西北地区春、夏季降水的水汽输送特征

运用1960—1997年内NCEP/NCAR的格点为2.5°×2.5°多个再分析气象要素资料以及西北地区95个加密测站降水资料,通过相关分析、合成分析等诊断方法对影响西北地区春、夏季降水的整层大气的水汽水平输送特征、各层水汽垂直输送特征以及西北地区春、夏季各个边界区域水汽输送特征进行了系列研究,揭示了西北地区季节性降水的水汽源以及水汽源三维输送路径特征;同时阐述了西北地区季节性降水与同期空中水汽含量显著性相关的原因。并用西北地区干、湿年份相关气象要素场对本文的一些分析结果进行了验证。     

贵州冬季层状云的观测研究

本文使用贵阳地区的探空、飞机探测、地面降水以及飞机撒播干冰人工增雨试验的初步结果等资料,对贵州冬季层状云的宏、微观结构,降水性质,降水的区域相关,云层对太阳辐射的影响以及人工催化增雨的可能性及实施作业的实际增雨效果等进行了综合的研究分析。 研究和试验结果表明,冬季层状云在贵州国民经济生产中,既是一种不利因素,又是一种可供实际开发的空中水资源。     

降水概率预报业务应用系统的研究

降水是大气中不同尺度天气系统相互作用的结果,降水概率预报是利用现代科技和手段,对未来天气出现降水的可能性用百分率定量表达的一种天气预报方法。黑龙江省气象台于１９９６年开始了对哈尔滨市降水概率预报系统的研究工作。这里简要介绍该预报系统的研究情况。     

自动雨量站资料在地质灾害监测中的应用

通过对滑坡、泥石流地质灾害发生地区地质条件、外在因素、前期降水的影响等分析研究,设计了滑坡、泥石流地质灾害等级判别标准,并研制了预报方法。利用ArcGIS Engine、MICAPS等语言工具开发了滑坡、泥石流预报系统,使用前期数据库中自动气象站逐小时雨量和本地区的逐日降水影响系数,以及地质灾害气象发生等级条件进行计算,制作地质灾害发生等级预报。该研究工作为各地防治地质灾害提供了帮助和指导。     

青藏高原北部荒漠化加剧的气候因素分析

青藏高原的荒漠化近年来显著加剧.通过空间自相关分析方法,对近50年来高原北部有代表性的5处荒漠化地区的降水、风速等气候因子在年内的时间分配格局及变化趋势进行了研究,并结合当地影响荒漠化的人为因素,与实地监测得到的荒漠化现状和动态指标进行了关联度分析.结果表明采用空间自相关分析等方法研究气象要素的时空分布特征能合理地揭示气候变化与荒漠化加剧等生态问题之间的因果关系.高原荒漠化加剧是一个受到气候因子、人为因子以及下垫面状况等多种因素综合影响的极为复杂的过程,气候因子是主导因子.在气候因素中一年内降水时间上分配不均衡趋势的增强对高原北部荒漠化加剧起到了关键作用.     

基于CLDAS-Prcp多源融合降水产品的WRF-Hydro模式在綦江流域的水文效用

为了提升对中小尺度流域的径流模拟和洪水预报能力,给防灾减灾和科学研究提供参考依据,本文评估了CLDAS-Prcp多源融合降水产品在中小尺度流域中的水文效用以及WRF-Hydro模式在中小尺度流域中的模拟效果。首先利用CLDAS-Prcp多源融合降水产品和IMERG-Final多源融合降水产品分析了綦江流域7个典型洪水个例中的累计降水量空间分布特征以及小时面雨量时序变化特征,再利用两种多源融合降水产品分别驱动WRF-Hydro模式对綦江流域7个典型的洪水个例进行模拟,并与实测径流量进行对比分析。结果表明：（1）CLDAS-Prcp在累计降水量空间分布上比IMERG-Final刻画出了更多的细节,大值落区和降水总量上也更为准确;两种降水产品都能较好地刻画流域小时面雨量在洪水时段的变化趋势,CLDAS-Prcp在面雨量峰值以及变化趋势上更贴近观测数据。（2）基于CLDAS-Prcp多源融合降水产品的4场径流模拟中,有3场径流模拟的纳什系数高于0.9,表现优异;基于IMERG-Final多源融合降水产品的4场径流模拟中,除20200622号洪水事件外,其余场次模拟的纳什系数皆低于0.7,说明基...     

