沙尘表面非均相吸附系数不确定性及其影响的数值模式研究

本文从实验气溶胶样品、实验技术和分析方法三个方面对以往的实验室研究结果进行综合分析, 归纳总结出适合东亚地区沙尘气溶胶的非均相吸附系数γ的参考值, 并利用区域大气化学模式, 模拟研究了非均相吸附系数γ的不确定性对东亚地区沙尘气溶胶非均相化学过程的影响。为了研究非均相反应对γ的敏感性, 针对其中四种物质(HNO3、N2O5、O3和SO2) 的γ上限值和下限值, 分别进行了T-up (上限值) 和T-low(下限值)两个敏感实验; 针对相对湿度对HNO3和N2O5非均相吸附系数的影响进行了T-rh敏感实验。模拟结果与观测资料进行了对比分析, 结果表明模式可以比较好地反映气态物质、气溶胶浓度的演变过程和非均相反应过程。考虑非均相反应后模拟的硫酸盐和硝酸盐浓度与观测值更接近一些。采用γ参考值的模拟结果总体上比采用γ上限值和γ下限值更合理, 把γ系数作为相对湿度的函数来处理比作为常数处理更合理。沙尘气溶胶通过非均相化学反应, 可以使模拟区域内SO2、NOx和O3的平均浓度下降, 使硫酸盐和硝酸盐颗粒物浓度增加, 采用γ参考值计算得到3 km以下的上述物质的变化率分别为－3.44%、－5.92%、－1.75%、5.22%和23.25%, 显示沙尘表面非均相化学反应对大气化学成分特别是气溶胶有较大的影响; 不同γ取值对上述物质变化率有一定影响, 其中对硝酸盐和臭氧的影响较大, T-up和T-low 模拟结果之间可以相差13.4%和10.1%。     

黑碳气溶胶及其在气候变化研究中的意义

简单介绍了黑碳气溶胶的一般性质，着重叙述了黑碳气溶胶在大气辐射强迫中的特殊作用以及对气候变化的影响，概括介绍了国内外相关领域的研究现状，指出黑碳气溶胶在气候变化以及大气环境等领域中具有重大的研究价值和意义。     

区域海气耦合模式RIEMS2.0-POM2K模拟的黑碳气溶胶对东亚春夏气候的影响

黑碳气溶胶的辐射强迫及其对东亚的气候效应仍有较大不确定性,同时在黑碳气溶胶气候效应的研究中对海洋的关注较少。为了量化分析黑碳气溶胶直接辐射效应和分析其通过海气相互作用对东亚夏季风的影响,用区域海气耦合模式进行黑碳气溶胶离线模拟的敏感试验。试验结果表明:东亚晴空大气顶和地面的净辐射强迫在春季分别为1. 58 W·m~(-2)和~(-2). 75 W·m~(-2),在夏季分别为1. 68 W·m~(-2)和~(-2). 62 W·m~(-2)。受黑碳气溶胶辐射效应影响,大气变暖,大气热力稳定度增加,云量减少。春季黑碳气溶胶的"热泵效应"引起华南降水增加和夏季风提前爆发。夏季孟加拉湾海表降温,南支槽加深,引起华南降水增加;另外中纬度附近经向温度梯度增大,进而增强冷空气势力和水汽辐散,引起华北降水减少。华南降水正异常和华北降水负异常有利于"南涝北旱"。黑碳气溶胶辐射效应能通过海气相互作用增加热带海表温度,减小经向温度梯度和海陆热力差异,进而减弱夏季风。此外,黑碳气溶胶辐射效应也能增强局域哈德莱环流及北风,进而减弱夏季风。     

黑碳气溶胶的气候效应和拓展的研究领域

 黑碳气溶胶不仅是全球变暖的重要影响因子，也可能对气候系统的多个参数产生影响，如大气环流、云和降水等。随着研究的深入，与黑碳有关的研究领域已经拓展到黑碳气溶胶与碳循环和大气环流的相互作用、黑碳表面与活性气态物种间的相互作用等方面。在评述国内外有关研究新进展的基础上，展望了黑碳气溶胶未来的研究领域。     

黑碳气溶胶对我国区域气候影响的数值模拟

利用区域气候模式RegCM3模拟研究了黑碳气溶胶对我国区域气候的影响。以2000年1、4、7、10月为代表,计算分析了黑碳气溶胶的辐射强迫作用、对大气温度和降水的影响及其季节变化特征。模拟结果显示：黑碳气溶胶在大气层顶产生正的辐射强迫,在地表产生负的辐射强迫;黑碳气溶胶的加入使中国大陆地区地面温度发生明显变化,并呈现显著的季节特征,即1月大部分地区的地面温度均有升高;7月北方增温、南方降温;4月和10月地面温度的变化不明显。模拟结果也表明,黑碳气溶胶的排放使我国长江中下游等南方地区夏季降水增加,而北方部分地区降水减少。     

