Impacts of meteorological parameters and emissions on decadal,interannual, and seasonal variations of atmospheric black carbon in the Tibetan Plateau

We quanti?ed the impacts of variations in meteorological parameters and emissions on decadal, interannual, and seasonal variations of atmospheric black carbon(BC) in the Tibetan Plateau for 1980-2010 using a global 3-dimensional chemical transport model driven by the Modern Era Retrospective-analysis for Research and Applications(MERRA) meteorological ?elds. From 1980 to 2010, simulated surface BC concentrations and all-sky direct radiative forcing at the top of the atmosphere due to atmospheric BC increased by 0.15 μg m^(-3)(63%) and by 0.23 W m^(-2)(62%), respectively, averaged over the Tibetan Plateau(75-105°E, 25-40°N). Simulated annual mean surface BC concentrations were in the range of 0.24-0.40 μg m^(-3) averaged over the plateau for 1980-2010, with the decadal trends of 0.13 μg m^(-3)per decade in the 1980 s and 0.08 in the 2000 s. The interannual variations were -5.4% to 7.0% for deviation from the mean, 0.0062 μg m^(-3) for mean absolute deviation, and 2.5% for absolute percent departure from the mean. Model sensitivity simulations indicated that the decadal trends of surface BC concentrations were mainly driven by changes in emissions, while the interannual variations were dependent on variations of both meteorological parameters and emissions. Meteorological parameters played a crucial role in driving the interannual variations of BC especially in the monsoon season.

Enhanced atmospheric phosphorus deposition in Asia and Europe in the past two decades

磷是植物生长必需的元素,磷缺乏将限制植被生产力及碳汇功能.为厘清全球大气磷沉降的时空格局,本文收集了1959-2020年发表的396条观测资料.结果发现,全球大气磷沉降的几何均值为0.32 kg ha~(-1)yr~(-1),全球大气磷库约4.4 Tg yr~(-1).与1959-2000年相比,近20年亚洲和欧洲大气磷沉降呈现上升趋势,主要来源是农业活动,沙尘传输和燃烧源排放.碳中和背景下,清洁空气行动是否会改变磷沉降的途径和形态,进而影响到生态系统的结构和功能,是需要回答的科学问题.

The research on boundary layer evolution characteristics of Typhoon Usagi based on observations by wind profilers

Vertically exploring the characteristics of the typhoon boundary layer(TBL) plays an important role in recognizing typhoon structure. The boundary layer radial direction and tangential wind characteristics of Typhoon Usagi based on the observational data of three boundary layer wind profiler stations along the route of Typhoon Usagi(No. 1319) and by combining with sounding data. The results show that:(1) maximum tangential wind appears in the vicinity of the eye area of Usagi, and it basically maintains a height of around 1 800 m when Usagi keeps a strong typhoon level, with the rapidly decreasing strength of Usagi after it lands, the speed of the maximum tangential wind and its vertical range both decrease;(2) the height of the maximum tangential wind is close to that of the inflow layer top of the typhoon, and is greater than that of the boundary layer estimated on the basis of Richardson number or potential temperature gradient, while the height of mixed layer judged on the basis of the signal-to-noise ratio(SNR) or its gradient is usually low;(3) the the boundary layer height can reach higher than2 100 m before Usagi lands. When the typhoon level or above is achieved, the boundary layer height observed by various stations does not change much, basically staying at between 1 200 and 1 600 m. With the decreasing strength of Usagi after its landfall, the boundary layer height rapidly drops.

Simulated Impacts of Sulfate and Nitrate Aerosol Formation on Surface-Layer Ozone Concentrations in China

The authors quantify the impacts of sulfate and nitrate aerosol formation on surface-layer O3 concentrations over China using the one-way nested-grid capability of the global three-dimensional Goddard Earth Observing System chemical transport model(GEOS-Chem). Chemical reactions associated with sulfate formation are simulated to generally increase O3 concentrations in China. Over the North China Plain(NCP) and the Sichuan Basin(SCB), where simulated sulfate concentrations are the largest, ozone concentrations show maximum increases in spring by 1.8 ppbv(3.2%) in the NCP and by 2.6 ppbv(3.7%) in the SCB. On the contrary, nitrate formation is simulated to reduce O3 concentrations by up to 1.0 ppbv in eastern China, with the largest reductions of 1.0 ppbv(1.4%) in summer over the NCP. Accounting for the formation of both sulfate and nitrate, the surface-layer O3 concentrations over a large fraction of eastern China are simulated to increase in winter, spring, and autumn, dominated by the impact of sulfate formation, but to decrease in summer because of the dominant contribution from nitrate formation.