大气MJO研究的几个前沿问题

就MJO研究的几个前沿问题进行简要归纳分析,主要包括:MJO对流的形成机制;MJO与ENSO的相互作用;MJO对天气气候的影响;MJO的数值模拟和预报等。在论述中更多地给出了中国学者的研究工作及其主要结果。在MJO的影响方面主要论及其对西太平洋台风、亚洲季风和中国东部降水的影响,目的在于能对中国的相关研究及其预报应用有所帮助。     

台风影响期间珠江三角洲局地强风暴和大暴雨发生的环境条件

采用１９７６－１９８３年６－８月珠江三角洲地区受台风影响期间区内各站逐日的强风暴和降水资料以及广泛站的探空资料，用相关对比度分析方法，对台风环流中的珠江三角洲局地强风暴和大暴雨发生的环境条件进行统计诊断，得出台风影响珠江三角洲时这两种强天气发生的有利的环境条件，并发现二者在气压、风速、层结稳定度和中下层位势不稳定等方面显著不同。     

漫话云室

云室,是一种人造云的实验室,它是研究云雾降水过程以及人工影响这些过程的地面实验设备。由于对自然云的直接探测相当困难,而且云和降水发展的过程又很复杂,因而云室就成为云雾物理和人工影响天气研究工作必不可少的实验手段了。     

前期热带太平洋、印度洋海温异常对长江流域及以南地区6月降水的影响

利用NCEP/NCAR提供的1951—2000年全球月平均海表温度距平资料及中国160个测站的月降水资料,采用相关关系分析、合成分析方法,研究了前期热带太平洋、印度洋海温异常对长江流域及以南地区6月降水的影响。结果表明:(1)Nino3指数与印度洋偶极子指数(IODI)有明显的季节变化,且两者同期相关关系随季节不同,以秋季的相关关系最好,相关系数达0.523,并且这时两种指数的强度也较大。作秋季ENSO和印度洋偶极子同时发生年至次年6月的时间序列,发现两事件存在2月左右的位相差,IODI在9—10月达到峰值,Nino3指数在12月达到峰值。说明在相关最好的秋季两事件并不是完全同步的;(2)前期秋季Nino3指数、印度洋偶极子指数及新定义的同时考虑两种指数的一个综合指数—IODN3这3种指数与中国6月降水的相关系数分布有相似特征,主要表现为相关显著区都在长江流域及以南地区。3种指数与降水的相关中,以IODN3与降水相关关系最为显著,显著区范围也最大;(3)前期秋季El Nio和印度洋偶极子正位相同时发生年6月的500 hPa位势高度、垂直速度、水汽输送等异常分布与其前期秋季反位相年6月的异常分布有相反的特征,表明海温异常对长江流域及以南地区降水有重要影响,对应该地区6月降水偏多或偏少;(4)前期秋季El Nio和印度洋偶极子正位相同时发生使菲律宾反气旋加强和维持,形成有利于降水的环流形势。     

Precipitation Chemistry in Semi-Arid Areas of Southern Africa: A Case Study of a Rural and an Industrial Site

Experimental data on the precipitation chemistry in the semi-arid savanna of South Africa is presented in this paper. A total of 901 rainwater samples were collected with automatic wet-only samplers at a rural site, Louis Trichardt, and at an industrial site, Amersfoort, from July 1986 to June 1999. The chemical composition of precipitation was analysed for seven inorganic and two organic ions, using ion chromatography. The most abundant ion was SO₄ ^{2 –} and a large proportion of theprecipitation is acidic, with 98% of samples at Amersfoort and 94% at LouisTrichardt having a pH below 5.6 (average pH of 4.4 and 4.9, respectively). This acidity results from a mixture of mineral and organic acids, with mineral acids being the primary contributors to the precipitation acidity in Amersfoort, while at Louis Trichardt, organic and mineral acids contribute equal amounts of acidity. It was found that the composition of rainwater is controlled by five sources: marine, terrigenous, nitrogenous, biomass burning and anthropogenic sources. The relative contributions of these sources at the two sites were calculated. Anthropogenic sources dominate at Amersfoort and biomass burning at Louis Trichardt. Most ions exhibit a seasonal pattern at Louis Trichardt, with the highest concentrations occurring during the austral spring as a result of agricultural activities and biomass combustion, while at Amersfoort it is less pronounced due to the dominance of relatively constant industrial emissions. The results are compared to observations from other African regions.     

