共查询到20条相似文献，搜索用时 31 毫秒
1.
Observations and numerical modelling of Lake Ontario breezes 总被引：1，自引：0，他引：1
Abstract Analysis of two years of land‐based data shows that the Lake Ontario breeze develops on 30% of the days during summer. It typically develops in mid‐morning and persists until the late evening when it is replaced by a well developed land‐breeze regime. Simulations of 4 cases with the Colorado State University mesoscale model show good agreement with observations and suggest that local lake breezes are strongly influenced by adjacent water bodies (e.g. Lake Erie), the elongated shape of the lake, and the large‐scale wind direction. With gradient flows across the long axis of the lake, a broad band of along‐lake flow develops during the afternoon (easterly winds during southerly gradient flows and westerly winds during northerly gradient flows). Furthermore, during west‐to‐northwesterly gradient flow a nocturnal cyclonic eddy is predicted at the western end of the lake. These results imply that wind‐field models applied in the vicinity of Lake Ontario should incorporate the entire lake in their modelling domain. 相似文献
2.
T. Maitani 《Boundary-Layer Meteorology》1979,16(3):49-65
The motions of individual plants and the turbulence statistics of surface winds measured near the top of a canopy are obtained
over a wheat field and a rush field. Two typical cases of motions of individual plants are presented. The displacements of
the ear of wheat (the plant height is 1.0 m) showed a natural oscillation in wind speeds of 1.6 m s−1 measured at a height of 30 cm over a wheat canopy, while displacements of the stem of a rush plant were closely related to
the fluctuations of surface winds in wind speeds of 1.7 m s−1 measured at the top of the rush plant. The power spectra of displacements of a rush plant seem to support the negative seven-third
power hypothesis proposed by Inoue. The frequency responses of displacements of plants to fluctuations of the instantaneous
momentum flux are also presented. 相似文献
3.
An observational study of wind-induced waving of plants 总被引：1，自引：0，他引：1
T. Maitani 《Boundary-Layer Meteorology》1979,16(1):49-65
The motions of individual plants and the turbulence statistics of surface winds measured near the top of a canopy are obtained over a wheat field and a rush field. Two typical cases of motions of individual plants are presented. The displacements of the ear of wheat (the plant height is 1.0 m) showed a natural oscillation in wind speeds of 1.6 m s–1 measured at a height of 30 cm over a wheat canopy, while displacements of the stem of a rush plant were closely related to the fluctuations of surface winds in wind speeds of 1.7 m s–1 measured at the top of the rush plant. The power spectra of displacements of a rush plant seem to support the negative seven-third power hypothesis proposed by Inoue. The frequency responses of displacements of plants to fluctuations of the instantaneous momentum flux are also presented. 相似文献
4.
Spatial and temporal aspects of the lake effect on the southern shore of Lake Superior 总被引：1，自引：0，他引：1
A climate-monitoring network was implemented in a large private preserve along the southern shore of Lake Superior. The network uses a dense sampling design to assess the spatial and temporal influence of a large, cold body of water on adjacent terrestrial surfaces. Based on a 3-year record, near-shore sites are 1–2°C cooler than sites 5?km inland in spring and summer, and 1°C warmer in winter. Near the shore, winds are from the NNW most of the year, and are much stronger in winter. Inland, southwesterly flow is typical and overall wind velocity is lower and more consistent. This decoupling is attributable to the influence of the Huron Mountains, a topographic barrier that restricts the lake effect to a narrow coastal zone. A 2-year record of hourly air temperature measurements from 26–30 sites across the study area demonstrates that the mean daily temperature can differ by as much as 11°C, but the average difference is 2.5–3.0°C. 相似文献
5.
Aspects of the Fine-Scale Climatology Over Lake Tanganyika as Resolved by a Mesoscale Model 总被引：1，自引：0，他引：1
Summary An hourly averaged climatology at 0.05 ° horizontal resolution over the Lake Tanganyika region was created by making simulations
with a mesoscale model (HIRLAM) using a high resolution physiography to represent the surface. Initial and boundary values
were interpolated from ECMWF analyses. Climatologies for a typical dry season month (July 1994) and wet season month (March
1994) were created by 7-day segmenting. Model results were validated by utilizing a special coastal observation network. A
number of experiments were made with changes to the physiography (mountains/no mountains, lake/no lake).