Preface to the Special Issue on Atmospheric Oxidation Capacity,Ozone,and PM_(2.5)Pollution:Quantification Methods,Formation Mechanisms,Simulation,and Control

The atmospheric oxidation capacity(AOC)is the essential driving force of atmospheric chemistry in forming complex air pollution,which determines the removal rate of trace gases and the production rates of secondary pollutants.The processes and rates of species being oxidized in the atmosphere thus constitute the key factors to quantify the AOC.

Description and Application of a Model for Simulating Regional Nitrogen Cycling and Calculating Nitrogen Flux

一个地区性的氮周期模型，命名 IAP-N，为模仿地区性的氮(N) 骑车并且计算流动在耕琢壤，庄稼，和家畜之中的 N 流动被设计，以及人，大气并且另外的系统。这个模型的概念的结构和计算方式和过程详细被描述。模型的所有方程被介绍。另外，所有深奥变量和参数的定义被给。在在国家规模的中国的模型的应用被介绍。在这个例子，消费合成 N 化肥的年度剩余；氧化氩氮的排出物(N 2 O ) ，氨(NH 3) 和氮氧化物(没有 x ) ；从农业陆地的 N 损失由于沥滤和流量；并且人为的反应 N (Nr ) 的来源和水池为时期被估计 1961 2004。模型估计证明 N 化肥的剩余开始发生在 1990 年代中并且在 2000 年代初等于 5.7 Tg N 年 −1 。N 2 与农业有关的 O 排出物在 2004 作为 0.69 Tg N 年 −1 被估计，哪个 58% 直接被免除加到农业土壤的 N。全部的 NH 3 和没有 x 在 2004 的排出物分别地等于 4.7 和 4.9 Tg N 年 −1, 。N 的大约 3.9 Tg N 年 −1 被估计在 2004 从耕琢壤层流动了，它说明了 33% 应用合成 N 化肥。从 2.8 改变的人为的 Nr 来源(1961 ) 到 28.1 Tg N 年 −1(2004 ) ，当移动(水池) 从到 2.1 ～ 8.4 Tg N 年 −1 变化了时。到水池的人为的 Nr 来源的比率仅仅在 2004 在 1961 而是 3.3 是 1.4。IAP-N 模型的进一步的开发被建议集中在之上：与另外的地区性的 N 内部比较的(a) 当模特儿；克服水流的限制的(b) 为版本建模，例如到另外的区域的改编，高分辨率的数据库等等；并且开发能力估计人为的 Nr 的安全阀值的(c) 采购原料压制比率。

Effects of Irrigation on Nitrous Oxide,Methane and Carbon Dioxide Fluxes in an Inner Mongolian Steppe

Increased precipitation during the vegetation periods was observed in and further predicted for Inner Mongolia. The changes in the associated soil moisture may affect the biosphere-atmosphere exchange of greenhouse gases. Therefore, we set up an irrigation experiment with one watered (W) and one unwatered plot (UW) at a winter-grazed Leymus chinensis-steppe site in the Xilin River catchment, Inner Mongolia. UW only received the natural precipitation of 2005 (129 mm), whereas W was additionally watered after the precipitation data of 1998 (in total 427 mm). In the 3-hour resolution, we determined nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes at both plots between May and September 2005, using a fully automated, chamber-based measuring system. N2O fluxes in the steppe were very low, with mean emissions (±s.e.) of 0.9±0.5 and 0.7±0.5 μg N m-2 h-1 at W and UW, respectively. The steppe soil always served as a CH4 sink, with mean fluxes of -24.1±3.9 and -31.1 ± 5.3 μg C m-2 h-1 at W and UW. Nighttime mean CO2 emissions were 82.6±8.7 and 26.3±1.7 mg C m-2 h-1 at W and UW, respectively, coinciding with an almost doubled aboveground plant biomass at W. Our results indicate that the ecosystem CO2 respiration responded sensitively to increased water input during the vegetation period, whereas the effects on CH4 and N2O fluxes were weak, most likely due to the high evapotranspiration and the lack of substrate for N2O producing processes. Based on our results, we hypothesize that with the gradual increase of summertime precipitation in Inner Mongolia, ecosystem CO2 respiration will be enhanced and CH4 uptake by the steppe soils will be lightly inhibited.