Amino acid nitrogen in atmospheric aerosols: Occurrence,sources and photochemical modification

The presence of amino acids in atmospheric precipitation and aerosols has been noted for many years, yet relatively little is known about these or other nitrogen containing organic compounds in the atmosphere. Marine and continental rainwater analyses indicate that atmospheric aerosols, and subsequently atmospheric precipitation, may contain substantial levels of free and combined amino acids. The most likely source of amino N in the remote marine atmosphere appears to be the injection of proteinaceous material through the action of bursting bubbles at the sea-air interface or the long range transport from terrestrial sources. The capacity of these substrates to undergo photooxidation and photodegradation in the atmosphere to simpler species, such as ammonium ions, carboxylic acids, and for the S containing amino acids, oxidized forms of sulfur, has received little attention from atmospheric chemists. The photochemistry of covalently bound amino groups, particularly as found in peptides and amino acids, is discussed here with the purpose of summarizing what is known of their occurrence and their possible importance to atmospheric chemistry.     

Role of organic acids (formic, acetic, pyruvic and oxalic) in the formation of cloud condensation nuclei (CCN): a review

Although it is believed that organic aerosols play a key role in cloud nucleation and make an important contribution to the cloud condensation nuclei (CCN) population, their specific species remain poorly characterized. This paper reviews the current knowledge of organic acids (mainly formic, acetic, pyruvic and oxalic acids). Without specification, organic acids in this paper refer to these four organic acids in the gas and aerosol phases. This paper analyzes the extent to which organic acids act as CCN and compares the physical and chemical properties of organic acids with those of CCN. The results show that aerosol formate and acetate concentrations range from 0.02 to 5.3 nmol m⁻³ and from 0.03 to 12.4 nmol m⁻³, respectively, and that between 34 to 77% of formate and between 21 to 66% of acetate are present in the fine fraction of aerosols. It was found that although most (98–99%) of these volatile organic acids are present in the gas phase, their concentrations in the aerosol particles are sufficient to make them a good candidate for CCN. The results also show that organic acids may make an important contribution to the formation of CCN in some special sources such as vegetation emissions and biomass-burning. Organic acids are expected to contribute significantly to the estimates of indirect (cloud-mediated) forcing due to aerosols.     

Precipitation Chemistry and Wet Deposition in Kruger National Park, South Africa

The chemical composition, as well as the sources contributing to rainwater chemistry have been determined at Skukuza, in the Kruger National Park, South Africa. Major inorganic and organic ions were determined in 93 rainwater samples collected using an automated wet-only sampler from July 1999 to June 2002. The results indicate that the rain is acidic and the averaged precipitation pH was 4.72. This acidity results from a mixture of mineral acids (82%, of which 50% is H₂SO₄) and organic acids (18%). Most of the H₂SO₄ component can be attributed to the emissions of sulphur dioxide from the industrial region on the Highveld. The wet deposition of S and N is 5.9 kgS⋅ha⁻¹⋅yr⁻¹ and 2.8 kgN⋅ha⁻¹⋅yr⁻¹, respectively. The N deposition was mainly in the form of NH₄ ⁺. Terrigenous, sea salt component, nitrogenous and anthropogenic pollutants have been identified as potential sources of chemical components in rainwater. The results are compared to observations from other African regions.     

