Atmospheric and Oceanic Science Letters最新文献

{"title":"Atlantic blocking events in a simplified nonlinear baroclinic model for local finite-amplitude wave activity","authors":"Ning Shi ,&nbsp;Bamidele Abiodun Paul ,&nbsp;Wencai Liu","doi":"10.1016/j.aosl.2024.100486","DOIUrl":"10.1016/j.aosl.2024.100486","url":null,"abstract":"<div><p>To better understand the mechanisms underlying the formation of blocking highs over the North Atlantic as a type of large-amplitude disturbance, this paper reports results from numerical experiments within the framework of local finite-amplitude wave activity (LWA). The numerical model employed in this study explicitly depicts two important atmospheric internal dynamic processes—nonlinear zonal eddy flux and Rossby wave packet propagation—which have been individually emphasized by different previous studies. The simulation results reveal that these two dynamic processes are the dominant contributors to the formation of Atlantic blocking cases. However, they exert different influences over different regions. The southern and northern parts of the primary LWA associated with the blocking cases are mainly induced by the nonlinear zonal eddy flux and Rossby wave packet propagation, respectively. Thus, this study reconciles and integrates insights from previous studies on Atlantic blocking events, providing a cohesive understanding of their formation.</p><p>摘要</p><p>为研究北大西洋阻高的形成机制, 本文在局部有限振幅波活动 (LWA) 框架下进行了一系列数值实验. 采用的数值模型能显式地描绘出两种重要的大气内部动力过程, 即非线性纬向位涡通量和Rossby波包传播. 模拟结果显示, 这两种动力学过程均是形成大西洋阻高的重要机理. 具体地, 非线性纬向位涡通量和Rossby波包传播, 分别是大西洋阻高南部和北部LWA形成的主导因子. 因此, 本研究综合了前人关于大西洋阻高的研究成果, 为其形成机理提供了新的认识.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 4","pages":"Article 100486"},"PeriodicalIF":2.3,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283424000357/pdfft?md5=5ec4935ee6f295fedc98880047adebab&pid=1-s2.0-S1674283424000357-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140275723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seasonal constraint of dynamic water temperature on riverine dissolved inorganic nitrogen transport in land surface modeling","authors":"Shuang Liu ,&nbsp;Kaiheng Hu ,&nbsp;Zhenghui Xie ,&nbsp;Yan Wang","doi":"10.1016/j.aosl.2024.100485","DOIUrl":"10.1016/j.aosl.2024.100485","url":null,"abstract":"<div><p>Riverine dissolved inorganic nitrogen (DIN) transport plays an important role in the link between terrestrial and marine ecosystems, while the seasonal changes of water temperature exert a strong control on DIN dynamics. However, the response of the flow of DIN to dynamic water temperature in large rivers is not well known at the global scale. In this study, based on a recently developed land surface model coupled with riverine water temperature and DIN transport schemes, two numerical simulations, with and without dynamic water temperature, were implemented to investigate the seasonal constraint of dynamic water temperature on the change in riverine DIN flow. Results show that the water temperature could be a key controlling factor for the spatial distribution of global DIN flows. After integrating dynamic water temperature estimation into land surface modeling, the annual amplitudes of DIN flow were 5%–25% smaller than before between 30°N and 30°S, while approximately 10% larger in other latitudinal zones. Less denitrification was out of the scope of 40°N–20°S in summer. In eastern China, the dynamic water temperature made the DIN flow reduce by 1%–3% in summer, while it made it increase by 1%–5% in winter. A seasonal constraint of dynamic water temperature, making the amplitude of monthly fluctuation reduce by about 60%, was found in global large rivers. This study shows the importance of dynamic water temperature in the seasonal modeling of riverine DIN flow, and provides a scientific reference for land surface model development and water environment management.