Subseasonal reversal of haze pollution over the North China Plain

China has been frequently suffering from haze pollution in the past several decades. As one of the most emission-intensive regions, the North China Plain (NCP) features severe haze pollution with multiscale variations. Using more than 30 years of visibility measurements and PM_2.5 observations, a subseasonal seesaw phenomenon of haze in autumn and early winter over the NCP is revealed in this study. It is found that when September and October are less (more) polluted than the climatology, haze tends to be enhanced (reduced) in November and December. The abrupt turn of anomalous haze is found to be associated with the circulation reversal of regional and large-scale atmospheric circulations. Months with poor air quality exhibit higher relative humidity, lower boundary layer height, lower near-surface wind speed, and southerly anomalies of low-level winds, which are all unfavorable for the vertical and horizontal dispersion and transport of air pollutants, thus leading to enhanced haze pollution over the NCP region on the subseasonal scale. Further exploration indicates that the reversal of circulation patterns is closely connected to the propagation of midlatitude wave trains active on the subseasonal time scale, which is plausibly associated with the East Atlantic/West Russia teleconnection synchronizing with the transition of the North Atlantic SST. The seesaw relation discussed in this paper provides greater insight into the prediction of the multiscale variability of haze, as well as the possibility of efficient short-term mitigation of haze to meet annual air quality targets in North China.摘要中国近几十年来频受雾霾污染问题困扰, 其中华北平原作为排放最密集的区域之一, 常遭遇不同尺度的严重雾霾污染. 本文利用30余年的能见度和颗粒物 (PM_2.5) 观测数据, 发现了华北平原地区在秋季和早冬时雾霾污染在次季节尺度上“跷跷板式”反向变化的关系. 研究发现, 当9–10月污染较轻 (重) 时, 11–12月的污染倾向于加重 (减轻) . 这种突然的变化与局地和大尺度环流的反向变化有关. 污染较重的月份常伴随有更高的相对湿度, 更低的边界层高度和近地面风速以及低层的南风异常, 均不利于污染的垂直和水平扩散和传输, 从而导致了次季节尺度上霾污染的加重. 进一步的研究发现环流场的突然转向与在次季节尺度上活跃的中纬度波列的传播密切相关, 而此波列可能主要与大西洋海温转变及引起的EA/WR遥相关型有关. 这一次季节反向变化为霾污染多尺度变率预测提供了新的理解, 同时为华北地区年度空气质量达标的短期目标提供了具有可行性的参考方法.     

Evaluation of CMP AS precipitation products over Sichuan,China

高质量和高分辨率的降水产品在天气预报,数值模式模拟和气象防灾减灾方面起着重要的作用.本文利用四川地区高密度的地面降水传感器观测数据,比较CMPAS四种不同时空尺度的降水实况分析产品,评估CMPAS的融合准确性与在四川地区的适用性.研究表明:四种CMPAS降水产品都在四川盆地内精度较高,攀西地区和川西高原次之.随着降水量...     

Impacts of changes in land cover and topography on a heavy precipitation event in Central Asia

Future variations in precipitation due to the effects of topography and possible trends in land-use change in Central Asia are evaluated by utilizing numerical experiments based on a case study. Considering possible changes in land cover, oasification leads to a 0.23 mm increase in regional-averaged precipitation, accounting for 3.0% of the total. Meanwhile, desertification and urbanization decrease precipitation, by about ?5.3% and ?4.7% proportionally, mainly through changing the near-surface humidity and thermal environment and related upward transport of heat fluxes in the boundary layer. Relatively, varied terrain height produces a more prominent impact on precipitation (up to ?13.1% and ?24.9% in the 1/2 and 1/4 original terrain height runs), mainly via varying the wind field and microphysical processes (low-level jet and cloud). Furthermore, the heavier rainfall happens over the mountains, while the more sensitive response of precipitation to varied topography and land use occurs over the plains. As the main microphysical conversion pathways of the rainwater budget, the greater peaks of PSMLT (snow melting into raindrops) and PGMLT (graupel melting into raindrops) present over the mountains but not the plains are responsible for the difference in precipitation between the mountains and plains. However, the more sensitive response of plain rainfall might be related to the rapid transit of rainfall over the plains but prolonged mountainous precipitation lasting together with relatively slowly varying microphysical conversion processes when airflows climb the mountains. The findings of this study have important strategic significance for improving the environment of ecosystems and strengthening the capacity for disaster prevention.摘要本研究利用数值试验方法, 定量评估了地形效应和土地利用类型的变化对中亚降水事件的影响. 考虑到可能的地表覆盖变化趋势, 绿洲化, 沙漠化和城市化可改变近地表湿热环境和边界层向上热通量, 导致区域平均降水增加3.0%, 减少5.3%和4.7%; 相对而言, 地形效应对降水的影响更为显著 (1/2和1/4原始地形高度时, 降水减少13.1%和24.9%), 主要影响途径是风场和微物理过程 (低空急流和云) 的变化. 以上研究结果对改善生态环境, 加强防灾能力具有重要战略意义.     