The results reveal local channelling and blocking effects of the near-surface southeasterly trade winds by the high mountain
chains in the region of the East African rift. Furthermore, surface winds display regular diurnal cycles in many places, due
to slope winds over hills and lake-land-type breezes near the coast. The diurnal coastal winds (defined by the observation
network) are reasonably well simulated. Precipitation patterns display the semi-annual march of the ITCZ across the area,
plus considerable topographic effects. There is high evaporation from lakes and wetlands during the windy dry season, while
evaporation from the moist land surface dominates the rainy season.
Received October 15, 1998/Revised September 2, 1999 相似文献
6.
In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong f?hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter f?hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986. 相似文献
7.
涡旋Rossby波传播和台风切向风速变化的数值研究 总被引：1，自引：0，他引：1
余锦华 《南京气象学院学报》2003,26(2):172-180
设计了一个高分辨率f平面准地转正压涡度方程半谱模式，用以研究非线性对台风切向风速变化，以及不同初始异常条件下台风环流内涡旋Rossby波传播和台风切向风速变化特征。6类(14组)试验的数值结果表明：非线性使台风切向风速的增强减弱，可能使最大风速半径收缩。初始扰动中心位置对涡旋Rossby波传播和台风切向风速变化的影响明显。扰动中心在最大风速半径附近时，台风最大切向风速增强最多；异常中心在台风外区时，使最大切向风速减小。初始异常尺度(范围)减小对台风最大切向风速变化的影响减弱。双涡分布条件下，台风环流外区的涡旋使内区或近眼壁区对流涡旋对台风最大切向风速的影响减弱。 相似文献
8.
一维热扩散湖模式在太湖的应用研究 总被引：2，自引：1，他引：1
利用在太湖获得的2010年8月11-28日的观测资料研究了一维热扩散湖模式在太湖的适用性,通过对比模拟进一步研究了影响太湖湖表温度模拟的主要因子。该湖模式对太湖最初的模拟结果并不理想,模拟的湖表面温度与观测有较大的系统性偏差,温度的日变化幅度与观测相比也偏小。通过分析该模式对太湖的模拟效果不理想的可能原因,针对太湖的生态环境和污染情况,设计了18个测试参数的敏感性试验,从敏感性试验的结果分析得到,适用于太湖的、依赖于湖泊类型的3个参数应做如下修改:消光系数（η0）应放大3倍,湖泊表层吸收的太阳辐射系数（β）应取0.8,粗糙长度（z0）采用公式计算得到。用新得到的适用于太湖的3个参数,模拟得到的结果与最初的模拟结果和观测资料对比,发现采用新的参数后,模拟结果比最初的模拟结果有了很大的改进,模拟的湖表温度基本接近观测,模拟的湖水垂直剖面时间序列图也跟观测吻合得较好,随之的感热、潜热通量的模拟也都与观测接近。最后,对输入湖模式的主要大气参量（太阳辐射、2 m气温及风场）±10%的误差引起的模式模拟的湖表面温度误差进行分析,结果表明该湖模式对大气强迫场的误差敏感度不高;相比之下,模拟结果对风场敏感性最小,对辐射和气温的敏感度相当。 相似文献
9.
Carl Anderson 《大气与海洋》2013,51(3):330-344
Abstract Surface mesonet winds recorded at 10‐min intervals are used to estimate the propagation velocities of atmospheric fronts in East Coast winter storms during the Canadian Atlantic Storms Program (CASP). The frontal motion is modelled locally as the translation of a line across which there is an abrupt shift in wind direction. The mesonet is used to detect the propagation velocity of the windshift line. Frontal velocities estimated using mesonet winds for all cases in which fronts passed through the mesonet (two cold fronts and three warm fronts) are in close agreement with those deduced from synoptic charts. Recommendations are given for using the method as a research tool to estimate frontal motions in oceanographic studies of wind‐driven circulation. 相似文献
10.