Simulating Dry Deposition Fluxes of PM_(10) and Particulate Inorganic Nitrogen over the Eastern China Seas During a Severe Asian Dust Event Using WRF-Chem Model

A WRF-Chem model including a comprehensive gas-phase nitrogen chemistry module was used to simulate a severe dust event appearing in the eastern China on 19-25 March, 2002. The modeling result well reproduced PM10 concentrations in various distances from the dust sources and the transport pathway of the dust strom. The results showed that both the concentrations and the dry deposition fluxes of PM10 increased over the China seas during the dust event following the passage of a cold front system. The maximum fluxes of PM10 in the Yellow Sea and the East China Sea during the dust event were 5.5 and 8.4 times of those before the event, respectively. However, the temporal variations of the dry deposition fluxes of particulate inorganic nitrogen differed over the Yellow Sea from those over the East China Sea. Nitrate and ammonium in the whole northern China rapidly decreased because of the intrusion of dust-loaded air on 19 March. The dust plume arrived in the Yellow Sea on 20 March, decreasing the particulate inorganic nitrogen in mass concentration accordingly. The minimum dry deposition fluxes of nitrate and ammonium in the Yellow Sea were about 3/5 and 1/6 of those before the dust arrival, respectively. In contrast, when the dust plume crossed over the Yangtze Delta area, it became abundant in nitrate and ammonium and increased the concentrations and dry deposition fluxes of particulate inorganic nitrogen over the East China Sea, where the maximum dry deposition fluxes of nitrate and ammonium increased approximately by 4.1 and 2.6 times of those prior to the dust arrival.

Influences of the Clearness Index on UV Solar Radiation for Two Locations in the Tibetan Plateau——Lhasa and Haibei

Ultraviolet (UV) solar radiation has a significant influence on human health, the environment and climate. A series of measurements, including UV radiation (290-400 nm) and global solar radiation (Rs), were continuously recorded from August 2004 at the Lhasa and Haibei sites on the Tibetan Plateau. Both observation sites' altitudes are above 3000 m and have similar meteorological conditions. The data from 2005-2006 was used to identify the varying characteristics of UV radiation. It's relation to the clearness index Ks, the relative optical mass mr, and Rs were established. The annual mean values of total daily UV radiation are 0.92 and 0.67 MJ m-2 at Lhasa and Haibei, respectively. The UV radiation in Lhasa represented 4.6% of the global solar radiation while in Haibei this percentage was 4.2%. In the case of clear days (Ks > 0.8), these percentages ranged between 4.0% and 4.5% in Lhasa and between 5.1% and 5.5% in Haibei. In the case of cloudy days (Ks < 0.4), these percentages ranged from 4.4% to 6.8% in Lhasa and from 5.1% to 5.5% in Haibei. The maximum values of UV radiation for each relative optical mass diminished exponentially with mr. Thus, for Lhasa and Haibei, UV=46.25m-r 1.29, and UV=51.76m-r 1.42, respectively. The results of this study can be used to obtain more UV radiation data for the study of UV climate characteristics, the effects of UV on ecological processes and the feedback of the thinning of the stratospheric ozone, from more routine measurements Rs data.

Simulation of the Direct Radiative Effect of Mineral Dust and Sea Salt Aerosols in a Doubled Carbon Dioxide Climate

The authors examine the equilibrium climatic response to the direct radiative effect(DRE)of mineral dust and sea salt aerosols in a doubled-CO2climate with two-way coupling of aerosol-climate interactions.In response to the drier and windier conditions,dust emissions increase by 26%in the Sahara Desert and by 18%on the global scale relative to present day.Sea salt emissions increase in high latitudes(>60°)but decrease in middle latitudes(30°–60°)of both hemispheres due to the poleward shift of westerlies,leading to a 3%decrease in global emissions.The burdens of dust and sea salt increase by 31%and 7%respectively,because reductions in rainfall over the tropical oceans increase the lifetime of particles in the warmer climate.The higher aerosol loading in the doubled-CO2climate reinforces aerosol DRE by0.2 W m 2,leading to an additional cooling of 0.1°C at the surface compared with the climatic effects of aerosols in present day.The additional cooling from changes in natural aerosols compensates for up to 15%of the regional warming induced by doubled CO2.