"黑碳的农业与生活源排放对东亚气候、空气质量的影响及其气候-健康效益评估"项目中期研究进展

国家重点研发计划“黑碳的农业与生活源排放对东亚气候、空气质量的影响及其气候-健康效益评估”课题的中期研究进展可归纳如下:1)针对观测和实验平台,课题组进行了针对飞机气路的重新设计和改装,加装了用于航测的大气黑碳(BC)、气溶胶光学、细颗粒物粒径谱、颗粒物组分及气体组分来源示踪相关仪器,对飞机设备进行了质量控制,并设计了针对课题研究的新飞行方案。搭建了多套源排放模拟燃烧实验平台和监测系统。2)开展了基于飞机和飞艇的针对华北、华中、长三角及山东地区的黑碳垂直廓线观测。通过空地联合观测,捕捉到了华北和华中等地跨区域的黑碳大气传输过程,探讨了传输的机制。3)组织了多次农村能源消耗调查。基于室内实验初步研究了民用燃料(煤和生物质)排放气溶胶的数浓度和单颗粒气溶胶(包括黑碳)组成、混合状态、实时演化特性。初步构建了中国民用燃煤和生物质燃烧的多污染物(包括黑碳)1 km×1 km排放清单。4)建立了黑碳的光学特性和混合特性模型。采用在线大气化学耦合模式(WRF-Chem)针对黑碳气溶胶对气象要素和边界层发展的影响进行模拟,探讨了黑碳-边界层相互作用机制对地面臭氧浓度的影响,揭示了黑碳对空气污染加剧/减弱影响的物理和化学机制。改进了地球系统模式,为后期开展黑碳气溶胶辐射效应的研究打下了坚实的技术基础。5)在北京和成都市开展了黑碳浓度对居民中不同类人群的呼吸及循环系统死亡率的影响研究,开展了黑碳浓度对居民急诊就诊人数的影响研究,分析了黑碳的健康效应。     

人为气溶胶对中国东部冬季风影响的模拟研究

采用美国国家大气研究中心(NCAR)的公共大气模式CAM5.1研究了人为气溶胶排放增加对中国东部冬季风的影响,同时通过对比中国东部地区不同人为气溶胶排放源的敏感性试验结果,探讨了人为硫酸盐、黑碳及总人为气溶胶(硫酸盐+黑碳)增加对东亚冬季风的影响。结果表明:冬季硫酸盐气溶胶排放增加的直接和第一间接效应减少了到达地表的短波辐射通量,引起了陆地地表和对流层低层降温,海平面气压升高,增加了海陆间气压梯度,使得东亚冬季风增强。其第二间接效应导致中国南部大尺度降水率减少;黑碳气溶胶排放增加导致到达地表的短波辐射通量减少和大气中短波辐射通量增加,其半直接效应部分抵消了直接效应,故地表温度变化微小且不显著。加热的对流层低层导致中国南部对流活动和对流降水率增加;总人为气溶胶排放增加导致的大气温度变化表现为弱的降温作用,引起中国北部对流和大尺度降水率减少,而南部对流降水率增加。总人为气溶胶和黑碳气溶胶排放增加是导致中国北(南)部的东亚冬季风增强(减弱)的重要因素。     

中国黑碳气溶胶分布特征与辐射强迫的模拟研究

利用区域气候模式RegCM3模拟2000年我国黑碳气溶胶的分布特征和辐射强迫。结果表明,黑碳气溶胶主要分布在我国黄河以南、青藏高原以东的广大区域,柱含量由南向北递减;柱含量最大值在0.6mg／m^2以上,出现在中南、四川盆地、湖南、贵州、广西、广东西部和云南南部等地区;青藏高原南侧黑碳气溶胶次高值区的存在,反映了气溶胶的跨国界输送并影响区域气候的特点。黑碳气溶胶的大气顶辐射强迫介于0.1—0.8w／m^2之间,地表辐射强迫介于-0.1— -2.0W／m^2之间,两者分布特征与柱含量分布特征基本一致。同柱含量相似,黑碳气溶胶大气顸辐射强迫和地表辐射强迫也有明显的季节性变化,春季最大,秋、冬季次之,夏季最小。     

黑碳气溶胶辐射强迫全球分布的模拟研究

利用一个改进的辐射传输模式,结合全球气溶胶数据集（GADS）,计算晴空条件下冬夏两季黑碳气溶胶的直接辐射强迫在对流层顶和地面的全球分布。计算结果表明,与温室气体引起的整层大气都是正的辐射强迫不同,黑碳气溶胶的辐射强迫在对流层顶为正值,而在地面的辐射强迫却是负值。作者从理论上解释了造成这种结果的原因。对北半球冬季和夏季而言,在对流层顶黑碳气溶胶的全球辐射强迫的平均值分别为0.085W/m2和0.155 W/m2,在地面则分别为-0.37 W/m2和-0.63 W/m2。虽然气溶胶的辐射强迫主要依赖于其本身的光学性质和在大气中的浓度,太阳高度角和地表反照率对黑碳气溶胶的辐射强迫会产生很大的影响。研究指出:黑碳气溶胶在对流层顶正的辐射强迫和在地面负的辐射强迫的绝对值都随太阳天顶角的余弦和地表反照率的增加线性增大;地表反照率对黑碳气溶胶辐射强迫的强度和分布都有重要影响。黑碳气溶胶的辐射强迫分布具有明显的纬度变化特征,冬夏两季的大值区都位于30°N~90°N之间,表明人类活动是造成黑碳气溶胶辐射强迫的主要原因。     

