0.056-0.209 ppm).During the fog process,VOCs' volume concentration exhibited an opposite trend to fog intensity.The height of the fog layer closely correlated with the sharp change in VOCs' volume concentration.In the fog layer (below 200 m),the VOC volume concentration (0.172-0.178 ppm) significantly decreased,being notably lower than pre-fog events (0.195-0.240 ppm).Above the fog layer (200-700 m),VOCs' volume concentrations underwent significant changes,which persisted for up to 1hour after fog dissipation.The stable high-humidity environment within the fog layer had a scavenging effect on water-soluble pollutants trapped within the temperature inversion layer,resulting in decreased concentrations of VOCs and O₃.

Abstract:In recent years,ozone pollution in the summer has increasingly become problem a significant concern affecting air quality and environment in eastern China.This study aims to quantitatively evaluate the impact of reducing ozone precursor emissions on ozone pollution.Using the ozone pollution episode in eastern China from June 19 to 30,2021,as a case study,we use CMAQ-DDM air quality model and satellite remote sensing inversion algorithm to analyze ozone concentration sensitivity to anthropogenic precursor emissions in the eastern region.Different reduction scenarios for ozone precursors are simulated by setting different reduction ratios.The findings reveal the following:1) From June 19 to 30,2021,an extended regional ozone pollution event occurred in eastern China,with most cities experiencing slight to moderate pollution levels;2) Throughout the pollution period,the eastern region was predominantly influenced by VOC control or a combination of VOC and NO_x control.Model simulations and satellite inversions exhibited good agreement.In the early stage of the pollution event (June 19-25),the eastern region was highly sensitive to VOCs,while in the latter stage (June 26—30),it transitioned into an area where coordinated control of VOCs and NO_x was crucial,especially in Henan,Anhui,and Jiangsu;3) When applying the same emission reduction ratio (VOCs∶NO_x=2∶1),larger emissions reductions led to greater reductions in ozone levels.Increasing the VOC reduction ratio from 20％ to 40％ resulted in an ozone concentration reduction ranging from 1.7％ to 3.6％.Phased emission reduction strategies outperformed single-period reduction plans,achieving a 0.1％ increase in the ozone improvement rate.Reducing only elevated NO_x sources did not significantly decrease ozone concentrations.

Abstract:Located in the hinterland of the North China Plain,Beijing,Tianjin and Hebei are facing serious air pollution,especially the key industrial city of Tangshan in Hebei,which has long been in the top ten of the worst air quality cities.To improve air quality,China has continuously enacted and implemented several pollution prevention and control programs over the past decade,but PM_2.5 and summer O₃ levels in Tangshan still exceed the national standards.This study quantifies the sectoral contributions to PM_2.5 and O₃ in Tangshan in 2020 using the WRF-CMAQ model and analyzes the feasibility of the synergistic control.Industrial sources contribute the most to PM_2.5 in Tangshan,accounting for about 45％,followed by residential sources with contributions of 16％.In winter,energy,residential sources and agricultural sources account for 17％,19％ and 11％,respectively.Background values of O₃ account for about more than half,with the highest percentage in April.Among the non-background values,the largest source of O₃ in Tangshan is industrial sources,accounting for about 53％,followed by traffic sources with contributions of 22％.The contributions from biological sources,traffic sources and energy sector increased in July,with values of 10％,27％ and 20％,respectively.Comparison of the sources of PM_2.5 and O₃ in Tangshan under different pollution scenarios reveals that industry and energy are the most important common sources.

