济南市区短时强降水特征分析与天气分型

利用2007—2015年济南市区及历城区自动气象观测站的逐小时降水量资料,以及常规高空、地面观测资料,统计了198次短时强降水过程的范围和强度特征,年际、月际变化特征,按照短时强降水发生时的天气形势和影响系统,分为切变线型、低槽冷锋型、西风槽型、冷涡型、台风外围型及无系统型6类,并分析了不同类型和不同范围短时强降水的关键环境参量。研究表明:短时强降水的强度与范围有较好的相关性,7月中旬—8月中旬出现强降水的次数最多;切变线型短时强降水发生范围与强度分布最广,7、8月的低槽冷锋型过程极易造成大范围高强度降水;地面露点(Td)、850 h Pa假相当位温(θse)、对流有效位能(CAPE)以及暖云层厚度能较好地区分不同范围的短时强降水过程。在天气分型的基础上,结合不同降水范围和不同降水类型环境参量箱线图与阈值表,可为济南市区短时强降水的预报提供有价值的参考。     

2007-2019年山东省短时强降水时空分布特征

选用山东123个国家级地面气象观测站2007-2019年地面逐小时降水资料,分析短时强降水分布特征,主要结论如下:1)其间共有695个短时强降水日、3 337个短时强降水时次和6 257个短时强降水样本,基于排序法确定山东省极端短时强降水阈值为71.2 mm·h-1,鲁东南地区阈值最高,鲁中地区阈值最低.2)各站年均发...     

青岛市短时强降水的气候特征和天气系统分型

利用1981—2012年4—10月青岛市7个观测站逐时降水量资料和同期NCEP再分析资料,统计分析青岛市短时强降水的时空分布特征,建立青岛市短时强降水天气概念模型。结果表明:青岛市年短时强降水日数无明显变化趋势;4—10月均有短时强降水出现,7—8月是多发月份;短时强降水的日变化有2个多发时段,主峰在下午到傍晚时段,次峰在凌晨时段;即墨、平度、黄岛为青岛市短时强降水的多发区域,其中黄岛为连续性短时强降水出现最多的区域;青岛市产生短时强降水的天气系统可分为六种类型,西风槽型、横槽型、冷涡型、热带低值系统型、西北气流型、切变线型,其中西风槽型出现次数最多。     

1822号台风“山竹”引起浙江东北部大暴雨成因分析

利用自动站资料、卫星云图以及NCEP再分析资料等,分析了1822号台风"山竹"登陆广东期间浙江东北部出现大暴雨的成因。结果表明:强降水发生在台风"山竹"登陆广东后减弱过程期间,伴有中尺度对流系统的发展,是由副热带高压、台风倒槽以及弱冷空气先后影响共同造成的;当对流不稳定时,与暖湿气流相关的湿位涡水平分量发展可触发垂直涡度的增长,使暴雨过程加强;强降水常发生在能量锋区附近,能量场的位置和梯度大小对此次强降水预报有12 h左右的提前量;来自台风东侧低层强的水汽输入和水汽辐合提供了本次强降水的水汽条件,水汽通量分布和水汽通量散度的增减相比雨量的增减有6 h左右的提前。     

佛山短时强降水时空特征及主要影响系统

利用佛山市152个自动气象观测站2012—2020年降水资料,根据强降水范围和性质,研究佛山市短时强降水的时空分布特征,并分析主要影响系统。结果表明：（1）短时强降水发生频次整体呈上升趋势,不同范围、不同性质的短时强降水时空差异性较大。局地性、区域性、突发型短时强降水主要发生在4—9月,全市性、增长型短时强降水主要发生在3—10月,持续型短时强降水5—6月发生频次最高。（2）从日变化来看,局地性、区域性呈单峰特征,全市性呈多峰特征,突发型、增长型呈双峰特征,持续型较平稳,06—09时略高,局地性、全市性和增长型短时强降水中分位值日变化较小,区域性、增长型和持续型短时强降水中分位值的日变化较大。（3）极大值出现的时间段也不相同,最大值的短时强降水是一次增长型的区域性过程。（4）空间分布上,局地性短时强降水在佛山西南部和北部发生的频次较高,全市性短时强降水发生频次的分布与之相反,而区域性短时强降水在西南部发生频次较低,增长型短时强降水发生频次高于突发型短时强降水,持续型短时强降水发生频次最低。（5）影响系统占比最大的分别是局地性、突发型短时强降水为副热带高压边缘,区域性、持续型、增长型短时强降水为热带系统,全市性短时强降水为西风槽,而西南低涡在各类中占比均最小。     

