CMIP 6 models simulation of the connection between North/South Pacific Meridional Mode and ENSO

The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.

A case study of continental shelf waves in the northwestern South China Sea induced by winter storms in 2021

This study aims to investigate characteristics of continental shelf wave(CSW)on the northwestern continental shelf of the South China Sea(SCS)induced by winter storms in 2021.Mooring and cruise observations,tidal gauge data at stations Hong Kong,Zhapo and Qinglan and sea surface wind data from January 1 to February 28,2021 are used to examine the relationship between along-shelf wind and sea level fluctuation.Two events of CSWs driven by the along-shelf sea surface wind are detected from wavelet spectra of tidal gauge data.The signals are triply peaked at periods of 56 h,94 h and 180 h,propagating along the coast with phase speed ranging from 6.9 m/s to18.9 m/s.The dispersion relation shows their property of the Kelvin mode of CSW.We develop a simple method to estimate amplitude of sea surface fluctuation by along-shelf wind.The results are comparable with the observation data,suggesting it is effective.The mode 2 CSWs fits very well with the mooring current velocity data.The results from rare current help to understand wave-current interaction in the northwestern SCS.

Circulation Pattern Controls of Summer Temperature Anomalies in Southern Africa

This study investigates the relationship between circulation patterns and austral summer temperature anomalies in southern Africa. The results show that the formation of continental lows tends to increase the thickness of the lower atmosphere. Further, the distinct variabilities of high and low pressure under the circulation types, influence air mass advection from the adjacent oceans, as well as atmospheric stability over land. Stronger anticyclonic circulation at the western branch of the Mascarene high-pressure system enhances the low-level cold air advection by southeast winds,decreases the thickness, and lowers the temperature over a majority of the land in southern Africa. Conversely, a weaker Mascarene High, coupled with enhanced cyclonic activity in the southwest Indian Ocean increases low-level warm air advection and increases temperature anomalies over vast regions in southern Africa. The ridging of a closed South Atlantic anticyclone at the southern coast of southern Africa results in colder temperatures near the tip of southern Africa due to enhanced low-level cold air advection by southeast winds. However, when the ridge is weak and westerly winds dominate the southern coast of southern Africa, these areas experience temperature increases. The northward track of the Southern Hemisphere mid-latitude cyclone, which can be linked to the negative Southern Annular Mode, reduces the temperature in the southwestern part of southern Africa. Also, during the analysis period, El Ni?o was associated with temperature increases over the central parts of southern Africa;while the positive Indian Ocean dipole was linked to a temperature increase over the northeastern, northwestern, and southwestern parts of southern Africa.

Distribution characteristics of historical earthquake classes in Jiangsu Province and South Huanghai Sea region

According to the analysis on the characteristics of historic earthquakes in Jiangsu Province and South Huanghai Sea region, the historical earthquakes in the studied area are divided into two kinds of comparatively safe class and comparatively dangerous class. Then the statistical result of earthquake class, the characteristics of geo-graphical distribution and geological structures are studied. The study shows: a) In Jiangsu Province and South Huanghai Sea region, the majority of historical strong earthquakes belong to comparatively safe class, only 13.8% belong to comparatively dangerous class; b) Most historical earthquakes belong to comparatively safe class in the land area of Jiangsu, eastern sea area of Yangtze River mouth and northern depression of South Huanghai Sea region. However, along the coast of middle Jiangsu Province and in the sea area of South Huanghai Sea, the distribution of historical earthquake classes is complex and the earthquake series of comparatively dan-gerous class and comparatively safe class are equivalent in number; c) In the studied area, the statistical results of historical earthquake classes and the characteristics of spatial distribution accord very well with the real case of present-day earthquake series. It shows that the seismic activity in the region has the characteristic of succession, and the result from this study can be used as a reference for early postseismic judgment in the earthquake emer-gency work in Jiangsu Province.

