"2006.10"云南严重秋季连阴雨水汽输送特征和湿Q矢量分析

应用常规气象资料通过诊断分析和湿Q矢量分析,探讨了2006年10月上旬云南严重连阴雨期间的水汽输送特征,进一步分析了期间持续性暴雨、大雨的落区分布,结果表明:连阴雨期间,ITCZ异常活跃,先后有4个热带气旋活动,200616号强台风"象神"横穿中南半岛进入孟加拉湾,减弱之后再度发展成孟加拉湾低压,由此提供了孟加拉湾水汽通道;ITCZ水汽通过副高外围气流向中南半岛输送,提供了第二条水汽通道,两条水汽通道呈"人"字形,为连阴雨发生发展提供了有利的水汽条件.湿Q矢量辐合中心在对流层中低层700～640 hPa之间,700 hPa上湿Q矢量散度辐合区与暴雨区对应较好;随着湿Q矢量辐合区加强、移动和减弱,暴雨随之发展、移动和结束.     

Long-Term and Short-Term Variations of Sea Level in Eastern Canada: A Review

This is a review of sea level data performed at three selected stations (Québec-Lauzon, Harrington Harbour,and Halifax) in eastern Canada in order to investigate the seasonal trends and other long-term and short-term changes which occurred since the beginning of the 20th century. Stations situated in riverine or estuarine regions (e.g., Québec-Lauzon) are significantly affected by freshwater flow in their annual cycle of sea level changes and exhibit a definite maximum in spring and minimum in autumn-winter. Other stations situated in the eastern half of the Gulf of St. Lawrence (e.g., Harrington Harbour) or near the open Atlantic coast (Halifax) mainly follow the general cycle of subarctic regions, with lows in spring-summer and highs in autumn-winter. Such seasonal variations appear to be related to the atmospheric pressure and baroclinic current variations. Secular trends in mean sea level in eastern Canadian waterbodies show a mean rise of about 2.56 mm/yr -1 due to tectonic motions, that is, land subsidence. At several stations in eastern Canada, evidence is found for the influence of the nodal tide (18.6 years), the sunspot cycle (10.8 years), the lunar perigee (8.47 years), the pole tide (14.5 months), the annual cycle (12 months), and semiannual tidal cycle (6 months) in sea level records. Beside long-term oscillations with periods of more than one year, evidence is found for high energetic semidiurnal and diurnal tides where they contribute largely (from 90-95%) to short term variability of sea level. In the residual signal (variations of sea level--tidal variations), short-term variations between 2 to 30 days can be attributed to meterological forcing (atmospheric pressure and winds), longitudinal seiches (2-10 h), atmospheric tides (12 h and 24 h) and inertial oscillations (16-18 h). A regressive model showed that the water discharge from the St. Lawrence River contributes 29% to the monthly residual sea level at Québec-Lauzon. The atmospheric pressure and winds contribute respectively 8.1% and 8.9% at this station. They contribute 52.1% and 7.7% at Harrington Harbour and 41.8% and 14.3% at Halifax. The regression coefficients of residual sea level on atmospheric pressure are respectively estimated to be -1.507 cm. ( hPa ) -1 ( - 0.345 cm. ( hPa ) -1 ), -0.776 cm. ( hPa ) -1 ( - 0.112 cm. ( hPa ) -1 ) and -0.825 cm. ( hPa ) -1 ( - 0.008 cm. ( hPa ) -1 ) at the three stations. Compared to the coefficient of the inverted barometer, estimated to be -1 cm. ( hPa ) -1 , these effects of the atmospheric pressure on sea level variations seem to be amplified at Que´bec-Lauzon by the wind effects (and water discharge) while they are reduced at Harrington Harbour and Halifax.     

