汾渭平原CUACE模式空气质量预报性能的检验订正及环境评估

利用2019年1—6月地面环境监测资料和PM_2.5气象条件评估指数，结合滚动偏差订正方法，对汾渭平原CUACE空气质量预报产品进行了检验订正，并对气象条件和污染减排影响进行了评估。结果表明：CUACE模式对空气质量指数(AQI)、PM_2.5和SO₂浓度预报值较接近观测值，PM₁₀、CO和NO₂预报值小于观测值，O₃预报值大于观测值；对首要污染物O₃和PM_2.5及重度和严重等级污染的预报的TS评分最高，漏报率和空报率最小，预报偏差最接近1；滚动偏差订正方法对改善CUACE空气质量预报效果较为明显，尤其是对PM₁₀、O₃和NO₂改善最为明显；汾渭平原2019年上半年气象条件变化使PM_2.5浓度较2018年同期和过去5年同期分别上升了18.26%和11.18%，减排措施使PM_2.5浓度较2018年同期和过去5年...     

彭州市大气污染物浓度变化特征研究

本文利用2017年彭州市大气污染物(SO₂、NO₂、O₃、CO、PM₁₀、PM_2.5)小时浓度数据并结合地面气象观测资料,统计分析了该地区大气污染物浓度的演变规律及影响因素。结果表明:该地区细粒子(PM₁₀和PM_2.5)污染较为严重,O₃次之,其它污染物浓度水平则低于国家新二级标准限值。观测期间,各污染物浓度表现出明显的日变化与季节变化,其中SO₂、O₃呈单峰型日变化,NO₂、CO和细粒子则呈双峰型日变化;污染物浓度的季节变化基本表现为冬高夏低、春秋次之的变化特征(O₃为夏高冬低),并且固态污染物(PM₁₀、PM_2.5)与气态污染物(NO₂、CO)之间有显著的相关性。在污染物浓度与气象要素相关性分析中表明,湿度对于污染物浓度的影响整体上要弱于温度和风速,除了O₃与温度、风速呈正相关外,其它污染物与两者均呈负相关。除此以外,风向对于当地各种大气污染物的积累与清除也有直接的影响。      

基于极端随机树方法的WRF-CMAQ-MOS模型研究

随着城市化、工业化的快速发展,空气污染已经成为了公众最关注的问题之一。为了提高空气质量预报的准确度,以多尺度空气质量模型（Community Multi-Scale Air Quality,CMAQ）为工具,结合中尺度WRF（Weather Research and Forecast Model）气象预报数据、气象观测数据、污染物浓度观测数据,基于极端随机树方法建立了WRF-CMAQ-MOS（Weather Research and Forecast Model-Community Multi-Scale Air Quality-Model Output Statistics）统计修正模型。结果表明,结合WRF气象预报的CMAQ-MOS方法明显修正了由于模型非客观性产生的模式预报偏差,提高了预报效果。使用线性回归方法不能获得较好的优化效果,选取极端随机树方法和梯度提升回归树方法对模型进行改进和比较,发现极端随机树方法对结合WRF气象要素的CMAQ-MOS模型有较大的提升。针对徐州地区空气质量预报,进一步使用基于极端随机树方法的WRF-CMAQ-MOS模型对2016年1、2、3月的空气质量指数（AQI）及PM_2.5、PM₁₀、NO₂、SO₂、O₃、CO六种污染物优化试验进行验证,发现优化效果最为明显的两种污染物分别是NO₂及O₃,2016年1、2、3月整体相关系数NO₂由0.35升至0.63,O₃由0.39升至0.79,均方根误差NO₂由0.0346减至0.0243 mg/m3,O₃由0.0447减至0.0367 mg/m3。文中发展的WRF-CMAQ-MOS统计修正模型可以有效提升预报精度,在空气质量预报中具有很好的应用前景。      

银川市主要污染物变化特征及其关系研究

利用2013-2019年银川市主要污染物浓度数据,分析了近年来银川市主要污染物浓度变化特征,并运用主成分分析法对主要污染物之间的关系进行研究。结果表明：近年来银川市主要污染物浓度除O₃逐年呈上升趋势外,其他均呈下降趋势;市区站O₃浓度较郊区背景站低,其他污染物市区较郊区背景站高;市区站PM₁₀和PM_2.5浓度超国家二级标准;除O₃浓度夏季高,冬季低外,其他污染物冬季高,夏季低;CO、NO₂、PM₁₀、PM_2.5浓度呈"双峰型"日变化特征,O₃和SO₂呈"单峰型"日变化特征。银川市主要污染物NO₂浓度与CO和O₃相关性显著,PM₁₀和PM_2.5之间相关性显著;污染物第一主成分是NO₂、CO和O₃,方差贡献率达到50%以上,加之银川市O₃浓度逐年呈升高趋势,表明近年来银川市大气光化学污染增加。     