PRINCIPAL MODES OF THE SOUTH PACIFIC SSTA IN JUNE, JULY AND AUGUST AND THEIR RELATIONS TO ENSO AND SAM

The relationships of variations of sea surface temperature anomalies (SSTA) in the South Pacificwith ENSO and Southern Hemisphere Annular Mode (SAM) are examined in the present article byemploying the NCEP-NCAR reanalysis from 1951 to 2006. Two principal modes of South Pacific SSTA areobtained using the EOF (Empirical Orthogonal Function) analysis for austral winter (June, July and August).Our results suggest that EOF1 is closely related with ENSO and EOF2 links to SAM. The EOF1 varieslargely on an interannual and EOF2 on a decadal scale. The time series of coefficients of EOF1 is highlycorrelated simultaneously with Nino3 index. However, the time series of coefficients of EOF2 issignificantly correlated with the March-April-May mean SAM index. Both the EOF1 and EOF2 are found insignificant correlation to summer precipitation over China. With higher-than-normal SSTs in the easternSouth Pacific and simultaneously lower SSTs in the western South Pacific in June-July-August, thesummertime rainfall is found to be less than normal in northern China. As displayed in EOF2 of SSTA, inyears with lower-than-normal SSTs in mid-latitude southern and equatorial eastern Pacific andhigher-than-normal SSTs in the equatorial middle Pacific in March-April-May, the summer precipitation inAugust tends to be more than normal in regions south of Yangtze River.

Coastline configuration and geomorphologic development mode of arc-shaped coast in South China

Coastline configuration indexes of 34 typical arc-shaped coasts in South China are investigated by the method of principal component analysis, and meanwhile deposition and geomorphologic features of arc-shaped coast are also analyzed. The results show: (1) The configuration of arc-shaped coast in South China is of the characteristic of variability and complexity. (2) The wave power and the openings of the bay are the decisive factors to result in the changes of the configuration of the arc-shaped coast in South China, however, incidence direction of the wave has no effect on configuration development of the coast. (3) Commonly, geomorphologic modes of the arc-shaped coast system in South China consist of barriers, lagoons and tidal-inlets, and can be divided into four types:the openings of the bay leaning to the east, the openings of the bay leaning to the south, the openings of the bay leaning to the west and the openings of the bay leaning to the north.

ON THE RELATIONSHIP BETWEEN 100-hPa SOUTH ASIA HIGH AND MEI-YU IN JIANGSU PROVINCE

By analyzing the change of an index for the characteristics of South Asia High and variations of upper-air troughs in 2002–2005,we studied the impact of South Asia high on the beginning and ending of the Mei-yu(i.e.sustained rain corresponding to the ripening season of plum)in Jiangsu province.Statistic verification is conducted on the relationships between the index and the Mei-yu season in 1991–2005 to examine the impacts of the SAH characteristics index on a rain intensity index of Mei-yu and regional distribution of a characteristics index for different annual patterns of Mei-yu.Historical composite is performed of the 100-hPa circulation field for these patterns using the 100-hPa geopotential height of Northern Hemisphere from 2002 to 2005 and 45-year NCEP reanalysis to study the difference in the circulation for different patterns of Mei-yu.Diagnostic and statistic conclusions,which share much in common,have been obtained as follows.(1)The characteristics preceding to and the advancement/retreat of SAH and the movement of westerly troughs are the factors that influence the onset time of the Mei-yu season;after the Mei-yu onset,the progression/withdrawal of SAH and how farther east it extends are determining how long the Mei-yu lasts and when it ends.(2)During the Mei-yu,the general 100-hPa circulation situation and average characteristics of the SAH are well corresponding to the characteristics of the season and annual patterns of Mei-yu.In addition,the averages of the SAH ridgeline and east-extending index for June,July and the Mei-yu season have some implications to the forecast of the index of Mei-yu intensity.These conclusions can be served as powerful means in determining the starting/ending dates, duration and annual pattern of the Mei-yu season.

