二参数Weibull分布函数对近地层风速的拟合及应用

该文用二参数Weibull分布函数对武汉地区3年近地层5～146 m塔层6个层次的风速进行拟合,主要分析了分布函数中形状参数和尺度参数的获取方法。通过与实际值的对比,表明经验法优于最小二乘法。运用此方法,对近地层风能进行估算,其结果与常规方法的最大相对误差为2.7%,最小仅为0.1%。并在最后讨论了风能和垂直分布规律。     

如东沿海近地层风速及风能时空分布特征研究

利用如东东凌风塔2005年观测资料,研究了该区域近地层风速及风能时空分布特征。结果表明,如东沿海地区5月前后是大风值时段,12月前后为次大风值时段;日变化中,风速最大值出现在17时左右,且高层滞后低层约1小时;风速随高度按自然对数规律增大,10～25m高度随高度递增较明显,40～60m高度的风速主要集中在4～8m·s^-1;距地面10m高度年平均风功率密度约175W·m^-2,随高度呈现乘幂增加趋势,60m高度处达333W·m^-2,平均约270W·m^-2。     

江苏沿海近地层风阵性及台风对其影响

为了研究风阵性特征,尤其是在受台风影响时湍流特征对安全开发利用风能资源的影响,利用江苏沿海5座测风塔2009年6月—2012年11月的梯度风观测数据,分析了近地层风阵性基本特征,并筛选了7个对江苏产生较大影响的台风,包括罕见的正面登陆台风达维（1210）,分析台风影响下风阵性特征。研究发现:江苏沿海地区低层的风脉动性比高层强,10 m高度的年平均阵风系数和湍流强度分别为1.50和0.20;海陆分布明显影响风阵性,离岸风的湍流强度明显大于向岸风;当风速等级小于6级时,风阵性随风速增大而一致性减小,之后则稳定少变;在台风中心附近,受风速、风向快速多变的影响,湍流强度和阵风系数均远大于台风外围和没有台风影响的情况,湍流强度和阵风系数在30~50 m高度之间增加,在6~7级风时出现风阵性的局部峰值区。     

北京市秋季城区和郊区大气边界层参数观测分析

应用2001年9月北京城区和郊区同步大气边界层观测资料,对大气边界层热力和动力参数进行了计算分析.结果表明:北京市秋季,逆温出现的时间城区滞后于郊区;逆温层高度城区大于郊区,200m通常为郊区的逆温层顶和城区的逆温层底部;逆温层强度城区弱于郊区;城市热岛强度为3℃;城区感热通量的输送大于郊区;城区下垫面粗糙度远大于郊区;郊区总辐射和紫外辐射的强度明显大于城区.     

琼州海峡沿岸大风分布规律及影响系统分析

利用琼州海峡南北沿岸自动气象站2007年9月至2010年8月风向、风速资料,分析了最大风和极大风两种大风事件标准下的海峡沿岸大风分布规律,并基于大风天气影响系统分析南北沿岸大风的差异。结果表明：琼州海峡南侧沿岸大风事件多于北侧沿岸,其中最大风标准下的大风事件南侧沿岸明显多于北侧沿岸,但极大风标准下的大风事件北侧沿岸则多于南侧沿岸,且极大风风速明显偏大;北侧沿岸两种大风事件及南侧沿岸最大风事件均主要出现在秋冬季节,其中,两侧沿岸最大风事件主要由冷空气影响造成,南侧沿岸极大风事件集中出现在秋季,由冷空气影响造成较少;两岸位于海峡东侧入口沿岸的自动站点出现大风频率最高,风速偏大,两侧入口沿岸站点次之,中间沿岸各站出现大风的频率相对较低;海峡南北沿岸出现的大风风向多为北到东风;东路冷空气比西路冷空气更易造成海峡南北沿岸同步大风,琼州海峡对冷空气湍流强度的消弱作用明显。     

Long-Term Trends in Pre-Summer Daytime and Nocturnal Extreme Hourly Rainfall in a Coastal City of South China

The long-term trends in the occurrence frequency of pre-summer daytime and nocturnal extreme hourly rainfall(EXHR) during 1988-2018 in Hong Kong and their spatial distributions are examined and analyzed. Despite a significant increasing trend observed in the occurrence frequency of pre-summer EXHRs during the investigated period,the increase in daytime and nocturnal EXHRs show distinct spatial patterns. Nocturnal EXHRs show uniform increasing trends over the entire Hong Kong. However, the increa...     

