江苏地区连续性雾霾天气的污染物浓度变化和特征分析

针对2013年1月江苏淮安地区发生的一次连续性雾霾天气过程,分析该天气过程中PM10和PM2.5的质量浓度演变特征、能见度与气象要素之间的关系、中低层环流特征以及污染物来源。结果表明:雾霾期间PM10和PM2.5质量浓度最低值出现在05:00至07:00(北京时间,下同)和13:00至17:00,最高值出现在21:00至23:00,PM10和PM2.5质量浓度并非同时达到极大值;持续变化较小的气压梯度、较低的风速、相对湿度的增大以及PM2.5和PM10质量浓度的增高是雾霾发生发展的必要条件;能见度与气压、相对湿度、PM2.5质量浓度的相关性较好,建立回归方程,对能见度的整体变化趋势拟合效果较好;高空环流形势平稳、中低层的暖平流、持续稳定少动的地面高压场分布为雾霾天气的持续发生发展提供了有利的形势背景;稳定的层结结构、中低层偏东及偏东北方向气团的输送、本地污染源以及严重的空气污染是此次过程中能见度偏低、霾天数较多的主要原因。     

一次持续性雾霾天气过程的阶段性特征及影响因子分析

应用常规与非常规气象观测资料及PM2.5浓度监测资料,对2013年1月20~24日山西区域一次持续性雾霾天气过程进行分析。研究发现：（1）本次雾霾天气过程具有明显的阶段性特征。2013年1月20日14时至23日11时,由于相对湿度的变化导致了3次轻雾转大雾过程;23日14~20时,由于PM2.5浓度的增大经历了1次轻雾转霾的天气过程。（2）地面弱的气压场和较小的风速以及PM2.5浓度的上升和相对湿度的增大为本次持续性雾霾天气过程的形成和发展提供了有利条件。（3）边界层逆温的存在是雾霾低能见度过程形成的必要条件,边界层有逆温层而不出现雾霾天气的条件是：相对湿度〈50%,PM2.5日均值浓度〈75μg·m-3;逆温层下相对湿度的大小是区别雾和霾天气的指标。（4）相对湿度和PM2.5是决定能见度大小的关键因子,其对能见度的影响体现出明显的阶段性特征,当相对湿度〈90%时,PM2.5浓度对能见度的作用强于相对湿度,是影响能见度变化的主要因子,但随着相对湿度的增大,其对能见度的影响相对增强,当能见度降至1 km以下时,相对湿度成为影响能见度变化的主要因子。     

天津市东丽区一次持续性雾霾天气过程的特征及影响要素分析

基于常规气象观测资料和PM_2.5浓度资料,分析了2019年1月10—14日天津市东丽区出现的一次持续性雾霾天气特征及其成因。结果表明：此次雾霾天气具有明显的阶段性特征,高空平直西风环流、中层暖脊和地面弱气压场为此次雾霾天气出现提供了有利的天气形势。轻雾和霾阶段,能见度变化更易受到相对湿度的影响;而雾阶段,能见度变化更易受到风速的影响。PM_2.5浓度与地面气象因子关系密切,与能见度、风速负相关,与相对湿度正相关。当其他气象条件稳定,且周边地区污染物浓度较高时,近地面风向转变,对本地区雾霾的出现起到关键性作用。     

一次热带气旋外围下沉气流造成的珠三角地区连续灰霾天气过程分析

通过研究广州番禺大气成分站的气溶胶颗粒物质量浓度(PM10和PM2.5)、黑碳浓度、臭氧浓度等大气成分要素,常规地面气象要素以及气流后向轨迹、垂直速度、位温和边界层高度等资料,结合热带气旋路径和天气形势对热带气旋外围下沉气流造成的一次珠三角地区连续灰霾天气过程的形成原因和变化特征进行了分析.由于热带气旋移动缓慢,其外围下沉气流使珠三角地区形成了层结稳定、静小风和晴朗少云的天气条件,导致珠三角地区出现连续的灰霾天气.在这次灰霾过程中,气溶胶粒子来源以本地源为主,并且以细粒子为主,PM2.5占PM10的比例接近70％,黑碳浓度占PM10的6.0％左右;在凌晨,由于边界层高度降至最低,垂直扩散条件差,同时相对湿度也达到峰值,气溶胶吸湿增长明显,易出现能见度低值.     