Abstract:This paper investigates the impact of the COVID-19 pandemic lockdown on urban air pollution in Nanjing during the summer of 2021.Using online monitoring data from the SORPES site at Nanjing University,we compared the concentrations of particulate matter and gaseous pollutants before,during,and after the lockdown.Additionally,we used the PMF model and the LPDM model to analyze the sources of volatile organic compounds (VOCs).The results show that,compared to the period before the lockdown,PM_2.5concentrations in Nanjing decreased by 40％-50％,while nitrate and organic matter concentrations decreased by 34.0％ and 16.5％,respectively.Urban areas experienced a significant increase in ozone concentration,approximately 50％.The two gaseous precursors of ozone exhibited opposite trends:NO_x concentrations dropped by 28％,while TVOCs increased by 49.6％.The OBM model and satellite data results indicate that ozone formation in Nanjing was in the VOC-limited regime during the lockdown.Air mass tracing results reveal that VOCs in Nanjing were jointly influenced by local and regional transport from surrounding cities,with increased contributions from the Shanghai-Suzhou-Changzhou-Zhenjiang and Tongling-Ma'anshan directions during the lockdown.
PMF source analysis results demonstrate that local VOCs in Nanjing primarily originate from motor vehicle emissions,plant sources,solvent sources,industrial production,and oil and gas volatile sources.Motor vehicle emissions exhibited the most significant variation among all sources,with a reduction of 15.1％ during the lockdown and an increase of 4.3％ after the lockdown.Oil and gas volatilization and solvent sources increased by 11.2％ and 1.7％,respectively,during the lockdown and decreased by 4.8％ and 4.3％,respectively,after the lockdown.

Abstract:In recent years,the intensification of O₃ pollution in Nanjing has raised concerns.To understand the influence of neighboring cities on O₃ levels in Nanjing,we used the source-oriented WRF/CMAQ regional air quality model to simulate air quality within the Yangtze River Delta (YRD) from March to October 2018.By tracking emissions from 41 cities within and outside the YRD,we conducted an analysis of O₃ transport characteristics in Nanjing under different wind conditions.Our findings reveal during March to October 2018,Nanjing contributed 56.8％ of local O₃ on polluted days and 49.5％ on non-polluted days.When pollution episodes occurred,contributions from surrounding cities to Nanjing increased from 36.4％ to 46.3％,whereas contribution from areas outside the YRD decreased from 6.8％ to 4.7％.On a daily basis,Nanjing accounted for over 70％ of local O₃ contributions during daytime hours,while at night,the majority of transport contributions originated from surrounding cities and areas outside the YRD (exceeding 95％).On days with O₃ pollution,contributions from Jiangsu Province constituted 73.1％,with 10.8％ from Zhejiang Province,10.5％ from Anhui Province,and 0.95％ from Shanghai.During pollution periods,the ratio of O₃ (O₃N) produced by NO_x as a precursor to O₃ (O₃V) produced by VOCs as a precursor in Nanjing was approximately 7∶13.Among all pollution episodes,southeast and northeast winds accounted for 38.0％ and 35.9％ respectively,with the dominant wind direction being northeast,resulting in the highest concentration of non-background O₃ in Nanjing.During periods of southeast winds,upwind areas such as Changzhou (7.3％),Zhenjiang (7.0％),and Wuxi (6.5％) contributed significantly O₃ levels in Nanjing.Therefore,strategies for controlling O₃ pollution in Nanjing should take into account pollutant transport from upwind cities.

Abstract:Utilizing datasets from the precipitation phenomenon instrument in Zhengzhou,dual-polarization radars,conventional observations,and China’s First Generation Global Atmosphere and Land Reanalysis data,this study analyzes the microphysical characteristics of the “7·20” extremely heavy rainfall event in Zhengzhou.The occurrence of this extremely heavy rainfall was influenced by multiscale weather systems,creating conducive environmental conditions for the development of complex microphysical characteristics.The results reveal significant changes in raindrop size distributions over time,with raindrop size distribution parameters exhibiting a wide range of values.These parameters encompass distributions typically seen in continental convective precipitation as well as maritime convective precipitation.Notably,the density of small drops exceeded that of common convective precipitation observed in East Asia and South China during the summer.Simultaneously,a large number of large drops existed,contributing to heightened precipitation efficiency,particularly during the most intense precipitation period,which occurred from 16:00 BST to 17:00 BST on July 20th.The dual-polarization radar observations illustrated a low-centroid structure within the convective storm,indicative of warm cloud characteristics.Furthermore,the study highlights the significant role played by intense warm-rain processes beneath the 0 ℃ layer in the formation of this extremely heavy rainfall event.This role involved the melting of numerous ice particles and the facilitation of efficient growth in raindrop size.

