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1.
Atmospheric turbulence is an important factor in the modelling of wind forces on structures and the losses they produce in
extreme wind events. However, while turbulence in non-hurricane winds has been thoroughly researched, turbulence in tropical
cyclones and hurricanes that affect the Gulf and Atlantic coasts has only recently been the object of systematic study. In
this paper, Florida Coastal Monitoring Program surface wind measurements over the sea surface and open flat terrain are used
to estimate tropical cyclone and hurricane wind spectra and cospectra as well as integral length scales. From the analyses
of wind speeds obtained from five towers in four hurricanes it can be concluded with high confidence that the turbulent energy
at lower frequencies is considerably higher in hurricane than in non-hurricane winds. Estimates of turbulence spectra, cospectra,
and integral turbulence scales presented can be used for the development in experimental facilities of hurricane wind flows
and the forces they induce on structures. 相似文献
2.
Summary Hurricanes cause a variety of damage due to high winds, heavy rains, and storm surges. This study focuses on hurricanes’
high winds. The most devastating effects of sustained high winds occur in the first few hours of landfall. During the short
period, hurricanes’ rainfall often increases, while the low-level pressure gradients continue to weaken. Latent heating does
not appear to strengthen the surface winds. The indicator is that dry mechanisms such as the boundary layer processes and
terrain are responsible for the damaging winds in the coastal areas. In this study, the design of a dry hurricane boundary
layer wind model is described. The goal is to develop a forecast tool with near-real time applications in expeditious wind
damage assessment and disaster mitigation during a hurricane landfall event.
Different surface roughness lengths and topographic features ranging from flat land to the mountainous terrain of Taiwan were
used in the model simulation experiments to reveal how the coastal environment affected the hurricane surface winds. The model
performed quite well in all cases. The experiments suggested that the downward transfer of high momentum aloft played a significant
role in the maintenance of high wind speeds at the surface. The surface wind maximums were observed on the lee sides of high
terrain. The surface streamline analyses showed that the high mountains tended to block the relatively weak flow and caused
small eddies, while they forced the stronger flow to turn around the mountains.
Due to great difficulty in data collection, the hurricane boundary layer over land remains one of the least understood parts
of the system. The dry model proves to be an effective way to study many aspects of hurricane boundary layer winds over a
wide range of terrain features and landfall sites. The model runs efficiently and can be run on a medium-size personal computer.
Received March 16, 2001 Revised September 10, 2001 相似文献
3.
基于宁波多普勒雷达、浙江省自动气象站、宁波凉帽山高塔梯度观测等资料,对1416号强热带风暴“凤凰”登陆浙江后的风场时空变化进行分析。结果表明:“凤凰”结构不对称,8级以上风速带主要位于风暴中心前进方向的前侧和右侧。前侧最大风速半径一直维持在60 km左右,最大风速带宽度约为50 km;其右侧最大风速半径为80~120 km,随中心北移有增大趋势,最大风速带宽度约100 km;其前侧和右侧最大风速半径在垂直方向上变化不大。“凤凰”前侧TREC（Tracking Radar Echoes by Correlation）风速在1 km高度最强,其上则随高度的增大而减小,其右侧1~3 km高度TREC风速的垂直变化明显小于前侧。宁波凉帽山高塔处TREC风和梯度观测表明:“凤凰”影响期间,高塔上空159 m和2~4 km高度出现多个风速高值中心;常通量层高度约为159 m;常通量层内风廓线遵从对数率,当高塔位于“凤凰”右前侧时塔层阵风系数随高度增大而减小,当高塔位于“凤凰”中心附近和右后侧时阵风系数明显增大,且层次差异减小;常通量层以上159~318 m的塔层风廓线不满足指数率或对数率,阵风系数上下差异不大。 相似文献
4.
琼州海峡沿岸大风分布规律及影响系统分析 总被引：1，自引：0，他引：1
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。 相似文献
5.