Development Mode of Mid-small Cities in Northern Jiangsu Based on the Growth Pole Theory

The development mode of mid-small cities in northern Jiangsu is analyzed on the Growth Pole theory.Depending on scales,endowment of resources,geographical positions,and industrial advantages of mil-small cities,we can divide the development mode of those mid-small cities within this context into five types:development through integration into big cities;independent development;resource-dependent development;single industry development;and mixed industry development.

Distribution characteristics of historical earthquake classes in Jiangsu Province and South Huanghai Sea region

According to the analysis on the characteristics of historic earthquakes in Jiangsu Province and South Huanghai Sea region, the historical earthquakes in the studied area are divided into two kinds of comparatively safe class and comparatively dangerous class. Then the statistical result of earthquake class, the characteristics of geo-graphical distribution and geological structures are studied. The study shows: a) In Jiangsu Province and South Huanghai Sea region, the majority of historical strong earthquakes belong to comparatively safe class, only 13.8% belong to comparatively dangerous class; b) Most historical earthquakes belong to comparatively safe class in the land area of Jiangsu, eastern sea area of Yangtze River mouth and northern depression of South Huanghai Sea region. However, along the coast of middle Jiangsu Province and in the sea area of South Huanghai Sea, the distribution of historical earthquake classes is complex and the earthquake series of comparatively dan-gerous class and comparatively safe class are equivalent in number; c) In the studied area, the statistical results of historical earthquake classes and the characteristics of spatial distribution accord very well with the real case of present-day earthquake series. It shows that the seismic activity in the region has the characteristic of succession, and the result from this study can be used as a reference for early postseismic judgment in the earthquake emer-gency work in Jiangsu Province.

Covariability of Subantarctic Mode Water and the Southern Branch of the Subtropical Indian Ocean Countercurrent in Argo Observations

The Subantarctic Mode Water(SAMW)forms in the deep mixed layer north of the Antarctic Circumpolar Current and spreads northward into the subtropical gyre.The subtropical South Indian Countercurrent(SICC)flows eastward on the north flank of the thick SAMW layer within 22°-32°S from south of Madagascar at around 25°S,50°E toward western Australia.The dynamical relation of the SAMW and the southern branch of the SICC(30°-32°S)is investigated in this work based on the monthly mean Argo data from 2004 to 2019.The physical properties of the SAMW and its pathway from the formation region are described.Most of the SAMW in the Indian Ocean sector originates from the deep mixed layers of the southeastern Indian Ocean(about 40°S,85°-105°E)and moves along the subtropical gyre.It takes around ten years to arrive east of Madagascar Island preserving its low potential vor-ticity characteristics.As a thick layer with homogeneous vertical properties,the SAMW forces the upper pycnocline to shoal,and the associated eastward shear results in the surface-intensified SICC.The SAMW forms a tongue-shaped thickness pattern,which influ-ences the southern branch of the SICC above the northern flank of the thickest SAMW layer between 24°S and 32°S.The seasonal,interannual,and decade variations of the southern branch of the SICC are closely related to the meridional gradient of the underlying SAMW thickness.The SAMW thickened and strengthened from 2005 to 2015,thereby anchoring a strengthened SICC.The interan-nual covariability of the SAMW and SICC further supports the SAMW’s role in driving SICC variability.

A 3-dimensional baroclinic circulation model of the South China Sea

The summer and winter circulations in the South China Sea (SCS) including the surface elevation and water temperature are simulated using the model described by Cai and Li (1996) with the monthly mean wind stress and air temperature field at the 1000 mb level from the European Centre for Medium-Range Weather Forecasts as inputs. The boundary conditions at Bashi Channel and Taiwan Strait are taken from the simulation results of the Kuroshio using the same numerical model with a grid size of 0.5°×0.5° and the results of Cai and Li (1996) as boundary conditions. The computational domain for the present paper is between 100°E and 123°E and between 4.5°N and 27°N. The horizontal resolution is 0.25°×0.25° and the vertical variations of the velocity components are resolved by 6 layers The computed steady flow, temperature and elevation fields are consistent with the corresponding fields observed. In particular, the temperature and elevation fields of the South China Sea Warm Current (SCSWC) have been successfully simulated. The paths of the branch of the Kuroshio entering the South China Sea (SCSBK) through Bashi Channel in winter and summer are discussed It is found that the SCSBK flows southward to the southern SCS from the coast of the Guangdong Province. A portion of the SCSBK returns to the Bashi Channel and subdivides again in deep waters in winter with a branch flows to the south along the coast of the Philippines instead of flowing back to the Pacific In addition, our results confirm the existence of a eastward current to the northeast of Dongsha in summer with the Kuroshio as its source as suggested by Huang et al. Since the value of the eddy viscosity adopted for the simulation of the Kuroshio is on the high side, resulting in a weaker west boundary current in the western Pacific as the boundary conditions for the present simulations, some deviations from the actual situations are expected although the results are in general consistent with observations.

