孟加拉湾上层环流研究综述

综述了孟加拉湾上层环流研究的主要成果并指出,研究海区环流与季风转换不完全同步。在西南季风期间,南、北海区各有一气旋式环流;在秋季季风过渡期间,出现海湾尺度的气旋式环流;在东北季风期间,气旋式环流减弱北移,南部则为一反气旋式环流控制;春季与秋季的情形相反,整个湾出现一海湾尺度的反气旋式环流。研究海区环流的变异主要受季风、赤道远地作用和浮力通量等复杂外源作用的影响。东印度沿岸流的季节变化与季风转换也不同步,局地风、内部Ekman抽吸、远地沿岸风及赤道远地作用的影响对沿岸流周年变化有重要作用。孟加拉湾上层环流年际变化显著,此年际变化主要受赤道风场的影响。     

Climatic structure of the wind fields in the Black-Sea region

For the Black-Sea region, we perform the dynamic reanalysis of the data on atmospheric circulation for the period 1958–2001 by using the HadRM3P model with a space resolution of 25 km. We estimate the mean climatic atmospheric fields of vorticity and divergence of the wind velocity and study their space structure and seasonal variability. The climatic estimates of the annual course of vorticity of the wind velocity over the sea are presented. The obtained large annual average values of vorticity of the velocity reveal the predominant role played by the wind action in the generation not only of the seasonal variability but also of the mean cyclonic circulation of waters in the Black Sea.     

On the influence of salinity exchange on the circulation of a fluid in an enclosed basin

The mechanism responsible for fluid circulation in an internal basin of the Black Sea type is studied using a two-dimensional model for convective currents generated by the inhomogeneous horizontal gradient of salinity exchange. Analytical investigations and calculations have shown that the generation of cyclonic motions occurs due to an imbalance of salt fluxes at the fluid lateral boundaries of the basin. Under the influence of salt fluxes from the straits and the fresh water from rivers, the circulation tends to become streamlike. At the site of reduced salinity, the stream narrows and becomes more intensive. Translated by V. Puchkin.     

南沙群岛海域混合层深度季节变化特征

基于南沙群岛海域综合科学考察11个航次的实测资料,研究了南沙群岛海域的混合层深度季节变化特征。研究结果表明,南沙群岛海域混合层深度存在明显的季节变化,并且与季风和海表热通量的变化密切相关。春季,风速较小且风向不稳定,海面得到的净热通量全年最大,上层水体层结稳定,混合层深度较小;夏季,南海西南季风盛行,上层为反气旋式环流,海面得到的净热通量减少,混合层呈加深的趋势;秋季,海面净热通量继续减少,混合层深度达到最大值;冬季,东北季风驱动下形成的上层气旋式环流引起深层冷水的上升,限制了混合层的加深。     

The mesoscale atmospheric vortex as a manifestation of the Novorossiysk bora

The WRF-ARW regional atmosphere circulation model has been used to reproduce a few episodes of cold intrusion and the Novorossiysk bora accompanied by the formation of the mesoscale cyclonic vortex over the Black sea, which can be clearly observed from satellite images of cloudiness. It has been shown that the vortex development is associated with the specific features of air flow around the northwestern edge of the Caucasus Mountains. We have estimated the vertical vorticity associated with the alongshore horizontal gradient of temperature. We have considered the field structure of wind velocity and temperature of the axisymmetric quasi-two-dimensional vortex generated in the coastal zone and displaced seaward after separating from the coast. With the background northerly wind, the coastal cyclonic circulation is not accompanied by the vortex separation from the coast. The specific feature of the development of the cyclonic vortex is the southeastern wind with velocities of up to 10 m/s in the Caucasus coastal area from Sochi to Sukhum.     

