Subtropical High Anomalies over the Western Pacific and Its Relations to the Asian Monsoon and SST Anomaly

Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical circulations including the Asian monsoon as well as the convective activity are studied. In order to study the physical process of the air-sea interaction related to STH anomaly, the correlation of STH with SST at various sea areas, lagged and simultaneous, has been calculated. Comparing the difference of OLR, wind fields, vertical circulations and SST anomalies in the strong and weak STH, we investigate the characteristics of global circulations and the SST distributions related to the anomalous STH at the western Pacific both in winter and summer. Much attention has been paid to the study of the air-sea interaction and the relationship between the East Asian monsoon and the STH in the western Pacific. A special vertical circulation, related to the STH anomalies is found, which connects the monsoon current to the west and the vertical flow influenced by the SST anomaly in the tropical eastern Pacific.

A numerical study of the impact of SST anomaly in the warm pool area on atmospheric circulation in winter

In this paper the impacts of the anomalous SST in the warm pool area of the Western Equatorial Pacific on the winter time circulation and the East Asian monsoon are studied by using the NCAR CCM. It is found that the abnormal heating in the warm pool area will change the strength and the position of the Walker Cell in the Equatorial Pacific and the anti-Walker Cell in the equatorial Indian Ocean. Both the Walker and anti-Walker Cells are strengthened. The local Hadley Cells over two hemispheres near the warm pool are also strengthened. The subtropical highs in two hemispheres become stronger and move poleward slightly. The westerly jets in the extratropical regions have similar changes as the subtropical highs. The winter monsoon in South-East Asia is weakened by the abnormal heating in the warm pool. The experiment also show that there are wave trains emanating from surrounding areas of the warm pool to the high latitudes, causing various changes in circulations and local weather.

A STUDY ON THE RELATIONSHIP BETWEEN THE SUMMER PRECIPITATION IN NORTHEAST CHINA AND THE GLOBAL SEA SURFACE TEMPERATURE ANOMALY (SSTA) IN PRECEDING SEASONS

Based on the NCEP/NCAR reanalysis global SST, 500-hPa geopotential height, 850-hPa wind monthly mean data and summer precipitation from 80 observation stations of Northeast China for the period 1961-2000, the summer precipitation field of Northeast China was decomposed by using the principal component analysis method, then the relationships between the first three precipitation leading modes and the global SSTA in preceding seasons were studied, and the responses of the 500-hPa atmospheric circulation in East Asia to the preceding winter SSTA in north Pacific and its influence on the summer precipitation in Northeast China were probed. The results show that the SSTA, especially the ENSO event in preceding seasons has really very important influence on the occurrence of the whole coincident precipitation episode in Northeast China, and relates to the precipitation episodes of the reverse variation in south-north and in west-east direction closely. The north Pacific SST anomalies in preceding winters are associated with the summer precipitation in Northeast China through its influence on the western Pacific subtropical high and the East Asia subtropical monsoon in summer. Therefore, taking the global SSTA distribution in preceding seasons, especially the ENSO event, as the precursor signal to predict the precipitation anomaly in Northeast China has good reliability and definite indicative significance.

Understanding the role of SST anomaly in extreme rainfall of 2020 Meiyu season from an interdecadal perspective

Extreme Meiyu rainfall in 2020,starting from early June to the end of July,has occurred over the Yangtze River valley(YRV),with record-breaking accumulated precipitation amount since 1961.The present study aims to examine the possible effect of sea surface temperature(SST)on the YRV rainfall in Meiyu season from the interdecadal perspective.The results indicate that YRV rainfall in June exhibits more significant variability on interdecadal time scale than that in July.The interdecadal-filtered atmospheric circulation in June,compared with the counterpart in July,shows a more predominant and better-organized Western North Pacific Anticyclone(WNPAC)anomaly,which could transport abundant moisture to the YRV by anomalous southwesterly prevailing in northwestern flank of anomalous WNPAC.Both observation and numerical experiment indicate that the interdecadal change of the SST anomaly in tropical western Indian Ocean(TWI)from preceding May to June can significantly affect the anomalous WNPAC,leading to enhanced YRV rainfall in June.The TWI SST anomaly shifts from a cold phase to a warm phase around the early 2000s,with a magnitude of 0.7°C in 2020,which implies that such interdecadal warming might partly contribute to the heavy rainfall in June 2020 by providing a large-scale favorable background flow.