Measurement of isoprene and its atmospheric oxidation products in a central Pennsylvania deciduous forest

Ambient concentrations of isoprene and several of its atmospheric oxidation productsmethacrolein, methylvinyl ketone, formaldehyde, formic acid, acetic acid, and pyruvic acid-were measured in a central Pennsylvania deciduous forest during the summer of 1988. Isoprene concentrations ranged from near zero at night to levels in excess of 30 ppbv during daylight hours. During fair weather periods, midday isoprene levels normally fell in the 5–10 ppbv range. Methacrolein and methylvinyl ketone levels ranged from less than 0.5 ppbv to greater than 3 ppbv with average midday concentrations in the 1 to 2 ppbv range. The diurnal behavior of formaldehyde paralleled that of isoprene with ambient concentrations lowest (1 ppbv) in the predawn hours and highest (>9.0 ppbv) during the afternoon. The organic acids peaked during the midday period with average ambient concentration of 2.5, 2.0, and 0.05 ppbv for formic, acetic, and pyruvic acid, respectively. These data indicate that oxygenated organics comprise a large fraction of the total volatile organic carbon containing species present in rural, forested regions of the eastern United States. Consequently, these compounds need to be included in photochemical models that attempt to simulate oxidant behavior and/or atmospheric acidity in these forested regions.     

Chromophoric Dissolved Organic Matter (CDOM) In Rainwater,Southeastern North Carolina,USA

The abundance and optical characteristics of dissolved organic matter (DOM) were determined in 120 rain samples collected in Wilmington, North Carolina, USA, between February 21, 2002 and August 11, 2003. All rainwater samples contained chromophoric dissolved organic matter (CDOM) as well as fluorescent compounds. The absorbance spectra of CDOM in the samples decreased exponentially with wavelength with little or no measurable absorbance past 550 nm. Fluorescence excitation emission spectra (EEMS) of the precipitation revealed the presence of four major peaks indicating both terrestrial and marine influences. There was a strong positive correlation between total integrated fluorescence and the absorbance coefficient at 300 nm in rainwater samples, suggesting that these optical properties are directly interrelated and that the compounds responsible for absorbance may be the same as those responsible for fluorescence. Air-mass back-trajectory analysis indicated elevated CDOM levels in continentally influenced rainwater relative to marine dominated events implying that anthropogenic and/or terrestrial sources are important contributors to CDOM levels in precipitation. The presence of highly absorbing and fluorescing CDOM in rainwater has significant ramifications in atmospheric chemistry and may play a previously unrecognized role in the wavelength dependent spectral attenuation of solar radiation by atmospheric waters.     

“碧利斯”(0604)暴雨过程不同类型降水云微物理特征分析

本文利用"碧利斯"(0604)暴雨增幅过程高分辨率的数值模拟资料, 将降水分成对流降水和层云降水, 对比分析了不同类型降水云微物理特征和过程的差异, 探讨了不同类型降水对暴雨增幅的贡献, 结果指出:(1)暴雨增幅前, 降水基本为层云降水, 对流降水只存在于零星的几个小区域, 暴雨增幅发生时段, 对流降水所占比例较暴雨增幅前有显著增加, 平均降水强度达层云降水强度的3倍多。(2)暴雨增幅时段, 云系发展更加旺盛, 云中各种水凝物含量较增幅前明显增加, 其中, 对流和层云降水区云中水凝物含量均有一定程度增长, 但对流降水区增加更显著;而无论增幅前还是增幅时段, 对流降水区云中水凝物含量均要明显大于层云降水区, 并且两者的这种差异随着地面降水强度的增强而增大。(3)暴雨增幅前后, 对流降水区雨滴的两个主要来源最终均可以追踪到云水, 通过云水与大的液相粒子(雨滴)和大的固相粒子(雪)之间、以及大的固相粒子(雪和霰)之间的相互作用和转化, 造成雨滴增长, 并最终形成地面降水, 而层云降水区中与雨滴形成相关的上述主要云微物理过程明显变弱, 但层云降水区中暴雨增幅时段的上述过程又要强于增幅前, 说明层云降水对暴雨增幅也有一定贡献。     

Aerosol Chemistry, and Light-Scattering and Hygroscopicity Budgets during Outflow from East Asia

