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1.
《中国海洋大学学报(英文版)》2020,19(5)
During the period from 9 to 11 November 2013, an explosive cyclone(EC) occurred over the Japan Sea-Okhotsk Sea. This EC initially formed around 18 UTC 9 November over the Japan Sea and developed over the Okhotsk Sea when moving northeastward. It had a minimum sea level pressure of 959.0 hPa, a significant deepening rate of central pressure of 2.9 Bergeron, and a maximum instantaneous wind speed of 42.7 ms~(-1). This paper aims to investigate the conditions that contributed to the rapid development of this low-pressure system through analyses of both observations and the Weather Research Forecasting(WRF) modeling results. The evolutionary processes of this EC were examined by using Final Analyses(FNL) data, Multi-Functional Transport Satellites-1 R(MTSAT-1R) data, upper observation data and surface observation data. WRF-3.5 modeling results were also used to examine the development mechanism of this EC. It is shown that the interaction between upper-level and low-level potential vorticity seemed to be very essential to the rapid development of this EC. 相似文献
2.
Spatial Distribution and Seasonal Variation of Explosive Cyclones over the North Atlantic 总被引：1，自引：0，他引：1
Spatial distribution and seasonal variation of explosive cyclones (ECs) over the North Atlantic from October 2000 to September 2016 are investigated using the reanalysis data of Final Analysis (FNL), Mean Sea Level Pressure (MSLP) and Optimum Interpolation (OI) Sea Surface Temperature (SST) provided by the National Centers for Environmental Prediction (NCEP), the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Oceanic and Atmospheric Administration (NOAA), respectively. Considering the meridional distribution of ECs and 10-m height wind field associated with the ECs, the definition of EC given by Yoshida and Asuma (2004) is modified. It is found that the ECs occurred mainly in four regions during winter season, namely, North America continent (NAC), the Northwest Atlantic (NWA), the North-central Atlantic (NCA), and the Northeast Atlantic (NEA), depending on the spatial distribution of EC’s maximum deepening rate of central sea level pressure (SLP). According to the magnitude of maximum deepening rate, the trend of EC numbers basically decrease with the increase of EC’s maximum deepening rate over the North Atlantic during the whole time period. Over the North Atlantic basin, for monthly statistics, the NEA, NCA, and NWA cyclones occur mainly in December, from December to March, and from January to February, respectively. NWA, NCA and NEA cyclones in winter are associated with low-level baroclinicity, both low-level baroclinicity and upper-level forcing and upper-level forcing, respectively. According to monthly variation, the averaged maximum deepening rate of central SLP firstly increases and then decreases from July to June. Overall, the distribution of ECs’ tracks is basically in the southwest-northeast direction. During winter circulation stage (from October to May), the averaged maximum deepening rate of central SLP and the averaged minimum central SLP of ECs decrease, and the averaged explosive-deepening duration of ECs shortens from west to east over the North Atlantic basin. During summer circulation stage (from June to September), the number of ECs is far less than that of winter circulation. NCA cyclones are the lowest in the average minimum central SLP of ECs, and the longest in the average explosive- deepening duration of ECs. NEA cyclones are the strongest in the average maximum deepening rate of central SLP. 相似文献
3.
《中国海洋湖沼学报》2021,(2)
We investigated the interaction between mesoscale eddies and the Kuroshio Current east of Taiwan,China,using a fine-resolution regional general circulation model.Mesoscale eddies are injected into a region east of Taiwan,China,according to the quasi-geostrophic theory of stratified fluids.Modeled eddies propagated westward at the velocity of the first baroclinic mode Rossby wave.When eddies collide with the Kuroshio Current east of Taiwan,China,the spatial structure and volume transport of the Kuroshio Current shows a significant variation.The upper 600 m of the anticyclonic eddy cannot cross the Kuroshio Current to reach the region west of the Kuroshio Current;rather,these waters flow northward along the eastern side of the Kuroshio Current.The upper water carried by the anticyclonic eddies cannot reach the shelf of the East China Sea(ECS).In contrast,the waters in the upper layer of the cyclonic eddy reach the western side of the Kuroshio Current and then flow northward.The dynamic mechanism analysis shows that the interaction between the Kuroshio Current and the cyclonic(anticyclonic) eddy decrease(increase)the horizontal potential vorticity(PV) gradient,or PV barrier,whereby the cyclonic(anticyclonic) eddy can(cannot) cross the Kuroshio Current.This study implies that the continental shelf could potentially be influenced by cyclonic eddies in the open ocean,which can transport heat and material from the upper open ocean acro s s the Kuroshio Current to the shelf waters. 相似文献
4.