苏南模式演进与发展

苏南模式是中国现代化经济发展中最有影响、最为成功的道路之一。苏南模式催生了:苏南模式乡镇集体经济代表——华西村的发展变迁;物质文明和精神文明相互促进、相得益彰共同成就的文明高地——张家港精神;不等不靠的苏南模式代表——昆山之路;新苏南模式走在前列创新演进的代表——苏州模式等多个鲜活的改革与发展创造样本。苏南模式如今是国资、外资、民资与股份制经济共同发展,是新时代中国特色社会主义市场经济的重要窗口。苏南模式的演进与发展,是发展经济学理论在中国的成功实践,苏南模式的最新发展,为构建中国发展经济学的理论体系,提供了丰富的实践土壤。

冬春两湖盆地地区大气气溶胶污染的年代际变化特征及其与东亚经向风南北反相位的联系

基于MERRA-2及ERA5逐月再分析资料,本文采用EOF分析、线性回归和合成分析等方法,分析了1980~2020年长江流域中游两湖盆地地区气溶胶光学厚度(AOD)的年代际变化特征及东亚经向风南北反位相模态对其的影响。结果表明,在年代际尺度上两湖盆地地区AOD呈现非线性的变化趋势,20世纪80、90年代处于低值,21世纪初AOD持续升高,2010年后开始下降。空间场上表现为全区一致的变化特征,高值区主要位于两湖盆地中部,以洞庭湖为中心呈南北纵向分布。进一步对两湖盆地AOD年代际变化与大气环流异常关系的分析表明,在东亚经向风南北反相模的影响下,偏北风输送是影响两湖盆地AOD年代际变化的主要气象原因。在年代际尺度上,当西伯利亚高压的强度、面积增大,东亚大槽西移,西北太平洋副热带高压脊线南移时,东亚经向风南北反相模趋于正相位(即长江以北有异常偏南风、长江以南有异常偏北风)。此时,两湖盆地位于气旋性环流异常的底部,在异常的偏北风的作用下,西北地区的气溶胶向两湖盆地输送加强。且两湖盆地处于两个异常气旋性环流的中间,气压梯度小,风速偏弱,使得两湖盆地气溶胶输入大于输出,促进21世纪初AOD年代际升高。

中国东部冬季气温变化的主要区域空间模态及其与大气环流的关系

本文利用1956—2017年我国519个站点逐日气温资料,通过旋转经验正交函数分析方法得到了近62年我国冬季气温变化主要的区域空间模态,研究了其与大气环流的关系,并进一步使用2018—2023年上述站点冬季气温资料进行验证分析。结果表明,我国冬季气温变化有两个较为稳定的区域空间模态:第一模态主要表现为南方大部分地区出现异常低温,低温极值区位于华南和东南沿海区,称之为南方型;第二模态的气温异常信号主要集中在东北地区,称之为东北型。其中,南方型模态与赤道中太平洋的海温呈显著负相关关系,与东亚冬季风的“南北反向”模态呈显著正相关。当冬季赤道中太平洋海温异常偏冷时,东亚南部地区表现为强烈的低层偏北风距平,北方则无显著偏北风距平,造成南方大部分地区出现异常低温。冬季北极涛动与东北型低温模态有显著联系,当北极涛动呈负位相时,冷高压主要集中在极区,高压东侧盛行东北风,造成东北地区冬季气温异常偏低。近6年中,2018年与2021年冬季呈东北型低温模态,其关键环流系统接近北极涛动负位相,验证了该结论。