0601号强台风“珍珠”路径变化因子及降水特征

利用天气学诊断分析方法,结合气象卫星云图、多普勒雷达回波、总能量场和中尺度自动气象站记录资料等,分析0601号强台风“珍珠”路径变化的原因以及逐时降水动态变化特点,并探讨了台风影响过程中强降水的主要成因．指出副高、西风槽、高能区对台风运动的影响;台风中心降水和外围降水强弱有反相关的关系,降水较集中在台风路径的左侧;台风“珍珠”登陆前持续加强和对流强烈发展所形成的深厚系统是出现强降水的重要基础,在卫星云图上密实的螺旋结构和中尺度对流云团的生成是台风云带中出现强降水的显著特征,而特定区域地形的多方面影响是降水幅度增加的原因．     

冷涡背景下两次强对流天气对比分析

2010年5月29—30日和2012年6月12日山东半岛均出现由高空冷涡造成的强对流天气,但其强度和范围却差异较大。综合分析天气形势、探空资料、卫星云图、多普勒雷达和风廓线仪等资料,结果表明:两者均受冷涡低槽影响,前者为地面气旋,后者为冷锋过境;水汽图上水汽区的干湿边界、暗区等与强对流的发生发展有着密切关系;红外云图TBB≤-48℃的范围基本与出现对流的区域吻合,TBB≤-52℃的区域与强降水区域比较吻合,但当湿层比较浅薄时,也可能只出现雷暴天气,而非强降水。     

“麦德姆”台风过程中冷空气活动分析及风廓线雷达资料的应用

利用NCEP/NCAR 1°×1°的6 h再分析资料、常规气象观测资料和潍坊风廓线雷达资料综合分析了台风"麦德姆"影响山东时的环流背景、冷空气活动和风廓线特征,结果表明:此次台风暴雨过程中,西风槽冷空气渗透到台风倒槽云系,通过在低层形成冷垫强迫暖空气抬升,形成斜压锋区后触发不稳定能量及潜热能释放,对暴雨的产生加强起了巨大作用;风廓线雷达的垂直风场分布对此次降水的强弱特别是短时强降水的预报有明显的指示作用,低层风速迅速加大的时段与潍坊短时强降水出现的时段是一致的。     

一次MCC过程雷达回波特征分析

2011年8月15—16日,在河北南部和山东北部地区的中尺度对流复合体(MCC)产生了区域性的暴雨,局部地区出现了大暴雨和特大暴雨。利用多普勒雷达、卫星云图、区域自动站等资料,对这次MCC过程进行了分析,结果表明:MCC中的中-β尺度结构显著,系统有多个中-β尺度对流云团发展而成;不同触发机制的对流回波的合并发展是MCC发展成熟的重要标志;辐合线右侧对流单体的生成、发展,且并入到对流云团主体,是MCC长时间维持的重要因素;径向速度场上表现为中尺度辐合线、局部逆风区和中-γ尺度气旋性涡旋等特征,为强降水提供了动力条件,是出现短时强降水的重要特征;雷达径向速度场直观反映MCC的内部气流结构状况,为判断MCC的演变和强降水落区提供了重要信息。     

一次低槽冷锋暴雨数值模拟和诊断分析

利用常规气象观测资料、GPS可降水资料、地闪定位资料以及NCEP 1°×1°再分析格点资料,对2011年7月2—3日山东中北部地区一次低槽冷锋暴雨天气过程进行分析,进一步采用中尺度模式WRF对此次降水过程开展了高分辨率数值模拟,并对模拟资料进行了诊断分析。得到如下结果:(1)此次降水过程具有强降水持续时间短,短时降水强度大、局地性强等特点,在空间和时间上都具有明显的中尺度特征。(2)整个强降水期间,负地闪占绝对优势,负地闪出现在强对流发展的整个阶段,正地闪出现在强对流减弱消散阶段。云顶温度越低,负地闪越密集,当系统减弱,正地闪迅速增加。当云顶亮温(TBB)下降到最低值,负地闪频数达到极大值时,降雨强度也达到最大。GPS可降水量在暴雨监测和预报中具有重要作用。(3)利用模拟结果的分析显示,散度、涡度和垂直速度的分布与对流系统的发生、发展较一致。     

Observation of polar lows by the Advanced Microwave Sounding Unit: potential and limitations

The potential of the Advanced Microwave Sounding Unit (AMSU) observations for the depiction and tracking of intense high-latitude mesoscale maritime weather systems, called polar lows, is explored. Since a variety of mechanisms are important for their development and maintenance, this investigation is based on three polar low cases of different types. The AMSU-B channels at 183 GHz are able to locate convective polar lows (PL) even in their incipient stage, at a time when there is considerable uncertainty as to the nature of the cloud structures seen in the visible or infrared imagery. This detection is based on temperature depression due to scattering by hydrometeors, as confirmed by comparison with radar data. These same channels will, however, fail to unambiguously detect weakly convective and mainly baroclinic PL. The AMSU-A channels help documenting the large-scale environment in which PL develop. Channel 5 clearly shows the cold air outbreaks associated with these developments, whereas the difference between channels 7 and 5 can be used to detect and locate positive upper-level potential vorticity anomalies. Because of the high temporal availability of AMSU observations and despite some limitations pointed out in this study, these results are relevant for PL forecasting and monitoring.     