有限区域风速场求解流函数和速度势场的有效方案

流函数和速度势是表示风场的一种变量, 在数值天气预报模式和分析、同化方案中经常使用, 通常可以用风速分量场求解Poisson方程得到。对于有限区域系统, 往往采用差分方法, 但由于存在边界问题, 用计算所得到的流函数和速度势场重建风速场, 在边界附近经常出现明显的偏差。基于差分方法、利用有限区域风速场求解流函数和速度势场的基本方法和特点的分析, 在Arakawa A网格分布的有限区域, 设计了一种用差分方法求解流函数和速度势场的有效方案。在该有效方案中, 通过将有限区域向外扩展二圈, 风速场线性外推, 改进计算边界风速值和边界定解条件的效果; 尽可能使用协调、一致的差分格式, 提高求解精度; 最后利用一种增量订正迭代方法, 迭代2~3次就可以获得令人满意的结果。实例试验的对比、检验显示, 用该方案计算求得的流函数和速度势场重建风速场, 具有非常高的精度。     

WT模型在山区高速公路风预报订正中的应用

利用2001—2020年河北省142个国家气象站逐日最大风速资料分析了近20年河北风速变化背景。择选2021年2—5月张家口、崇礼区域日极大风速13.9 m/s以上、日10 min平均风速最大值8 m/s以上的30个代表日,运用张承高速公路沿线崇礼国家气象站、南窝铺及场地2套区域气象站、高家营及西湾子2套交通气象站的逐分钟风向风速观测资料,ECMWF数值模式输出的地面10 m风预报资料,以及3″分辨率的SRTM3地形资料,应用Meteodyn WT模型对张承高速公路沿线2个解域区域内的风预报结果进行了订正和检验。结果表明：WT模型输出风速与实际观测风速相关系数可达0.6225并通过0.001显著性检验,各代表站模拟的结果与实况的误差80%以上在±2 m/s之间,地形开阔处误差明显减小;风向也表现出很高的一致性。说明应用WT模型对山区高速公路沿线风数值预报进行订正是可行的,各地可结合本地地形数据以及相对稳定可靠的风的数值预报产品作为WT模型的驱动数据源,开展本地山区高速公路沿线风的订正应用。     

城区与郊区不同地形地貌下云地闪分布规律初步研究

利用上海3台SAFIR3000闪电定位仪的测量数据、计算机软件技术和数据统计方法对上海地区云地闪的分布规律进行了研究,得出了以下结论：①受地形地貌及高大建筑的影响,上海地区的云地闪分布规律是南北多,东西少,城区多,郊区少;②在郊区发生的云地闪密度虽然低于城区,但是其雷电流的平均强度要高于城区;③上海地区14：00-21：00是云地闪发生最为频繁的时间段。雷暴日是用于表征某地雷电活动的频繁程度并据此进行风险评估及确定雷电防护等级的一个重要参数,但此参数在实际应用过程中存在着一些问题,文章提出了用＂闪电密度＂或者＂地闪密度＂代替雷暴日的设想。     

青海高原干热风的分布特征及其对气候变化的响应

基于青海省56个气象站1961—2010年50年气象资料对干热风的发生日数、空间分布及其变化特征分析表明:青海高原干热风主要分布在柴达木盆地且以小灶火为高发地,其次为东部农业区且以循化为高发地;近50年来干热风日数、强度均呈逐年上升趋势,2001—2010年年平均达到29站次,分别较20世纪60和70年代偏多17和ll站次;近年来平均最高气温的明显升高与相对湿度逐年减小是干热风日数增多的主要原因。     

Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model

We evaluate the sensitivity of simulated turbine-height wind speeds to 26 parameters within the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height wind speeds. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. The parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height wind speeds. A larger Prandtl number results in smaller nighttime wind speeds. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of wind speed. All of the above parameters significantly affect the vertical profiles of wind speed and the magnitude of wind shear. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.     