一次华南飑线的观测分析和数值模拟研究

利用多种气象观测资料和高分辨率的数值模拟结果,对2020年5月11日华南地区一次飑线的初生、增强、成熟和衰亡等4个阶段的对流组织特征和模态的演变及机理进行了分析。结果表明:该飑线发生于高空急流入口右侧的高空辐散区,伴随着南支槽的加深东移,低层暖湿平流以及地面的中尺度辐合线为其提供了有利的水汽、热力和抬升触发条件。初始阶段,飑线呈断线型发展,在较大的环境热力条件下具有中到强的对流有效位能和最大的对流抑制。成熟期形成拖尾层状云型飑线,低层风切变和冷池强度逐渐达到平衡状态。在衰亡阶段,飑线的组织模态发生转变,其中环境热力条件是后向新生型对流单体发生的主要原因,且低层不同的水汽和风切变条件也对模态的变异存在一定作用。在华南地区,以断线型模态生成拖尾层状云型模态的飑线所需的对流有效位能更高,且飑线的维持也需要更强的热力条件。对流有效位能、对流抑制能量、粗理查森数、风暴相对螺旋度等在对流单体形成的种类和组织模态方面均有一定的指示意义。

南水北调受水区工业需水量的多方法组合预测

以南水北调东线江苏段受水区为对象,2020年为现状年,在趋势法、多元线性回归和BP神经网络的基础上,利用相对误差-反距离权重法构建了一种组合模型。采用该组合模型预测江苏段受水区2030年工业需水量。结果表明:基于趋势法、多元线性回归和BP神经网络所得的工业需水量预测值之间的偏差均小于10%,各单一方法与真实值之间的平均误差均小于10%;组合预测模型所得工业需水量的决定系数(R^(2))比单一需水预测模型高0.02~0.09;江苏段受水区2030年工业需水总量预测值为14.68×10^(8) m^(3),相比现状年工业需水总量增加了70.3%。研究成果不仅可为南水北调东线江苏段受水区提供可靠的工业需水量预测数据,也可为其他南水北调受水区工业需水量预测提供方法借鉴。

Seasonal Variation and Heat Preference of the South Asia High

By use of the NCEP/ NCAR reanalysis data, the seasonal variation of the South Asia high (SAH) is analyzed. The influences of temporal and spatial variations of the middle and upper level atmospheric temperatures, the visible heat sources, and the diabatic heating rates in the whole atmospheric column on the seasonal variation of the SAH are discussed. Results show that the SAH has two seasonal balancing modes, one of which is the land high in summer and the other the ocean high in winter. The land high itself can be divided into two patterns as well, that is the Tibetan high and the Iranian high. Heating fields have important impacts on the seasonal variation of the SAH. The SAH is a warm high and its center has the property of heat preference, usually locating over or moving to an area with relatively larger heating rates. The annual cycle of the SAH is mainly controlled by the seasonal process of the latent and sensible heating in South Asia. Strong shortwave radiative heating in the north at high latitudes and over the Tibetan Plateau also has an effects on the northward movement and maintenance of the SAH. The cooling effect of infrared radiation is an important cause in weakening the SAH.

Shoaling of the internal solitary waves over the continental shelf of the northern South China Sea

The activities of internal solitary waves （ISWs） over the continental shelf of the northern South China Sea （SCS） are of high complexity. In this study, we investigated the spatial-temporal characteristics of the shoaling ISWs over the northern SCS continental shelf using the satellite images and the results of numerical simulation. The examination of the ISW signals in the satellite optical images revealed the existence of three types of iSWs in the region north to the Dongsha Island, namely, mode-1 depression ISW, mode-1 elevation ISW, and mode-2 convex ISW. The geographical distributions of these ISWs were derived from the satellite images. Numerical results exhibited the process of polarity conversion of ISWs, by which mode-1 elevation waves were transformed from the shoaling mode-1 depression waves. The mode-2 convex ISWs generally followed the mode-1 depression ISWs. The numerical results suggested that the interaction of the mode-1 depression ISWs with the up-slope topography locally generated mode-2 ISWs, and such waves of high vertical mode dissipated rapidly during the inshore propagation.