Effect of Salinity and Currents on Sea Level Variation Along the Indian Coast: A Numerical Study

The process of upwelling/sinking and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. Further,precipitation and monsoonal floods, apart from the marine meteorological parameters, are expected to influence the sea level fluctuations along the coast. This study comprises determining the sea level from the various parameters together with the pure wind stress forcing, which is compared with the observed cycle. However, it is found that there is considerable difference between the computations and observations. This suggests that the sea level is dependent not just on the local forcing alone, but also on the induced background circulation as well. For example, the sea level changes along the east coast of India, particularly the northern region, are more sensitive to freshwater discharge from various rivers joining the Bay of Bengal. This is due to more frequently occurring pre- and postmonsoon cyclonic storms and the associated surges in the Bay of Bengal as compared to the Arabian Sea. Hence the salinity effects are particularly important in the coastal waters off the east coast of India during monsoon months (June-September). For the west coast of India, however, it is expected that the large-scale coastal circulation may play a role in determining sea level changes in addition to other forcings. The salinity effects are negligible along the west coast in the absence of any major river systems that join the Arabian Sea. The local advection currents caused by the offshore directed freshwater discharge from various estuaries joining the coastal bay also seemed to influence the sea level. In order to elucidate the essential dynamics involved and to study the effect of the remote forcing, a three-dimensional baroclinic, nonlinear numerical model is used with appropriate open boundary conditions. The local effect of the current has been incorporated in the west coast model by means of opening a channel at Cochin through which the rainwater is carried away to the model ocean. The low saline plume, cascading from north along the east cost of India, has been incorporated in the east coast model through a proper forcing applied at the northern boundary of the model. With the inclusion of these remote forcings in the models, the disagreement between the simulations and the observations is minimized.     

一次南方春季强对流过程中影响对流发展的环境场特征分析

利用地面自动站资料、多普勒雷达资料、FY-2E卫星云图及NCEP FNL 1°×1°逐6h分析场资料,分析了2010年5月5-7日我国南方春季大范围强对流天气过程中尺度对流系统(MesoscaleConvective System,MCS)的发生、发展特征,重点探讨了环境条件差异及其对MCS的影响。结果表明,由于环境场三维动力结构、水汽条件和热力不稳定条件配置的差异,造成对流发展的多样化特征。利用相对风暴螺旋度分析了环境场动力特征对MCS组织结构的影响。重庆上空中高层较干且具有较强的垂直切变,环境场气旋式旋转相对深厚,随着锋面强迫抬升克服对流抑制作用后,局地激发出相对孤立的类似超级单体的强对流风暴,造成冰雹和雷暴大风等天气;而贵州湿层相对深厚,高低空急流的耦合机制更明显,贵州北部的多单体对流风暴组织程度较高,MCS尺度相对较大,局地短时强降水较明显;广东具有最强的垂直切变和深厚湿层,在浅薄冷空气的触发机制下,发展出深厚湿对流形式的中尺度对流复合体,出现了高度组织化的线状对流带,MCS尺度大、持续时间长,造成较强的降水。     

Coastal flooding: impacts of coupled wave–surge–tide models

Wind waves and elevated water levels together can cause flooding in low-lying coastal areas, where the water level may be a combination of mean sea level, tides and surges generated by storm events. In areas with a wide continental shelf a travelling external surge may combine with the locally generated surge and waves and there can be significant interaction between the propagation of the tide and surge. Wave height at the coast is controlled largely by water depth. So the effect of tides and surges on waves must also be considered, while waves contribute to the total water level by means of wave setup through radiation stress. These processes are well understood and accurately predicted by models, assuming good bathymetry and wind forcing is available. Other interactions between surges and waves include the processes of surface wind-stress and bottom friction as well as depth and current refraction of waves by surge water levels and currents, and some of the details of these processes are still not well understood. The recent coastal flooding in Myanmar (May 2008) in the Irrawaddy River Delta is an example of the severity of such events, with a surge of over 3 m exacerbated by heavy precipitation. Here, we review the existing capability for combined modelling of tides, surges and waves, their interactions and the development of coupled models.     