利用PCA-kNN方法改进广州市空气质量模式PM2.5预报

为了提高广州市PM_2.5客观预报能力,采用主成分分析结合机器学习算法k近邻（PCA-kNN）方法,基于空气质量模式（CMAQ）预报产品、中尺度天气模式（GRAPES-MESO）预报产品和2017年上半年广州PM_2.5观测实况,试验确定PCA-kNN方法的最佳参数方案,建立广州市空气质量模式PM_2.5预报客观订正方法。结果表明:与CMAQ模式的PM_2.5预报相比,在第1~3天预报时效上,PCA-kNN订正结果与实况的相关系数分别提高20%、15%、29%,均方根误差分别降低17%、16%、20%,平均偏差更接近0,PM_2.5浓度等级TS评分接近或优于CMAQ预报,PCA-kNN订正结果优于CMAQ预报。机器学习算法PCA-kNN方法可有效改进广州市空气质量模式PM_2.5预报,本研究对其他地区、其他污染物客观预报研究具有借鉴意义。      

基于GRAPES-CMAQ的中山市空气质量预报系统预报效果评估

对基于GRAPES-CMAQ模式的广东省中山市空气质量预报系统2016年的AQI等级、首要污染物、PM_2.5和O₃浓度预报数据进行检验评估。预报系统对中山市全年的AQI等级24小时预报TS评分为0.66, TS评分在6—7月最高。当实况AQI等级为一级, TS为0.84, 当空气质量变差时, TS明显下降, 说明模式目前对空气重污染事件的预报能力不足。模式对中山市的主要污染物O₃、PM和NO₂的预报TS评分分别为0.21、0.24和0.24, 其中对O₃和NO₂的漏报率达到0.78和0.76, 而PM的空报率高达0.71。预报系统对PM_2.5的浓度预报总体略偏高, 相关系数为0.59, 但在霾污染较严重的月份中预报效果并不稳定。对O₃的预报全年相关系数达到0.7, 且在O₃污染较严重的7—11月, 相关系数均能达到0.5以上, 但这几个月的O₃预报浓度均比实况明显偏低。从气象预报入手分析预报系统对10月2—7日中山市一次连续O₃污染过程漏报的原因, 发现GRAPES模式对这段时间内整个珠三角地区日间降水的预报范围偏大, 强度偏强, 且预报的地面风速也比实况要偏大, 导致模拟O₃浓度比实况明显偏低。      

河源市空气质量首要污染物特征及其与气象条件的关系

基于2017-2019年河源市空气质量数据,分析了河源市首要污染物的年际变化特征,同时利用2019年东埔国控站点的首要污染物与气象要素进行了相关性分析,并以典型污染日为案例,分析了气象条件对污染过程的影响。结果表明：2017-2019年细颗粒物（PM_2.5）污染日比重大幅度降低,以臭氧（O₃）为首要污染物的污染日逐年增加,污染形式逐渐从颗粒物污染向臭氧污染发生转变。O₃浓度与温度和湿度分别呈正负相关关系,高浓度O₃主要出现在（20-30℃,25%-55%）阈值之间,在吹西北偏北风时O₃浓度也较高。PM_2.5和PM₁₀与湿度也呈负相关关系,温度与湿度组合在（8-13℃,40%-55%）范围内时两者容易同时出现高值;在夏季PM_2.5和PM₁₀还与温度具有较强的正相关关系,这意味着高温情况下河源有出现颗粒物与O₃复合污染的可能。河源市典型污染日具有风速较小局部扩散不利的特征,低温低湿条件下容易出现PM_2.5污染,且主要受到区域的传输影响;而高温低湿条件下容易发生O₃污染,且较高的前体物浓度容易加剧O₃的本地污染。     

银川大气污染物浓度变化特征及其与气象条件的关系

利用2013年银川地区6个监测点污染物质量浓度和同期气象要素数据,对区域内污染物浓度变化特征及其与气象条件的关系进行分析。结果表明：银川市区PM10年均值超标0.7倍,PM_2.5年均值超标0.4倍,SO₂和NO₂也有一定程度超标,CO和O₃未超标|1、2、11月和12月为SO₂、NO₂、PM₁₀、PM_2.5、CO质量浓度较高月,O₃浓度最高月为5月,次高月为10月|9:00-12:00和21:00-00:00是SO₂、NO₂、PM₁₀、PM_2.5和CO质量浓度较高的两个时段,O₃浓度一般于15:00达到最大;6类污染物普遍表现出季节性的准7 d周期和全年性的准30 d周期|空气质量状况良的频率是56 %,轻度污染26 %,优仅为12%;首要污染物以PM₁₀、PM_2.5和SO₂为主|风速与SO₂、NO₂和CO具有良好的负相关关系,与O₃则呈显著正相关关系,风速对PM₁₀和PM_2.5影响较复杂,当风速小于某一值时,有利于PM₁₀和PM_2.5扩散,当风速达到一定程度后,又会导致PM₁₀和PM_2.5浓度的增加|降水对污染物有较好的冲刷作用,且对SO₂的清除作用最明显,对O₃的清洁作用最弱。     