</p><p>摘要</p><p>水体温度变化对河流可溶性无机氮(DIN)输送有着强烈控制作用. 然而, 在全球尺度上河流DIN输送量对水温度变化的响应尚不清楚. 因此, 本文基于陆面过程模式, 耦合河流水温估算和DIN传输方案, 设定有, 无动态水温情景, 对比研究陆面模拟中水温变化对河流DIN通量变化的影响. 结果表明: 在考虑水温动态变化后, 在30°N和30°S之间, DIN通量年振幅减小5%–25%. 在中国东部地区, 水温动态变化使河流DIN通量在夏季减少1%–3%, 在冬季增加1%–5%, 对DIN通量具有明显的季节性约束作用, 表明动态水温的表达在河流DIN输送模拟中的重要性.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 4","pages":"Article 100485"},"PeriodicalIF":2.3,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283424000333/pdfft?md5=bc88c22bf354b6722972ec7739982016&pid=1-s2.0-S1674283424000333-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140267995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of tropical cyclone thermal structures derived from ATMS and synthetic AMSU-A/MHS","authors":"Wenyu Li ,&nbsp;Fuzhong Weng","doi":"10.1016/j.aosl.2024.100484","DOIUrl":"10.1016/j.aosl.2024.100484","url":null,"abstract":"<div><p>The warm core of a tropical cyclone (TC) reflects its intensity and evolution. In the past, microwave sounding data have been widely used for detecting the TC warm core. However, the observed magnitude of the TC warm core can vary with instruments. This study utilizes the oversampling data from the Advanced Technology Microwave Sounder (ATMS) to reconstruct the brightness temperature data consistent with the data from Advanced Microwave Sounding Unit-A (AMSU-A), which is referred to as AMSU-like data. Through comparisons, it is found that brightness temperature from the original ATMS has more detailed structures, depicting well the TC eye region and cloud bands. Both ATMS and AMSU-like data are used as inputs to the Global Scene-Dependent Atmospheric Retrieval Testbed (GSDART) to retrieve the warm cores of multiple TCs. At 250 hPa, the warm-core intensity retrieved using ATMS data is about 1–2 K higher than that from AMSU-like data and the warm-core structure from ATMS is more detailed. It is recommended that the warm-core intensity retrieved from AMSU-A be corrected to the ATMS values for multi-sensor monitoring of TCs using our newly defined relationship.</p><p>摘要</p><p>热带气旋(TC)的暖心反映了其强度和变化. 微波探测数据被广泛用于探测TC暖心, 但观测到的 TC 暖心强度可能因仪器而异. 本研究利用先进技术微波探测仪 (ATMS) 的过采样数据重采样至与先进微波探测仪 (AMSU-A) 一致的亮温, 称为类-AMSU数据. 通过对比发现, ATMS的观测更加细致, 较好地刻画了TC眼区和云带. 使用ATMS和类-AMSU数据反演多个TC的暖心发现, 在250 hPa, 使用ATMS数据反演的暖心强度比类-AMSU高约1–2K, 并且其暖心结构更详细.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 4","pages":"Article 100484"},"PeriodicalIF":2.3,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283424000321/pdfft?md5=827bb8f367e7fffaa2a6e569d0a209e9&pid=1-s2.0-S1674283424000321-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140280405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climatic drivers of the Canadian wildfire episode in 2023","authors":"Yihan Hu,&nbsp;Xu Yue,&nbsp;Chenguang Tian","doi":"10.1016/j.aosl.2024.100483","DOIUrl":"10.1016/j.aosl.2024.100483","url":null,"abstract":"<div><p>Extreme wildfires broke out in Canada from May 2023 and persisted four months. Tremendous fire emissions posed significant impacts on the air quality in both local and downwind regions. Here, the authors explored the meteorological factors driving this wildfire episode and the associated large-scale circulation. Relative to the mean value of 2001–2022, the 2023 Canadian fires released 0.37 Gt more CO₂ (527.1%) during May–August. Such enhancement was strongly associated with the anomalous surface warming, especially in May–June, when the