冬季太平洋SSTA对北太平洋风暴轴年际变化的影响

研究了冬季北太平洋风暴轴的年际异常及其与500hPa高度以及热带和北太平洋海温的联系。结果发现，冬季北太平洋风暴轴中心有线性增强、偏北、偏东的趋势。对15个冬季北太平洋风暴轴区域 500 hPa天气尺度滤波位势高度方差与同期热带和北太平洋海温的 SVD分析表明，第一对空间典型分布反映了 ENSO区海温异常对风暴轴年际变化的影响，而第二对空间典型分布反映了黑潮区域海温异常对风暴轴年际变化的影响。进一步的合成分析显示，ENSO区海温异常可以通过激发500hPa高度场上的PNA遥相关型影响冬季北太平洋风暴轴的东西摆动和中、东端的强度变化，而黑潮区域海温异常则通过激发 500 hPa高度场上的 WP遥相关型，主要影响冬季北太平洋风暴轴中、西端的强度变化和南北位移。     

暴雨信号发布思路

深圳2000年4月份出现了4次暴雨和大暴雨，其中“4.14”为打破历史纪录的特大暴雨。深圳市气象台所发布的黄、红、蓝色暴雨信号是历史上次数最多，最频繁之一。本文通过对这几次不同量级的暴雨过程中暴雨信号发布情况以及短期天气预报和云图、雷达和自动站等中尺度资料在暴雨预警信号发布中所发挥作用的分析，总结发布暴雨信号的发布思路；并得到十分有益的经验。     

Pliocene marine deposits at Punta Maldonado, Guerrero state, Mexico

Diverse and abundant Foraminifera and Ostracoda assemblages were recovered from a measured stratigraphic section at Punta Maldonado, Guerrero state, Mexico. The planktonic species indicate an early Pliocene age, between 5.3 and 3.6 Ma; an early late Pliocene (around 2.4 Ma) planktonic assemblage also was recorded from isolated deposits. These ages contradict the Cretaceous–Paleogene age previously assigned to the sedimentary succession at Punta Maldonado. All indicators—benthic assemblages, ichnofacies, lithology, grain size, primary structures, mineralogy, body rock geometry, and facies—suggest deposition in the foreshore and offshore transition zones of a storm-dominated shallow siliciclastic shelf. The Ostracoda and Foraminifera indicate deposition around the outer neritic/upper bathyal boundary, which suggests an uplift of 320–400 m in the area during the Pliocene. This study represents the first report of Pliocene marine rocks in the southwestern coast of Mexico; the data presented contribute to regional geotectonic models.     

天津市暴雨内涝灾害风险分析

分析了城市化对暴雨内涝灾害风险分布的影响，介绍了天津市暴雨内涝灾害仿真模型的基本原理及实际暴雨过程的验证情况。在分析天津市暴雨频次分布的基础上，根据天津市的暴雨特点和汛期排水运作规则，利用天津市内涝灾害仿真模型，对不同类型的降水过程进行了数值模拟，并对暴雨引起内涝灾害的风险进行了初步的量化评估。     

龙卷型强风暴——1995年4月19日洪奇沥龙卷风剖析

1995年4月19日13:00至21:00，一次范围较广的强对流天气过程波及了肇庆、佛山、顺德、南海、番禺、中山市等地。广州雷达站探测了这一过程，并取得了较为完整的雷达资料。该文主要对受灾严重的番禺市万顷沙地区龙卷风进行剖析，所得结果表明:（1）该龙卷是反气旋式龙卷，实属罕见；（2）尺度属微尺度—小尺度范围（120～4000 m）（3）与该龙卷伴随的风暴单体生命史长达4～5小时；（4）计算出的该龙卷风的破坏力以及龙卷环流等参量与Dellas、Fargo等龙卷风所得出的参量的量级比较一致。