障碍物对风速风向影响的观测试验

随着城市化进程的加大,测站周围障碍物的存在使风观测资料失去代表性、准确性和比较性。为定量化研究障碍物对风观测的影响,开展了河北沽源构筑物观测试验,通过对比构筑物修建前后各测点的风速风向资料,分析了障碍物对风速风向的影响。分析结果显示:1障碍物对风速的衰减作用与背景风速大小有关,风速越大,衰减作用越强;2背景风速在2~6m/s时,障碍物背风面测点风速衰减随距离增大而减小,在10倍障碍物高度距离处平均约衰减15%;背景风速大于6m/s时,背风面各测点风速衰减先增大后减小,在大约5倍障碍物高度的距离处衰减最大,10倍障碍物高度的距离处平均约衰减20%~30%;3障碍物的存在使主风向的风向频率减小,对风向的影响距离为6倍障碍物高度。     

桦南地区风能资源数值模拟误差分析

本文使用中尺度数值模型MM5结合微尺度模型CALMET对黑龙江省桦南地区2009年6月-2010年5月进行风能资源数值模拟,并与测风塔实测风速进行误差对比分析。结果表明各高度模拟风速与实测风相关系数在0.47-0.64,除10 m高度外,年平均风速模拟值都略大于实测值,>10 m/s区间与实测风速频率基本相当,高度越高与实测风速越接近。风向模拟随高度增加趋于稳定,主导风向与实测风向也越接近,70 m高度主导风向与实测风主导风向相一致。模型对风能频率的模拟效果优于对风速频率与风向频率的模拟。     

基于探空秒级数据的鄂西南高空风特征分析

利用鄂西南2个探空站(恩施、宜昌)L波段雷达的探空秒级资料,分季节分高度分析了鄂西南高空风向风速特征。结果显示:总体而言,鄂西南高空平均风速随高度为先迅速增大后迅速减小,至20.0kgpm后随高度趋于稳定的变化趋势;平均风向随高度则为由NE风以顺时针方向转为偏W风后趋于稳定,之后又转为偏E风的趋势;在距海平面位势高度20.0kgpm以下时,高空平均风速表现为明显的冬季春秋夏季;而在20.0kgpm以上时,则夏季明显大于其余三季;在3kgpm以下时四季的最多风向、次多风向表现明显不同,但各季的风向除在近地层偏N风稍多外基本以偏S风为主;在中层四季最多、次多风向基本均为偏W风,而在18.0kgpm以上时,四季最多、次多风向均逐渐转为偏E风。     

泰来城市化对风影响研究

本文使用泰来气象站1971-2004年十六方位风速、风向资料,2009年7月-2010年6月气象站与附近测风塔10 m高度逐时风速、风向资料,分析城市化对风序列的影响。结果表明:泰来县年平均风速呈明显减弱趋势,每10 a大约下降0.36 m/s;泰来测风塔与气象站各方向风速比较,无论是风速差值,还是相对误差均表明城市对风速影响显著,对风向也有较大影响;结合城市空间布局及气象站在城市中的位置,分析泰来十六方位风速变化速率,发现各方向风速下降趋势较为明显,其中受城市影响较大方向风速减弱趋势明显,受城市影响小的方向风速减小趋势较弱。     

高密度建筑群及超高建筑物对风环境影响的风洞试验

利用风洞试验方法,以上海陆家嘴金融贸易区建筑群及上海中心大厦为研究对象,讨论了不同粗糙度、不同风向条件下,高密度建筑群和超高建筑物对风环境的影响。结果表明:1)地表粗糙度越小,大风区范围越大。此外,建筑群的分布、排列形式会明显改变来流走向。2)超高建筑物由于其形态上下不一致,在一定条件下,不同高度处的风矢量存在明显差异。3)参照国外建筑物风环境舒适度评估标准,对模拟区域内行人高度处的舒适度进行了评估,并给出了3个风环境较差的区域。     