daily maximum temperature on average increased by 8.11°C, with regional hotspots up to 10°C in central and eastern Canada. Consistent with the surface warming, positive anomalies of geopotential height were observed at high levels in central and western Canada. The dispersion of Rossby waves led to the long-lasting dominance of high-pressure systems and the consequent warming through anomalous subsidence. The phase-locked wave pattern induced by favorable topography and the strong warming tendency in the pan-Arctic regions are expected to jointly escalate the probability of extreme wildfires over central and western Canada in the future.</p><p>摘要</p><p>2023年5月加拿大发生极端野火事件并持续4个月时间. 野火污染物排放对当地和下风向的空气质量造成了严重影响. 本文对驱动此次野火事件的气象因子和相关大尺度环流进行了探究. 研究表明, 此次极端野火排放的二氧化碳相较往年同期增长了0.37Gt (527.1%) . 受罗斯贝波频散影响, 同期加拿大中西部区域出现持续的位势高度正异常, 促进气流下沉并引发局地高温, 中西部区域5–6月最高温平均上升8.11°C, 部分区域甚至超过10°C, 导致野火排放的显著增长. 受有利地形和泛北极地区快速增暖的影响, 预期未来加拿大中西部发生极端野火的概率可能会显著上升.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 4","pages":"Article 100483"},"PeriodicalIF":2.3,"publicationDate":"2024-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S167428342400031X/pdfft?md5=35ca9f541382e11fcc04e824b69d7fd6&pid=1-s2.0-S167428342400031X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140092503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhanced rainfall in North China in July 2021: Role of the North Pacific SST gradient","authors":"Zhaoyang Du ,&nbsp;Lian-Tong Zhou ,&nbsp;Kui Liu ,&nbsp;Xiaoxue Yin","doi":"10.1016/j.aosl.2023.100444","DOIUrl":"10.1016/j.aosl.2023.100444","url":null,"abstract":"<div><p>The rainfall over North China (NC) in July 2021 was the most since 1980, and coincided with a meridional gradient of sea surface temperature anomaly (MGSSTA) in the Pacific. The present study shows that the gradient between the positive sea surface temperature anomaly (SSTA) over the northwestern Pacific and the negative SSTA over the tropical central Pacific was the main reason for the enhanced rainfall in NC in July 2021 because of its influence on the anomalous northward movements of the western North Pacific anticyclone (WNPAC) and its southern cyclone. The associated easterly wind anomalies along the southern flank of the WNPAC converged with the anomalous easterly along the north flank of the anomalous cyclone, transporting more moisture from south to NC. Meanwhile, the MGSSTA likely induced an anomalous reversed Hadley circulation accompanied by distinct southerly wind anomalies in the low troposphere. These anomalies favored a strong monsoon circulation, which is often accompanied by a rain band in a more northern location.</p><p>摘要</p><p>2021年7月, 华北地区的降水量突破1980年以来的极值, 这与太平洋海温异常的经向梯度相吻合. 研究表明, 西北太平洋正海温异常与热带中太平洋负海温异常之间的梯度是2021年7月华北地区降水异常偏多的主要原因, 该梯度使得西北太平洋反气旋及其南部的气旋北移, 汇合的偏东风将大量水汽从海洋输送到华北地区, 使得华北地区降水偏多. 同时, 太平洋海温异常的经向梯度可能在对流层低层触发异常的反向哈德利环流, 伴随着南风异常, 使得季风环流增强, 雨带偏北.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 2","pages":"Article 100444"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283423001435/pdfft?md5=8b73d0cb919e5f12dfbfbe6da3af2e8b&pid=1-s2.0-S1674283423001435-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135670576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recent urbanization increases exposure to humid-heat extreme events over populated regions of China","authors":"Huopo Chen ,&nbsp;Wenyue He ,&nbsp;Shuhui Zhang","doi":"10.1016/j.aosl.2023.100409","DOIUrl":"10.1016/j.aosl.2023.100409","url":null,"abstract":"<div><p>Extreme-heat research has largely focused on dry heat, while humid heat, which presents a major societal impact, especially on human health, remains relatively understudied. Previous