Structures and Evolutions of Explosive Cyclones over the Northwestern and Northeastern Pacific 总被引：1，自引：0，他引：1
In this study, the structures and evolutions of moderate(MO) explosive cyclones(ECs) over the Northwestern Pacific(NWP) and Northeastern Pacific(NEP) are investigated and compared using composite analysis with cyclone-relative coordinates. Final Operational Global Analysis data gathered during the cold seasons(October–April) of the 15 years from 2000 to 2015 are used. The results indicate that MO NWP ECs have strong baroclinicity and abundant latent heat release at low levels and strong upper-level forcing, which favors explosive cyclogenesis. The rapid development of MO NEP ECs results from their interaction with a northern cyclone and a large middle-level advection of cyclonic vorticity. The structural differences between MO NWP ECs and MO NEP ECs are significant. This results from their specific large-scale atmospheric and oceanic environments. MO NWP ECs usually develop rapidly in the east and southeast of the Japan Islands; the intrusion of cold dry air from the East Asian continent leads to strong baroclinicity, and the Kuroshio/Kuroshio Extension provides abundant latent heat release at low levels. The East Asian subtropical westerly jet stream supplies strong upper-level forcing. While MO NEP ECs mainly occur over the NEP, the low-level baroclinicity, upper-level jet stream, and warm ocean currents are relatively weaker. The merged cyclone associated with a strong middle-level trough transports large cyclonic vorticity to MO NEP ECs, which favors their rapid development. 相似文献
5.
With the use of data from the National Centers for Environmental Prediction Climate Forecast System Reanalysis, the environment and structure of typhoon Toraji (2001) are investigated during the re-intensification (RI) stage of its extratropical transition (ET), a process in which a tropical cyclone transforms into an extratropical or mid-latitude cyclone. The results provide detailed insight into the ET system and identify the specific features of the system, including wind field, a cold and dry intrusion, and a frontal structure in the RI stage. The irrotational wind provides the values of upper-and lower-level jets within the transitioning tropical cyclone and the cyclone over Shandong Peninsula, accompanied with the reduced radius of maximum surface winds around the cyclone center in the lower troposphere. Simultaneously, dry air intrusion enhances the formation of fronts and leads to strong potential instability in the southwest and northeast quadrants. The distribution of frontogenesis shows that the tilting term associated with vertical motion dominates the positive frontogenesis surrounding the cyclone center, especially in the RI stage. The diagnostics of the kinetic energy budget suggest that the divergent kinetic energy generation whose time evolution corresponds well to that of cyclone center pressure is the primary factor for the development of Toraji in the lower troposphere. The ET of Toraji is a compound pattern that contains a development similar to that of a B-type extratropical cyclone within the maintaining phase and an A-type extratropical cyclone within the strengthening period, which corresponds to the distribution of the E-P fluxes with vertically downward propagation in the maintaining stage and upwards momentum in the strengthening phase. 相似文献
6.
7.
The Arctic vortex is a persistent large-scale cyclonic circulation in the middle and upper troposphere and the stratosphere. Its activity and variation control the semi-permanent active centers of Pan-Arctic and the short-time cyclone activity in the subarctic areas. Its strength variation, which directly relates to the atmosphere, ocean, sea ice and ecosystem of the Arctic, can affect the lower atmospheric circulation, the weather of subarctic area and even the weather of middle latitude areas. The 2003 Chinese Second Arctic Research Expedition experienced the transition of the stratosphereic circulation from a warm anticyclone to a cold cyclone during the ending period of Arctic summertime, a typical establishing process of the polar vortex circulation. The impact of the polar vortex： variation on the low-level circulation has been investigated by some scientists through studying the coupling mechanisms of the stratosphere and troposphere. The impact of the Stratospheric Sudden Warming （SFW） events on the polar vortex variation was drawing people＇s great attention in the fifties of the last century. The Arctic Oscillation （ AO）, relating to the variation of the Arctic vortex, has been used to study the impact of the Arctic vortex on climate change. The recent Arctic vortex studies are simply reviewed and some discussions on the Arctic vertex are given in the paper. Some different views and questions are also discussed. 相似文献
8.