一套基于FY-3B/MWRI观测的热带气旋微波亮温数据集

利用风云三号B星(FY-3B)微波成像仪(Microwave Radiation Imager, MWRI)一级亮温数据和每6 h一次的热带气旋(tropical cyclone, TC)最佳路径数据进行时空匹配,建立了TC微波亮温数据集。该数据集包含了2011—2016年全球六大海盆生成的热带风暴级别以上的TC共计538个,以及对应每个TC的微波十通道亮温和36.50 GHz、89.00 GHz的极化校正亮温度,并简要阐明了该数据集在热带气旋研究方面的潜在应用,尤其对TC生命周期内的微波亮温特征及TC强度变化研究提供了有力的数据支撑。     

Short-term temperature and salinity variations in the Tsushima Strait in 2004: Behavior of the surface low-salinity water in the strait

Temporal variations in temperature and salinity observed in 2004 were investigated on a short time scale in the Tsushima Strait. The data were obtained by long-term in situ measurements at Mitsushima and Futaoi Island using an instrument equipped with a piston-type wiper to avoid biofouling. In addition, the temperature and salinity values of the surface layer obtained by a commercial ferryboat between Hakata and Busan were used to investigate their spatiotemporal variations. Temperature and salinity variations with a time scale of several days had a negative correlation in the summer. This evidence suggests that a warm and less saline water mass, which is considered to be mainly the Changjiang Diluted Water (CDW), flowed intermittently through the Tsushima Strait in summer. In late July 2004, a large low-salinity water mass was detected in the Tsushima Strait. At that time, the freshwater transport through the Tsushima Strait transiently reached about 12 × 10⁴ m³s⁻¹, which is estimated from observed acoustic Doppler current profiler (ADCP) data along a ferryboat line and inferred salinity profiles. This estimated value is more than double the maximum of the climatological monthly mean of the Changjiang discharge. Furthermore, salinity and surface current data obtained by high frequency ocean radar (HF radar) indicate that water properties at Mitsushima may occasionally represent part of the water flowing through the western channel via a countercurrent, although Mitsushima is geographically located in the eastern channel.     

基于MTSAT卫星的我国东部沿海雾区的自动识别

本文综合运用可见光反射率阈值法,3×3像元空间一致性检测法,红外亮温阈值法及双通道差值法,建立全天候海雾遥感监测算法,并利用MTSAT卫星资料,对2006年4～5月间我国东部沿海海雾进行个例监测试验,并进行卫星图象的目视真实性检验.监测结果表明,该方法能较好地实现云雾自动分离.在夜间,能有效分离低层云雾和晴空像元;当出现逆温雾时,雾仍可以被有效地判识出来.     

Reestablishment of an accretionary prism after the subduction of a spreading ridge—constraints by a geometric model for the Golfo de Penas, Chile

Seismic studies offshore southern Chile have revealed the presence of a 70–80 km wide accretionary prism seaward of the Golfo de Penas (GPAP), where the Chile Ridge collided with the South American Plate between 3 and 6 Ma ago. Using the paleo-positions of the Chile Ridge relative to South America, the maximum age of this accretionary prism, which continues to be formed in the aftermath of the ridge–continent collision, has been estimated. Building on these earlier findings, this study presents a mass balance analysis based on a 2D model of accretionary wedge and trench geometry. This model can explain the relative importance of sedimentary fluxes and deformation front migration for the wedge restoration. The proposed model can also serve to evaluate the effects of fluctuations in (1) terrigenous sediment flux related to climate change, and (2) subduction channel thickness on the accretionary prism growth. Notably, the data reveal that the key parameters controlling the rebuilding of the GPAP are the terrigenous sediment flux (75 km²/10⁶ years), the relative advance of the deformation front (39.6 km/10⁶ years), and the thickness of the subduction channel (0.1 km). Moreover, the range of possible solutions for the observed size of the accretionary prism is narrowed by fitting the present-day thickness of sediments at the deformation front. Finally, climate-induced variations in sedimentary fluxes on the margin can affect the rate of growth of the accretionary prism during short periods of time (<100,000 years).     