Louis M. Michaud 《Meteorology and Atmospheric Physics》2012,118(1-2):21-29
Warm seawater is the energy source for hurricanes. Interfacial sea-to-air heat transfer without spray ranges from 100?W?m?2 in light wind to 1,000?W?m?2 in hurricane force wind. Spray can increase sea-to-air heat transfer by two orders of magnitude and result in heat transfers of up to 100,000?W?m?2. Drops of spray falling back in the sea can be 2–4?°C colder than the drops leaving the sea, thus transferring a large quantity of heat from sea to air. The heat of evaporation is taken from the sensible heat of the remainder of the drop; evaporating approximately 0.3?% of a drop is sufficient to reduce its temperature to the wet bulb temperature of the air. The heat required to evaporate hurricane precipitation is roughly equal to the heat removed from the sea indicating that sea cooling is due to heat removal from above and not to the mixing of cold water from below. The paper shows how case studies of ideal thermodynamic processes can help explain hurricane intensity. 相似文献
6.
Rochelle P. Worsnop George H. Bryan Julie K. Lundquist Jun A. Zhang 《Boundary-Layer Meteorology》2017,165(1):55-86
Offshore wind-energy development is planned for regions where hurricanes commonly occur, such as the USA Atlantic Coast. Even the most robust wind-turbine design (IEC Class I) may be unable to withstand a Category-2 hurricane (hub-height wind speeds >50 m s\(^{-1}\)). Characteristics of the hurricane boundary layer that affect the structural integrity of turbines, especially in major hurricanes, are poorly understood, primarily due to a lack of adequate observations that span typical turbine heights (<200 m above sea level). To provide these data, we use large-eddy simulations to produce wind profiles of an idealized Category-5 hurricane at high spatial (10 m) and temporal (0.1 s) resolution. By comparison with unique flight-level observations from a field project, we find that a relatively simple configuration of the Cloud Model I model accurately represents the properties of Hurricane Isabel (2003) in terms of mean wind speeds, wind-speed variances, and power spectra. Comparisons of power spectra and coherence curves derived from our hurricane simulations to those used in current turbine design standards suggest that adjustments to these standards may be needed to capture characteristics of turbulence seen within the simulated hurricane boundary layer. To enable improved design standards for wind turbines to withstand hurricanes, we suggest modifications to account for shifts in peak power to higher frequencies and greater spectral coherence at large separations. 相似文献
7.
阵风特性研究是大风预报和服务的基础。基于2011-2013年浙江省自动气象站逐日逐10 min测风资料,分析了浙江省陆地和近海海面冷空气、热带气旋和强对流大风的阵风系数特征。结果表明:冷空气和热带气旋大风阵风系数空间分布基本相同,大风主要发生在近海海面和沿海地区,海面阵风系数一般小于1.5,等值线平行于海岸线且自西向东逐渐减小,陆地阵风系数一般大于2.0,山区可超过3.0,表现出地形对阵风系数的增强作用。强对流大风阵风系数明显高于业务规范平均值,发生地点遍及浙江省各地,但发生概率超过10%的站点主要位于沿海地区和近海海面。风向基本不影响阵风系数空间分布。冷空气和热带气旋站点阵风系数与海拔高度有较高正相关性。模糊聚类分析发现:浙江省400 m以上山区站与70 m以下的低海拔站点在阵风系数特征上分属不同空间类型;基于逐步回归建立站点阵风系数预报模型,检验表明:模糊聚类可帮助提高模型阵风系数预报能力。 相似文献
8.
下投式探空资料对Debby飓风路径预报影响的数值试验 总被引：1，自引：0，他引：1
在飓风路径的数值预报中，对于初始场的要求很高，然而，由于初始资料的缺乏，经常导致路径预报的误差较大，尤其是当飓风处于远离陆地的海上时，这种误差更大，通过利用UM模式在Debby飓风活动期间，对下投式探空仪所获取探空资料，采用不同使用方案的三个时次共计10次数值试验的结论分析，给出一些有意义的 结论，即非实时资料对实时资料的有效补充，能够提高飓风路径预报精度，而在众多气象要素场中，风场和湿度场对飓风路径预报的影响更大。 相似文献
9.