studies have revealed that a wet-bulb temperature (TW) of 35 °C marks our upper physiological limit, and much lower values also have serious health impacts. Our evaluations from observations showed that the daily maximum TW values over China have been scarcely reported above 35 °C, but humid-heat extreme days of TW above 30 °C have been reported each year during the past four decades, being mainly centered over the highly populated regions, including East China, South China, and the Sichuan basin. Further analyses indicated that the recent rapid urbanization process in China has amplified the societal impacts of humid-heat extremes, and land exposure to humid heat over urban regions is expected to increase at a faster rate than other regions of China. This suggests increasing risks of humid-heat extremes on human health in big cities of densely populated regions due to rapid urbanization. As indicated here, the population of China has become increasingly exposed to such extremes, with a strong increasing tendency of about 3100 persons per day per year since 2000.</p><p>摘要</p><p>目前对于高温的研究主要侧重于干热, 针对湿热的研究相对较少, 但它通常会造成更大的社会影响, 尤其对人体健康的威胁. 已有研究证实, 当环境湿球温度超过35 °C时, 它会破坏人体正常生理代谢, 进而威胁人体健康. 本研究指出在过去四十年, 中国区域日最高湿球温度几乎没有超过35 °C, 但部分地区日最高湿球温度超过了30 °C, 主要集中在中国的人口密集区, 包括华东, 华南和四川盆地等. 进一步分析发现, 中国区域近期的快速城市化加剧了极端湿热事件的社会影响, 城市地区暴露于极端湿热事件的范围的增加速率明显大于其他地区, 这也意味着快速城市化使得人口密集区暴露于极端湿热事件的风险明显增加. 初步估算指出, 自2000年以来, 中国区域暴露于极端湿热事件的人口数以每年每天约3100人次的速率显著增加.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 2","pages":"Article 100409"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283423000958/pdfft?md5=f05ff4372a37e50f093e88e2e5943a28&pid=1-s2.0-S1674283423000958-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48750216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Westward extension of summer atmospheric circulation over the North Pacific after the 1990s","authors":"Guowa Tang ,&nbsp;Tingting Han ,&nbsp;Botao Zhou ,&nbsp;Qiushi Zhang","doi":"10.1016/j.aosl.2023.100408","DOIUrl":"10.1016/j.aosl.2023.100408","url":null,"abstract":"<div><p>This paper documents the westward extension of the summer atmospheric circulation over the North Pacific (NP circulation) around the 1990s and investigates the possible reason, based on the North Pacific index. The NP circulation was centered in the Northeast Pacific during 1961–1983 and in the central North Pacific during 1994–2016. Further results show that the westward movement of the NP circulation was closely linked with an intensification of the relationship between the NP circulation and the previous spring sea surface temperature of the midlatitude North Pacific (SST_NP) after the 1990s. The spring SST_NP anomalies exerted considerable impacts on surface heat flux (i.e., sensible heat flux and latent heat flux) and vertical motion anomalies over the central North Pacific during the following summer, facilitating a westward shift in the summer NP circulation. Additionally, the interannual variability of the sea level pressure over the central North Pacific increased after the 1990s, which was likely a contributing factor to the westward extension of the NP circulation.</p><p>摘要</p><p>本文研究了20世纪90年代前后夏季北太平洋大气环流 (NP circulation) 向西扩展, 并探讨了其可能的原因. 结果表明, 在1961–1983年期间NP中心主要位于东北太平洋, 而在1994–2016年期间NP中心发生西移, 至北太平洋中部. 进一步分析指出, 90年代以后NP活动中心的西移和春季中纬度北太平洋海温(SST_NP) 与NP关系的加强有关. 春季SST_NP异常通过引起后期夏季北太平洋中部地表热通量(即感热通量和潜热通量)和垂直运动异常, 有利于NP活动中心向西移动. 此外, 20世纪90年代以后, 北太平洋中部海平面气压的年际变率增加, 这可能是NP向西扩展的另一原因.