Abstract:Ensemble forecasting has emerged as a crucial method for enhancing quantitative precipitation forecasting in operational meteorology.To advance our understanding and improve effectiveness of ensemble predictions,it is imperative to rigorously and accurately assess the predictive skills of ensemble forecast systems.This study offers a comprehensive evaluation of prediction performance using statistical scoring methods such as Threat Score (TS),Equitable Threat Score (ETS),and spatial forecast verification (SAL) based on precipitation forecasts from perturbation and control ensemble members.Our results reveal the following:1) Ensemble members that initialize disturbances based on local breeding growth processes exhibit distinct advantages in forecasting heavy rainfall,yielding predictions that closely align with observed precipitation intensity and spatial distribution.2) Among all ensemble members,member e003 demonstrates the highest TS and ETS scores,along with the lowest false alarm rate and missing alarm rate.These scores are associated with superior accuracy in forecasting rainfall intensity (A) and rain area (L) in SAL verification.Conversely,member e008 displays the lowest scores for TS and ETS related to heavy rainfall,indicating a certain positional deviation in the SAL evaluation.3) Model precipitation forecast bias primarily arises from deviations in forecasting the low vortex system.Furthermore,the evaluation results of precipitation forecast scores for proficient ensemble members tend to exhibit a high degree of consistency.

Abstract:In this study,we conduct a numerical simulation of the dry dynamical processes induced by boundary layer convection on the generation and propagation of gravity waves on the northeastern slope of the Qinghai-Tibet Plateau under complex terrain conditions.This simulation is based on field-observed sounding data from the Qilian station in July 2007,coupled with a high-resolution 3D boundary layer model.The results reveal significant variations in the spatial structure of convection and gravity waves over the complex terrain of the northeastern plateau slope,contingent on different background forcing scenarios.Specifically,when the background wind direction is perpendicular to the mountain,an increase in wind speed enhances atmospheric instability energy near the top of the mixed layer on the leeward slope of the ridge,thereby exciting a more pronounced gravity wave signal in the downstream region.In contrast,when the background wind direction aligns parallel to the ridge,vigorous convection develops over the summit,resulting in a more stable atmospheric state at the top of the mixed layer on the leeward ridge slope.This,in turn,weakens the topographic gravity wave signal,yielding a shorter wave train.Additionally,there is less water vapor near the top of the entire mixed layer,diminishing the conditions conducive to convective cloud formation.Also,decreased background atmospheric buoyancy frequency leads to more vigorous yet less organized convection across the region,reducing the upward transmission distance of gravity waves downstream of the leeward slope and yielding in less significant signals.Furthermore,under these conditions,there is a uniform distribution of water vapor near the top of the mixed layer with minimal amplitude changes,which mitigates conditions conducive to convective cloud formation.

Abstract:To study the differences and similarities between high-resolution and conventional observations of fog microstructure,we conducted an extensive 58-day field observation of fog during the winter of 2020 in Donghai,Lianyungang.Two fog monitors operating at different frequencies (5 Hz and 1 Hz) were employed simultaneously to measure radiation fog on December 28,2020.Our observations revealed that the 5 Hz measurements exhibited a greater range of extreme values compared to the 1 Hz data.Over the entire fog process,the 5 Hz fog droplet spectrometer measurements,when averaged to 1 Hz,demonstrated less similarity to the original 1 Hz results during the fog's generation and dissipation stages,while showing more similarity during the maturation and development stages.Concerning spectral patterns,both 5 Hz and 1 Hz measurements exhibited similarities,with notable differences occurring at the peaks.Both 5 Hz and 1 Hz measurements effectively depicted the relationship between microphysics at different stages of the fog process,with primary differences emerging during the fog generation stage.This divergence may be attributed to the relatively limited activation and condensation growth of new fog droplets observed by the 5 Hz instrument during this stage.