Dynamic processes observed at a gas hydrate outcropping on the continental slope of the Gulf of Mexico

A deep-sea time-lapse camera and several temperature probes were deployed on the Gulf of Mexico continental shelf at a biological community associated with a gas hydrate outcropping to study topographic and hydrologic changes over time. The deployment site, Bush Hill (GC-185), is located at 27°47.5′ N and 91°15.0′ W at depths of ∼540 m. The digital camera recorded one still image every 6 h for July-October in 2001, every 2 h for the month of June 2002, and every 6 h for the month of July 2002. Temperature probes were in place at the site for the entire experimental period. The data recovered provide a record of processes that occur at gas hydrate mounds. Sediment resuspension over the mound causes significant variation in luminosity of the time-lapse photographs. A marked diurnal pattern can be seen in the temperature and luminosity records. No major change in shape or size of the gas hydrate outcrop at this site was observed during this study. Stable topography of the gas hydrate mound, combined with high bacterial activity and sediment turnover, appears to focus biological activity in the mound area. Frequency and recurrence of sediment resuspension indicate that short-term change in the depth and distribution of surface sediments is a feature of the benthos at the site. Because the sediment interface is a critical environment for hydrocarbon oxidation and chemosynthesis, short-term variability and heterogeneity may be important characteristics of these settings.     

0216号台风引起内陆降雨的水汽分析

本文主要对0216号台风登陆时的水汽变化，利用GMS-5水汽图、NOAA-16——AMSUB微波图以及一些常规资料进行分析阐明台风登陆后低层水汽输送首先被切断，如果后面有热带气旋的水汽流与前—登陆台风的水汽流接通，并与冷锋水汽流相汇合，在内陆将产生更大降水。     

Forecasting ocean waves: Comparing a physics-based model with statistical models

The literature on ocean wave forecasting falls into two categories, physics-based models and statistical methods. Since these two approaches have evolved independently, it is of interest to determine which approach can predict more accurately, and over what time horizons. This paper runs a comparative analysis of a well-known physics-based model for simulating waves near shore, SWAN, and two statistical techniques, time-varying parameter regression and a frequency domain algorithm. Forecasts are run for the significant wave height, over horizons ranging from the current period (i.e., the analysis time) to 15 h. Seven data sets, four from the Pacific Ocean and three from the Gulf of Mexico, are used to evaluate the forecasts. The statistical models do extremely well at short horizons, producing more accurate forecasts in the 1–5 hour range. The SWAN model is superior at longer horizons. The crossover point, at which the forecast error from the two methods converges, is in the area of 6 h. Based on these results, the choice of statistical versus physics-based models will depend on the uses to which the forecasts will be put. Utilities operating wave farms, which need to forecast at very short horizons, may prefer statistical techniques. Navies or shipping companies interested in oceanic conditions over longer horizons will prefer physics-based models.     

Increased water-vapor content in the atmosphere of tropical latitudes as a necessary condition for the genesis of tropical cyclones

The hypothesis about the interrelation of the integral water-vapor concentration (from data of microwave satellite systems) and plural tropical cyclogenesis in cyclonogenerating water areas of the World Ocean in 2001 is verified with the aid of the EVA-01 (IKI RAN) database (DB) with elements of the objectrelation type formed by the authors. It is experimentally proved in the work that there is a critical value of the integral water-vapor concentration (a peculiar necessary condition) at which the mature form of a tropical cyclone (TC) is formed with a lifetime exceeding 24 h. It is also experimentally proved that, in the same time interval, there is another group of TCs with a short lifetime (less than than 24 h) which do not possess a clearly pronounced boundary value of the water-vapor intensity and can be formed in a wide range of its values. The relations between the regions with an increased concentration of water vapor and genesis of TCs have become obvious only with the use of object-relation computer technologies.     

蒸发波导环境中微波传播敏感性分析

海洋蒸发波导是微波通信的优良天然信道,但微波信号在波导中传播时容易受气海环境因素变化的影响。本文采用扩展傅里叶幅度敏感性分析法（Extended Fourier Amplitude Sensitivity Test,EFAST）,分析了蒸发波导环境中微波传播路径损失对空气温度、海表温度、近海面风和相对湿度等气海环境因素变化的敏感性特点。敏感性分析结果呈现一种频率相关的频散特性,而信号极化方式影响较小。这4种环境因素中,相对湿度对路径损失的整体影响最大;在传播距离较近且高度较高的范围内近海面风速对传播的影响占据主导;空气温度和海表温度的敏感性大致相当;风速的影响是4种环境因素中最为复杂的,这也是在实际分析中需要额外重视的。本文对蒸发波导环境参数的敏感性分析结果对现场波导观测试验具有重要的参考意义,对敏感度高的环境参数可以考虑优先进行高时空分辨率观测。此外,在运用中尺度数值天气预报模式进行蒸发波导预报时,优先发展与敏感度高的气海参数有关的物理过程参数化方案,可以节约计算时间和资源。