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 2","pages":"Article 100408"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283423000946/pdfft?md5=1eadc2585b56705ddecf3f3ac9c13c6e&pid=1-s2.0-S1674283423000946-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45672548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate prediction of the seasonal sea-ice early melt onset in the Bering Sea","authors":"Baoqiang Tian ,&nbsp;Ke Fan","doi":"10.1016/j.aosl.2023.100417","DOIUrl":"10.1016/j.aosl.2023.100417","url":null,"abstract":"<div><p>Based on the impact of large-scale circulation anomalies on sea-ice melting, this paper develops a statistical forecasting model for the seasonal sea-ice early melt onset (EMO) in the Bering Sea using the interannual increment prediction method. The prediction model considers three physically meaningful predictors: the January Beaufort High (P1-H500), the November sea-level pressure (P2-SLP) over eastern Siberia, and the November snow cover over the eastern European Plain (P3-Snowc). P1-H500 can influence the sea surface temperature (SST) anomaly in the Bering Sea through ocean–atmosphere interactions, and this SST anomaly can persist from January to March. Subsequently, it affects the EMO in the Bering Sea. P2-SLP exhibits a close association with the east part of the midlatitude North Pacific SST in November. The colder midlatitude North Pacific SST anomalies, which persist from November until January and February of the following year, will be accompanied by warmer SST anomalies in the Bering Sea, which result in a decreased sea-ice extent and a later-than-usual EMO. The Arctic dipole anomaly in January is one of the ways in which P3-Snowc affects the EMO in the following year. The predicted EMO shows good agreement with the observed EMO in the cross-validation test for 1981–2022, with a temporal correlation coefficient of 0.45, exceeding the 99% confidence level. The prediction accuracy of the prediction model for positive and negative abnormal years of EMO is 60% and 41%, respectively.</p><p>摘要</p><p>基于大尺度环流异常对海冰消融的影响过程, 本文采用年际增量预测方法研制了白令海季节性海冰早期消融开始日期(EMO)的统计预测模型. 预测模型选取了3个具有明确物理意义的预测因子: 1月波弗特高压, 前期11月东西伯利亚地区海平面气压, 以及11月东欧平原积雪覆盖率. 1月波弗特高压可以通过海气相互作用影响白令海地区海温异常, 该海温异常能够从1月持续到3月, 进而影响白令海EMO. 11月东西伯利亚地区海平面气压与11月至次年2月北太平洋中纬度东部海温密切相关. 伴随着北太平洋中纬度东部冷海温异常的出现, 白令海地区会出现暖海温异常, 进而导致白令海海冰范围减少, EMO较晚. 1月北极偶极子异常是11月东欧平原积雪覆盖率影响次年白令海EMO的桥梁之一. 1981−2022年的交叉检验结果表明: 统计模型对白令海EMO具有较好的预测能力, 预测与观测的EMO之间时间相关系数达到了0.45, 超过了99%的置信水平. 统计模型对白令海EMO正常年份和异常年份的预测准确率分别为60%和41%.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 2","pages":"Article 100417"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283423001034/pdfft?md5=811012057c575862d0c9e49a13d1d654&pid=1-s2.0-S1674283423001034-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48941926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pollution characteristics of peroxyacetyl nitrate in karst areas in Southwest China","authors":"Songjun Guo ,&nbsp;Xu Wei ,&nbsp;Hongjiao Li ,&nbsp;Wen Qin ,&nbsp;Yijun Mu ,&nbsp;Jiongli Huang ,&nbsp;Chuan Nong ,&nbsp;Junchao Yang ,&nbsp;Dabiao Zhang ,&nbsp;Hua Lin ,&nbsp;Jingying Mao ,&nbsp;Zhaoyu Mo","doi":"10.1016/j.aosl.2023.100442","DOIUrl":"10.1016/j.aosl.2023.100442","url":null,"abstract":"<div><p>In recent years, the issue of photochemical pollution in the Guangxi region of China has escalated considerably. However, there remains a notable dearth of related research in this area. Peroxyacetyl nitrate (PAN), recognized as a reliable indicator of photochemical pollution, was the focus of our study. This study marks the inaugural observation of PAN levels in Guilin, a renowned world tourist destination situated in a typical karst region, during 1–31 October 2021. Throughout this observation period, the average volume concentration of PAN ranged from 0.087 to 2.559 ppb, which