中国10个地方大气气溶胶1980～1994年间变化特征研究

作者发展了一个从地面上太阳短波直射辐射和能见度信息综合确定大气柱气溶胶总光学厚度和平流层气溶胶光学厚度的方法，并应用这个方法从气象台站观测资料反演得到北京、昆明、喀什、上海、广州、郑州、沈阳、武汉、格尔木和乌鲁木齐等10个地方从1980到1994年间晴天气溶胶光学厚度资料，分析了这些地方气溶胶光学厚度月变化和年变化特征，并侧重分析了1982年墨西哥厄尔奇琼火山和1991年菲律宾皮纳图博火山爆发对气溶胶光学厚度的影响。     

北京晴天紫外波段气溶胶光学厚度反演与分析

利用太阳一大气紫外光谱辐射计(SAUVS)，测量到达北京地表的太阳直接和散射紫外光谱辐射，给出反演大气气溶胶光学厚度的一种方法。结果表明：在紫外波段，大气气溶胶的光学厚度随波长的增加而单调减小，用指数函数可以很好地拟合反演结果。统计得到了3个水平能见度状况下拟合函数的系数值，与全球气溶胶监测网络(AERONET)北京站的资料对比，表明反演结果基本合理。     

关于中国大气气溶胶光学厚度的一个参数化模式

应用中国 1 6个气象台站探测的 1 990年太阳宽带直射辐射信息 ,反演得到了这些台站大气气溶胶光学厚度资料 ,发展了一个应用地面气象能见度和水汽压信息确定大气柱气溶胶光学厚度的参数化模式 ,它比 Elterman模式更适合中国的广大地区。研究还发现 ,比较 Elter-man气溶胶粒子浓度垂直分布模式 ,中国许多地方气溶胶粒子浓度垂直衰减较慢。     

云层与气溶胶对大气吸收太阳辐射的影响

云通过辐射过程对地气系统的能量平衡起着特别显著的调节作用 ,是影响天气、气候以及全球变化的重要因子。近年来 ,有云大气对太阳短波辐射的“异常吸收”又成为云—辐射研究中的一个争论热点。有云大气的短波吸收受到多种因素的影响 ,关于这方面的研究还不够充分。本文通过计算 ,从理论上探讨了若干因素的组合对大气吸收的综合影响。在计算中 ,同时考虑了不同太阳辐射波段、不同太阳入射天顶角、不同云顶高度以及不同下垫面的影响 ,并考虑了包含大气分子、气溶胶和云滴的吸收与散射 ,以及在近红外波段大气自身的热辐射等过程 ,阐明了云与气溶胶在不同波段对大气吸收太阳辐射的影响。     

近几十年青藏高原与华北地区地表太阳辐射变化特征及其影响因素的对比分析

地表太阳总辐射具有较大的时空变化特征,不同地区的影响因素也存在显著差异。本文利用1961—2016年青藏高原与华北地区的地表太阳总辐射资料,在进行严格的质量控制和均一化处理的基础上,深入分析了两个地区总辐射的年际变化趋势,同时结合云量和气溶胶光学厚度观测资料,探讨了两个地区总辐射变化的影响因素。结果表明:(1)1961—2016年青藏高原和华北地区总辐射总体呈下降趋势,但2008年后青藏高原西部和东部地区总辐射变化趋势相反,而华北地区站点总辐射均呈上升趋势。(2)青藏高原西部地区总辐射的下降主要受到云量变化的影响,而东部地区低云量和气溶胶的下降是总辐射上升的重要原因。(3)在2006—2016年,华北地区总辐射的变化受气溶胶的影响更加显著。     

气溶胶辐射特性的观测研究

利用一个简化的辐射平衡模式,讨论了气溶胶直接辐射强迫和气溶胶辐射特性以及与地面反射率之间的关系。模式分析表明,增加气溶胶层以后,地气系统对太阳辐射的反射率可能增大,也可能减少,取决于气溶胶的单散射反射率~ω0、不对称度因子g与地面反射率αg之间的配置,但与气溶胶光学厚度δ没有直接的关系。气溶胶光学厚度值仅和反射率变化的幅度成正比。从辐射平衡模式的结果可知,为了定量地研究气溶胶直接辐射强迫作用,需要有系统的有关气溶胶辐射特性的观测资料。从地面和空间对中国地区气溶胶的辐射特性开展了观测研究,包括从地面用太阳光度计测量气溶胶的光学厚度、用浊度计测量气溶胶的散射系数、黑碳仪测量气溶胶的吸收系数,并且利用MODIS资料反演气溶胶的光学厚度。地面太阳光度计观测的气溶胶光学厚度用于检验卫星遥感的气溶胶光学厚度值,对中国东部地区,遥感的结果是可以接受的,主要是由于这一地区存在较低的地表反射率;但对中国北方植被条件不很好的地区,在遥感反演时对地面反射率的估计可能偏低,如做适当的修改还有可能提高遥感反演的精度。从地面直接测量气溶胶的散射系数和吸收系数算出的气溶胶单散射反射率在0.8左右,需要有更多的观测,以便进一步查清这一问题。     