Climatic parameters of wind-field variability in the Black Sea region: Numerical reanalysis of regional atmospheric circulation

A reanalysis of atmospheric circulation in the Black Sea region is performed with a high spatial resolution of 25 × 25 km for the period from 1958 to 2001. Climatic wind speed fields are estimated, as are their spatial structure and seasonal variability. Mesoscale regions of cyclonic and anticyclonic speed vorticity, which are connected with edge effects and orography, are distinguished. To single out the monsoon mechanism in the annual votricity cycle, numerical experiments on the sensitivity that the regional atmospheric circulation has to the sea-surface temperature perturbations have been carried out. Large-scale regional peculiarities of the surface wind field are considered for different seasons. The vorticity of the surface wind speed and strength is assessed. Large annual average values of the vorticity are obtained which are comparable with the range of seasonal variability; they evidence the defining role that wind plays in the generation and seasonal variability, as well as the average cyclonic water circulation in the Black Sea.     

Long-term tendencies in the variability of characteristics of the Black Sea pycnocline

The rise of the waters of the main pycnocline in the central part of the western cyclonic gyre at the end of the winter in the 1960s–1970s and their deepening in the eastern cyclonic gyre from the mid-1960s to the late 1980s were revealed on the basis of archival hydrologic data obtained on the standard sections of the Black Sea in 1957–1992. It is shown that, simultaneously, the waters of the pycnocline descended in the Sevastopol anticyclone and rose in the Yalta and Batumi anticyclones. These tendencies indicate that the water circulation intensified in the region of the western cyclonic gyre (off the southwestern coast of the Crimea) and weakened in the vicinity of the eastern cyclonic gyre at the end of the winter season in the 1960s–1970s and in the 1960s–1980s, respectively. It is shown on the basis of NCEP reanalysis data and archival hydrometeorological data that all major circulation factors, such as a decrease in the cyclonic vorticity in the wind field during the winter season, changes in its spatial structure, an increase in the river discharge, and a decrease in the turbulent heat fluxes at the Black Sea surface, affect the energy redistribution between the gyres. The role of each of these factors is analyzed.     

Numerical Study of the Upper-Layer Circulation in the South China Sea

Upper-layer circulation in the South China Sea has been investigated using a three-dimensional primitive equation eddy-resolving model. The model domain covers the region from 99° to 122°E and from 3° to 23°N. The model is forced by the monthly averaged European Centre for Medium-Range Weather Forecasts (ECMWF) model winds and the climatological monthly sea surface temperature data from National Oceanographic Data Center (NODC). Inflow and outflow through the Taiwan Strait and the Sunda shelf are prescribed monthly from the Wyrtki estimates. Inflow of the Kuroshio branch current in the Luzon Strait is assumed to have a constant volume transport of 12 Sv (1 Sv = 10⁶ m³/s), and the outflow from the open boundary to the east of Taiwan is adjusted to ensure the net volume transport through all open boundaries is zero at any instant. The model reveals that a cyclonic circulation exists all year round in the northern South China Sea. During the winter time this cyclonic eddy is located off the northwest of Luzon, coinciding with the region of positive wind stress curl in this season. This cyclonic eddy moves northward in spring due to the weakening of the northeast winds. The cyclonic circulation becomes weak and stays in the continental slope region in the northern South China Sea in the summer period. The southwest wind can raise the water level along the west coast of Luzon, but there is no anticyclonic circulation in the northern South China Sea. After the onset of the northeast monsoon winds in fall, the cyclonic eddy moves back to the region off the west coast of Luzon. In the southern South China Sea and off the Vietnam coast, the model predicts a similar flow structure as in the previous related studies. This revised version was published online in July 2006 with corrections to the Cover Date.     

西北太平洋海气界面热通量时空分布特征研究

基于第三版本HOAPs (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data)海表面温度、潜热通量、感热通量、海表面空气比湿以及海表面风场5个参量的18 a(1988～2005年)逐月平均资料,利用经验正交函数和奇异值分解方法分析了异常潜热和感热通量场在西北太平洋的时空分布特征及造成这种分布的主要影响因素.EOF的分析结果表明,异常潜热通量场主要体现为第一第二两个模态的变化,第一模态显示整个海域呈同相变化且在时间上呈准年周期变化,第二模态则描述了分别位于10°N,25°N和40°N的3个极值中心并伴随多年振荡,由因子载荷分布可知热带太平洋是第二模态的行为中心,因此该模态可能与ENSO事件相关.异常感热通量场则主要表现为第一模态的变化,在时间上呈准年周期变化并伴随有多年时间尺度的振荡.奇异值分解方法的分析结果表明异常海表面风场是异常潜热和感热通量场时空变化的重要影响因素.     

