热带西太平洋定点海域降水的化学特征研究

对热带西太平洋定点（４°Ｓ，１５６°Ｅ）海域长达４个月的降水化学调查，研究了降水中化学成分的变化特征、连续性与断续性降水过程和西风暴发事件（ＷＷＢＥ）及大风暴降雨过程中降水的化学成分。结果表明：定点海域（４°Ｓ，１５６°Ｅ）纯“海洋性”降水的ｐＨ为５．５５，其Ｍｎ／Ｆｅ比值为０．５４，Ｃｌ－与ＳＯ２－４是降水中最大量的离子；连续性降水ｐＨ呈“∨”型分布，Ｅｈ呈“∧”分布，总－２价硫的浓度Ｓ（－Ⅱ）呈降低分布，且最后趋于稳定，ＳＯ２－４，ＮＨ＋４，ＰＯ３－４等在降雨开始后一段时间出现最大值，呈现与其它组分相反的行为；断续性降水ｐＨ，Ｅｈ趋于升高。西风暴发事件（ＷＷＢＥ）期间，绝大多数组分在降水中浓度高于ＷＷＢＥ发生前、后的浓度，而ＮＨ＋４低于ＷＷＢＥ发生前、后的浓度，ＰＯ３－４，ＳｉＯ２－３则是低于ＷＷＢＥ发生前的浓度，而高于发生后的浓度，大风暴降雨Ｃｌ－，ＳＯ２－４的浓度比正常降雨时可高达数倍，说明海上大风暴使大量海水滴被卷入空中，又随降雨落下，这时的降水ｐＨ也有显著增高。     

春季江淮气旋发展的诊断研究

本文在等熵面上对１９９６年４月２８日－３０日发生在江淮地区的气旋作了分析和诊断研究。     

松花江干流洪水发生规律与1998年松嫩流域洪水成因

松花江干流洪水发生有２４年和３￣４年的变化周期,洪水出现的阶段性明显,其可分为４段：即１９１１￣１９１４,１９３０￣１９４０,１９５４￣１９５８,１９８４￣１９９８年。洪水随时间推移,发生频次明显增加。嫩江流域及第二松花江和拉林河流域７、８月过量降水是造成洪水发生的直接原因。分析了造成洪水的５００ｈＰａ环流背景：７、８月西藏高原至阿拉斯加距平场分布为“＋－＋－”流型,鄂霍茨克海为阻塞高压,东北区为     

E-601B型蒸发器使用经验点滴

Ｅ－６０１Ｂ型蒸发器使用经验点滴１９９７年４月份,我省国家基准、基本站全部更换或新安装上了Ｅ－６０１Ｂ型水面蒸发器。根据我站一个多月的试观测记录,笔者认为应注意如下几个问题：１．测针对零要准确,避免误读发生。在预审我站１９９７年４月份观测记录时,发现...     

过冷云风洞中初始冰晶的初步研究

本着重研究了在过冷云风洞中，温度为－４—１６℃，含水量为１．４ｇｍ＾－３，爆泡后增长４５ｓ的初始冰晶的一些特性。结果表明：（１）初始冰晶质量在－４—１３℃有两个峰值，它们是－５．７℃时的１．８×１０＾－８与－１１．４℃时的６．３×１０＾－８ｇ，而在－８．４℃和－１３℃时出现的极小值分别为２×１０－９ｇ和５×１０＾－９ｇ。（２）初始冰晶的浓度值随着温度的降低出现三个递减的峰值，它们分别是－４．２℃     

RYJ－2与RYJ－4型全自动辐射记录器的异同

ＲＹＪ－２与ＲＹＪ－４型全自动辐射记录器的异同彭劲云（西安市气象局西安·７１００１５）我省现有辐射观测站均配发了ＲＹＪ－４型全自动辐射记录器（以下简称ＲＹＪ－４），与ＲＹＪ－２型全自动辐射记录器（以下简称ＲＹＪ－２）可交替使用。由于ＲＹＪ－２台站已使...     