我国南方中东部地区地面太阳总辐射变化规律

为进一步探讨我国地面太阳辐射的变化规律及其原因,选择我国南方中东部地区,利用该区域1961—2007年33个站点的地面太阳总辐射资料,结合云量、大气水汽含量和能见度等观测资料,综合研究该区域地面太阳总辐射的变化规律及其原因。结果表明:1961—1989年,我国南方中东部地区地面太阳总辐射呈下降趋势,之后发生逆转,1995年后其变化趋于缓和,1961—2007年总体呈现变暗—变亮—变缓的趋势。究其原因,该区域云量平均值由峰入谷、云量下降速率由快变慢可能是产生此变化趋势的原因之一;其次,20世纪80年代到21世纪初,气溶胶光学厚度上升趋势减缓,气溶胶地面辐射强迫变化趋于缓和,某些区域甚至出现下降,也导致部分站点地面太阳总辐射由暗变亮。     

中国大气气溶胶辐射特性参数的观测与研究进展

长期系统的气溶胶辐射特性观测资料是定量研究气溶胶辐射和气候效应的重要基础.本文综合介绍中国大气气溶胶辐射特性观测与研究现状和成果,重点包括以下内容:地面太阳光度计联网观测气溶胶光学厚度、单次散射反照率、尺度谱;从全波段太阳辐射反演气溶胶光学厚度、单次散射反照率;浊度计和黑碳仪测量地面气溶胶散射系数和吸收系数;地基/星载激光雷达观测气溶胶(后向散射系数)垂直分布;极轨/静止卫星遥感反演气溶胶光学特性.     

30年来我国大气气溶胶光学厚度平均分布特征分析

利用北京等46个甲种日射站1961～1990年逐日太阳直接辐射日总量和日照时数等资料,反演了30年来各站逐年、逐月0.75μm大气气溶胶光学厚度(Aerosol OpticalDepth,简称AOD)平均值,分析了我国大气气溶胶光学厚度的年、季空间分布特征和年代际之间的变化.结果表明:我国大气气溶胶光学厚度的多年平均分布具有典型的地理特征,除个别大城市外,100°E以东,AOD以四川盆地为大值中心向四周减少;100°E以西,南疆盆地为另一个相对大值中心.气溶胶光学厚度的各季分布具有各自的特征.20世纪60年代,我国大气气溶胶光学厚度的平均分布特征是以四川盆地和南疆盆地为两个大值中心向四周减少;70年代,绝大多数地区AOD值增加,其中从四川盆地到长江中下游地区以及华南沿海等地,AOD增加较为明显,AOD的分布和60年代较相似;到80年代,我国大范围地区AOD继续呈增加趋势,其中长江中下游地区,AOD增加相当明显,气溶胶光学厚度的分布发生了一定的变化.     

利用水平面太阳直接辐射日曝辐量反演大气气溶胶光学厚度的方法研究

本文发展了一个从宽带水平面太阳直接辐射日曝辐量 (总辐射与散射辐射日曝辐量之差) 反演光谱大气气溶胶光学厚度的方法, 包括建立一个 “等效” 的瞬时太阳天顶角模型, 并提出了一个基于气溶胶标高的云影响甄别方法。对该反演方法的数值模拟和误差分析表明: “等效” 瞬时太阳天顶角模型的不稳定性引起的光学厚度反演误差平均为3.66％; 光学厚度日变化对一段较长时间的平均光学厚度的影响不显著; 订正造成的散射辐射误差≤20％时, 光学厚度平均偏差≤4％。通过与AERONET产品的比对验证表明: 本文发展的光学厚度反演方法和云影响甄别方法都是有效的; 晴空反演的0.75 μm光学厚度与AERONET的相关系数超过0.95, 平均误差约0.02; 云甄别方法计算的季节和年平均光学厚度与AERONET具有较好的一致性。     

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.     

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