Local Circulation Diurnal Patterns and Their Relationship with Large-Scale Flows in a Coastal Area of the Tyrrhenian Sea

In order to characterise the local low-level circulation in the Tyrrhenian Sea coastal area near Rome, the wind field observed by conventional anemometers, Doppler sodar, and rawinsonde has been analysed. The prevailing diurnal behaviour of wind speed and direction as a function of season was highlighted, and the existence of two different patterns of the local circulation, mainly due to land and sea breezes and to the drainage flow from the mouth of the Tiber valley, revealed. The comparison between the low-level circulation and synoptic flow allowed us to determine the influence of the large-scale flow on nocturnal currents that are observed at the Pratica di Mare site and the way that wind direction evolves during the day. Numerical simulations are consistent with experimental data and depict the main features of the low-level wind field in the area.     

塔中春季阴天近地层风速、温度和湿度廓线特征分析

利用塔中最新安装的80 m梯度观测塔探测系统采集的资料,详细分析了2006年4月2日1次阴天天气时塔克拉玛干沙漠腹地近地层风速、温度和湿度廓线演变特征,并与典型晴天廓线做了对比,得到以下结果:(1)阴天,夜间风速廓线风速值随高度增高而增大,但不是以对数增长,而是以比对数关系更快的速度增长;白天,风速很小,近地层10 m上下廓线分布规律各异;(2)温度廓线有夜间辐射型、早上过渡型、白天日射型及傍晚过渡型4种类型,与晴天类似;(3)比湿廓线存在一个极小值,其出现高度以上比湿随高度增加而增加,廓线呈逆湿特征,极小值出现高度以下比湿随高度减小而增加。     

Maximum fluctuations of wind direction in limited time intervals at the levels up to 300 m from observations at a meteorological tower

On the basis of wind direction measurements with 1-s discreteness at the meteorological tower VMM-310 in the town of Obninsk, maximum fluctuations of wind direction are obtained with 10-s averaging over limited time intervals that correspond to the transport of pollutant puffs at distances about 10 km from the source at altitudes up to 300 m. Average values of maximum fluctuations of wind direction decrease with increasing wind speed, level of measurements, and stratification stability. Examples are presented of distributions of maximum fluctuations of wind direction as dependent of these factors. Parameters are given of distributions of maximum fluctuations of wind direction at six levels under different wind speeds and different atmospheric stability. The empirical distributions are approximated by Weibull distribution, and parameters of the latter are presented for separate levels. The results obtained can be used for estimation of an angular size of an area of possible pollution under different conditions of atmospheric stratification, wind speed, and levels of transport of an instantaneous puff of pollutants for the pollutant cloud motion up to a distance of 10 km from the source.     

北京地区一次重污染天气气溶胶分布与传输特征研究

针对北京地区2004年10月26～31日的一次典型重污染天气个例,分析了此次污染过程产生的天气背景和污染物对近地层接收太阳总辐射的削减作用,同时应用MODIS卫星遥感气溶胶产品和地面风场的分布分析了大气污染物的分布和输送特征。结果表明,此次污染过程与大尺度的天气背景有密切关系,地面气压减小和偏南气流导致了此次污染过程;通过比较中国科学院大气物理研究所325m铁塔观测到的2m和280m高度处太阳总辐射可知,在空气质量较好天气,地面以上2～280m大气能够减少太阳总辐射的15%;而在重污染天气时,地面以上2～280m大气能够使太阳总辐射减少20%以上,低层大气显著地影响城市区域下垫面和大气之间的辐射交换;分析MODIS气溶胶分布和地面风场可知,此次污染过程可能是局地污染物积累和外界污染输送造成的。     

Local and Global Similarity in Turbulent Transfer of Heat, Water Vapour, And CO 2 in the Dynamic Convective Sublayer Over a Suburban Area

We investigated the ‘local’ and ‘global’ similarity of vertical turbulent transfer of heat, water vapour, and CO₂ within an urban surface layer. The results were derived from field measurements in a residential area of Tokyo, Japan during midday on fair-weather days in July 2001. In this study, correlation coefficients and quadrant analysis were used for the evaluation of ‘global’ similarity and wavelet analysis was employed for investigating ‘local’ similarity. The correlation coefficients indicated that the transfer efficiencies of water vapour and CO₂ were generally smaller than that of heat. Using wavelet analysis, we found that heat is always efficiently transferred by thermal and organized motions. In contrast, water vapour and CO₂, which are passive quantities, were not transferred as efficiently as heat. The quadrant analyses showed that the heat transfer by ejection exceeded that by sweep, and the ratios of ejection to sweep for water vapour and CO₂ transfer were less than that for heat. This indicated that heat is more efficiently transferred by upward motions and supported the findings from wavelet analysis. The differences of turbulent transfer between heat and both CO₂ and water vapour were probably caused both by the active role of temperature and the heterogeneity in the source distribution of scalars     