静止气象卫星云导风的结果分析

对利用静止气象卫星云导风系统生成的云迹风资料与无线电探空风资料对比分析 ,估计云迹风资料的可靠性与精度。选取2001年5～7月间12天共16个时次的资料 ,采用临近层比较法 ,对气象卫星的红外图像云迹风与水汽图像的轨迹风计算结果分别与探空风进行对比分析 ,水汽图像的导风效果略好于红外图像。把云迹风矢和探空风矢分为高、低空两层 ,分别统计给出高、低空云迹风的误差 ,在高空 ,风速误差大、风向误差小 ;在低空 ,风速误差小 ,风向误差大。对卫星云迹风与无线电探空风的最佳层比较 ,在最佳层的风速误差均方根与风向差绝对平均值均明显地减小。     

台风莫拉克 (0908) 影响期间近地层风特性

通过对台风莫拉克 (0908) 影响范围内的33座测风塔观测资料的分析可知:台风莫拉克越靠近陆地,风场的非对称性越明显,其行进方向的左侧测风塔风向呈逆时针旋转,右侧测风塔风向顺时针旋转。在远离台风莫拉克的地方风向稳定,湍流强度变化较平稳;在台风莫拉克登陆点附近,风向、风速和湍流强度均会出现突变。台风莫拉克影响期间,湍流强度与风速的关系未出现IEC标准曲线那样随风速增大稳定减小,其I₁₅达B级和A级及以上的平均湍流强度会在风速7~17 m·s-1形成一个峰值;无论南风或北风,风速越大,各层湍流强度差异趋于减小,同等风速、高度的湍流强度偏南大风均大于偏北大风。位于台风莫拉克登陆点北侧测风塔湍流强度随风速的增加先减小后增大,最终各高度全部超过IEC标准A级曲线,而位于南侧测风塔湍流强度随风速的变化比北侧小,并随风速增大趋于标准A级曲线;另外北侧测风塔湍流强度大于南侧,且各高度偏北大风湍流强度之间的差异比南侧相应风向明显,表明北侧垂直方向的扰动更强。台风莫拉克阵风系数为1.2~1.7,其随高度变化与地形有关,一般情况下随高度升高而减小,在复杂地形条件下不符合随高度升高减小的规律。     

西昌发射场L波段雷达、风廓线雷达与GPS测风对比分析

对西昌发射场L波段雷达、风廓线雷达和GPS测风数据进行对比分析,对不同季节、不同风速条件、不同高度下的风向和风速数据进行相关性分析,结果表明:发射场干季风速数据相关性较高,风向数据相关性较低,雨季风速数据相关性较低,风向数据相关性较高;随风速变大,L波段雷达和GPS测风的数据相关性越来越高,二者与风廓线雷达测风数据的相关性明显变低;在各高度层风向相关性均较高,在低层风速相关性较低,在中高层风速相关性较高。      

西安城区与郊区风向风速差异分析

利用西安国家一般气象站和泾河国家基本气象站2006—2013年同期风向风速地面观测资料,分析比较了西安城区与郊区风向及风速的差异。结果表明:西安城区的月平均风速均小于郊区,城区比郊区偏小50%左右;两地逐月月平均风速波动趋势基本一致,郊区波动较大,城区较平缓;两地年平均风速均呈缓慢减小趋势,城区比郊区减小趋势明显;郊区极大风速远大于城区;郊区大风日较多,城区仅有1d,郊区出现大风的概率远高于城区。城区和郊区最多风向略有偏差,偏离1~20个方位;城区四季的最多风向均不同,郊区四季的最多风向变化不大;城区极大风风向较为分散,郊区较集中。     

1961～2010年河北省地面风变化特征及成因探讨

利用1961~2010年河北省73个地面气象站风观测资料,结合NCEP/NCAR(2.5°×2.5°)月平均再分析资料和国家气候中心下发的环流指数,采用线性趋势拟合方法,分析地面风速的空间分布以及风速和最大主风向风频的时间变化特征,并对风速减小的成因进行探讨。结果表明:空间上风速呈东北西南向带状分布,依次有大、小、大3个风速带。年平均风速呈减小趋势,减小速率为0.207 m·s-1/10 a;3.0 m/s以下的风速日数呈明显增加趋势,8.0 m/s以上的日数呈显著减小趋势,3.0~8.0 m/s风速的日数没有明显变化趋势。代表站最大主风向为偏南风,最大主风向风频平均每年增加0.54 d。风速的减小与1980年代以后影响我国的环流经向度减小、西风指数增加有关,也与城市化效应的影响有关。     

