【作者】 高瑞华；

【导师】 尚可政； 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2007， 硕士

【摘要】 渤海海峡是我国内外海运交通的一条极其重要的交通要道和航运枢纽，地理位置十分重要，然而，由于海况及气候条件非常复杂，这里又是我国发生海难最为密集的区域之一，其中，恶劣的大风天气是造成渤海海峡海难事故频发的重要原因之一。本文首先统计了烟台、大连沿海共6个台站1975～2005年共31年的逐日风资料，对累年大风日数、风向、风速级别、持续日数等基本气候特点进行了初步分析。在此基础上，着重对渤海海峡时、空分布特征进行了详细分析。时间分布特征方面，重点分析了大风的年际变化和年变化特点；空间分布特征方面，进行了大风的分区对比分析。利用南隍城资料对渤海海峡大风进一步加深认识，还分析了渤海海峡产生大风的天气形势，重点分析了寒潮大风和蒙古气旋大风两种重要天气系统。最后，利用烟台多普勒雷达资料，分析了渤海海峡雷雨大风的多普勒雷达图象特征。分析表明，渤海海峡大风年平均大风曰数为73．3d，强风日数为4．9d，明显多于周围内陆地区，但与曹钢锋等人统计的山东北部沿海年平均大风日数150．4d的结果有很大的出入，从统计的角度分析了产生出入的原因，认为本文结果更为可靠。渤海海峡大风的风力以6～7级为主，8级以上的强风只占总次数的6．7％，最大和极大风速均可达12级。极大风速一般比最大风速大2个等级左右，但强对流天气造成短时阵风可能大5个等级。渤海海峡的大风不但出现几率高，而且时常出现持续时间很长的连续大风，其中4月各站大风最长持续日数平均值达到11．3d。从时间分布特征来看，渤海海峡大风日数存在逐年减少的变化趋势，以-2．4d／年的趋势递减，但也存在着突变的特点。渤海海峡具有典型的季风性气候特征，冬季以偏北大风为主，春秋季开始出现偏南大风，年变化呈现两峰一谷的形势。分析各站逐年大风日数序列最大熵谱分析结果，发现渤海海峡大风主要有15～16年、5～6年、2～3年3个主要周期。从各站逐年大风日数序列连续小波变换(mexh子波)小波系数分布图上可以看出，序列变化表现为10～16年的大尺度变化，尺度为3～5年的变化也很明显。同时，通过小波分析，证实了大风日数存在突变的特点。分析各站逐月大风日数序列离散小波变换(db3子波)的结果，可以发现序列存在长期减少的变化趋势。从空间分布特征来看，海岛站不仅大风日数多，且风力大，能较好的代表渤海海峡大风的情况，渤海海峡大风的主导风向为NW—NNE，大连沿海以北大风为主，烟台沿海春秋季南大风次数明显增多，偏北风和偏南风较大，而偏东风和偏西风较小。分析南隍城的大风资料，发现南隍城大风日数明显比长岛多，风力比长岛大，渤海海峡大风增大时间存在明显的时间差。所以，预报着眼点要放在这些海岛站上，并且要进一步加强渤海海峡大风的监测能力，为提高“安全气象”服务能力和水平提供重要的参考和分析依据。渤海海峡产生大风的天气形势，可归纳总结为冷锋后部的偏北大风、北(西)高南(东)低形势下的偏北大风、气旋大风、南(东)高北(西)低形势下的偏南人风、华北地形槽形势下的偏南大风、台风大风和强对流系统产生的短时大风共7种形势，其中比较典型的风力强、危害性大的有寒潮大风和蒙古气旋大风。根据烟台新一代天气雷达的速度和反射率因子及其导出产品，归纳几种类型的中小尺度天气的多普勒雷达图象特征，认为雷雨大风在平均径向速度图上经常表现为大风区型和近地层辐散型，大风区和辐散区离地面越近，发生下击暴流、造成地面灾害性大风的可能性就越大。径向速度峰值越高，地面风速就越大。逆风区型也是雷暴大风的重要指标。中气旋特征出现的几率虽然不高，但却是强烈天气的重要标志，一旦出现中气旋特征，往往预示着短时暴雨或大暴雨、冰雹、灾害性大风等强烈天气的发生。产生雷雨大风的回波以线状回波居多，弓形、钩状和V形等特殊形状回波与强烈天气的发生密切相关。雷雨大风出现时，风场上表现为较为明显的垂直切变。造成雷雨大风的回波强度强，移速快，垂直累积含水量也高得多。这些预报指标将有助于提高对新一代天气雷达资料及其产品分析和强对流识别的能力。更多还原