Hydroxyl and Peroxy Radical Chemistry in a Rural Area of Central Pennsylvania: Observations and Model Comparisons

Atmospheric hydroxyl (OH), hydroperoxy (HO₂), total peroxy (HO₂ and organic peroxy radicals, RO₂) mixing ratios and OH reactivity (first order OH loss rate) were measured at a rural site in central Pennsylvania during May and June 2002. OH and HO₂ mixing ratios were measured with laser induced fluorescence (LIF); HO₂ + RO₂ mixing ratios were measured with chemical ionization mass spectrometry (CIMS). The daytime maximum mixing ratios were up to 0.6 parts per trillion by volume (pptv) for OH, 30 pptv for HO₂, and 45 pptv for HO₂ + RO₂. A parameterized RACM (Regional Atmospheric Chemistry Mechanism) box model was used to predict steady state OH, HO₂ and HO₂ + RO₂ concentrations by constraining the model to the measured OH reactivity and previously measured volatile organic compound (VOC) distributions. The averaged model calculations are generally in good agreement with the observations. For OH, the model matched the observations for day and night, with an average observed-to-modeled ratio of 0.80. In previous studies such as PROPHET98, nighttime NO was near 0 pptv and observed nighttime OH was significantly larger than modeled OH. In this study, nighttime observed and modeled OH agree to within measurement and model uncertainties because the main source of the nighttime OH was the reaction HO₂ + NO → OH + NO₂, with the NO being continually emitted from the surrounding fertilized corn field. The observed-to-modeled ratio for HO₂ is 1.0 on average, although daytime HO₂ is underpredicted by a factor of 1.2 and nighttime HO₂ is over-predicted by a factor of ∼2. The average measured and modeled HO₂ + RO₂ agree well during daytime, but the modeled value is about twice the measured value during nighttime. While measured HO₂ + RO₂ values agree with modeled values for NO mixing ratios less than a few parts per billion by volume (ppbv), it increases substantially above the expected value for NO greater than a few ppbv. This observation of the higher-than-expected HO₂ + RO₂ with the CIMS technique confirms the observed increase of HO₂ above expected values at higher NO mixing ratios in HO₂ measurements with the LIF technique. The maximum instantaneous O₃ production rate calculated from HO₂ and RO₂ reactions with NO was as high as 10–15 ppb h⁻¹ at midday; the total daily O₃ production varied from 13 to 113 ppbv d⁻¹ and was 48 ppbv d⁻¹ on average during this campaign.     

用有限区域风速场准确求解流函数和速度势场的方法

流函数和速度势是气象业务和研究中常用于表述风速的一组变量。用有限区域风速场, 使用有限差分方法求解得到的流函数和速度势场重建初始风速场, 由于受区域边界的限制往往有明显的偏差。虽然有许多求解方法的研究, 但是, 至今仍尚未见到一种真正准确的求解计算方案。首先, 介绍用Arakawa A网格和D网格分布的有限区域风速场求解流函数和速度势场的一般有限差分计算方法, 探讨用它们的解重建风速场产生误差的原因。然后, 针对这些原因, 对给定的有限区域, 通过线性外推初始风速场, 扩展求解计算区域, 使用协调、一致的有限差分格式方案, 准确计算求解区域的边界有旋风速、散度风速和速度势的定解边界条件, 以及恰当选择流函数、速度势、涡度和散度等变量的分布网格, 设计了用上述两种网格分布的风速场准确求解流函数、速度势场的方案, 并对其正确性加以证明, 它们可以推广应用于其他Arakawa网格。用实际资料试验同样显示, 方案避免了重建风速场误差的出现, 与初始风速场相比, 全场风速最大偏差精度达到10-12m/s或以上, 在计算机精度造成的计算误差影响范围内。本文的研究很好解决了长期以来用有限区域风速场、 使用有限差分方法无法准确求解流函数和速度势场的问题。