Fourier transform infrared studies of the reaction of Cl atoms with PAN,PPN, CH3OOH,HCOOH, CH3COCH3 and CH3COC2H5 at 295±2 K

The relative rate technique has been used to measure rate constants for the reaction of chlorine atoms with peroxyacetylnitrate (PAN), peroxypropionylnitrate (PPN), methylhydroperoxide, formic acid, acetone and butanone. Decay rates of these organic species were measured relative to one or more of the following reference compounds; ethene, ethane, chloroethane, chloromethane, and methane. Using rate constants of 9.29×10^–11, 5.7×10^–11, 8.04×10^–12, 4.9×10^–13, and 1.0×10^–13 cm³ molecule^–1 sec^–1 for the reaction of Cl atoms with ethene, ethane, chloroethane, chloromethane, and methane respectively, the following rate constants were derived, in units of cm³ molecule^–1 s^–1: PAN, <7×10^–15; PPN, (1.14±0.12)×10^–12; HCOOH, (2.00±0.25)×10^–13; CH₃OOH, (5.70±0.23)×10^–11; CH₃COCH₃, (2.37±0.12)×10^–12; and CH₃COC₂H₅, (4.13±0.57)×10^–11. Quoted errors represent 2 and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295±2 K and 700 torr total pressure of nitrogen or synthetic air. The results are discussed with respect to the previous literature data and to the modelling of nonmethane hydrocarbon oxidation in the atmosphere.In recent discussions with Dr. R. A. Cox of Harwell Laboratory, UKAEA, we learnt of a preliminary value for the rate constant of the reaction of Cl with acetone of (2.5±1.0)×10^–12 cm³ molecule^–1 sec^–1 measured by R. A. Cox, M. E. Jenkin, and G. D. Hayman using molecular modulation techniques. This value is in good agreement with our results.     

A smog chamber for studies of the reactions of terpenes and alkanes with ozone and OH

The design and performance of a smog chamber for the study of photochemical reactions under simulated environmental conditions is described. The chamber is thermostated for aerosol experiments, and it comprises a gas chromatographic sample enrichment system suitable for monitoring hydrocarbons at the ppbv level. By irradiating NO _x /alkane-mixtures rate constants for the reaction of OH radicals with n-alkanes are determined from n-pentane to n-hexadecane to be (k±2)/10^–12 cm³ s^–1=4.29±0.16, 6.2±0.6, 7.52 (reference value), 8.8±0.3, 10.2±0.3, 11.7±0.4, 13.7±0.3, 15.1±0.5, 17.5±0.6, 19.3±0.7, 22.3±1.0, and 25.0±1.3, respectively at 312 K. Rate constants, (k±2)/10^–17 cm³ s^–1, for the reaction of ozone with trans-2-butene (21.2±1.0), cis-3-methylpentene-(2) (47.2±1.7), cyclopentene (62.4±3.5), cyclohexene (7.8±0.5), cycloheptene (28.3±1.5), -pinene (8.6±1.3), and -pinene (1.4±0.2) are determined in the dark at 297 K using cis-2-butene (13.0) as reference standard.     

Trace elements in urban and suburban rainfall, Mersin, Northeastern Mediterranean