Oceanic eddy-driven atmospheric secondary circulation in the winter Kuroshio Extension region

In the winter Kuroshio Extension region, the atmospheric response to oceanic eddies is studied using reanalysis and satellite data. The detected eddies in this region are mostly under the force of northwesterly wind, with the sea surface temperature (SST) anomaly located within the eddy. By examining the patterns of surface wind divergence, three types of atmospheric response are identified. The first type, which occupies 60%, is characterized by significant sea surface wind convergence and divergence at the edge and a vertical secondary circulation (SC) aloft, supporting the “vertical momentum mixing mechanism”. The SCs on anticyclonic eddies (AEs) can reach up to 300 hPa, but those on cyclonic eddies (CEs) are limited to 700 hPa. This can be explained by analyzing vertical eddy heat transport: When northwesterly wind passes the warmer center of an AE, it is from the cold to warm sea surface, resulting in stronger evaporation and convection, triggering stronger upward velocity and moist static heat flux. For the cases of CEs, the wind blows from warm to cold, which means less instability and less evaporation, resulting in weaker SCs. The second type, which occupies 10%, is characterized by divergence and a sea level pressure anomaly in the center, supported by the “pressure adjustment mechanism”. The other 30% are mostly weak eddies, and the atmospheric variation aloft is unrelated to the SST anomaly. Our work provides evidence for the different atmospheric responses over oceanic eddies and explains why SCs over AEs are much stronger than those over CEs by vertical heat flux analysis.     

Numerical study of rapid cyclogenesis over sea

A five-layer primitive equation model was used in the study of rapid cyclogenesis over sea. The numerical simulations show that'the Tibetan Plateau, large-scale baroclinicity and heat flux from the sea surface are the three important agents to produce cyclonic vorticity along the east coast of China. The diagnostic computation of a 24 h control simulation indicates that the nonlinear vorticity advec-tion, baroclinicity and diabatic heating are also responsible for the development of the extratropical cyclones over seas.     

热带太平洋海温异常对北极海冰的可能影响

本文利用1950-2015年间Hadley环流中心海冰和海温资料及NCEP/NCAR再分析资料,研究了热带太平洋海温异常对北极海冰的可能影响,并从大气环流和净表面热通量两个角度探讨了可能的物理机制。结果表明,在ENSO事件发展年的夏、秋季节,EP型与CP型El Niño事件与北极海冰异常的联系无明显信号。而La Niña事件期间北极海冰出现显著异常,并且EP型与CP型La Niña之间存在明显差异。EP型La Niña发生时,北极地区巴伦支海、喀拉海关键区海冰异常减少,CP型La Niña事件则对应着东西伯利亚海、楚科奇海地区海冰异常增加。在EP型La Niña发展年的夏、秋季节,热带太平洋海温异常通过遥相关波列,使得巴伦支海、喀拉海海平面气压为负异常并与中纬度气压正异常共同构成类似AO正位相的结构,形成的风场异常有利于北大西洋暖水的输入,同时造成暖平流,偏高的水汽含量进一步加强了净表面热通量收入,使得巴伦支海、喀拉海海冰异常减少。而在CP型La Niña发展年的夏季,东西伯利亚海、楚科奇海关键区受其东侧气旋式环流的影响,以异常北风分量占主导,将海冰从极点附近由北向南输送到关键区,海冰异常增加,而净表面热通量的作用较小。     