Expansion of the South China Sea basin:Constraints from magnetic anomaly stripes,sea floor topography,satellite gravity and submarine geothermics

The widely distributed E-W-trending magnetic anomaly stripes in the central basin and the N-Etrending magnetic anomaly stripes in the southwest sub-basin provide the most important evidence for Neogene expansion of the South China Sea.The expansion mechanism remains,however,controversial because of the lack of direct drilling data,non-systematic marine magnetic survey data,and irregular magnetic anomaly stripes with two obvious directions.For example,researchers have inferred different ages and episodes of expansion for the central basin and southwest sub-basin.Major controversy centers on the order of basinal expansion and the mechanism of expansion for the entire South China Sea basin.This study attempts to constrain these problems from a comprehensive analysis of the seafloor topography,magnetic anomaly stripes,regional aeromagnetic data,satellite gravity,and submarine geothermics.The mapped seafloor terrain shows that the central basin is a north-south rectangle that is relatively shallow with many seamounts,whereas the southwest sub-basin is wide in northeast,gradually narrows to the southwest,and is relatively deeper with fewer seamounts.Many magnetic anomaly stripes are present in the central basin with variable dimensions and directions that are dominantly EWtrending,followed by the NE-,NW- and NS-trending.Conversely such stripes are few in the southwest sub-basin and mainly NE-trending.Regional magnetic data suggest that the NW-trending Ailaoshan-Red River fault extends into the South China Sea,links with the central fault zone in the South China Sea,which extends further southward to Reed Tablemount.Satellite gravity data show that both the central basin and southwest sub-basin are composed of oceanic crust.The Changlong seamount is particularly visible in the southwest sub-basin and extends eastward to the Zhenbei seamount.Also a low gravity anomaly zone coincides with the central fault zone in the sub-basin.The submarine geothermic distribution demonstrates that the southwest sub-basin has a higher geothermal value than the central basin,and that the central fault zone is defined by a low thermal anomaly.This study suggests that NW-SE expansion of the southwest subbasin is later than the N-S expansion of the central basin with the sub-basin extending into the central basin and with both expansions ending at the same time.The expansion of southwestern sub-basin,similar to the Japanese Sea,is likely caused by left-lateral strike slip on the central fault zone in the South China Sea,which may have significance for finding oil and gas in this region.

A study of sea level variability and its long-term trend in the South China Sea

On the basis of the satellite maps of sea level anomaly（MSLA） data and in situ tidal gauge sea level data,correlation analysis and empirical mode decomposition（EMD） are employed to investigate the applicability of MSLA data,sea level correlation,long-term sea level variability（SLV） trend,sea level rise（SLR） rate and its geographic distribution in the South China Sea（SCS）.The findings show that for Dongfang Station,Haikou Station,Shanwei Station and Zhapo Station,the minimum correlation coefficient between the closest MSLA grid point and tidal station is 0.61.This suggests that the satellite altimeter MSLA data are effective to observe the coastal SLV in the SCS.On the monthly scale,coastal SLV in the western and northern part of SCS are highly associated with coastal currents.On the seasonal scale,SLV of the coastal area in the western part of the SCS is still strongly influenced by the coastal current system in summer and winter.The Pacific change can affect the SCS mainly in winter rather than summer and the affected area mostly concentrated in the northeastern and eastern parts of the SCS.Overall,the average SLR in the SCS is 90.8 mm with a rising rate of（5.0±0.4） mm/a during1993–2010.The SLR rate from the southern Luzon Strait through the Huangyan Seamount area to the Xisha Islands area is higher than that of other areas of the SCS.