The diurnal variation of surface winds off the coast of Oregon is described and compared with a recent analysis of winds off the coast of Peru. The Oregon wind speeds have a distinct 24-h periodicity, while the Peru wind speeds were reported to have an irregular 12-h variation. The long-and trans-shore components of both winds exhibit 24-h periodicities; the ratio of the long-shore to trans-shore diurnal amplitudes off Oregon is 2.8, twice the ratio found off Peru. Although meteorological conditions off Oregon were quasi-stationary during the period investigated, there were considerable day-to-day variations in diurnal amplitudes and phases. Diurnal amplitudes were found to be correlated with the daily mean long-shore winds. 相似文献
11.
Abstract The spatial characteristics of the wind speeds from ships, drilling platforms, and satellites (SASS and SMMR) were investigated through autocorrelation analysis. Values of the spatial correlation coefficient in minimum separation classes revealed that SASS winds contained the least noise, followed by drilling‐platform and SMMR winds, measured ship winds and estimated ship winds. The variances explained by wind‐speed observations within a 100‐km radius of each other were found to be 86, 72, 62, 48 and 41%, respectively. Ship wind‐speed estimates made during hours of darkness showed significantly higher noise than daytime reports. 相似文献
12.
Summary
This study investigates the impact of lateral boundary conditions on the propagation and dispersion of locally excited Rossby
waves in a zonally periodic, barotropic, quasigeostrophic channel model on the β-plane. We use basic flows with either a linear
meridional shear or a jet-like profile. On the southern boundary of the channel we impose either a rigid wall or a radiation
condition, whereas the northern sidewall is permeable for Rossby waves. We compare the numerical solutions found for a reflecting
southern boundary in a weakly dissipative flow to the solutions obtained from a WKB-analysis for the corresponding unforced
nondissipative situation. Furthermore, we compare the generalized Eliassen-Palm flux vectors to the ray paths of Rossby wave
packets, obtained from WKB ray tracing. In particular, we focus our investigation on the two-dimensional structure of trapped
modal waves and wavetrains in a simple linear numerical model.
Summarizing our results, we find that along the reflective wall, trapped modal wave structures as well as reflected wavetrains
occur with characteristics (e.g., wavenumbers, turning latitudes) similar to the ones computed using asymptotic methods. In
a linear sheared flow wave packets are trapped for all zonal wave numbers in contrast to a jet-like mean flow which has a
selective effect on the waves; i.e., a turning latitudes phenomenon between the coast and the flow maximum occurs for short
waves, while long waves can propagate freely across the zonal mean flow. This comes out clearly when studying the stream lines
of the Eliassen-Palm flux vectors of the numerical model simulations. Furthermore, due to the reflected wave activity, the
dispersion of Rossby waves is influenced by the southern boundary condition not only in the vicinity of the border but also
in regions away from the boundary. These results appear to be important on the one hand for the existence of trapped Rossby
waves in large-scale oceanic shear flows along a zonally oriented coast. And, on the other hand for large-scale boundary waves
in conceptional atmospheric channel models which can lead to unwanted resonance effects.
Received July 18, 2000/Revised June 9, 2001 相似文献
13.
2018年和2021年末我国南方分别发生了一次大范围的低温雨雪天气,对生活、生产造成了严重影响,因此对比分析这两次低温雨雪天气成因具有重要意义。结果表明：两次过程期间,对流层中层中高纬阻塞流场显著,阻高位于贝加尔湖西侧,脊前偏北气流在下游横槽后部堆积,使得西伯利亚高压强度增强。东传的Rossby波在阻高区域发生能量频散,利于阻高减弱、崩溃,横槽转竖引导槽后冷空气南下,导致地面强烈降温,同时在西伯利亚高压东侧和南侧,低频风温度平流是造成强降温的主要原因。低纬南支槽活跃,向北的暖湿空气与中高纬南下的冷空气汇合,造成我国南方大范围的低温雨雪、冻雨天气。与2018年过程相比,2021年过程持续时间较短,降水范围小,关键区降温幅度更大,是因为2021年过程期间Rossby波能量频散更快,阻高维持时间较短,冷空气从中高纬地区直接南下侵袭我国,而2018年冷空气在贝加尔湖附近发生堆积、西折,向南渗透时势力减弱。 相似文献
14.