2005—2017年白云机场能见度变化特征及其与影响因子关系研究

利用广州白云机场2005-2017年的大气能见度、相对湿度、风速、气温等要素的逐时观测资料,结合花都花东站2012-2017年PM2.5浓度的逐时观测数据,分析了近年来白云机场能见度的变化特征,探究了能见度与气象要素、大气污染物之间的关系。结果表明:2005-2017年白云机场能见度呈逐年增大趋势,低能见度出现次数总体呈减少趋势。2-4月是机场低能见度时期,7月能见度最大。能见度日变化显著,最低能见度通常出现在清晨,午后明显好转。白云机场能见度与相对湿度、PM2.5浓度呈负相关关系,与风速、气温成正相关关系,其中PM2.5浓度对能见度的影响最明显。当相对湿度小于80%时,能见度下降得较为缓慢;而当相对湿度超过80%时,能见度急剧降低。相对湿度越大,出现低能见度所需的PM2.5浓度值就越小。地面风速在0~4 m·s-1时,相对湿度越大,能见度随风速的增长趋势越显著。     

北京地区一次持续性雾霾天气分析

2015年11月27日至12月1日,北京地区出现了一次十分严重的雾、霾天气过程。综合分析此次雾、霾天气过程的天气形势、加密自动站、探空、风廓线雷达以及连续观测的PM2.5资料,结果表明:本次雾、霾过程,能见度的恶化与天气形势、PM2.5持续性波动增长、相对湿度增加、逆温出现频率高、近地层风速小及近地面偏南风输送有密切关系:(1)此次雾、霾过程期间,华北地区较长时间被地面高压后部的弱气压场和低压辐合区控制,地面风速和近地层风速较小,北京大部分地区处于弱的偏南风或偏东风控制中,很不利于污染物的水平扩散;(2)地面增湿趋势明显,低层偏南和偏东气流将水汽和上游污染物向北京地区输送,加之29日气温明显回升,导致地面积雪融化,近地面相对湿度增加,有时接近饱和;(3)边界层逆温一直存在,很不利于污染物的垂直扩散。     

连续雾霾天气污染物浓度变化及天气形势特征分析

利用MICAPS资料、地面观测资料、NCEP资料和衡水市环境监测站细颗粒物(PM2.5)及PM10浓度资料,对2013年1月衡水市出现的连续雾霾天气从PM10及细颗粒物浓度演变、雾霾天气污染物浓度与地面要素关系、中低层环流形势特征进行了分析,结果表明:1)雾霾天气期间06:00(北京时间,下同)至07:00和16:00至21:00为PM10和细颗粒物浓度较低时段,PM10最大值出现在15:00,细颗粒物最大值出现在02:00,两者并不同时达到极值。2)雾霾天气污染物浓度与地面湿度并不是简单的正相关或负相关关系,还和许多其它因素有关。3)衡水市污染源主要来源于工业污染源、扬尘污染、冬季燃煤采暖、局部污染源及区域性污染。4)雾霾天气相对湿度和能见度基本呈负相关,气压变化不大,风向频率最多为北到东北风,平均风速一般都在2 m/s以下。雾日时大部分时段为雾和霾的混合物。5)重污染日期间500 hPa为平直偏西气流或西北偏西气流,没有明显的槽脊活动。而污染较轻的时段500 hPa为明显的西北气流控制或有槽脊活动。6)雾霾天气期间大部分日数08:00在850hPa以下都存在逆温层;地面气压场偏弱,尤其河北平原一带基本为均压场。最后对雾霾天气影响及对策进行了简单探讨。     