A numerical model is developed to explain the response of the shelf sea to the abrupt imposition of a steady, secular mean
windstream field and the basic characteristics of the wintertime circulation in the Northern Huanghai Sea (Yellow Sea) and
the Bohai Sea by using equidistant, staggered grid points, an implicit finite difference scheme and our new “splitting computational
method” of adjustment, development, and dissipation processes. So far as the major tendency of the circulation is concerned,
the numerical result agrees with the observational data. The computational results show that the eastern anticyclonic and
the western cyclonic circulations constitute the main body of the wintertime circulation in the Northern Huanghai Sea, and
that the northern anticyclonic and the southern cyclonic circulations constitute the main body of the wintertime circulation
in the Bohai Sea.
Contribution No. 1508 from the Institute of Oceanology, Academia Sinica 相似文献
9.
大量穿越山地丘陵区的高压输电线路杆塔基础常位于滑坡灾害高易发斜坡地段, 施加适当防护措施提高其稳定性, 是保障输电线路持续安全运行的关键。为研究不同防护措施对杆塔基础滑坡的防护效果, 以湖北省巴东县燕子滑坡为地质原型, 设计制作物理试验模型, 分别开展了极端降雨条件下滑坡在无防护、施加抗滑桩与格构护坡时的物理模型试验, 从试验角度揭示了滑坡变形破坏特征与不同防护措施的防护效果。试验结果表明: 在2种极端降雨工况(50, 100 mm/h)下, 无防护的滑坡体历经了坡表冲刷、裂缝扩展、局部垮塌变形与整体滑动的演化过程; 抗滑桩措施对滑坡整体的防护效果显著, 滑坡整体处于稳定状态, 杆塔基础变形较小, 杆塔倾斜率满足规范, 但坡表会出现冲刷垮塌现象; 格构护坡措施能有效减少坡面冲刷和坡脚垮塌风险, 但在持续强降雨条件下对杆塔基础的整体稳固作用稍弱。物理模型试验结果与滑坡历史变形和实际治理效果吻合, 试验结论可为类似杆塔基础滑坡的破坏机理研究与防护工程设计提供借鉴。 相似文献
10.
Based on a barotropic inflow-outflow model,we examine the formation of the Kuroshio large meander(LM) using conditional nonlinear optimal perturbation(CNOP) method.Both linear and nonlinear evolutions of such perturbations obtained by this method are investigated.The results show that the nonlinear evolution can result in the Kuroshio transition from a straight to LM path,whereas the linear evolution cannot.This implies that nonlinearity plays an important role in the formation of the Kuroshio LM path.The nonlinearity exists as advection in the evolution equations of the perturbation derived from the barotropic inflow-outflow model,namely the nonlinear advection of the perturbation by the perturbation(NAPP).By examining the role of this nonlinearity,we find that the NAPP tends to move the cyclonic eddy induced by the CNOP-type perturbation westward.Together with the beta effect,this offsets part of the eastward advection caused by the interaction between the perturbation and the background flow.Hence,the eastward movement of the cyclonic eddy is significantly weakened,effectively causing the eddy to develop.The sufficient evolution of this cyclonic eddy leads to the formation of the Kuroshio LM. 相似文献
11.
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12.
Long-term variabilities of thermodynamic structure of the East China Sea Cold Eddy in summer 总被引：6，自引：0，他引：6
Based on more than 30 years observed sectional temperature data since the 1960s, and compared with multi-year wind and Changjiang (Yangtze) River discharge data, spatial-temporal variations of the East China Sea Cold Eddy (ECSCE) in summer was analyzed in relationship to ocean circulation and local atmospheric circulation. Empirical Orthogonal Function (EOF) and Singular Value Decomposition (SVD) analyseswere applied to this study. The results show that: l) The ECSCE in summer possesses significant interannual variabilities, which are directly associated with oceanic and atmospheric circulation anomaly. Main fluctuations demonstrate their falling in basically with E1 Nino events (interannual) and interdecadal variability. 2) The ECSCE in summer is closely related to the variation of the Yellow Sea Warm Current (YSWC) and the Changjiang River discharge. The stronger the YSWC, the more intensive the ECSCE with its center shifting westward,and vice versa. However, a negative correlation between the Changjiang River discharge and the ECSCE strength is shown. The ECSCE was strengthened after the abrupt global climate change affected by the interdecadal variation of the YSWC. 3) SVD analysis suggested a high correlation between the variation of the ECSCE in summer and the anomalous cyclonic atmospheric circulation over the ECS. Intensification of the cyclonic wind strengthens the ECSCE, and vice versa. 4) The cyclonic atmospheric circulation has dominant influence on the interannual variation of the ECSCE, and the influence of the ocean circulation takes the second in. The ECSCE was usually stronger in E1 Nifio years affected by strong cyclonic circulation in the atmosphere. The variation in strength of the ECSCE resulted from the joint effect of both oceanic and atmospheric circulation. 相似文献
13.