1994年4月9—11日强寒潮天气过程分析

对１９９４年４月９－１１日发生的强寒潮天气过程进行分析，以提高该类形势下寒潮的预报能力。     

一次暴雨—大暴雨过程的熵诊断分析

该文利用熵平衡方程，对１９９３年８月４－５日，在河北省中南部地区发生的暴雨－大暴雨，局部特大暴雨天气过程进行了熵诊断分析。指出，在湿饱和大气下，降水过程实质上是熵由不平衡通过垂直运动达到平衡的过程。     

成都市区酸雨监测分析

该文统计整理了成都市区５个监测点１９９２－１９９４年５７７次降水样品的ｐＨ值和电导率，并结合气象条件进行了分析，结果表明，成都市区降水的年平均ｐＨ值（ｐＨ）为５．５７，酸雨发生频率为３７．４％，酸雨相对集中在７－９月。     

热带太平洋地区SSTA和风应力场的海气耦合模态

按国家气象局“八五”攻关力专家组提出的有关近海热带气候强度突变的标准，对１９７０－１９９１年在我国的近海发生强度突为的热带气旋进行了分类统计，发现如下气候特征：平均每年有８－９个热带气旋移到我国近海时发生强度突变，其中突然减弱的居多，占总个数的７９．６％，突然增强的只占总个数的２０．４％，突然增强只发和天５－１０月，而突然减弱到５－１２月均可发生；突然增强主要出现在浙闽沿海、南海中部，珠江口外西侧     

沙尘气溶胶粒子表面变性对云滴形成过程的影响

利用1997年5月14日辽宁省气溶胶和云滴谱航测资料,讨论了沙尘气溶胶粒子表面变性产生的不溶性沙尘粒子外包可溶性硫酸铵层的混合气溶胶粒子作为凝结核的增长规律,计算了由混和核形成的云滴谱特征,并与纯硫酸铵盐核进行对比.结果表明:混和核上初期形成的云滴谱型比纯硫酸铵盐核上初期形成的云滴谱型要宽,更接近实际观测到的云滴谱分布.     

中国平流层CH4的分布特征和季节变化

利用UARS卫星上HALOE试验的1992—2003年CH4资料,分析了中国平流层的CH4混合比分布特征,并对CH4混合比在不同纬度上的季节变化作了详细分析。结果表明,中国平流层CH4混合比随着高度逐渐减小,在经向上有较大差异,总是南边大于北边,而各个纬度带上的分布则较均匀。分析结果还表明,中国平流层CH4混合比在DJF的季节距平与MAM有相反的符号,而且中心位置基本吻合。此外,季节变率最大的是MAM—DJF,而不是JJA—DJF。并且在平流层低层的夏半年有明显的高值带,这可能与上升运动和辐散辐合作用有关。     

Application of a “Big-Tree” model to regional climate modeling: a sensitivity study

Summary ¶In order to better understand land-atmosphere interactions and increase the predictability of climate models, it is important to investigate the role of forest representation in climate modeling. Corresponding to the big-leaf model commonly employed in land surface schemes to represent the effects of a forest, a so called big-tree model, which uses multi-layer vegetation to represent the vertical canopy heterogeneity, was introduced and incorporated into the National Center for Atmospheric Research (NCAR) regional climate model RegCM2, to make the vegetation model more physically based. Using this augmented RegCM2 and station data for China during 1991 Meiyu season, we performed 10 experiments to investigate the effects of the application of the big-tree model on the summer monsoon climate.With the big-tree model incorporated into the regional climate model, some climate characteristics, e.g. the 3-month-mean surface temperature, circulation, and precipitation, are significantly and systematically changed over the model domain, and the change of the characteristics differs depending on the area. Due to the better representation of the shading effect in the big-tree model, the temperature of the lower layer atmosphere above the plant canopy is increased, which further influences the 850hPa temperature. In addition, there are significant decreases in the mean latent heat fluxes (within 20–30W/m²) in the three areas of the model domain.The application of the big-tree model influences not only the simulated climate of the forested area, but also that of the whole model domain, and its impact is greater on the lower atmosphere than on the upper atmosphere. The simulated rainfall and surface temperature deviate from the originally simulated result and are (or seem to be) closer to the observations, which implies that an appropriate representation of the big-tree model may improve the simulation of the summer monsoon climate.We also find that the simulated climate is sensitive to some big-tree parameter values and schemes, such as the shape, height, zero-plane displacement height and mixing-length scheme. The simulated local/grid differences may be very large although the simulated areal-average differences may be much lower. The area-average differences in the monthly-mean surface temperature and heat fluxes can amount to 0.5°C and 4W/m², respectively, which correspond to maximum local/grid differences of 3.0°C and 40W/m² respectively. It seems that the simulated climate is most sensitive to the parameter of the zero-plane displacement among the parameters studied.     