2016年12月青岛一次持续重污染天气的观测分析与数值模拟

选取2016年12月17—22日青岛一次典型重污染天气,利用大气污染物监测结果、地面气象要素观测资料和欧洲中期天气预报中心（ECMWF）ERA5再分析数据对此次过程中大气污染物及气象场的变化特征进行分析。观测分析表明此次污染过程持续时间长达5 d以上,其中19—21日为重污染天气（PM 2.5 日均质量浓度ρ>150 μg·m-3）。根据气象场和PM2.5质量浓度变化特征,此次污染过程可分为3个阶段：17日02时—19日08时为青岛污染物累积阶段,研究区受西南风控制,PM2.5质量浓度逐渐上升,700 hPa等压面上高空槽的维持及槽前持续的南风、西南风有利于污染物累积,同时近地面相对湿度增加,是此次持续性重污染天气形成的重要条件;19日09时—20日20时为青岛污染维持加剧阶段,相对湿度大、风速很小,污染物扩散条件差,PM2.5质量浓度最高;20日21时—22日08时为青岛污染消散阶段,青岛对流层中下层及地面风速均增大并产生弱降水,有利于污染物扩散稀释和湿清除,PM2.5质量浓度逐渐降低。WRF-Chem数值模式能够较好地模拟出主要气象要素和青岛PM2.5 质量浓度的变化特征,模拟结果表明山东省内污染物排放贡献了青岛PM2.5的49.5%;污染物跨省输送对此次污染事件也有重要贡献,其中来自研究区以南的安徽和江苏的排放对青岛PM2.5的贡献率可达25.5%。     

哈尔滨一次灰霾天气污染物浓度变化及气象条件分析

2014年10月22-24日,哈尔滨地区发生了一次持续性的灰霾天气过程。本文利用气象观测资料和污染物浓度监测资料,分析了颗粒物的浓度演变特征、气象要素特征及产生持续性灰霾天气的可能原因。研究表明,该次过程中绝大部分时间能见度低于10 km,空气质量指数(AQI)指数最大时达到500。此次灰霾天气高空主要受偏西气流控制,环流较平直,过程前期地面受高压场后部影响,后期位于低压前部,灰霾期间风力较小,空气湿度条件较低,地面空气干燥;近地层虽然没有出现逆温,但气温垂直递减率较小,大气层结较稳定。     

2013年初江苏连续性雾-霾天气的特征分析

利用FNL资料、污染物颗粒浓度资料以及常规气象资料对2013年1月12—16日江苏地区的连续性雾 霾天气过程的环流形势、地面气象要素特征、大气边界层结构及大气污染状况等进行了分析。结果表明：高空形势变化平稳、中低层的暖平流配合稳定少动的地面气压场为雾 霾天气的发生提供了有利的环流形势;持续变化较小的气压梯度和较低的风速以及相对湿度的增大和PM2.5、PM10的浓度的变化为雾 霾形成和发展提供了条件;雾 霾期间低层都存在不同程度的逆温现象,混合层高度与AQI呈反相关关系,当混合层高度越低,AQI就越高,污染就越严重,能见度就越差;相对湿度的升高和PM2.5在污染物颗粒中的富集,是导致能见度下降和持续污染的首要原因,而强冷空气带来的大风降温是污染物颗粒被快速清除的重要动力机制;影响南京的污染物来源为：黄海、安徽地区、北方污染物的输送和本地的局地污染。     

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     

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。     

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.     

Retrieval of outgoing longwave radiation from COMS narrowband infrared imagery

Hourly outgoing longwave radiation(OLR) from the geostationary satellite Communication Oceanography Meteorological Satellite(COMS) has been retrieved since June 2010. The COMS OLR retrieval algorithms are based on regression analyses of radiative transfer simulations for spectral functions of COMS infrared channels. This study documents the accuracies of OLRs for future climate applications by making an intercomparison of four OLRs from one single-channel algorithm(OLR12.0using the 12.0 μm channel) and three multiple-channel algorithms(OLR10.8+12.0using the 10.8 and 12.0 μm channels; OLR6.7+10.8using the 6.7 and 10.8 μm channels; and OLR All using the 6.7, 10.8, and 12.0 μm channels). The COMS OLRs from these algorithms were validated with direct measurements of OLR from a broadband radiometer of the Clouds and Earth's Radiant Energy System(CERES) over the full COMS field of view [roughly(50°S–50°N, 70°–170°E)] during April 2011.Validation results show that the root-mean-square errors of COMS OLRs are 5–7 W m-2, which indicates good agreement with CERES OLR over the vast domain. OLR6.7+10.8and OLR All have much smaller errors(～ 6 W m-2) than OLR12.0and OLR10.8+12.0(～ 8 W m-2). Moreover, the small errors of OLR6.7+10.8and OLR All are systematic and can be readily reduced through additional mean bias correction and/or radiance calibration. These results indicate a noteworthy role of the6.7 μm water vapor absorption channel in improving the accuracy of the OLRs. The dependence of the accuracy of COMS OLRs on various surface, atmospheric, and observational conditions is also discussed.