This paper focuses on the effects of two types of El Niño events on tropical cyclone activity. We classified El Niño events from 1961 to 2015 according to their sea surface temperature (SST) anomalies into an eastern type and a central type. Then we selected strong tropical cyclones to statistically analyze the tropical cyclone characteristics during different events and their effects, as well as to study the possible mechanisms related to thermodynamic and dynamic factors. The tropical cyclone generation areas were found to be very similar during the two kinds of events. The average number of tropical cyclone in the eastern event is more than that in central event, and the hurricane in northeastern Pacific (HNP) has more energy than the typhoon in northwestern Pacific (TNP) in all cases. The seasonal distribution of the TNP high-incidence centers during central El Niño events is opposite to that of the HNP. The TNP accumulated cyclone energy (ACE) intensity is similar in the fall and summer, and the HNP ACE intensity in the summer is greater than that in the fall. The SSTs are consistent with the TNP and HNP movement trends. The Walker circulation intensity was strongly affected by the eastern events, but it quickly returned to its normal state, while the intensity was slightly reduced in the central events, and it slowly returned to its normal state. The vertical velocity distributions in the Pacific are different at different stages of both events, and the distributions of vertical velocity anomalies for typhoons and hurricanes are consistent. 相似文献
14.
The synoptic situation and mesoscale structure of an explosive extratropical cyclone over the Northwestern Pacific in March 2007 are investigated through weather station observations and data reanalysis. The cyclone is located beneath the poleward side of the exit of a 200 hPa jet, which is a strong divergent region aloft. At mid-level, the cyclone lies on the downstream side of a well-developed trough, where a strong ascending motion frequently occurs. Cross-section analyses with weather station data show that the cyclone has a warm and moist core. A ‘nose' of the cold front, which is characterized by a low-level protruding structure in the equivalent potential temperature field, forms when the cyclone moves offshore. This ‘nose' structure is hypothesized to have been caused by the heating effect of the Kuroshio Current. Two low-level jet streams are also identified on the western and eastern sides of the cold front. The western jet conveys cold and dry air at 800–900 hPa. The wind in the northern part is northeasterly, and the wind in the southern part is northwesterly. By contrast, the eastern jet carries warm and moist air into the cyclone system, ascending northward from 900 hPa to 600–700 hPa. The southern part is dominated by the southerly wind, and the wind in the northern part is southwesterly. The eastern and western jets significantly increase the air temperature and moisture contrast in the vicinity of the cold front. This increase could play an important role in improving the rapid cyclogenesis process. 相似文献
15.
An MOM2 based 3-dimentional prognostic baroclinic Z-ordinate model was established to study the circulation in eastern China seas, considering the topography, inflow and outflow on the open boundary, wind stress, temperature and salinity exchange on the sea surface. The results were consistent with observation and showed that the Kuroshio intrudes in large scale into the East China Sea continental shelf East China, during which its water is exchanged ceaselessly with outer sea water along Ryukyu Island. The Tsushima Warm Current is derived from several sources, a branch of the Kuroshio, part of the Taiwan Warm Current, and Yellow Sea mixed water coming from the west of Cheju Island. The water from the west of Cheju Island contributes approximately 13% of the Isushima Warm Current total transport through the Korea Strait. The circulation in the Bohai Sea and Yellow Sea is basically cyclonic circulation, and is comprised of coastal currents and the Yellow Sea Warm Current. Besides simulation of the real circulation, numerical experiments were conducted to study the dynamic mechanism. The numerical experiments indicated that wind directly drives the East China Sea and Yellow Sea Coastal Currents, and strengthens the Korea Coastal Current and Yellow Sea Warm Current. In the no wind case, the kinetic energy of the coastal current area and main YSWC area is only 1% of that of the wind case.Numerical experiments also showed that the Tsushima Warm Current is of great importance to the formation of the Korea Coastal Current and Yellow Sea Warm Current. 相似文献
16.
粤西近岸环流研究进展 总被引：2，自引：0，他引：2
粤西近岸环流对粤西乃至北部湾海域的物质输送、水质环境、渔业养殖等都具有重要影响.本研究就粤西沿岸环流(尤其是夏季环流)的基本特征、驱动机制、及其与琼州海峡流关系等方面的研究进展进行了概述,并对存在的问题进行了探讨.前人对粤西沿岸流终年向西以及夏季沿岸流外侧存在气旋式环流等定性特征已达成共识,然而,对环流的主要影响机制以及与琼州海峡流的关系尚有争议,关于环流的定量结果也较为缺乏,还需进行长时间的连续观测以及适合近岸海域的数值模拟. 相似文献
17.