Synergistic Effects of Nitrogen Amendments and Ethylene on Atmospheric Methane Uptake under a Temperate Old-growth Forest

An increase in atmospheric nitrogen (N) deposition can promote soil acidification, which may increase the release of ethylene (C2H4) under forest floors. Unfortunately, knowledge of whether increasing N deposition and C2H4 releases have synergistic effects on soil methane (CH4) uptake is limited and certainly deserves to be examined. We conducted some field measurements and laboratory experiments to examine this issue. The addition of (NH4)2SO4 or NH4Cl at a rate of 45 kg N ha-1 yr-1 reduced the soil CH4 uptake under a temperate old-growth forest in northeast China, and there were synergistic effects of N amendments in the presence of C2H4 concentrations equal to atmospheric CH4 concentration on the soil CH4 uptake, particularly in the NH4Cl-treated plots. Effective concentrations of added C2H4 on the soil CH4 uptake were smaller in NH+4 -treated plots than in KNO3-treated plots. The concentration of ca 0.3 μl C2H4 L-1 in the headspace gases reduced by 20% soil atmospheric CH4 uptake in the NH4Cl-treated plots, and this concentration was easily produced in temperate forest topsoils under short-term anoxic conditions. Together with short-term stimulating effects of N amendments and soil acidification on C2H4 production from forest soils, our observations suggest that knowledge of synergistic effects of NH+4 , rather than NO3- , amendments and C2H4 on the in situ soil CH4 uptake is critical for understanding the role of atmospheric N deposition and cycling of C2H4 under forest floors in reducing global atmospheric CH4 uptake by forests. Synergistic functions of NH4+ -N deposition and C2H4 release due to soil acidification in reducing atmospheric CH4 uptake by forests are discussed.     

An Extension of the Dimension-Reduced Projection 4DVar

This paper extends the dimension-reduced pro- jection four-dimensional variational assimilation method （DRP-4DVar） by adding a nonlinear correction process, thereby forming the DRP-4DVar with a nonlinear correction, which shall hereafter be referred to as the NC-DRP- 4DVar. A preliminary test is conducted using the Lorenz-96 model in one single-window experiment and several multiple-window experiments. The results of the single-window experiment show that compared with the adjoint-based traditional 4DVar, the final convergence of the cost function for the NC-DRP-4DVar is almost the same as that using the traditional 4DVar, but with much less computation. Furthermore, the 30-window assimilation experiments demonstrate that the NC-DRP-4DVar can alleviate the linearity approximation error and reduce the root mean square error significantly.     

瓦里关山大气甲烷本底浓度变化特征的分析

用气相色谱法在瓦里关全球基准站进行了大气甲烷（CH4）的连续测量,结合NOAA/CMDL气瓶采样CH4浓度资料的分析结果,给出了我国内陆高原大气CH4本底浓度的变化特征。分析结果表明:瓦里关山大气CH4浓度在1780×10-9～1840×10-9范围内波动,浓度值的变化范围符合中高纬度地区CH4浓度分布;CH4浓度有明显的日变化,夏季的变化趋势及振幅与冬春季有所不同;季节变化幅度不大,与全球大气CH4浓度本底值季节变化的特征及变化幅度的地理分布不太一致;有明显的年际变化,CH4年平均浓度表现为逐年升高,年     

Introduction to the Regional Coupled Model WRF4-LICOM: Performance and Model Intercomparison over the Western North Pacific