北部湾的环流和水团对季节性强迫的响应

In the past 20 a, the gulf-scale circulation in the Beibu Gulf has been commonly accepted to be driven by a wind stress or density gradient. However, using three sensitive experiments based on a three-dimensional baroclinic model that was verified by observations, the formation mechanisms were revealed： the circula- tion in the northern Beibu Gulf was triggered by the monsoon wind throughout a year; whereas the southern gulf circulation was driven by the monsoon wind and South China Sea （SCS） circulation in winter and sum- mer, respectively. The force of heat flux and tidal harmonics had a strong effect on the circulation strength and range, as well as the local circulation structures, but these factors did not influence the major circulation structure in the Beibu Gulf. On the other hand, the Beibu Gulf Cold Water Mass （BGCWM） would disappear without the force of heat flux because the seasonal thermocline layer was generated by the input of heat so that the vertical mixing between the upper hot water and lower cold water was blocked. In addition, the wind-induced cyclonic gyre in the northern gulf was favorable to the existence of the BGCWM. However, the coverage area of the BGCWM was increased slightly without the force of the tidal harmonics. When the model was driven by the monthly averaged surface forcing, the circulation structure was changed to some extent, and the coverage area of the BGCWM almost extended outwards 100%, implying the circulation and water mass in the Beibu Gulf had strong responses to the temporal resolution of the surface forces.     

台风"摩羯"(1814)残涡经渤海突然增强成因分析

利用气象常规资料、自动站资料、FY-4 可见光云图和 NCEP/NCAR 1毅伊1毅再分析资料,对 2018 年 14 号台风“摩羯”残涡经渤海增强前后热力、动力和水汽特征进行分析,结论如下：台风登陆北上后变性为温带气旋,其热力结构呈非对称分布,垂直风切变具有温带气旋特征,台风残涡入海后高空辐散、整层涡度、水汽通量和水汽通量速度等物理因子均明显增强。利用 Petterssen 气旋发展公式探讨入海增强原因,台风残涡入海前,温度平流对台风发展起主要作用,涡度平流对台风发展起抑制作用,台风残涡入海后,温度平流和涡度平流皆有利于台风残涡增强。非绝热加热作用在整个研究时段有利于台风发展,降水释放潜热加热对台风入海增强有正反馈作用,这种作用表现为一种突发性增大的特征。海洋平坦下垫面和适宜的海温是台风残涡入海增强的原因之一。     

中低风速下海洋飞沫对海气热通量的影响

基于2016-02-01—2016-05-21在南海博贺海洋气象观测平台观测的实验资料,首先利用整体空气动力学算法分别计算海气界面处感热通量与潜热通量,同时利用涡动相关法计算液滴蒸发层处总的感热通量与潜热通量。然后比较海气界面处热通量与液滴蒸发层处热通量的值,并利用差比法分别对2处感热通量和潜热通量进行做差计算。结果表明:液滴蒸发层处热通量与海气界面处热通量存在明显差异。通过与海洋飞沫引起的热通量值比较,结果表明液滴蒸发层处热通量与海气界面处热通量的差值由海洋飞沫作用引起;且在中低风速条件下,海洋飞沫引起的热通量与风速呈正相关;相比感热通量而言,潜热通量随着风速的变化更为显著。     

Model of the Dead Sea. Simulation of the Variability of the Thermohaline Water Structure in 1992–2000

Within the framework of the integral model in isopycnic coordinates including the upper mixed layer, we study the rearrangement of temperature and salinity fields in the Dead Sea. It is forced by the variability of atmospheric factors and mass fluxes through the lateral boundaries of the basin, which are connected with the freshwater run-off to the sea and the outflow from the sea to the shallow south bay, where evaporator installations for salt extraction are located. Such factors as solar radiation, wind velocity, air temperature, and relative humidity are prescribed. Evaporation is calculated with the use of a bulk formula, whereas precipitation intensity and discharge through the lateral boundaries are determined as functions of the sea level obtained from observations. This model reflects the specific character of the Dead Sea and takes into account the effect of water salinity on its evaporation, salt concretion, and mechanical evaporation. Comparison with the data of observations shows that the proposed model fairly precisely describes the observed specific features of the thermohaline water structure in the meromictic (1992–1996) and holomictic (1996–2000) periods.     