Aerosol absorption optical depth of fine-mode mineral dust in eastern China

由气溶胶自动观测网(AERONET)反演的细模态气溶胶的吸收光学厚度(AAOD)通常被认为是黑碳气溶胶的AAOD,并且通过这种方法得到的黑碳AAOD已经被用在计算黑碳辐射强迫的研究中。但是这种方法是基于如下假设:直径小于1μm的细模态气溶胶和直径大于1μm的粗模态气溶胶对光的吸收主要分别归功于黑碳和沙尘。为了定量描述细模态沙尘气溶胶对全部细模态气溶胶的AAOD的贡献,我们利用地球系统交互模式(CESM)模拟了中国东部(104–122°E,29–41°N)细模态沙尘气溶胶的AAOD。其中,我们根据9个中国气象局大气观测网(CAWNET)站点观测的细模态沙尘地表浓度调整了模拟的细模态沙尘气溶胶的浓度。结果显示,模拟的中国东部年平均细模态沙尘气溶胶的AAOD的值为3.6×10-3,其中AAOD的最大和最小值分别出现在春季和冬季。细模态沙尘气溶胶对总的细模态气溶胶(细模态沙尘、黑碳和有机碳气溶胶的总和)的AAOD的贡献在春季、夏季、秋季和冬季分别为3.4%、25.2%、12.5%和14.9%,其年平均值为15.1%。这些结果显示当利用AERONET反演得到的细模态气溶胶的AAOD来计算中国东部BC气溶胶的辐射强迫时,去除细模态沙尘粒子的影响显得尤为重要。     

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.     

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.     

IMPACT OF ATMOSPHERIC LOW-FREQUENCY OSCILLATION ON THE IMMIGRATION OF NILAPARVATA LUGENS(STL) IN HUNAN AND JIANGXI PROVINCES

Various features of the atmospheric environment affect the number of migratory insects, besides their initial population. However, little is known about the impact of atmospheric low-frequency oscillation(10 to 90 days) on insect migration. A case study was conducted to ascertain the influence of low-frequency atmospheric oscillation on the immigration of brown planthopper, Nilaparvata lugens(Stl), in Hunan and Jiangxi provinces. The results showed the following:(1) The number of immigrating N. lugens from April to June of 2007 through 2016 mainly exhibited a periodic oscillation of 10 to 20 days.(2) The 10-20 d low-frequency number of immigrating N. lugens was significantly correlated with a low-frequency wind field and a geopotential height field at 850 h Pa.(3) During the peak phase of immigration, southwest or south winds served as a driving force and carried N. lugens populations northward, and when in the back of the trough and the front of the ridge, the downward airflow created a favorable condition for N. lugens to land in the study area. In conclusion, the northward migration of N. lugens was influenced by a low-frequency atmospheric circulation based on the analysis of dynamics. This study was the first research connecting atmospheric low-frequency oscillation to insect migration.     

A COMPARATIVE ANALYSIS OF ATMOSPHERIC AND OCEANIC CONDITIONS BEFORE THE OCCURRENCE OF TWO TYPES OF EL NIO EVENTS

The atmospheric and oceanic conditions before the onset of EP El Ni?o and CP El Ni?o in nearly 30 years are compared and analyzed by using 850 hPa wind, 20℃ isotherm depth, sea surface temperature and the Wheeler and Hendon index. The results are as follows: In the western equatorial Pacific, the occurrence of the anomalously strong westerly winds of the EP El Ni?o is earlier than that of the CP El Ni?o. Its intensity is far stronger than that of the CP El Ni?o. Two months before the El Ni?o, the anomaly westerly winds of the EP El Ni?o have extended to the eastern Pacific region, while the westerly wind anomaly of the CP El Ni?o can only extend to the west of the dateline three months before the El Ni?o and later stay there. Unlike the EP El Ni?o, the CP El Ni?o is always associated with easterly wind anomaly in the eastern equatorial Pacific before its onset. The thermocline depth anomaly of the EP El Ni?o can significantly move eastward and deepen. In addition, we also find that the evolution of thermocline is ahead of the development of the sea surface temperature for the EP El Ni?o. The strong MJO activity of the EP El Ni?o in the western and central Pacific is earlier than that of the CP El Ni?o. Measured by the standard deviation of the zonal wind square, the intensity of MJO activity of the EP El Ni?o is significantly greater than that of the CP El Ni?o before the onset of El Ni?o.     

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.     

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