Chad Shouquan Cheng 《大气与海洋》2014,52(3):232-241
In the field of climate change impact analysis, bidirectional changes in projections of future wind regimes varying among studies, locations, and models have been described in the literature, which is understandable from a global perspective. However, we should attempt to find evidence in the historical record to support these projections. This paper attempts to address this issue by analyzing historical wind gust observations for up to 57 years (1953–2009) over Canada. Two wind gust analysis techniques were used: the speed of daily wind gust events ≥50?km?h?1 was compared with (1) the climatological daily temperature anomaly and (2) the climatological daily sea level air pressure anomaly. In addition, the frequency of daily wind gust events ≥90?km?h?1 was compared with both daily temperature and pressure anomalies. The results indicate that during the past five decades gust wind speed over Canada increased significantly as the daily temperature anomaly increased and the daily pressure anomaly decreased. About 50–60% of daily wind gust events ≥90?km?h?1 occurred with positive daily temperature anomalies and negative daily pressure anomalies. One major conclusion is that the methods used in and results derived from this study might be applied to climate change impact analysis to support projections of future wind regimes. 相似文献
10.
S. R. H. Rizvi E. L. Bensman T. S. V. Vijaya Kumar A. Chakraborty T. N. Krishnamurti 《Meteorology and Atmospheric Physics》2002,79(1-2):13-32
Summary
In the past, various field experiments were conducted using special aircrafts to enhance the observational database of hurricanes.
Dropwindsondes (or “dropsondes”) are generally deployed to collect additional observations in the vicinity of the hurricane
center. In addition to dropsondes, during the Third Convection and Moisture Experiment (CAMEX-3), which was conducted over
the Atlantic Ocean and Gulf of Mexico during August–September 1998, LASE was also used to measure vertical moisture profiles.
Four hurricanes: Bonnie, Danielle, Earl and Georges were targeted during this campaign.
This paper describes the resulting impact of CAMEX-3 data, especially the LASE moisture profile data, on the hurricane analysis
and forecast. The data were analyzed using a spectral statistical interpolation technique and the forecasts were made using
the FSUGCM at T126 resolution with 14 σ-vertical levels. Results indicate that the LASE data had a significant impact on the
moisture analysis. The reanalysis was slightly drier away from the hurricane center and wetter close to the center. Spiraling
bands, both dry and wet, of moisture were clearly seen for hurricane Danielle. The LASE data did not affect the wind analysis
significantly, however when it was used along with dropsonde observations the hurricane intensity and its structure were well
represented and the forecast track produced from the reanalyzed initial condition had less forecast errors. The LASE and dropsonde
observations were in good agreement.
Received February 27, 2001 Revised July 31, 2001 相似文献
11.
根据2016—2017年大理机场航空器报告的风切变事件,利用同时段的自动气象观测资料、风廓线雷达资料对大理机场风切变进行了统计和分析。结果表明:①风切变均发生在每年的11月至次年4月,1月、2月最多;主要发生于07:00—13:00,一半出现在晴天;发生在350m以下占83%。②100m以下的风切变,地面均有阵性风,最大最小风速差6m/s;发生在15～91m的6次风切变,5次报告风切变的一端风向变化超过180°,南北两端地面风出现对头风,风速差异明显。AWOS(Automated Weather Observation System)捕捉到风向风速的明显变化可为近地层风切变预警提供参考。③发生在高度较高的风切变,雷达资料在遭遇风切变高度的上下层存在≥8m/s风速差,能确定上下层风不连续的准确高度、开始时间和结束时间。④机场区域常出现地面风速大而上空风速小或地面风速小而上空风速大的情况,结合地面风和风廓线雷达资料可为今后低高度风切变的初步预警提供参考。 相似文献
12.
Dissipative heating and hurricane intensity 总被引：3，自引：0，他引：3
Summary Dissipative heating has not been accounted for in either numerical simulations of hurricanes or in theories for the maximum intensity of hurricanes. We argue that the bulk of dissipative heating occurs in the atmospheric boundary layer near the radius of maximum winds and, using both theory and numerical simulation, show that dissipative heating increases maximum wind speeds in tropical cyclones by about 20%.With 4 Figures 相似文献
13.