The Response of Anomalous Vertically Integrated Moisture Flux Patterns Related to Drought and Flood in Southern China to Sea Surface Temperature Anomaly

With the extreme drought(flood)event in southern China from July to August in 2022(1999)as the research object,based on the comprehensive diagnosis and composite analysis on the anomalous drought and flood years from July to August in 1961-2022,it is found that there are significant differences in the characteristics of the vertically integrated moisture flux(VIMF)anomaly circulation pattern and the VIMF convergence(VIMFC)anomaly in southern China in drought and flood years,and the VIMFC,a physical quantity,can be regarded as an indicative physical factor for the"strong signal"of drought and flood in southern China.Specifically,in drought years,the VIMF anomaly in southern China is an anticyclonic circulation pattern and the divergence characteristics of the VIMFC are prominent,while those are opposite in flood years.Based on the SST anomaly in the typical draught year of 2022 in southern China and the SST deviation distribution characteristics of abnormal draught and flood years from 1961 to 2022,five SST high impact areas(i.e.,the North Pacific Ocean,Northwest Pacific Ocean,Southwest Pacific Ocean,Indian Ocean,and East Pacific Ocean)are selected via the correlation analysis of VIMFC and the global SST in the preceding months(May and June)and in the study period(July and August)in 1961-2022,and their contributions to drought and flood in southern China are quantified.Our study reveals not only the persistent anomalous variation of SST in the Pacific and the Indian Ocean but also its impact on the pattern of moisture transport.Furthermore,it can be discovered from the positive and negative phase fitting of SST that the SST composite flow field in high impact areas can exhibit two types of anomalous moisture transport structures that are opposite to each other,namely an anticyclonic(cyclonic)circulation pattern anomaly in southern China and the coastal areas of east China.These two types of opposite anomalous moisture transport structures can not only drive the formation of drought(flood)in southern China but also exert its influence on the persistent development of the extreme weather.

NUMERICAL EXPERIMENT ON MID-LATITUDE SST ANOMALY AND VARIATION IN CIRCULATION PATTERN

By means of simulation experiments with a two-dimensional zonal-mean model,a study is made of the influence of the western North-Pacific midlatitude sea-surface temperature(SST)anomalies on the circulation pattern and wet-seasonal precipitation over the East-China Changjiang-Huaihe reaches and the North-China plain.The SST anomalies are divided into two types,one being“colder in the south and warmer in the north”and the other just opposite,depending on season.Results show that the occurrence of the anomalies is followed by considerable changes in the position of the subtropical high happening for 3-5 months to come.For instance,the spring“colder in the south and warmer in the north”anomalous type (i.e.,colder for 20—35°N,and warmer north of 35°N)leads to the intensification of the summer subtropical high,with the ridge line moved slightly northward,resulting in drought over Changjiang reaches for July-August and in excessive rainfall in the North-China plain,and vice versa.

Numerical Simulation of the Effect of the SST Anomalies in the Tropical Western Pacific on the Blocking Highs over the Northeastern Asia

The effects of the sea surface temperature (SST) anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are simulated by the IAP-GCM with an observed and idealized distributions of the SST anomalies in the tropical western Pacific,respectively.Firstly,the atmospheric circulation anomalies during July and August,1980 are simulated by three anomalous experiments including the global SST anomaly experiment,the tropical SST anomaly experiment and the extratropical SST anomaly experiment,using the observed SST anomalies in 1980.It is shown that the SST anomalies in the tropical ocean greatly influence the formation and maintenance of the blocking high over the northeastern Asia,and may play a more important role than the SST anomalies in the extratropical ocean in the influence on the atmospheric circulation anomalies.Secondly,the effects of the SST anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are also simulated with an idealized distribution of the SST anomalies in the tropical western Pacific.The simulated results show that the negative anomalies of SST in the tropical western Pacific have a significant effect on the formation and maintenance of the blocking high over the northeastern Asia.

