北京及周边地区雷暴阵风锋特征统计分析     

何娜  丁青兰  俞小鼎  付宗钰  周璇  刘璐  李桑  柳克 《气象学报》2020,78(2):250-259

为全面和系统研究北京及周边地区阵风锋各方面特征,使用2006—2015年暖季（5—9月）北京多普勒雷达探测资料及北京、河北、天津自动气象站观测资料对北京及周边地区的阵风锋过程进行综合统计分析。结果表明,346次阵风锋过程有232次触发了对流,占总数的67%,表明阵风锋对雷暴具有较强的抬升触发能力。阵风锋在6—8月出现的日数占5—9月阵风锋总日数的85%;出现的时段主要是午后至傍晚（12—21时,北京时）,维持时间0.5—3 h;阵风锋在北京东南方向生成的数量最多,且触发对流的次数也最多;其次为偏东和东北方向;偏南和西南方向生成阵风锋数量居中,而偏北、偏西和西北地区阵风锋个例相对较少,触发对流的比例也相对较低。产生阵风锋的母风暴中48%为孤立雷暴（包括孤立多单体和超级单体风暴）,31%为雷暴群,21%为飑线;97%的母风暴最强回波在50 dBz以上,阵风锋的回波强度为10—25 dBz。91%的阵风锋移动速度集中在10—60 km/h,84%的阵风锋与母风暴的最大距离为1—60 km;在母风暴回波强度减弱到30 dBz以下时,80%的阵风锋能够继续维持的时间不超过2 h。阵风锋母风暴向东南方向移动的个例最多,从阵风锋和母风暴移动方向的关系来看,阵风锋与母风暴移向一致的情况占比最高,为32%,其次为母风暴无移动及阵风锋弧形扩散情况,各占17%;阵风锋与母风暴移向相反情况所占比例最低,只有3%。最后统计了阵风锋经过地面自动气象站时,自动观测量的变化情况。结果显示,阵风锋在经过地面自动气象站时会造成风速增大、温度降低、相对湿度增大、气压升高。   相似文献   

The 2.9-4.2 micron spectrum of Saturn: Clouds and CH₄, PH₃, and NH₃     

Sang J. Kim  T.R. Geballe 《Icarus》2005,179(2):449-458

We have used synthetic spectra to analyze a medium resolution 2.9-4.2 μm spectrum of Saturn's temperate region observed at UKIRT using CGS4. The synthetic spectra include CH₄, PH₃, and NH₃ lines, for which mixing ratios were adopted from recent Cassini results. The observed absorption features in the spectrum are well accounted for by lines of these molecular species formed 22 +/− 8 km above the 1 bar pressure level at ∼610 mbar. The influence of optically thin haze particles at higher altitudes on the spectrum is not pronounced, with higher spectral resolution probably required to constrain the effects of haze in this wavelength region. Fluorescent line emission by CH₄ in its ν₃ and ν₃+ν₄−ν₄ bands, detected in the 3.2-3.5 μm region, originates between 400 km (∼0.06 mbar) and 800 km (∼0.01 μbar) above the 1 bar level, with peak contributions from the two major contributing bands at 550 km (∼3 μbar) and 700 km (∼0.1 μbar), respectively.  相似文献   

贺兰山东麓宁夏一次极值暴雨过程分析   总被引：5，自引：1，他引：4  

纪晓玲  桑建人  马筛艳  胡文东  杨侃 《气象科学》2010,30(3):332-337

利用常规气象资料和NCEP再分析资料,结合宁夏业务化的中尺度数值预报模式MM5输出产品,对2006年7月14日发生在贺兰山东麓宁夏的极值暴雨过程从降水特征、环流背景、影响系统、强降水落区及物理量特征等方面进行了分析。表明:此次极值暴雨是在2006年第4号台风"碧利斯"与副热带高压系统的相互作用、中β尺度低值系统影响和地面静止锋的触发下爆发的。强降水落区位于200 hPa青藏高压前部西北气流辐散区与500 hPa西南气流、700 hPa西南或偏南低空急流、850 hPa偏东气流三股气流辐合区相重叠区,中β尺度低值系统的右前侧与湿焓平流最强的区域。对流层高层干冷空气下侵是强降水的主要触发机制之一。非地转湿Q矢量与强降水落区有良好的对应关系,对短时强降水天气具有较好的描述能力和预报指导意义。  相似文献   

Jupiter's hydrocarbon polar brightening: Discovery of 3-micron line emission from south polar CH₄, C₂H₂, and C₂H₆     