Evaluation and Evolution of MAX-DOAS-observed Vertical NO_(2) Profiles in Urban Beijing

Multiaxis differential absorption spectroscopy(MAX-DOAS)is a newly developed advanced vertical profile detection method,but the vertical nitrogen dioxide(NO_(2))profiles measured by MAX-DOAS have not yet been fully verified.In this study,we perform MAX-DOAS and tower gradient observations to simultaneously acquire tropospheric NO_(2)observations in the Beijing urban area from 1 April to 31 May 2019.The average values of the tropospheric NO_(2)vertical column densities measured by MAX-DOAS and the tropospheric monitoring instrument are 15.8×1015 and 12.4×1015 molecules cm−2,respectively,and the correlation coefficient R reaches 0.87.The MAX-DOAS measurements are highly consistent with the tower-based in situ measurements,and the correlation coefficients R from the ground to the upper air are 0.89(60 m),0.87(160 m),and 0.76(280 m).MAX-DOAS accurately measures the trend of NO_(2)vertical profile changes,although a large underestimation occurs by a factor of two.By analyzing the NO_(2)vertical profile,the NO_(2)concentration reveals an exponential decrease with height.The NO_(2)vertical profile also coincides with the evolution of the boundary layer height.The study shows that the NO_(2)over Beijing mainly originates from local sources and occurs in the boundary layer,and its vertical evolution pattern has an important guiding significance to better understand nitrate production and ozone pollution.

Multifractal Characteristics of Intermittent Turbulence in the Urban Canopy Layer

The multifractality of energy and thermal dissipation of fully developed intermittent turbulence is investigated in the urban canopy layer under unstable conditions by the singularity spectrum for the fractal dimensions of sets of singularities characterizing multifractals. In order to obtain high-order moment properties of smallscale turbulent dissipation in the inertial range, an ultrasonic anemometer with a high sampling frequency of 100 Hz was used. The authors found that the turbulent signal could be singular everywhere. Moreover, the singular exponents of energy and thermal dissipation rates are most frequently encountered at around 0.2, which is significantly smaller than the singular exponents for a wind tunnel at a moderate Reynolds number. The evidence indicates a higher intermittency of turbulence in the urban canopy layer at a high Reynolds number, which is demonstrated by the data with high temporal resolution. Furthermore, the temperature field is more intermittent than the velocity field. In addition, a large amount of samples could be used for verification of the results.

Consistency Problem with Tracer Advection in the Atmospheric Model GAMIL

氡运输测试，是为大气的运输模型的一个广泛地使用的测试用例，被执行在 IAP-LASG (GAMIL ) 的格子点大气的模型评估 tracer 移流计划。在模型的三个可得到的计划中的二个被发现在极的区域并且在空气的上面的部分与重要偏爱被联系，它在像臭氧的 tracers 的模拟暗示潜在地大的错误。矛盾在 GAMIL 并且因而的动态核心在移流计划和分离连续性方程之间存在的理论分析表演导致假来源并且在 tracer 运输方程下沉。这类矛盾的影响被理想化的测试表明并且作为上述的偏爱的原因识别了。这个矛盾的另外的潜在的效果也被讨论。这研究的结果为在 GAMIL 模型选择合适的移流计划提供一些提示。至少为 polar-region-concentrated 大气的部件和密切相关的化学种类，没有显著地增加计算开销，流动形式 Semi-Lagrangian 移流计划生产大规模运输过程的更合理的模拟。

Effects of transport on aerosols over the eastern slope of the Tibetan Plateau:synergistic contribution of Southeast Asia and the Sichuan Basin

为探究南亚与四川盆地对青藏高原污染物传输的影响,论文利用青藏高原东坡区域背景站贡嘎山站2012–2014年地基观测数据,系统揭示了青藏高原东坡大气气溶胶浓度、化学成分与光学特性的变化特征。气溶胶光学厚度AOD年均值0.35左右,在夏冬季较高,春秋较低。干季钾离子(K+)、二次无机气溶胶(SIAs)与一次有机碳(POC)的浓度均高于湿季,湿季二次有机碳(SOC)为干季的3.1倍。结合后向轨迹分析,来自东南亚地区气团对应的高浓度K+、元素碳(EC)及POC表明生物质燃烧源对青藏高原东坡干季气溶胶有显著贡献;湿季气溶胶主要来源于四川盆地可挥发性有机物(VOCs)的氧化。