Characteristics of diurnal variations of warm-season precipitation over Xinjiang Province in China

降水日变化受大气热力,动力过程以及复杂地形影响,演变特征复杂且区域差异显著.本文采用中国气象局发布的中国地面与CMORPH融合逐小时降水产品(2008-2019年),分析了新疆省暖季降水日变化特征.研究结果表明:(1)新疆大部分地区降水主峰值发生在清晨;(2)持续时间超过三小时的降水事件是新疆地区主要降水事件,贡献了南...     

Aerosol characteristics over the Tibetan Plateau simulated with a coupled aerosol–climate model (FGOALS-f3-L) 耦合气溶胶气候模式FGOALS-f3-L模拟青藏高原地区气溶胶特性

This study presents the simulated aerosol spatiotemporal characteristics over the Tibetan Plateau (TP) with a newly developed coupled aerosol–climate model (FGOALS-f3-L). The aerosol properties are simulated over the TP for the period 2002–11. The results indicate that soil dust, sulfate, and carbonaceous aerosols (black carbon (BC), organic carbon (OC) and BC/OC) account for 53.6%, 32.2%, and 14.2% of the total aerosol mass over the TP, respectively. The simulated aerosol surface mass concentrations and aerosol optical depths (AODs) are evaluated with ground-based and satellite observations, respectively. Underestimations of the aerosol surface mass concentration are found at the Lhasa site, especially for BC and OC. The spatial distribution and interannual variation of AOD are consistent with MODIS observations, with the RMSE of 0.081 and bias of 0.036. Due to the uncertainty of the parameterization of dust emissions, the model's performance in summer and autumn is much better than that in spring.摘要基于新耦合气溶胶气候模式FGOALS-f3-L模拟分析了2002–2011年青藏高原地区气溶胶时空分布特征.结果表明:青藏高原地区, 沙尘,硫酸盐,碳质气溶胶 (包括黑碳,有机碳和混合碳) 地表质量浓度分别占比为53.6%, 32.2%, 14.2%;在拉萨站点, 模拟的气溶胶地表质量浓度被低估, 尤其是黑碳和有机碳气溶胶;模拟的气溶胶光学厚度 (AOD) 时空分布与卫星观测结果较为一致, 均方根误差和偏差分别为0.081和0.036;由于模式中沙尘排放参数化的不确定性, 模式对AOD的模拟效果在夏季和秋季优于春季     

Maintenance and development of the Ural high and its contribution to severe cold wave activities in winter 2020/21

2020年底至2021年初,连续两次强寒潮入侵中国东部地区,导致大范围强降温.本文研究这两次寒潮的特征和形成机理.主要结果如下:从2020年12月中旬到2021年1月中旬,乌拉尔山地区维持一宽阔的高压脊.脊前北风的维持和加强导致局地斜压性增加,导致下游横槽槽底等高线梯度加大,冷平流加强,西伯利亚高压加强和向南扩张.准定...     