Sang J. Kim  T.R. Geballe  J.H. Kim 《Icarus》2009,202(1):354-357

Jupiter exhibits bright H⁺₃ auroral arcs at 3-4 microns that cool the hot (>1000 K) ionosphere above the ∼¹⁰−7 bar level through the infrared bands of this trace constituent. Below the ¹⁰−7 bar level significant cooling proceeds through infrared active bands of CH₄, C₂H₂, and C₂H₆. We report the discovery of 3-micron line emission from these hydrocarbon species in spectra of the jovian south polar region obtained on April 18 and 20, 2006 (UT) with CGS4 on the United Kingdom Infrared Telescope. Estimated cooling rates through these molecules are 7.5×¹⁰−3, 1.4×¹⁰−3, and , respectively, for a total nearly half that of H⁺₃. We derive a temperature of 450 ± 50 K in the ¹⁰−7-¹⁰−5 bar region from the C₂H₂ lines.  相似文献   

Measurement of the deformation of sand in a plane strain compression experiment using incremental digital image correlation     

Wang  Pengpeng  Sang  Yong  Shao  Longtan  Guo  Xiaoxia 《Acta Geotechnica》2019,14(2):547-557

Acta Geotechnica - This work presents the results from a series of plane strain compression experiments on medium-density sands. In these experiments, a new type of plane strain experimental...  相似文献   

城市规划对大气环境变化及空气质量的影响   总被引：8，自引：3，他引：5  

佟华  刘辉志  胡非  桑建国 《气候与环境研究》2003,8(2):167-179

采用北京大学三维复杂地形中尺度数值模式,利用Landsat-TM卫星影像图和"北京海淀区北部地区总体规划--用地规划图",分别模拟了北京海淀区北部规划完成后和目前情况下的气象场和大气环境,并分析了规划区的建成对本地和整个海淀区的影响.通过将观测的直径小于10 μm的粒子即PM10总量加权分配得到源强分布,计算海淀区的PM10浓度分布,在目前源强分布调查很困难的情况下不失为一种较为合理可行的方法.试验表明规划区的建成会增加当地和其下风方向的热岛强度和PM10浓度.对规划区进行较为合理的布局,如相对增加树木减少建筑物的面积将会缓和上述影响.  相似文献   

对流云街激发的重力波和波动阻力   总被引：4，自引：0，他引：4  

桑建国  王保民  孙向明 《气候与环境研究》2002,7(1):114-120

大气边界层中的对流活动,可以在其上部稳定层中激发出重力波,并引起垂直动量输送,影响到对流层和平流层中的动量平衡过程.从二层模式中大气波动方程的线性解出发,得出了对流云街激发的重力波波阻解析表达式,并讨论了大气条件对波阻的影响.这些分析可有助于大气环流模式(GCM)中此类重力波波阻参数化表达式的建立和改进.  相似文献   

A Review on Marine N2 Fixation: Mechanism,Evolution of Methodologies,Rates, and Future Concerns     

Bhavya  P. S.  Min  Jun-Oh  Kim  Min-Seob  Jang  Hyo Keun  Kim  Kwanwoo  Kang  Jae Joong  Lee  Jae Hyung  Lee  Dabin  Jo  Naeun  Kim  Myung Joon  Kim  Yejin  Lee  Junbeom  Lee  Chang Hwa  Bae  Hyeonji  Yoo  Hyeju  Park  Sanghoon  Yun  Mi Sun  Lee  Sang Heon 《Ocean Science Journal》2019,54(4):515-528

Ocean Science Journal - Investigations on marine N2 fixation have gained momentum since 1960s with eventual establishments of relevant methodologies to identify species involved and quantify the...  相似文献   

Possible influence of Arctic oscillation on precipitation along the East Asian rain belt during boreal spring     

Qu  Jingxuan  Gong  Daoyi  Mao  Rui  Yang  Jing  Li  Sang 《Theoretical and Applied Climatology》2017,129(1-2):487-502

Theoretical and Applied Climatology - The sandy land in the southern region of the Tengger Desert is adjacent to cities and towns, and land desertification poses a threat to the livelihood and...  相似文献   

Probabilistic corrosion rate estimation model for longitudinal strength members of bulk carriers     

Jeom Kee Paik  Sung Kyu Kim  Sang Kon Lee 《Ocean Engineering》1998,25(10):837-860

Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. Clearly, in such cases, vessels that start out being adequate somehow become marginal later in life. Fatigue and corrosion-related potential problems may be the most important factors affecting such age related vessel damage. With respect to fatigue, extensive studies have been done worldwide both experimentally and theoretically, and the results have been applied to some extent. However, in the case of corrosion effects, additional research is still needed to better understand, clarify and address the various strength uncertainties and their effects on structural behaviour. This paper develops a probabilistic corrosion rate estimation model for the longitudinal strength members of bulk carriers. The model is based on available statistical data for corrosion of existing bulk carriers. The corrosion data collected are documented for future use.  相似文献