Assessment of aerosol effective radiative forcing and surface air temperature response over eastern China in CMIP5 models

气溶胶有效辐射强迫是评估气溶胶气候效应的有效指标。本文利用国际耦合模式比较计划(CMIP5)中7个模式的模拟结果,评估了模式对东亚地区气溶胶光学厚度和有效辐射强迫的模拟水平,并分析了东亚地区平均地表温度对局地人为气溶胶强迫的响应。研究结果显示,大部分模式低估了中国东部和西南部污染地区的气溶胶光学厚度,这可能与模式中气溶胶局地排放、化学过程以及模式分辨率有关;多模式平均的东亚地区气溶胶有效辐射强迫为.4.14 W m.2,气溶胶在东亚地区有明显的降温效应,1850–2005年气溶胶浓度增加使得东亚地区降温.1.05°C。

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.

The impacts of different surface boundary conditions for sea surface salinity on simulation in an OGCM

盐度是海洋的一个基本状态变量,在海洋环流中起着重要的作用。少量的盐通量扰动都会改变海洋的经向翻转环流和海表温盐场。因此,本文使用了海洋环流模式LICOM2.0研究了不同盐度边界条件对全球总盐量、海表盐度和大西洋经圈翻转环流模拟的影响。结果表明:洋面上的弱恢复项对合理地模拟海表盐度起着重要的作用,且对全球总盐量起着递增的作用;在虚盐通量中使用模拟的海表盐度而非定常的参考盐度能够更合理地模拟大西洋经圈翻转环流;除此之外,含有实盐通量的盐度边界条件能够更好地维持全球总盐量的守恒。

Temperature oscillations observed in the stable boundary layer over four different underlying surfaces

夜间边界层内的温度时空特征决定了边界层的稳定性。由于稳定边界层的间歇性和复杂性,模式在夜间的参数化方案还不完善,研究夜间边界层的温度变化有助于改进模式在夜间的表现。本文利用四座在不同下垫面上的气象塔的数据,研究了夜间边界层中的温度波动。研究表明,无论是海边、草原还是沙漠下垫面,夜间形成的稳定边界层中,振幅大约2摄氏度,周期在数分钟的温度波动非常频繁地出现。而在北京,由于城市下垫面较大的热容量和人为热源使得稳定边界层不容易形成,温度波动也较弱。用布朗特维萨拉频率代表的静力稳定度是影响温度脉动强弱的重要因子。

Estimating emissions and concentrations of road dust aerosol over China using the GEOS-Chem model

本文利用嵌套版本的GEOS-Chem和美国环保署推荐的AP-42经验公式,估算了2006至2011年中国地区的道路扬尘排放并模拟了中国地区的道路扬尘浓度。多年平均的道路扬尘年排放量为2331.4 kt,且在中国东部地区的排放量要大于西部。由于降水月变化的影响,中国地区道路扬尘月排放量在12月最大而在6月最小。由于道路长度和车辆保有量逐年增加,2006–2011年期间,中国、京津唐、珠江三角洲和长江三角洲地区道路扬尘年排放量分别增加了260%、239%、266%和59%,这使得道路扬尘浓度在这些区域分别增加了233%、243%、273%和100%。

Wet deposition and scavenging ratio of air pollutants during an extreme rainstorm in the North China Plain

大气湿沉降是陆地和水体环境中营养成分和有毒物质的重要来源。以往湿沉降研究较多关注年尺度或年际变化,极端降水事件鲜见报道。通过实验观测,发现2016年7月19–21日华北极端暴雨(北京观测站325.6 mm)有效清除了区域大气颗粒物,但不同化学成分被湿清除的效率存在差异(无机离子比有机物和气态污染物更容易被湿清除)。此次极端降水铵盐和硝酸盐的湿沉降通量占北京全年的22%和4%,相当于青藏高原一年的氮沉降。考虑到气候背景下极端暴雨出现的频次,极端降水的生态环境影响需要更精细化的评估。