Spatial/temporal variabilities of rainwater constituents are examined based on soluble/insoluble trace elements, pH and electrical conductivity measurements in rainfall sampled during December 2003–May 2005 at two urban and two suburban sites in Mersin, an industrialized city of 850,000 inhabitants on the southern coast of Turkey. In the analyses, backward air mass trajectories for rainy days were used in addition to factor analyses, enrichment factors, phase distributions and correlations between trace elements. The pH varied from 4.8 to 8.5 with an average value of 6.2, reflecting a mainly alkaline regime. Mean concentrations of trace elements collected from urban and suburban sites are spatially variable. Based on the overall data, total concentrations of trace elements were ordered as Ca > Na > Fe > Al > Mg > K > Zn > Mn > Sr > Pb > Ni > Cr > Ba > Cu > Co > Cd. Mainly terrigeneous (Ca, Fe, Al) and, to a lesser extent, sea salt particles (Na, Mg) were shown to be the major source of trace elements. Excluding major cations, the solubilities of trace elements were found to be ordered as Sr > Zn > Ba > Mn > Cu > Ni > Cr > Fe > Al, confirming the lower solubility of crustal elements. Cd, Co and Pb were excluded from the above evaluation because of the low numbers of soluble samples allowing quantitative measurements. The solubilities of Al, Fe, Mn and particularly of Ni were found to be considerably lower than those reported for various sites around the world, most likely due to the effect of pH. During the entire sampling period, a total of 28 dust transport episodes associated with 31 red rain events were identified. Extremely high mean concentration ratios of Al (8.2), Fe (14.4) and Mn (13.1) were observed in red rain, compared to normal rain. The degree of this enhancement displayed a decrease from crustal to anthropogenic origin elements and the lowest enhancements were found for anthropogenic origin elements of Zn and Cd (both having a ratio of 1.1). Aerosol dust was found to be the main source of almost all analyzed elements in Mersin precipitation, regardless that they are crustal or anthropic derived elements. The magnitude of crustal source contribution to trace element budget of precipitation was at its highest levels for crustal originated elements, most probably due to much higher scavenging ratios of crustal elements compared to anthropogenic ones.     

Asian Dust effects on Total Suspended Particulate (TSP) compositions at Gosan in Jeju Island, Korea

The compositions of TSP between AD and NAD storm periods were compared to study their long-term variations and chemical characteristics. TSP samples were collected at Gosan site in Jeju Island of Korea from February to May of 1992–2004. The major ionic and elemental species of TSP aerosols were analyzed. During AD periods, the concentrations of crust components (nss-Ca²⁺, Al, Fe, Ca, Mg, Ba, Sr, Ti) increased remarkably, and the concentrations of anthropogenic components (nss-SO₄²⁻, NO₃⁻, S, Zn, Pb, Cr, Ni, Cd), with the exception of NH₄⁺, increased weakly. The concentration ratios of all major components between AD and NAD periods showed ranges from 1.2 to 8.5, except for NH₄⁺. The slope of the linear regression indicated that the contribution of CO₃²⁻ may have comprised up to 17% of the total anions. Our results suggested that the AD storm greatly influenced TSP compositions. Linear regression analyses indicated that NH₄⁺ was not correlated with NO₃⁻, but highly correlated with nss-SO₄²⁻ during both periods. The nss-SO₄²⁻ was also correlated with NH₄⁺, K⁺, nss-Mg²⁺, and nss-Ca²⁺ during both periods. Interestingly, NO₃⁻ was associated with nss-Ca²⁺ and nss-Mg²⁺ during AD periods. Of the metal elements, Fe, Ca, Mg, Ti, Mn, Ba, Sr, V, and Co were highly correlated with Al during both periods, signifying that these metals were mostly originated from soils.     

SHEBA flux–profile relationships in the stable atmospheric boundary layer

Measurements of atmospheric turbulence made during the Surface Heat Budget of the Arctic Ocean Experiment (SHEBA) are used to examine the profile stability functions of momentum, φ _m , and sensible heat, φ _h , in the stably stratified boundary layer over the Arctic pack ice. Turbulent fluxes and mean meteorological data that cover different surface conditions and a wide range of stability conditions were continuously measured and reported hourly at five levels on a 20-m main tower for 11 months. The comprehensive dataset collected during SHEBA allows studying φ _m and φ _h in detail and includes ample data for the very stable case. New parameterizations for φ _m (ζ) and φ _h (ζ) in stable conditions are proposed to describe the SHEBA data; these cover the entire range of the stability parameter ζ = z/L from neutral to very stable conditions, where L is the Obukhov length and z is the measurement height. In the limit of very strong stability, φ _m follows a ζ ^1/3 dependence, whereas φ _h initially increases with increasing ζ, reaches a maximum at ζ ≈ 10, and then tends to level off with increasing ζ. The effects of self-correlation, which occur in plots of φ _m and φ _h versus ζ, are reduced by using an independent bin-averaging method instead of conventional averaging.     