Climatic conditions that affect the interannual variability of Caribbean hurricanes are studied. Composite meteorological and oceanographic reanalysis fields are constructed for active and inactive seasons since 1979, and differences are calculated for spring and summer periods to provide guidance in statistical analysis. Predictors are extracted for areas exhibiting high contrast between active and inactive seasons, and intercomparisons are made. Zonal winds north of Venezuela exhibit westerly anomalies prior to active years, so coastal upwelling and the north Brazil current are diminished. Rainfall increases in the Orinoco River basin, creating a fresh warm plume north of Trinidad. The predictor time series are regressed onto an index of Caribbean hurricanes, and multivariate algorithms are formulated. It is found that atmospheric kinematic and convective predictors explain only ??20% of hurricane variance at 3?C5-month lead time. Subsurface ocean predictors offer higher levels of explained hurricane variance (42%) at 3?C5-month lead time, using 1?C200-m-depth-averaged temperatures in the east Pacific and southern Caribbean. We place the statistical results in a conceptual framework to better understand climatic processes anticipating Caribbean hurricanes. 相似文献
14.
Spectra and gust factors for gale force marine winds 总被引：1，自引：0，他引：1
Wind turbulence measurements obtained at a stable floating platform 10 km off the coast of Nova Scotia are unique in the range of wind speeds covered, and in freedom from influences of platform motion and flow distortion. Spectra of wind velocity components are presented according to Monin-Obukhov similarity theory. Gust factors for downwind, lateral and vertical components are reported for a range of gust durations and sampling intervals. These results are compared with published values, confirming the concept of similarity theory for spectra in gale force winds, and resolving a discrepancy among published gust factors. 相似文献
15.
Corene J. Matyas 《Meteorology and Atmospheric Physics》2010,106(3-4):135-148
This study examines relationships between the extent of hurricane rain fields, storm size, and the environment surrounding the storm. A Geographic Information System is employed to measure the extent of the rain fields in each quadrant of 31 hurricanes at landfall-time. After correlating the extents with measures of storm size, multiple linear regression models are developed to determine which atmospheric forcing(s) at 0, 12, and 24 h prior to landfall are most highly related to rain field size in each quadrant. Results show that the radius of the outermost closed isobar encompasses the rain fields in 90% of the observations. Strong vertical wind shear from the southwest correlates with a larger (smaller) rain field extent toward the northeast (southwest), while higher relative humidity values correlate with a larger extent toward the northwest, southwest, and southeast. Storm intensity and location also exhibit statistically significant correlations with rain field size. 相似文献
16.
Accurate forecasting of the intensity changes of hurricanes is an important yet challenging problem in numerical weather prediction. The rapid intensification of Hurricane Katrina(2005) before its landfall in the southern US is studied with the Advanced Research version of the WRF(Weather Research and Forecasting) model. The sensitivity of numerical simulations to two popular planetary boundary layer(PBL) schemes, the Mellor–Yamada–Janjic(MYJ) and the Yonsei University(YSU) schemes, is investigated. It is found that, compared with the YSU simulation, the simulation with the MYJ scheme produces better track and intensity evolution, better vortex structure, and more accurate landfall time and location. Large discrepancies(e.g.,over 10 hPa in simulated minimum sea level pressure) are found between the two simulations during the rapid intensification period. Further diagnosis indicates that stronger surface fluxes and vertical mixing in the PBL from the simulation with the MYJ scheme lead to enhanced air–sea interaction, which helps generate more realistic simulations of the rapid intensification process. Overall, the results from this study suggest that improved representation of surface fluxes and vertical mixing in the PBL is essential for accurate prediction of hurricane intensity changes. 相似文献
17.
Impacts of Four Types of ENSO Events on Tropical Cyclones Making Landfall over Mainland China Based on Three Best-track Datasets简 总被引：1，自引：0，他引：1
Impacts of EI Nino Modoki （ENM）, La Nina Modoki （LNM）, canonical EI Nifio （CEN） and canonical La Nifia （CLN） on tropical cyclones （TCs） that made landfall over mainland China during 1951-2011 are analysed using best-track data from China, the USA and Japan. Relative to cold phase years （LNM and CLN）, landfalling TCs in warm years （ENM and CEN） have a farther east genesis location, as well as longer track lengths and durations, both in total and before landfall. ENM demonstrates the highest landfall frequency, most northerly mean landfall position, and shortest after-landfall sustainability （track length and duration）, which indicate a more frequent and extensive coverage of mainland China by TCs, but with shorter after-landfall influence. CEN has low landfall frequency and the most southerly mean landfall location. LNM has the most westerly genesis location, being significantly farther west than the 1951-2011 average and leading to short mean track lengths and durations both in total or before landfall, all of which are significantly shorter than the 1951-2011 average. Variations in the low-level wind anomaly, vertical wind shear, mid-level relative humidity, steering flow, the monsoon trough and the western Pacific subtropical high （WPSH） can to some extent account for the features of frequency, location, track length and duration of landfalling TCs. Since ENSO Modoki is expected to become more frequent in the near future, the results for ENSO Modoki presented in this paper are of particular significance. 相似文献
18.