Abstract:Five different cloud microphysical process parameterization schemes in the mesoscale numerical model WRF3.9 were used to simulate a heavy rainfall event in the Yangtze River Basin from June 9 to 10,2017.This study discusses the impact of varying cloud microphysical schemes on the simulation of rainstorms in the Yangtze River Basin.The experiments conducted in this research reveal that the rainstorm process exhibits greater sensitivity to changes in cloud microphysical processes compared to the precipitation process,whether it’s light or heavy rain.The precipitation trend simulated by the Lin scheme aligns with observed data,but underestimates precipitation.The WSM5 scheme demonstrates the most favorable overall performance,surpassing other schemes in simulating both precipitation and its spatial distribution.Conversely,the Goddard scheme exhibits the least favorable results.Examination of the structural evolution of hydrometeors within the clouds indicates that the well-simulated WSM5 scheme features higher levels of rainwater,cloud water,snow,and ice water,with temporal evolution aligning with ground precipitation intensity.Furthermore,differences in vertical velocity induced by distinct microphysical schemes result in variations in cloud cover and cloud height above the precipitation area,thereby influencing the model’s simulation accuracy for precipitation processes.

Abstract:This study investigates the primary dynamic forcing factors and sources of water vapor influencing remote heavy rainfall over North China,generated by Typhoon Lekima on August 10,2019.We utilize surface rain gauge data,ERA5 reanalysis data,and ECWMF ensemble forecast data.Ensemble sensitivity analysis reveals that low-level relative vorticity over the remote typhoon precipitation (TRP) area plays a pivotal role as the most significant dynamic factor facilitating TRP.The intensification of low-level relative vorticity closely correlates with the strengthening northerly winds in the northern region,induced by the deepening of the low-level short-wave trough.These winds are jointly related to the reinforcement of low-level southerly winds between the TRP and typhoon precipitation (TP) areas.The divergence term of relative vorticity emerges as the crucial dynamic process governing the periods of TRP strengthening and weakening.During the phase of TRP enhancement,positive vorticity is primarily attributed to positive divergence,while negative divergence leads to the reduction of relative vorticity and the weakening of TRP intensity.At 500 hPa,water vapor in the TRP region mainly originates from the local area and Typhoon Lekima,while 60％ of the water vapor at 700 hPa is sourced from Typhoon Lekima.At 850 hPa,40％ of the water vapor is contributed by Typhoon Rosa,with the remaining 60％ of water vapor being transported from Typhoon Lekima and the local area.

Abstract:TraCE-21ka represents a pioneering endeavor in transient climatic simulation,elucidating the evolution from the Last Glacial Maximum (LGM) to the Present Day (PD) through a fully coupled climate model.In this paper,we utilize PD reanalysis data and the reconstructed continuous permafrost boundary of the Last Permafrost Maximum (LPM) and Holocene Optimum (HO) to evaluate the performance of TraCE-21ka.Our results show that the TraCE-21ka effectively simulates the spatial pattern of hemispheric-scale circulation and precipitation during the PD period.Notably,while the TraCE-21ka excels in simulating East Asian winters,it exhibits deficiencies in representing summer conditions.Furthermore,the TraCE-21ka consistently simulates significantly colder North hemispheric surface temperatures (by an average of approximately 3—4 ℃) compared to reanalysis data.Particularly in East Asia,the ratio of PD temperature errors to temperature changes from LGM to PD in TraCE-21ka emerges as substantial,implying reduced reliability in simulating the evolution of the East Asian climate.In retrospective analyses,a comparative assessment of continuous permafrost boundaries between reconstructed data and TraCE-21ka reveals disparities.TraCE-21ka indicates Eurasia as warmer (or colder) than observed reality during the LGM (Mid-Holocene) periods,signifying an underestimation of the amplitude of temperature changes.As continuous permafrost boundaries closely align with the -7 ℃ isothermal line of annual mean surface temperature,we quantitively evaluate the mid-latitude Eurasian warming amplitude of the TraCE-21ka,indicating that the TraCE-21ka approximates only 40％ of the warming witnessed in the real world from the LGM to the PD.Furthermore,a comparison of the global warming rate of TraCE-21ka with reanalysis data and CMIP5 historical greenhouse gas simulations over the past century confirms the significantly low climate sensitivity of the model.This discrepancy raises concerns about the cumulative errors that may affect transit paleoclimate simulations using TraCE-21ka.