Kinetics of the Gas-Phase Reactions of OH and NO3 Radicals and O3 with the Monoterpene Reaction Products Pinonaldehyde, Caronaldehyde, and Sabinaketone

Using a relative rate method, rate constants have been measured for the gas-phase reactions of OH and NO3 radicals with pinonaldehyde, caronaldehyde and sabinaketone at 296 ± 2 K. The OH radical reaction rate constants obtained are (in units of 10–12 cm3 molecule–1 s–1): pinonaldehyde, 48 ± 8; caronaldehyde, 48 ± 8; and sabinaketone, 5.1 ± 1.4, and the NO3 radical reaction rate constants are (in units of 10–14 cm3 molecule–1 s–1): pinonaldehyde, 2.0 ± 0.9; caronaldehyde, 2.5 ± 1.1; and sabinaketone, 0.036 ± 0.023, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. Upper limits to the O3 reaction rate constants were also obtained, of <2 × 10–20 cm3 molecule–1 s–1 for pinonaldehyde and caronaldehyde, and <5 × 10–20 cm3 molecule–1 s–1 for sabinaketone. These reaction rate constants are combined with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals and O3 to calculate tropospheric lifetimes and dominant transformation process(es) of these and other monoterpene reaction products.     

Stratospheric N2O5, CH4, and N2O profiles from IR solar occultation spectra

Stratospheric volume mixing ratio profiles of N₂O₅, CH₄, and N₂O have been retrieved from a set of 0.052 cm^–1 resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur l'Adour, France (44° N latitude) on 12 October 1990. The N₂O₅ results have been derived from measurements of the integrated absorption by the 1246 cm^–1 band. Assuming a total intensity of 4.32×10^–17 cm^–1/molecule cm^–2 independent of temperature, the retrieved N₂O₅ volume mixing ratios in ppbv (parts per billion by volume, 10^–9), interpolated to 2 km height spacings, are 1.64±0.49 at 37.5 km, 1.92±0.56 at 35.5 km, 2.06±0.47 at 33.5 km, 1.95±0.42 at 31.5 km, 1.60±0.33 at 29.5 km, 1.26±0.28 at 27.5 km, and 0.85±0.20 at 25.5 km. Error bars indicate the estimated 1- uncertainty including the error in the total band intensity (±20% has been assumed). The retrieved profiles are compared with previous measurements and photochemical model results.Laboratoire associé aux Universités Pierre et Marie Curie et Paris Sud.     

Influence of traffic emissions on the composition of atmospheric particles of different sizes – Part 1: concentrations and elemental characterization

Epidemiological studies initially considered the impact of total solid particles on human health, but according to the acquired knowledge about the worse effect of smaller particles, those studies turned to consider the impact of PM₁₀. However, for the last decade PM_2.5 began to be more important, once as they are smaller they can penetrate deeper in the lungs, being possible their trapping in alveoli and worse effects on human health. Therefore, more information on PM_2.5 should be provided namely concerning the levels and elemental composition. Considering the relevance of traffic on the emission of particles of small sizes, this work included the detailed characterization of PM₁₀ and PM_2.5, sampled at two sites directly influenced by traffic, as well as at two reference sites, aiming a further evaluation of the influence of PM₁₀ and PM_2.5 on public health. The specific objectives were to study the influence of traffic emission on PM₁₀ and PM_2.5 characteristics, considering concentration, size distribution and elemental composition. PM₁₀ and PM_2.5 samples were collected using low-volume samplers; the element analyses were performed by particle induced X-ray emission (PIXE). At the sites influenced by traffic emissions PM₁₀ and PM_2.5 concentrations were 7–9 and 6–7 times higher than at the background sites. The presence of 17 elements (Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb) was determined in both PM fractions; particle metal contents were 3–44 and 3–27 times higher for PM₁₀ and PM_2.5, respectively, than at the backgrounds sites. The elements originated mostly from anthropogenic activities (S, K, V, Mn, Ni, Zn and Pb) were predominantly present in PM_2.5, while the elements mostly originated from crust (Mg, Al, Si and Ca) predominantly occurred in PM_2.5–10. The results also showed that in coastal areas sea salt spray is an important source of particles, influencing PM concentration and distributions (PM₁₀ increased by 46%, PM_2.5/PM₁₀ decreased by 26%), as well as PM compositions (Cl in PM₁₀ was 11 times higher).     