Monthly Variation of Sea-Air Temperature Differences in the Korean Coast

Monthly variations of sensible heat, latent heat and momentum fluxes and the modification of sea temperature to air temperature were examined at four coastal stations—Sokcho, Kangnung, Ulsan and Chungmu in the path of the East Korea Warm Current from the year of 1981 to 1990, which was one of main migration routes of Japanese common squid. The difference between monthly averaged sea surface and air temperatures at the 10 m height above the sea surface mainly became negative values from April through August, while they had positive ones from September through March. Monthly variability of the temperature differences is significant in both summer and winter, while it is generally small in spring and fall. Negative values of sensible heat fluxes, which indicated a heat gain by the sea through heat conduction across the air-sea interface were found at the four coastal stations from April to August. Minimum values of sensible heat fluxes at Sokcho, Kangnung and Chungmu were in June, except for Ulsan in August. To the contrary, positive sensible heat flux implying a heat loss from sea toward atmosphere occurred from October to February with a maximum in December. Latent heat fluxes due to condensation of moist air over sea surface had small magnitudes from April to August and those due to evaporation of water particles from the sea surface into the lower atmosphere had relatively large magnitudes from October to March. Minimum values of latent heat fluxes also occurred in June except for August in Ulsan. Momentum flux was small from June to August under weak wind in summer, but it was large from December to February under strong wind in winter. Regression equations between sea surface temperature and air temperature at the 10 m height above the sea surface had very high correlation coefficients from 0.92-0.98, except for 0.78-0.84 of Ulsan, which was partially affected by upwelling of cool water from the bottom into the sea surface. Similar to the sea surface, correlation coefficients were over 0.83-0.97 except for 0.70-0.79 for Ulsan at the 10 m depth of sea and were over 0.70-0.95 except for 0.59-0.82 for Ulsan at the 20 m depth.     

大西洋热盐环流年代际变化机制研究Ⅲ.北大西洋海气要素对热盐环流年代际振荡的影响

基于该系列文章前文研究中构建的海气耦合气候模式和所揭示的北大西洋热盐环流年代际振荡机制,针对海气要素对该振荡机制的影响问题进行了重点的探讨.为细致准确的研究北大西洋海洋要素同北大西洋热盐环流年代际振荡的关系,有针对性的定义了副极地海区表层密度指数和北大西洋暖流强度指数并对模式结果进行了全面分析.分析结果表明副极地海区表...     

大西洋热盐环流年代际变化机制研究Ⅲ.北大西洋海气要素对热盐环流年代际振荡的影响

基于该系列文章前文研究中构建的海气耦合气候模式和所揭示的北大西洋热盐环流年代际振荡机制,针对海气要素对该振荡机制的影响问题进行了重点的探讨。为细致准确的研究北大西洋海洋要素同北大西洋热盐环流年代际振荡的关系,有针对性的定义了副极地海区表层密度指数和北大西洋暖流强度指数并对模式结果进行了全面分析。分析结果表明副极地海区表层密度变化领先大西洋径向翻转环流(MOC)变化7 a,北大西洋暖流的变化领先 MOC变化4 a,格陵兰－苏格兰海脊溢流水强度(包括丹麦海峡溢流水和法鲁海峡溢流水,是北大西洋深层水的重要来源)的变化领先 MOC的变化3 a;北大西洋大气要素变化对北大西洋热盐环流年代际振荡有非常重要的调制作用,当副极地流环和北大西洋暖流(NAC)达到最强的2 a之前,高纬度地区大气为气旋式环流异常,中纬度地区大气为反气旋式环流异常,海表热通量在大西洋副极地海区是负异常,这都有利于副极地流环和NAC的加强,更多高盐度的北大西洋水进入格陵兰-冰岛-挪威海(GIN)海域,由此可以导致GIN海域表层密度上升,使水体的层结稳定性减弱,有利于深层对流的发生,同时大气变化通过风应力旋度和海表热通量也直接影响GIN海域深层水的生成,进而导致格陵兰－苏格兰海脊溢流水的强度增加。