本文推导出柱坐标系下含有粘性摩擦项的正压方程组。选取2005年台风麦莎登陆浙江过程中的8月6日15时的WRF(Weather Research and Forecasting)模式输出资料,利用数值差分方法对该正压方程组求特征波解,分析粘性摩擦对台风麦莎内部正压特征波动的影响。结果表明,重力惯性外波在粘性摩擦的影响下,最不稳定波的波数为45左右,波动在摩擦的影响下衰减,波动沿逆时针传播,在半径1000 km处,1波波速为47.43 m/s,在半径r>800 km的范围内,径向风分量扰动加大,辐合辐散运动增强;而摩擦影响下的涡旋Rossby波,2波最不稳定,波动增长率减小,在半径r=200 km处波动相速度为4.282~29.172 m/s,扰动涡度大值区范围减小,涡旋Rossby波的波动区域沿着径向向台风中心收缩。分析包含所有波动时,考虑摩擦后,最不稳定波数在45左右且波动衰减,1波波速在r=1000 km处(外螺旋雨带)为26.374 m/s;在半径r=200 km(内螺旋雨带)为5.275 m/s,考虑径向基本气流后,最不稳定波的波数保持不变,半径r=1000 km处的波速增加为30.324 m/s,r=200 km(内螺旋雨带)处波速为6.065 m/s,摩擦使得径向风分量扰动明显增大,辐合辐散运动加强。 相似文献
15.
K.F. Drinkwater 《大气与海洋》2013,51(2):252-266
Abstract The vertical structures of the mean and tidal flows in Hudson Strait are described from moored current‐meter data collected during an 8‐week period in August to October of 1982. The residual flow in the strongly stratified waters off Quebec is directed along the Strait to the southeast, is highly baroclinic and is concentrated near shore (within an offshore length scale of approximately an internal Rossby radius). Maximum mean speeds of 0.3 m s?1 were observed near‐surface (30 m). In the weakly stratified waters on the northern side of the Strait along Baffin Island the mean flow is northwestward. The maximum speeds are 0.1 m s?1 near‐surface (30 m) and the current amplitudes decrease to 0.05 m s?1 at 100 m. The mean southeastward transport is estimated to be 0.93 ±0.23 × 106 m3 s?1 with a northwestward transport of 0.82 ± 0.24 × 106 m3 s?1. Over most of the Strait the across‐channel residual currents are directed towards the Quebec shore with velocities ranging from 0.02 to 0.1 ms?1. Current variability is dominated by the tides, the M2 being the major tidal constituent. In the vicinity of the mooring the M2 tide is primarily barotropic, progressive in nature, and has along‐channel current amplitudes varying across the Strait from 0.20 to 0.45 m s?1. Observed differences in tidal sea‐level elevations across the Strait can be accounted for by the cross‐channel variations characteristic of Kelvin waves. 相似文献
16.
Norman Thyer 《大气与海洋》2013,51(4):337-344
Abstract Analysis of diurnal variations of upper winds in summer in Alberta reveals features consistent with the hypothesis of a thermally‐induced wind system resulting from the juxtaposition of the Rocky Mountains and the Prairies. These include diurnal variation of flow that is most pronounced at two levels, one near the surface and one near the level of the mountain tops. Attempts to find a connection between such a system and occurrence of hail were unsuccessful. 相似文献
17.
An analysis of the wind data recorded at the fifteen stations in the Salt Lake Valley indicates that the distributions of the kinetic energy of the mean and turbulent motions in the valley are generally inhomogeneous and nonstationary. The mean motion in the valley, which is strongly affected by the mountain-valley winds, shows a southeasterly flow in the evening and early morning, a northwesterly flow in the afternoon, and a transitional flow in the late morning and after sunset. The mountain winds generally associate with a horizontally convergent flow, whereas the valley winds associate with a horizontally divergent flow. The distributions of the kinetic energy of the mean and turbulent motions show a maximum occurring in the central part of the valley and two minimums, one in the northern and one in the southern part of the valley. In the afternoon, both the mean and turbulent motions increase their intensities, particularly in the western part of the valley. An analysis of the dispersion characteristics indicates that the rate of diffusion in the valley changes with time and space, with a maximum occurring in the early afternoon and minimum in the early morning. 相似文献
18.