2018年冬季鲁西北大气污染特征及影响因子分析

利用2018年12月至2019年2月滨州、德州和聊城PM_2.5、PM₁₀、NO₂、SO₂、CO和O₃逐日质量浓度及其对应的气象资料,分析了鲁西北大气污染特征和影响因子。结果表明：2018年冬季鲁西北大气污染比较严重,聊城、德州和滨州轻度及以上污染天数分别占61%、60%和54%,重度以上染污天数分别占24%、11%和9%;首要污染物均为PM_2.5、PM₁₀和NO₂,其中PM_2.5占60%以上。PM_2.5、PM₁₀、SO₂、NO₂和CO日变化呈双峰双谷型,谷值分别出现在04-07时和15-17时,且下午比清晨更低,峰值出现在上午和下午交通高峰期后2-3 h,且峰值上午大于下午;O₃呈单峰型分布,09时出现极小值,18-19时出现极大值。PM_2.5是鲁西北主要的首要污染物,与PM₁₀、CO、NO₂均为显著正相关,并通过0.01水平显著性检验,与NO₂的相关性在低相对湿度(< 60%)时大于高相对湿度(≥ 60%),与CO的相关性在高相对湿度时大于低相对湿度;污染时段(PM_2.5>75 μg·m^-3)的平均相对湿度和平均温度明显大于清洁时段(PM_2.5 ≤ 75 μg·m^-3),清洁时段风速和气压比污染时段明显偏大。     

四川盆地最大混合层厚度与大气污染物浓度的关系

基于2015～2018年四川盆地温江站、宜宾站、达川站和沙坪坝站的探空和地面观测资料以及同期AQI、6种主要污染物(SO₂、NO₂、CO、O₃、PM_2.5、PM₁₀)质量浓度资料,使用逐步逼近法计算得到了四川盆地成都、宜宾、达州、重庆四城市的每日最大混合层厚度(Maximum mixing depth,MMD),并对其时间变化特征及其与各种污染物浓度之间的关系进行了分析。结果表明,四川盆地年平均MMD约1200m。季节变化明显,春夏高、秋冬低。9月至次年1月MMD相对较小。相关分析显示,剔除降水影响后,MMD与AQI、PM_2.5、PM₁₀、SO₂、NO₂、CO浓度均呈负相关,而与O₃浓度显著正相关。在污染最为严重的冬季,MMD明显低于春夏季节。MMD越小、颗粒物浓度越高。低MMD大大压缩了近地面污染物的扩散空间,污染物在有限的空间内不断累积、浓度增大。      

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms.     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region.     

Could the Recent Taal Volcano Eruption Trigger an El Ni?o and Lead to Eurasian Warming?

正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment.     

VARIABILITY OF INTER-ANNUAL RELATIONSHIP BETWEEN INDIAN OCEAN DIPOLE AND HUAXI REGION’S AUTUMN PRECIPITATION

The moving-window correlation analysis was applied to investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the synchronous autumn precipitation in Huaxi region, based on the daily precipitation, sea surface temperature (SST) and atmospheric circulation data from 1960 to 2012. The correlation curves of IOD and the early modulation of Huaxi region’s autumn precipitation indicated a mutational site appeared in the 1970s. During 1960 to 1979, when the IOD was in positive phase in autumn, the circulations changed from a “W” shape to an ”M” shape at 500 hPa in Asia middle-high latitude region. Cold flux got into the Sichuan province with Northwest flow, the positive anomaly of the water vapor flux transported from Western Pacific to Huaxi region strengthened, caused precipitation increase in east Huaxi region. During 1980 to 1999, when the IOD in autumn was positive phase, the atmospheric circulation presented a “W” shape at 500 hPa, the positive anomaly of the water vapor flux transported from Bay of Bengal to Huaxi region strengthened, caused precipitation ascend in west Huaxi region. In summary, the Indian Ocean changed from cold phase to warm phase since the 1970s, caused the instability of the inter-annual relationship between the IOD and the autumn rainfall in Huaxi region.     

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on     

COMPARATIVE ANALYSIS OF VARIOUS DATA OF AIR–SEA TEMPERATURE DIFFERENCE AND ITS VARIATION ACROSS SOUTH CHINA SEA IN THE PAST 35 YEARS

Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter.     

全球贸易隐含碳变化及其影响分析

基于最新的GTAP8 (Global Trade Analysis Project）数据库,使用投入产出法,分析了2004年到2007年全球贸易变化下南北集团贸易隐含碳变化及对全球碳排放的影响。结果显示,随着发展中国家进出口规模扩张,全球贸易隐含碳流向的重心逐渐向发展中国家转移。2004年到2007年,发达国家高端设备制造业和服务业出口以及发展中国家资源、能源密集型行业及中低端制造业出口的趋势加强,该过程的生产转移导致全球碳排放增长4.15亿t,占研究时段全球贸易隐含碳增量的63%。未来发展中国家的出口隐含碳比重还将进一步提高。贸易变化带来的南北集团隐含碳流动变化对全球应对气候变化行动的影响日益突出,发达国家对此负有重要责任。     

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正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.SUBMISSIONAll submitted