Impacts of strong El Niño on summertime near-surface ozone over China

The influences of strong El Niño events (1997/98 and 2015/16) on summertime near-surface ozone (O₃) concentrations over China are investigated using the GEOS-Chem model. The results show that near-surface O₃ concentrations increased by a maximum of 6 ppb (parts per billion) during the summer of the developing phase of the 1997/98 El Niño in northeastern China, mainly due to the increased chemical production related to the hot and dry conditions. Besides, the O₃ concentration increased by 3 ppb during the developing summer of both the 1997/98 and 2015/16 El Niño in southern China. It was linked to the weakened prevailing monsoon winds, which led to the accumulation of O₃ in southern China. In contrast, in the summer of the decaying phase of the two El Niño events, O₃ concentrations decreased over many regions of China when the El Niño reversed to the cooling phase. This highlights that El Niño plays an important role in modulating near-surface O₃ concentrations over China.摘要利用全球大气化学三维模式 (GEOS-Chem) 模拟研究两次强厄尔尼诺事件 (1997/98和2015/16) 对中国夏季近地面臭氧 (O₃₎ 浓度的影响. 结果表明1997/98年厄尔尼诺事件发展期夏季中国东北区域O₃浓度升高, 最大值超过6ppb, 这主要归因于高温晴朗低湿等气象因素导致O₃化学生成升高. 此外, 两次厄尔尼诺事件发展期夏季O₃浓度在中国南部均增加了3ppb, 这与盛行季风减弱导致中国南方O₃局地积累有关. 相反, 在两次强厄尔尼诺衰减期夏季, 中国大部分地区O₃浓度下降伴随着海温模态转变为拉尼娜事件. 这表明厄尔尼诺在调节中国近地面O₃浓度中发挥着重要作用.     

Response of a westerly-trough rainfall episode to multi-scale topographic control in southwestern China

This study aims to quantify the response of a westerly-trough rainfall episode that occurred in summer 2020 to multi-scale topographic control in southwestern China, based on observations and numerical simulations. The multi-scale topography is composed of the Tibetan Plateau, Hengduan Cordillera (HC), and Sichuan Basin (SB). The westerly trough was characterized by southeastward deepening together with an in-phase propagating rainfall episode. By utilizing the results of numerical experiments, how the multi-scale topography impacted this westerly trough rainfall episode is explored. It is found that HC was the pivotal topographic factor affecting the southeastward extension of the trough and related rainfall, while SB accerelated the eastward movement of the westerly trough and changed the tilting direction of the trough line, thus further changing the location and orientation of precipitation. For extreme rainfall with intensity exceeding 10 mm h^?1, a roughly threefold rise in the cover ratio (from 1.8% to 7.2%) and fourfold increase in the areal rainfall amount per hour occurred by removing the HC barrier, due to the strongest vorticity and long-distance transport capacity to potential vorticy mass accompanying the southeast-stretching trough. Our results quantitatively reveal a strong response of westerly trough rainfall to multi-scale topographic control in southwestern China, therefore serving as an important reference for future decision making and effective model improvement.摘要中国西南部地形复杂, 降水频发, 地形对降水的影响至关重要. 本文基于观测和数值模拟, 定量揭示了青藏高原, 横断山脉和四川盆地多尺度地形对该地区西风槽降水的影响. 发现横断山脉是影响槽东南伸展, 降水传播的关键地形要素, 而四川盆地可加速西风槽东移, 改变槽线倾斜方向, 进而改变降水的位置和方向. 对于极端降水事件, 移除横断山脉屏障后, 降水覆盖率约增加3倍 (从1.8%增至7.2%), 小时面雨量增强4倍. 这些研究, 可为地形复杂地区降水的未来预报决策和有效模式改进提供参考.     

Evaluation of multiple surface irradiance-based clear sky detection methods at Xianghe—A heavy polluted site on the North China Plain: 香河站太阳辐射识别晴空方法的评估

Surface irradiance measurements with high temporal resolution can be used to detect clear skies, which is a critical step for further study, such as aerosol and cloud radiative effects. Twenty-one clear-sky detection (CSD) methods are assessed based on five years of 1-min surface irradiance data at Xianghe—a heavily polluted station on the North China Plain. Total-sky imager (TSI) discrimination results corrected by manual checks are used as the benchmark for the evaluation. The performance heavily relies on the criteria adopted by the CSD methods. Those with higher cloudy-sky detection accuracy rates produce lower clear-sky accuracy rates, and vice versa. A general tendency in common among all CSD methods is the detection accuracy deteriorates when aerosol loading increases. Nearly all criteria adopted in CSD methods are too strict to detect clear skies under polluted conditions, which is more severe if clear-sky irradiance is not properly estimated. The mean true positive rate (CSD method correctly detects clear sky) decreases from 45% for aerosol optical depth (AOD) $\le$ 0.2% to 6% for AOD > 0.5. The results clearly indicate that CSD methods in a highly polluted region still need further improvements.摘要根据位于华北平原的重污染站点——香河5年的分钟级别地表太阳辐射和人工订正的全天空成像仪数据, 对21种晴空识别 (CSD) 方法进行了评估:晴空识别准确率较高的方法云天识别准确率较低, 反之亦然;由于CSD 方法采用的参数阈值不适用于污染情况, 当气溶胶含量增加时, 识别准确率呈下降趋势.研究结果显示, 利用太阳辐射数据识别晴空的方法在高污染地区使用时需进行改进.     