研究巢湖流域流场特征对于认识该地区热量、水汽交换和水流运动规律具有重要意义。利用2006年合肥、肥东、巢湖、庐江站以及姥山岛自动气象站的风场资料,分析了巢湖流域典型站点的风速和风向变化特征。结果表明,陆面站点年平均风速为2.17m/s,湖面站点风速为2.41m/s。所有站点春夏季风速大于秋冬季,陆上风速具有明显的日变化,白天风速大于夜间,而湖面风速日变化较不显著。陆面站点风向季节变化明显,春夏季以偏南风为主,秋冬季以偏北风为主,春夏季的风向日变化特征较秋冬季明显,湖面站风向没有明显的季节变化。陆面站点不同程度地受到湖陆风的影响,距离湖面较近的站点受到的影响较大。湖面和陆面站点风向差距平与气温差距平的日变化保持一致,表明湖陆温差是影响巢湖流域湖陆风的关键因子。 相似文献
19.
Diurnal and Seasonal Variations of Thermal Stratification and Vertical Mixing in a Shallow Fresh Water Lake 总被引：1，自引：0，他引：1
Yichen Yang Yongwei Wang Zhen Zhang Wei Wang Xia Ren Yaqi Gao Shoudong Liu Xuhui Lee 《Acta Meteorologica Sinica》2018,32(2):219-232
Among several influential factors, the geographical position and depth of a lake determine its thermal structure. In temperate zones, shallow lakes show significant differences in thermal stratification compared to deep lakes. Here, the variation in thermal stratification in Lake Taihu, a shallow fresh water lake, is studied systematically. Lake Taihu is a warm polymictic lake whose thermal stratification varies in short cycles of one day to a few days. The thermal stratification in Lake Taihu has shallow depths in the upper region and a large amplitude in the temperature gradient, the maximum of which exceeds 5°C m–1. The water temperature in the entire layer changes in a relatively consistent manner. Therefore, compared to a deep lake at similar latitude, the thermal stratification in Lake Taihu exhibits small seasonal differences, but the wide variation in the short term becomes important. Shallow polymictic lakes share the characteristic of diurnal mixing. Prominent differences on the duration and frequency of long-lasting thermal stratification are found in these lakes, which may result from the differences of local climate, lake depth, and fetch. A prominent response of thermal stratification to weather conditions is found, being controlled by the stratifying effect of solar radiation and the mixing effect of wind disturbance. Other than the diurnal stratification and convection, the representative responses of thermal stratification to these two factors with contrary effects are also discussed. When solar radiation increases, stronger wind is required to prevent the lake from becoming stratified. A daily average wind speed greater than 6 m s–1 can maintain the mixed state in Lake Taihu. Moreover, wind-induced convection is detected during thermal stratification. Due to lack of solar radiation, convection occurs more easily in nighttime than in daytime. Convection occurs frequently in fall and winter, whereas long-lasting and stable stratification causes less convection in summer. 相似文献
20.
大气细颗粒物PM2.5污染引起的雾霾天气既与本地污染物排放密切有关,也受局地特殊的风场影响.本文以武汉城市区域为研究对象,分别研究了长江沿岸的江陆风环流、东湖沿岸湖陆风环流的形成与转化特征,发现江风、湖风开始时间均为07：00-08：00,一年中最大风速均能达到2 m/s左右,而春夏季江风的持续时间高于秋冬季,夏季湖风的持续时间高于春季.同时发现区域附近温度和相对湿度之间有明显的相关性,湿度变化趋势大体上跟温度变化趋势相反,且温度对相对湿度的影响存在一定的滞后性,延迟时间大约为1 h. 相似文献