复杂的面状空间实体如海洋涡旋、环流和降雨过程在运动过程中会产生更复杂的轨迹,即具有分支结构的复杂轨迹。为了挖掘这类复杂轨迹的运动模式特征,本文从复杂轨迹的拓扑结构和空间特征出发,创新性地提出复杂轨迹的空间-拓扑结构相似性度量算法（Spatial-Topological Similarity Measurement, STSM）,该算法是基于图同构算法VF2改进的。首先STSM算法将复杂轨迹用带有节点和边的图结构表达,并将空间信息融入图结构的节点属性中,通过匹配复杂轨迹之间所有最大公共子结构,找到匹配结构中节点之间一一对应的关系,利用加权的欧式距离计算复杂轨迹匹配结构中点对之间的空间距离。然后,基于STSM相似性算法进行层次聚类分析,旨在发现复杂轨迹之间相似的拓扑结构在空间上的聚集模式。最后,利用1993-2016年长时间序列的中国南海冷涡复杂轨迹验证方法的有效性,并对比分析复杂轨迹拓扑结构相似性算法CSM。结果表明：单纯用拓扑结构相似性算法CSM进行聚类分析,不能充分挖掘空间的聚集模式,因为不同空间位置也存在拓扑结构相似的轨迹。而本文提出的STSM算法将南海冷涡复杂轨迹分为5类,第一类分布在南海北部、第二类分布在南海中部、其他三类交错在南海南部。这种聚集模式在一定程度上反映了冷涡的生成和演化过程在南海北部、中部、南部的差异性,同时也表明了冷涡移动在南海南部存在更为复杂的异质性。因此,本文提出的方法可以有效地从复杂轨迹数据中发现其演化过程的潜在聚集模式,为认识这类复杂动态现象的时空演化特征提供了一种新的方法。 相似文献
18.
Interannual variations of Pacific North Equatorial Current (NEC) transport during eastern-Pacific El Niños (EP-El Niños) and central-Pacific El Niños (CP-El Niños) are investigated by composite analysis with European Centre for Medium-Range Weather Forecast Ocean Analysis/Reanalysis System 3. During EP-El Niño, NEC transport shows significant positive anomalies from the developing to decay phases, with the largest anomalies around the mature phase. During CP-El Niño, however, the NEC transport only shows positive anomalies before the mature phase, with much weaker anomalies than those during EP-El Niño. The NEC transport variations are strongly associated with variations of the tropical gyre and wind forcing in the tropical North Pacific. During EP-El Niño, strong westerly wind anomalies and positive wind stress curl anomalies in the tropical North Pacific induce local upward Ekman pumping and westward-propagating upwelling Rossby waves in the ocean, lowering the sea surface height and generating a cyclonic gyre anomaly in the western tropical Pacific. During CP-El Niño, however, strength of the wind and associated Ekman pumping velocity are very weak. Negative sea surface height and cyclonic flow anomalies are slightly north of those during EP El Niño. 相似文献
19.
雷小途 《成都信息工程学院学报》2000,15(3):196-203
利用含地形、摩擦及非绝热加热外源强迫的准地转正压涡度方程模式 ,通过构造理想的坡地地形及椭圆型岛地形 ,首先分析了孤立地形的动力抬升作用及动力抬升、摩擦、非绝热加热 3者共同作用下对热带气旋 (TC)移动的影响。发现 :地形的动力抬升、摩擦作用以及地形附近海域的非绝热加热对TC移动均有影响 ;然后 ,引入了我国东南近海的实际地形 ,通过数值试验分析了TC移经或登陆在近海不同位置时TC移向、移速的可能变化 ,并给出了近海地形对TC移向、移速影响的空间分布。 相似文献
20.
The sea surface height oscillation with a quasi-four-month period (SSHO4) along continental slope in the northern South China Sea (NSCS) is detected using satellite altimeter data and an ocean model simulation. The SSHO4 is at southwest of Dongsha Island, and is characterized by a wavelength of ~600 km and a southwestward phase speed of ~0.1 m/s. Crossing the climatological background SST front, geostrophic currents corresponding to the SSHO4 generally induce sea surface temperature (SST) "tongues" during January-March. The cold and warm SST tongues appear southwest of cyclonic and anticyclonic eddies, respectively. The distance between the warm and cold SST tongues is about half the wavelength of the SSHO4. The geostrophic currents play an important role in lateral mixing, as manifested by the SST tongue phenomena in the NSCS. 相似文献