Strengthening the three-dimensional comprehensive observation system of multi-layer interaction on the Tibetan Plateau to cope with the warming and wetting trend

Changes in the water cycle on the Tibetan Plateau (TP) have a significant impact on local agricultural production and livelihoods and its downstream regions. Against the background of widely reported warming and wetting, the hydrological cycle has accelerated and the likelihood of extreme weather events and natural disasters occurring (i.e., snowstorms, floods, landslides, mudslides, and ice avalanches) has also intensified, especially in the high-elevation mountainous regions. Thus, an accurate estimation of the intensity and variation of each component of the water cycle is an urgent scientific question for the assessment of plateau environmental changes. Following the transformation and movement of water between the atmosphere, biosphere and hydrosphere, the authors highlight the urgent need to strengthen the three-dimensional comprehensive observation system (including the eddy covariance system; planetary boundary layer tower; profile measurements of temperature, humidity, and wind by microwave radiometers, wind profiler, and radiosonde system; and cloud and precipitation radars) in the TP region and propose a practical implementation plan. The construction of such a three-dimensional observation system is expected to promote the study of environmental changes and natural hazards prevention.摘要青藏高原的水循环变化对于高原及其下游区域人类的生产生活具有举足轻重的影响. 在高原暖湿化的背景下, 其水文循环加快, 极端天气和自然灾害事件概率增大, 比如, 雪灾, 洪水, 滑坡, 泥石流, 冰崩在山区频发. 因此, 如何准确的估算青藏高原水循环各分量的大小及变化幅度是评估高原环境变化影响亟需解决的科学问题. 根据水在各圈层间转换过程, 我们提出了建立第三极地区 (尤其是复杂山区) 的三维立体多圈层地气相互作用综合观测系统(包括涡动相关系统, 行星边界层塔, 微波辐射计, 风廓线仪和无线电探空系统观测的风温湿廓线及云雨雷达等)的紧迫性和具体方案, 进而为研究青藏高原环境变化和山区灾害预测服务.     

Impact of Saharan dust on landfalling North Atlantic tropical cyclones over North America in September

Using reanalysis data and model simulations, this study reveals an increase in September landfalling North Atlantic tropical cyclones (TCs) during years that have a strengthened Saharan dust plume, and the related physical processes are investigated by analyzing the relationship of dust aerosol optical depth with TC track, intensity, and the related meteorological environment. Suppression of the sea surface temperature (SST) by the Saharan dust plume can hinder TC tracks over the central tropical North Atlantic, inducing westward development of TC tracks to the western tropical North Atlantic with higher SST, which is more conducive to TCs forming major hurricanes. This physical process increases TC landfalls in North America, especially major hurricane landfalls in the continental United States, leading to greater potential destructiveness.摘要本项研究利用再分析数据和模式模拟数据分析了沙尘的气溶胶光学厚度与台风的登陆, 轨迹, 强度及相关气象环境参数的关系, 揭示了9月北大西洋台风的登陆次数会在撒哈拉沙尘较强的年份中增加, 以及这一现象的物理机制. 撒哈拉沙尘对热带北大西洋中部海表温度具有抑制作用, 会阻碍该地区的台风活动, 因此台风只能向西移动进入海表温度较高的热带北大西洋西部, 从而更易于形成强台风. 这一物理过程将导致台风登陆北美大陆的频次增加, 特别是强台风登陆美国的可能性增强, 产生更大的潜在破坏性.     

Microphysical characteristics of precipitating cumulus cloud based on airborne Ka-band cloud radar and droplet measurements

在积云中,大多数云粒子的直径在7到10微米之间,而在层云中,大多数云粒子的直径不超过2微米.云滴有效半径与云中行星边界层(PBL)及PBL上层的气溶胶数浓度(Na)呈负相关.在1500米以上的高液态水含量区域,云滴浓度(Nc)变化不大,Na含量降低.高雷达反射率对应于大的FCDP云粒子浓度和小的气溶胶粒子浓度.积云中的...     