was 3.61 times higher than the South China background site of the Nanling. Combined with meteorological factors and potential source analysis, the causes of a typical high-value PAN process were explored during 24–29 October. The results showed that, during this high-value PAN event, pollution primarily originated from the horizontal transport of polluted air masses and the descent of high-altitude air masses from Hunan Province in the northeast direction. Additionally, the meteorological conditions, including high temperatures, intense radiation, and low humidity, fostered local PAN formation. Notably, traffic emissions emerged as the primary source of PAN's locally generated precursor volatile organic compounds. Furthermore, we estimated the background concentration of O₃ to be approximately 20.347 ppb based on PAN monitoring data, constituting 44.4% of the total O₃ levels in Guilin City. This study offers valuable insights for addressing and mitigating photochemical pollution in southern Chinese cities, while providing a theoretical foundation for regional pollution control efforts.</p><p>摘要</p><p>桂林是世界著名的地处喀斯特地区的旅游胜地, 其光化学污染问题日益严重.过氧乙酰硝酸酯(PAN)被认为是光化学污染的可靠指标, 也是本研究的重点. 本研究于2021年10月首次观测了桂林的PAN的浓度为0.087–2.559 ppb, 同时探讨了PAN典型高值过程的成因. 此次污染主要来源于东北方向污染气团的水平和高空输送, 同时, 高温, 强辐射和低湿度等气象条件也促进了本地PAN的形成. 本研究同时估算了桂林市的O₃背景浓度为20.347 ppb.这项研究为城市的光化学污染控制工作提供了理论基础.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 2","pages":"Article 100442"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283423001411/pdfft?md5=62b9396a1cd2fa6d8a16c0410de43d8b&pid=1-s2.0-S1674283423001411-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136127690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impacts of monsoon break events in the western North Pacific on the cross-equatorial flows over the Maritime Continent","authors":"Xiaoxuan Zhao ,&nbsp;Minghao Bi ,&nbsp;Ke Xu ,&nbsp;Jianqi Sun ,&nbsp;Riyu Lu","doi":"10.1016/j.aosl.2023.100443","DOIUrl":"10.1016/j.aosl.2023.100443","url":null,"abstract":"<div><p>This study examines the possible impacts of western North Pacific (WNP) monsoon break events on the cross-equatorial flows (CEFs) over the Maritime Continent using daily data from ERA5 for 1979–2020. It reveals that WNP monsoon break events can cause significant weakening of CEF in the both upper and lower troposphere, i.e., weaker southerlies in the lower level and northerlies in the upper level. These CEF anomalies are associated with a baroclinic structure of circulation anomalies over the WNP, consisting of upper-level cyclonic and lower-level anticyclonic anomalies. Furthermore, statistical analysis indicates that WNP monsoon break events correspond more closely to weakening of upper-level CEF, in comparison with lower-level CEF: 92% of WNP monsoon break events correspond to upper-level CEF weakening, while this decreases to 70% for lower-level CEF. This relatively lower proportion for lower-level CEF is largely attributable to the impact of the warm phase of ENSO.</p><p>摘要</p><p>本文利用ERA5逐日再分析资料, 探讨了1979–2020年间西北太平洋季风中断事件对海洋性大陆越赤道气流的影响. 合成结果表明, 西北太平洋季风中断事件会造成高, 低空越赤道气流减弱, 即高层南风异常, 低层北风异常, 与此相关的环流异常表现为西北太平洋高层气旋, 低层反气旋的斜压结构. 特别的是, 西北太平洋季风中断对高空越赤道气流的影响更为显著, 92%的季风中断事件都导致高空越赤道气流减弱, 而只有70%的事件造成低空越赤道气流减弱, 这是由于低空越赤道气流同时还受到赤道中东太平洋海温异常的调控.</p></div>","PeriodicalId":47210,"journal":{"name":"Atmospheric and Oceanic Science Letters","volume":"17 2","pages":"Article 100443"},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674283423001423/pdfft?md5=92df2842db1c13299954a89869a557b5&pid=1-s2.0-S1674283423001423-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135763516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}