利用广东省徐闻县西连镇90 m测风塔在1409号超强台风威马逊登陆期间获取的具备完整的台风代表性的观测数据以及处于台风外围的广东省茂名市博贺镇100 m测风塔的观测数据,对台风威马逊的近地层强风特性进行了分析,西连测风塔结果表明:风速时程曲线呈明显的"M"型分布特征,台风中心经过测风塔前后,风向沿逆时针方向大幅偏转约170°。风速随高度增加而增大,风速廓线较好地符合对数和幂指数律;台风过境前后,各强风区的风速廓线幂指数和粗糙长度呈先减小后增大的特点;粗糙陆地下垫面的风速廓线幂指数和粗糙长度较大。湍流强度和阵风系数在前外围强风区或后外围强风区较大,在前眼壁强风区或后眼壁强风区较小,湍流强度和阵风系数随高度增加而减小,基本符合指数为负值的幂指数律;粗糙下垫面对湍流强度和阵风系数有增大的作用。外围强风区和眼壁强风区的10 min风向变率变化较为平稳,而在眼区变动较为剧烈,在眼区,当风速达到最低值或次低值时,10 min风向变率幅值达到最大值。博贺测风塔结果表明其总体上与西连测风塔台风前外围和前眼壁强风区的情形相似。 相似文献
19.
We analyzed the frequency distribution characteristics of wind speeds occurring at different offshore sites within a range of 0–200 km based on the sea surface wind data captured via buoys and oil platforms located along the east coast of Guangdong Province. The results of the analysis showed that average wind speed measured for each station reached a maximum in winter while minima occurred in summer, corresponding to obvious seasonal variation, and average wind speed increased with offshore distance. The prevailing wind direction at the nearshore site is the easterly wind, and the frequency of winds within 6–10 m s–1 is considerable with that of winds at > 10 m s–1. With the increase of the offshore distance, the winds were less affected by the land, and the prevailing wind direction gradually became northerly winds, predominately those at > 10 m s–1. For areas of shorter offshore distance (< 100 km), surface wind speeds fundamentally conformed to a two-parameter Weibull distribution, but there was a significant difference between wind speed probability distributions and the Weibull distribution in areas more than 100 km offshore. The mean wind speeds and wind speed standard deviations increased with the offshore distance, indicating that with the increase of the wind speed, the pulsation of the winds increased obviously, resulting in an increase in the ratio of the mean wind speed to the standard deviation of wind speed. When the ratio was large, the skewness became negative. When a relatively great degree of dispersion was noted between the observed skewness and the skewness corresponding to the theoretical Weibull curve, the wind speed probability distribution could not be adequately described by a Weibull distribution. This study provides a basis for the verification of the adaptability of Weibull distribution in different sea areas. 相似文献
20.
Hurricane intensity and track are strongly affected by air-sea interactions. Classified as following swells, crossing swells, and opposing swells, the observed wave height was parameterized by using the 10-m wind speed collected on 5 buoys by the National Buoy Data Center during 13 hurricane events. The path information of these 13 hurricanes was obtained from the National Hurricane Center Best Track (NHC-BT). Results show that the wave height increases exponentially with the 10-m wind speed, and the wave height reaches the maximum value, 11.2 m (8.1 m), when 10-m wind speed is 40 m s-1 under the following and crossing (opposing) swell conditions. We find that the wave steepness (the ratio of wave height to wave length) is proportional to the -2/3 power of the wave age (the ratio of wave phase velocity to 10-m wind speed). The parameterizations of friction velocity and drag coefficient are tested using the buoy data collected in moderate to high wind under following, crossing and opposing swell conditions. A wave age dependent equation for drag coefficient is found more accurate and suggested for future usage in numerical models. Further, these algorithms also suggest that wind-swell orientation needs to be considered to retrieve accurate surface drag under high winds and strong swells. 相似文献