Strength of the North African monsoon in the Last Interglacial and under future warming

The authors explore the response of the Northern African (NAF) monsoon to orbital forcing in the Last Interglacial (LIG) compared with its response to greenhouses gas (GHG) forcing under the SSP5-8.5 scenario simulated in CMIP6. When the summer surface air temperature increases by 1 °C over the Northern Hemisphere, the NAF monsoon precipitation and its variability during the LIG increase by approximately 51% and 22%, respectively, which is much greater than under SSP5-8.5 (2.8% and 4.3%, respectively). GHG forcing enhances the NAF monsoon mainly by increasing the atmospheric moisture, while the LIG's orbital forcing intensifies the NAF monsoon by changing the monsoon circulation. During the LIG, models and data reconstructions indicate a salient hemispheric thermal contrast between the North and South Atlantic, strengthening the mean-state NAF monsoon precipitation. The interhemispheric temperature contrast enhances atmosphere–ocean interaction and the covariability of the northward sea surface temperature gradient and Saharan low, strengthening the NAF monsoon variability.摘要与人为强迫引起的全球变暖相比, 末次间冰期是轨道强迫引起的过去80万年来最暖的一个间冰期, 但鲜有人研究末次间冰期中北非季风的响应. 因此, 本文基于CMIP6多模式模拟结果对比研究了末次间冰期和SSP5–8.5情景下北非季风的响应, 发现末次间冰期下北非季风平均降水及其降水变率均远大于SSP5–8.5情景下的结果. 轨道强迫导致的北大西洋暖于南大西洋增加了北非季风环流和平均降水, 同时, 南北大西洋海温梯度变化通过增强热带北大西洋的海气相互作用增大了海温梯度和撒哈拉低压的变率, 从而增强了北非季风降水变率.     

Oceanic thermal forcing of North Atlantic tropical cyclones

The relationship between North Atlantic tropical cyclone (TC) peak intensity and subsurface ocean temperature is investigated in this study using atmospheric and ocean reanalysis data. It is found that the peak intensity of basin-wide strong TCs (Categories 4 and 5) is positively correlated with subsurface ocean temperature in the extratropical North Atlantic. A possible physical mechanism is that subsurface ocean temperature in the extratropical North Atlantic can affect local sea surface temperature (SST); on the other hand, the moisture generated by the warming SST in the extratropical North Atlantic is transported to the main region of TC development in the tropics by a near-surface anticyclonic atmospheric circulation over the tropical North Atlantic, affecting TC peak intensity. Moreover, coastal upwelling off Northwest Africa and southern Europe can affect subsurface ocean temperature in the extratropical North Atlantic. Therefore, the peak intensity of strong TCs is also found to be directly correlated with the water temperature in these two upwelling regions on an interdecadal timescale.摘要利用大气与海洋再分析数据等相关资料, 本项研究发现, 北大西洋强台风 (Saffir–Simpson分类中的第4和第5类) 的最大强度与亚热带北大西洋的次表层海温呈正相关. 由于亚热带北大西洋的次表层海温会影响当地的海表温度, 该地区海面产生的水汽通过近地面的反气旋大气环流可被输送到位于热带的台风主要发展区域, 进而影响台风的最大强度. 与此同时, 位于西非北部和南欧的近岸涌升流会影响亚热带北大西洋的次表层海温. 因此, 强台风的最大强度也被发现与上述两个涌升流区域的海温具有相关性, 但是这种相关性主要体现在年代际时间尺度上.     

Key regions where land surface processes shape the East Asian climate

Land–atmosphere interaction, as one of the key processes affecting the atmosphere and climate over East Asia, has drawn increasing attention during the past few decades. However, the current level of understanding regarding the mechanisms through which land surface processes impact the East Asian climate needs to be improved. Based on existing studies, six key regions where land surface processes affect the East Asian climate are proposed in this study, which can provide a valuable reference for future research into land–atmosphere interaction in East Asia.摘要陆气相互作用是影响东亚大气环流和气候的一个关键过程, 受到了越来越多的关注. 然而, 关于陆面过程影响东亚气候的相关机理的理解还有待提升. 在已有研究基础上, 提出了陆面过程影响东亚气候研究值得关注的青藏高原, 欧亚中高纬地区, 中国东部季风区, 中南半岛, 中亚中纬度区域, 西亚等6个关键区, 期待为加强陆面过程与东亚气候研究提供一定参考.     