A three-dimensional model of the global ammonia cycle

Using a three-dimensional (3-D) transport model of the troposphere, we calculated the global distributions of ammonia (NH₃) and ammonium (NH ₄ ⁺ ), taking into account removal of NH₃ on acidic aerosols, in liquid water clouds and by reaction with OH. Our estimated global 10°×10° NH₃ emission inventory of 45 Tg N-NH₃ yr^– provides a reasonable agreement between calculated wet NH ₄ ⁺ deposition and measurements and of measured and modeled NH ₄ ⁺ in aerosols, although in Africa and Asia especially discrepancies exist.NH₃ emissions from natural continental ecosystems were calculated applying a canopy compensation point and oceanic NH₃ emissions were related to those of DMS (dimethylsulfide). In many regions of the earth, the pH found in rain and cloud water can be attributed to acidity derived from NO, SO₂ and DMS emissions and alkalinity from NH₃. In the remote lower troposphere, sulfate aerosols are calculated to be almost neutralized to ammonium sulfate (NH₄)₂SO₄, whereas in the middle and upper troposphere, according to our calculations, the aerosol should be more acidic, as a result of the oxidation of DMS and SO₂ throughout the troposphere and removal of NH₃ on acidic aerosols at lower heights. Although the removal of NH₃ by reaction with the OH radical is relatively slow, the intermediate NH₂ radical can provide a substantial annual N₂O source of 0.9 _–0.4 ^+0.9 Tg, thus contributing byca. 5% to estimated global N₂O production. The oxidation by OH of NH₃ from anthropogenic sources accounts for 10% of the estimated total anthropogenic sources of N₂O. This source was not accounted for in previous studies, and is mainly located in the tropics, which have high NH₃ and OH concentrations. Biomass burning plumes, containing high NO _x and NH₃ concentrations provide favourable conditions for gas phase N₂O production. This source is probably underestimated in this model study, due to the coarse resolution of the 3-D model, and the rather low biomass burning NH₃ and NO _x emissions adopted. The estimate depends heavily on poorly known concentrations of NH₃ (and NO _x ) in the tropics, and uncertainties in the rate constants of the reactions NH₂ + NO₂ N₂O + H₂O (R4), and NH₂ + O₃ NH₂O + O₂ (R7).     

Trends in chemical composition of precipitation in Nanjing, China, during 1992–2003

In this study, variations of the chemical composition of precipitation in Nanjing, China, over a 12-year period (1992–2003) are presented. The average annual concentration of pH value was 5.15, ranging from 4.93 to 5.36, and there was no significant trend in the acidity of precipitation. SO₄²⁻, Cl⁻ and NO₃⁻ were the main anions, while Ca²⁺, NH₄⁺ and Mg²⁺ were the main cations. The concentrations of these main ions were very high compared to those reported in many other areas around the world. Most of the ions came from anthropogenic and crustal sources. High correlations were found among dust-derived cations Ca²⁺, Mg²⁺and K⁺, between Cl⁻ and SO₄²⁻, between Cl⁻ and NH₄⁺ and between acidic anions and dust-derived cations, such as SO₄²⁻ and Ca²⁺, SO₄²⁻ and K⁺, Cl⁻ and Ca²⁺, Cl⁻ and K⁺, F⁻ and Mg²⁺ and F⁻ and K⁺. A significant decreasing trend was observed in concentration of SO₄²⁻ because of the abatement strategies for SO₂ emissions and energy policy change, while a significant increasing trend was found in the contribution of NO₃⁻ to acidification due to the rapidly growing number of motor vehicles. A significant decreasing trend was found in dust-derived cation Ca²⁺ due to more stringent controls of industrial dust emissions and rapid urbanization reducing the amount of open land, while the contribution of NH₄⁺ to neutralization increased relatively.