【Abstract】 The Bohai straits is an important sea transportation in China and the geography position is very important. However, because of the complicated sea conditions and the weather, here is one of the most shipwrecks happened in China. Among them, strong wind weather frequently results in the shipwreck.In this paper we firstly investigate the wind data of 6 stations in the coastal area of Yantai and Dalian from 1975 to 2005 total 31 years, the basic climatic characteristics such as the distributions of the gale days, wind direction and power, lasting days etc. have been preliminary analyzed. On this foundation, time and space distribution of gale characters over Bohai straits has been studied. On one side time distributes, the variation of the gale days in annual is studied, on the other side space distributes, area distribution compared each other. Using data in Nanhuangcheng, further studies are carried to the gales over Bohai straits. Weather conditions bring gales are analyzed. Two kinds of weather systems such as cold wave gales and Mongolia cyclone gales are deeply researched. Finally, thunder gale’s Doppler radar characters are analyzed over Bohai straits using the NEXRAD (CINRAD/SA) data in YantaiResults show that average gale days over Bohai straits are 73.3d, and fresh gales are 4.9d, obviously larger than the inland region, different from the data 150.4d statisticed by Caogangfeng etc. The reason was studied from statistics and considered that conclusions are more realizable in this paper.The gale’s speed over Bohai straits mainly varies from 6th to 7th grade, over 8th grade merely 6.7%. The infinite and maximum gale’s speed all reaches 12th grade. The infinite gale’s speed is stronger 1 or 2 grades than the maximum. But strong convection weather result in short-time gust often larger than 5 grades. The gales over Bohai straits appears not only frequently but also last a long time. The longest average last days are 11.3d in April.From time distribution characters, the gale days over Bohai straits have a trend to reduce year after year. Gradually decrease with the trend -2.4d annually, but also exist break. The Bohai straits has the typical feature of monsoon, which the gale’s direction is northern in winter and is southern in spring and autumn mainly, annual variation tendency configuration has 2 apexes and 1 valley.By means of maximum entropy spectral the series of each station annual gale days are analyzed, detect that gale over Bohai straits have 3 main periods in 15-16 years, 5-6 years and 2-3 years. By means of wavelet transform(mexh wavelet) the wavelet coefficient distribution diagram of each station annual gale days series are studied, results show that series variation appears in 10-16 years in large scale, scale in 3-5 years too. By means of wavelet analysis, it is confirmed that gale days have a break. The series has a reduce trend in long term using scatter wavelet transform(db3 wavelet) to study the results of each station monthly gale days.From space distribution characters, island stations have more gale days and strong wind power and represent gale situation perfectly over Bohai straits. The main gale’s direction over Bohai straits is NW-NNE. The gale’s direction is northern in Dalian coastal, and the south gale days increase obviously in Yantai coastal in spring and autumn; north and south gale days is more than east and west.By studying the data of Nanhuangcheng station, it is discoverd that the gale days in Nanhuangcheng station are more than those in Changdao station, and wind power are stronger than those in Changdao station. The begining time difference when wind power become large is evident between both stations. So, forecasting focuses should be put on these island stations, and further monitoring ability should be strengthened in Bohai straits, then it can provide important reference and analysis foundation to enhance "safe weather" service ability.The weather conditions which can bring about gales over Bohai straits, can be summarized to 7 patterns, including northern gale behind the cold front, northern gale caused by the pattern of high in north (west) and low in south (east), cyclone gale, southern gale caused by the pattern of low in north (west) and high in south (east), southern gale caused by the Huabei topography trough, typhoon gale and the brief gale cause by severe and convective system. Typical systems, which bring strong gale and serious disaster, are cold wave gales and Mongolian cyclone gales.Based on the radial velocity, reflectivity and educed other products of NEXRAD (CINRAD/SA) data in Yantai, mesoscale and microscale weather gales are analyzed. The results show that thunder gale often happened under strong wind region pattern and divergence area near the surface in radial velocity, the more close the strong wind region, divergence area near ground, the more thunder-storm and disaster strong wind in ground occur. The radial velocity is as big as the ground wind. Adverse wind area is also an index of the strong wind. Although mesoscale cyclone doesn’t often appear, it is an important sign of the strong weather. Once it appears, strong weathers, such as short time rain-storm, hail and disaster strong wind etc. usually appear, too. Thunder-storm gales are often caused by line form. Bow form, hook form and V form etc. often closely related to the occurrence of strong weather. When thunder-storm gale appears, obvious vertical wind shear appears too. The thunder-storm gale has a strong echoes, the VIL is also high. These forecast signs will enhance the ability in the analysis of Doppler radar characters and the detection of strong convection.更多还原