Regional coupled modeling is one of the frontiers of regional climate modeling, but intercomparison has not been well coordinated. In this study, a community regional climate model, WRF4, with a resolution of 15 km, was coupled with a high-resolution(0.1°) North Pacific Ocean model(LICOM_np). The performance of the regional coupled model,WRF4_LICOM, was compared to that of another regional coupled model, RegCM4_LICOM, which was a coupling of version 4 of the Regional Climate Model(RegCM4) with LICOM_np. The analysis focused on the 2005 western North Pacific summer monsoon rainfall. The results showed that the regional coupled models with either RegCM4 or WRF4 as their atmospheric model component simulated the broad features over the WNP reasonably well. Quantitative intercomparison of the regional coupled simulations exhibited different biases for different climate variables.RegCM4_LICOM exhibited smaller biases in its simulation of the averaged June–July–August SST and rainfall, while WRF4_LICOM better captured the tropical cyclone(TC) intensity, the percentage contributions of rainfall induced by TCs to the total rainfall, and the diurnal cycle of rainfall and stratiform percentages, especially over land areas. The different behaviors in rainfall simulated by the two models were partly ascribed to the behaviors in the simulated western North Pacific subtropical high(WNPSH). The stronger(weaker) WNPSH in WRF4_LICOM(RegCM4_LICOM) was driven by overestimated(underestimated) diabatic heating, which peaked at approximately 450 hPa over the region around the Philippines in association with different condensation–radiation processes. Coupling of WRF4 with LIOCM is a crucial step towards the development of the next generation of regional earth system models at the Chinese Academy of Sciences.     

Gas and Particulate Products Distribution from the Photooxidation of α-Humulene in the Presence of NOx, Natural Atmospheric Air and Sunlight

The photooxidation of -humulene in the presence of NO_x, natural sunlight, and rural background air was investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). Identification and quantification of gas and particulate reaction products were reported over the course of the reaction. The daytime photooxidation was carried out in a large outdoor smog chamber (190 m³). A wide range of ring retaining and ring opening products in the gas and particle phase are reported. On average, measured gas and particle phase products accounted for 44% of the reacted -humulene carbon. Measurements show that a number of reaction products with low vapor pressures (e.g. 3-seco--humulone aldehyde, 7-seco--humulone aldehyde, -humulal aldehyde, -humulene 3-oxide or -humulene 7-oxide, -humulaic/alic acid isomers, and 3-seco--14-hydroxyhumulone aldehyde) were found in the early stage of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.     

Four-dimensional variational data assimilation for mesoscale and storm-scale applications

Summary ?The status and progress of the four-dimensional variational data assimilation (4DVAR) are briefly reviewed focusing on application to prediction of mesoscale/storm-scale atmospheric phenomena. Theoretical background is provided for each important component of the 4DVAR system – forecast and adjoint models, observations, background, cost function, preconditioning, and minimization. An overview of practical issues specific for mesoscale/storm-scale 4DVAR is then presented in terms of high-resolution observations, nonlinearity and discontinuity problem, model error, errors from lateral boundary condition, and precipitation assimilation. Practical strategies for efficient and simplified 4DVAR are also introduced, e.g., incremental 4DVAR, poor man’s 4DVAR, and inverse 3DVAR. A new concept on hybrid approach is proposed to combine an efficient 4DVAR scheme and the standard 4DVAR scheme aiming at reducing computational demand required by the standard 4DVAR while improving the accuracy of the simplified 4DVAR. Applications to both hydrostatic and nonhydrostatic models are illustrated and our vision on opportunities and directions for future research is provided. Received March 12, 2001; revised July 24, 2001; accepted September 5, 2001     

Mitigating Agricultural Emissions of Methane

Agricultural crop and animal production systems are important sources and sinks for atmospheric methane (CH4). The major CH4 sources from this sector are ruminant animals, flooded rice fields, animal waste and biomass burning which total about one third of all global emissions. This paper discusses the factors that influence CH4 production and emission from these sources and the aerobic soil sink for atmospheric CH4 and assesses the magnitude of each source. Potential methods of mitigating CH4 emissions from the major sources could lead to improved crop and animal productivity. The global impact of using the mitigation options suggested could potentially decrease agricultural CH4 emissions by about 30%.