During the ACE-Asia field campaign, 41 aerosol filter samples were obtained by airborne sampling over the ocean to the north, south and west of Japan, generally under conditions of outflow from the Asian continent. These samples were analyzed for their water-soluble chemical components, particularly organic species. Suites of inorganic anions, carbohydrates, organic acids and metallic elements were identified and quantified (21 distinct species). Simultaneously, measurements were made of the aerosol hygroscopicity and light scattering. A factor analysis performed on the compositional data identified several sources for the aerosols sampled during the field campaign. Regression of the light-scattering data onto tracers for each of these factors suggests that the aerosol light scattering could be largely attributed to three of these factors: anthropogenic emissions, biomass burning, and soil dust. Similarly, the aerosol hygroscopicity was largely consistent with an empirical mixing model based on past measurements of the hygroscopicity of these individual aerosol types. Limited size-resolved , aerosol composition measurements were also obtained and suggested different sources for various chemical species.     

Rainwater Chemistry and Wet Deposition over the Equatorial Forested Ecosystem of Zoétélé (Cameroon)

Within the framework of IDAF (IGAC DEBITS AFRICA: International GlobalAtmospheric Chemistry/DEposition of Biogeochemically Important TraceSpecies/Africa) network, data analysis is realised on precipitation chemical composition collected in Zoétélé, in Southern Cameroon. This station, located atabout 200 km from the Atlantic Ocean, is representative of a so-called `Evergreen Equatorial Forest' ecosystem. An automatic wet-only precipitation collector was operated at the station from 1996 to 2000. The rainfall regime, associated with eastward advection of moist and cool monsoon air masses, amounts to an average of 1700 mm/year. Inorganic and organic content of the precipitation were determined by IC in 234 rainfall events, representing a total 4,583 mm of rainfall from an overall of 7,100 mm.The mean annual precipitation chemistry and wet deposition fluxes characteristic of an African equatorial forest are quantified. Typical atmospheric gases and particles sources influence the precipitation chemical content and the associated deposition of chemical species. Indeed, hydrogen concentration is the highest (12.0 eq.L^–1) of the IDAF measurements, leading to acid rains with a low mean pH 4.92. The mineral species are dominated by nitrogenous compounds (NH₄ ⁺:10.5 and NO₃ ^–: 6.9 eq.L^–1), Ca²⁺ (8.9 eq.L^–1) and SO₄ ^{2 –} 5.1 eq.L^–1. Relationship between Ca^{2 +} and SO₄ ^{2 –} indicated aterrigeneous particulate source and an additional SO₄ ^{2 –} contributionprobably due to swamps and volcano emissions. Na⁺ and Cl^–concentrations, around 4.0 eq.L^–1, seem very low for this site,accounting for the marine source. Besides, strong correlations between NH₄ ⁺/K⁺/Cl^– indicate the biomass burning originof these species. Accordingly, precipitation chemistry in Zoétéléis influenced by three major sources: biogenic emissions from soil and forest ecosystems, biomass burning from savannah, and terrigenous signature from particles emissions of arid zones; and three minor sources: marine, volcano and anthropogenic. In spite of the relatively low concentration of all these elements, the wet deposition is quite significant due to the high precipitation levels, with for example a nitrogenous compounds deposition of 34 mmol.m^–2.yr^–1.     

Physicochemical modeling of composition of the organic matter in precipitation over the White Sea Islands

Carried out is a broadened study of the chemical composition of precipitation obtained by the direct analytic determination using the physicochemical modeling (the Selektor software package) within the framework of the Al-B-Br-Ar-He-Ne-C-Ca-Cl-F-K-Mg-Mn-N-Na-P-S-Si-Sr-Cu-Zn-H-O-e system with the addition of thermodynamic parameters of low-molecular alifatic acids. The results of the modeling enable the supposition that the composition of precipitation can be determined at the metastable state in the case of weak complex formation of metals and dominance of simple salts of low-molecular organic acids (formates and acetates). The analysis of the obtained information indicates the urgency of taking account of the organic matter impact for predicting the migration activity of pollutants and the determination of the critical load on marine ecosystems.