Comparisons in the global planetary boundary layer height obtained from COSMIC radio occultation,radiosonde, and reanalysis data 基于无线电掩星数据, 探空资料以及再分析资料估算大气边界层高度的比较

The global planetary boundary layer height (PBLH) estimated from 11 years (2007–17) of Integrated Global Radiosonde Archive (IGRA) data, Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) soundings, and European Center for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) data, are compared in this study. In general, the spatial distribution of global PBLH derived from ERA-Interim is consistent with the one from IGRA, both at 1200 UTC and 0000 UTC. High PBLH occurs at noon local time, because of strong radiation energy and convective activity. There are larger differences between the results of COSMIC and the other two datasets. PBLHs derived from COSMIC are much higher than those from radiosonde and reanalysis data. However, PBLHs derived from the three datasets all exhibit higher values in the low latitudes and lower ones in the high latitudes. The latitudinal difference between IGRA and COSMIC ranges from −1700 m to −500 m, while it ranges from −500 m to 250 m for IGRA and ERA-Interim. It is found that the differences among the three datasets are larger in winter and smaller in summer for most studied latitudes.摘要用11年的全球无线电掩星数据 (COSMIC) , 无线电探空数据 (IGRA) 以及欧洲中心再分析资料 (ERA-Interim) 对全球大气边界层高度 (PBLH) 进行估算比较. 结果表明: (1) 在1200 UTC和0000 UTC, 由ERA-Interim和IGRA数据估算得到的全球PBLH空间分布较为一致, 相关性较好, 在白天正午时候太阳辐射能力较强, 对流活动频繁, 估算得到的大气边界层高度较高. (2) 由COSMIC掩星数据估算得到的边界层高度比探空数据和再分析数据估算结果整体偏大. (3) COSMIC掩星数据, IGRA 探空数据以及 ERA-Interim 再分析资料估算结果都表明边界层高度在低纬度地区偏大, 高纬度地区偏小. (4) 分析不同数据估算边界层高度纬向季节性差异表明, IGRA探空数据和COSMIC数据间差异为-1700m至-500m, IGRA与ERA-Interim之间的差异为-500m至250m.此外, 对于大多数纬度而言, 三个数据集之间的差异在冬季较大, 在夏季较小.     

Impacts of ENSO on wintertime PM2.5 pollution over China during 2014–2021

China has implemented a series of emission reduction policies since 2013, and the concentration of air pollutants has consequently decreased significantly. However, PM_2.5 (particulate matter with an aerodynamic diameter less than 2.5 µm) pollution still occurs in China in relation to the interannual variations in meteorological conditions. Considering that El Niño–Southern Oscillation (ENSO) is the strongest signal modulating the interannual variation in the atmosphere–ocean system, in this study the authors investigate the variations in PM_2.5 concentrations in four megacity clusters of China during the winter season associated with four individual ENSO events from 2014 to 2021. Results show that the wintertime PM_2.5 concentrations in the Beijing–Tianjin–Hebei and Fenwei Plain regions during El Niño years are higher than those during La Niña years, which can be explained by the anomalous southerly (northerly) winds during El Niño (La Niña) favoring PM_2.5 accumulation (diffusion). In the Pearl River Delta region, PM_2.5 concentrations decrease in El Niño relative to La Niña years owing to the enhanced water vapor flux and precipitation, removing more PM_2.5 from the atmosphere. The comprehensive effects of wind and precipitation anomalies lead to the unpredictability of the impacts of ENSO on PM_2.5 over the Yangtze River Delta region, which should be analyzed case by case.摘要2013年以来中国实施了一系列减排政策, 大气污染物浓度明显下降, 但由于气象条件的年际变化, 中国PM_2.5 (空气动力学直径小于2.5 µm的颗粒物) 污染仍然存在. 厄尔尼诺–南方涛动 (ENSO) 是调节大气–海洋系统年际变化的最强信号. 本文研究了2014–2021年四次ENSO事件期间, 中国四个特大城市群冬季PM_2.5浓度的变化. 结果表明, 在京津冀和汾渭平原地区, 由于厄尔尼诺 (拉尼娜) 期间的偏南风 (偏北风) 异常有利于 PM_2.5 的积累 (扩散), 冬季PM_2.5浓度在厄尔尼诺年高于拉尼娜年. 在珠三角地区, 由于厄尔尼诺冬季水汽通量和降水的增加有利于大气中PM_2.5的湿清除, 冬季PM_2.5浓度在厄尔尼诺年低于拉尼娜年. 在环流和降水异常的综合作用下, ENSO对长三角地区PM_2.5浓度的影响难以预测, 应逐案分析.     

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.     

Analysis of aerosol distribution variations over China for the period 2045–2050 under different Representative Concentration Pathway scenarios: 不同代表性浓度路径情景下 2045-2050 年中国气溶胶分布变化的分析

The regional air quality modeling system RAMS-CMAQ was applied to simulate the aerosol concentration for the period 2045–2050 over China based on the downscaled meteorological field of three RCP scenarios from CESM (NCAR's Community Earth System Model) in CMIP5. The downscaling simulation of the meteorological field of the three RCP scenarios showed that, compared with that under RCP2.6, the difference in near-surface temperature between North and South China is weakened and the wind speed increases over North and South China and decreases over central China under RCP4.5 and RCP8.5. Under RCP2.6, from 2045 to 2050, the modeled average PM_2.5 concentration is highest, with a value of 40–50 µg m⁻³, over the North China Plain, part of the Yangtze River Delta, and the Sichuan Basin. Meanwhile, it is 30–40 µg m⁻³ over central China and part of the Pearl River Delta. Compared with RCP2.6, PM_2.5 increases by 4–12 µg m⁻³ under both RCP4.5 and RCP8.5, of which the SO₄²⁻ and NH₄⁺ concentration increases under both RCP4.5 and RCP8.5; the NO₃⁻ concentration decreases under RCP4.5 and increases under RCP8.5; and the black carbon concentration changes very slightly, and organic carbon concentration decreases, under RCP4.5 and RCP8.5, with some increase over part of Southwest and Southeast China under RCP8.5. The difference between RCP4.5 and RCP2.6 and the difference between RCP8.5 and RCP2.6 have similar annual variation for different aerosol species, indicating that the impact of climate change on different species tends to be consistent.摘要基于来自于 CMIP5 中 CESM 模式的三种 RCP 情景下的气象场的降尺度模拟, 应用区域空气质量模式系统 RAMS-CMAQ 模拟 2045-2050 年中国地区气溶胶浓度.三种 RCP 情景下气象场的降尺度模拟表明, 与 RCP2.6 相比, 在 RCP4.5 和 RCP8.5 下, 华北和华南的近地表温度差减小, 风速在华北和华南地区增加, 在中部地区下降. RCP2.6 情景下, 模拟的 2045 年到 2050 年平均的 PM _2.5浓度在华北平原, 长三角的部分地区和四川盆地最高, 约为 40-50 µg m^–3, 在中国中部和珠三角的部分地区约为 30-40 µg m^–3. 与 RCP2.6 相比, 在 RCP4.5 和 RCP8.5 下, PM_2.5增加了 4-12 µg m^–3, 其中在 RCP4.5 和 RCP8.5 下, SO₄^2–和 NH₄⁺的浓度增加, 在 RCP4.5 下, NO^3–浓度降低, 在 RCP8.5 下, NO^3–浓度升高, 在 RCP4.5 和 RCP8.5 下, BC 浓度变化很小, 而 OC 浓度下降, 其中在 RCP8.5 下, 西南和东南部分地区的 OC 有所增加.不同的气溶胶物种浓度在 RCP4.5 和 RCP2.6 之间的差异以及 RCP8.5 和 RCP2.6 之间的差异具有相似的年度变化, 这表明气候变化对不同物种的影响趋于一致.     

Relationship between cross-equatorial flows over the Bay of Bengal and Australia in boreal summer:Role of tropical diabatic heating

本文通过对1979-2017年夏季925 hPa经向风异常进行经验正交函数(EOF)分解,研究了亚澳季风区内越赤道气流的年际变化特征.结果表明,越赤道气流的第一模态表现为亚澳季风区内不同通道间的同相变化,即一致加强或减弱;第二模态表现为孟加拉湾和澳大利亚越赤道气流的反相变化,其中新几内亚和孟加拉湾越赤道气流的反相变化最...