Interannual and Decadal Variability of the North Pacific Blocking and Its Relationship to SST, Teleconnection and Storm Tracks

Climalological features of mid-latitude blocking occurring over the North Pacific Ocean during 52 winters (December to February) of 1948/1949-1999/2000 are statistically analyzed based on NCEP/ NCAR reanalysis data. Significant interannual variation with a period of about 3-7 years as well as decadal variability is found by wavelet analysis and power spectrum analysis. A decreasing trend of the 2-7 year bandscale-averaged variance occurs throughout the 52 years and an abrupt shift from a higher state to a lower state during the 1970s is also found, which suggests an interdecadal variation of the North Pacific blocking. The possible relationship between the variability of blocking and sea surface temperature (SST), storm tracks and teleconnection are shown using composite analysis. In strong blocking anomaly winter (SBW), the geopotential height anomaly at 500 hPa exhibits a typical PNA (Pacific-North American)-like wave-train pattern in the North Pacific. The storm tracks, representing the activity of transient eddies, extend northeastward to the western coast of North America along the mid latitudes of about 40°-50°N, with the SST anomaly exhibiting a Pacific decadal oscillation (PDO) mode at mid-latitude and a La Niña-like pattern along the equator. Contrasting features appear in weak blocking anomaly winter (WBW).

Synergistic Interdecadal Evolution of Precipitation over Eastern China and the Pacific Decadal Oscillation during 1951-2015

By using the multi-taper method(MTM)of singular value decomposition(SVD),this study investigates the interdecadal evolution(10-to 30-year cycle)of precipitation over eastern China from 1951 to 2015 and its relationship with the North Pacific sea surface temperature(SST).Two significant interdecadal signals,one with an 11-year cycle and the other with a 23-year cycle,are identified in both the precipitation and SST fields.Results show that the North Pacific SST forcing modulates the precipitation distribution over China through the effects of the Pacific Decadal Oscillation(PDO)-related anomalous Aleutian low on the western Pacific subtropical high(WPSH)and Mongolia high(MH).During the development stage of the PDO cold phase associated with the 11-year cycle,a weakened WPSH and MH increased the precipitation over the Yangtze River Basin,whereas an intensified WPSH and MH caused the enhanced rain band to move northward to North China during the decay stage.During the development stage of the PDO cold phase associated with the 23-year cycle,a weakened WPSH and MH increased the precipitation over North China,whereas an intensified WPSH and the weakened MH increased the precipitation over South China during the decay stage.The 11-year and 23-year variabilities contribute differently to the precipitation variations in the different regions of China,as seen in the 1998flooding case.The 11-year cycle mainly accounts for precipitation increases over the Yangtze River Basin,while the 23-year cycle is responsible for the precipitation increase over Northeast China.These results have important implications for understanding how the PDO modulates the precipitation distribution over China,helping to improve interdecadal climate prediction.

SPATIO-TEMPORAL VARIATION OF SEASONAL EXTREME WET DAYS IN CHINA AND ITS RELATIONSHIP WITH SST ANOMALIES

With daily precipitation records at 586 stations in China for 1960-2004, this study investigates the spatio-temporal variation of the number of extreme wet days (NEWD) for each season in China and its relationship with SST anomalies and associated atmospheric circulation anomaly patterns, in which a threshold of extreme precipitation for a season and a station is defined as the value of the 90th percentile when the precipitation records for wet days during the season are ranked in an increasing order. Results show that there are significant increases of the NEWD along the Yangtze River valley during winter and summer, in North China during winter, in South China during spring, in Northeast China during winter and spring, and in Northwest China throughout the seasons, while there is a remarkable decrease in North China during summer. Besides the linear trend, the NEWD also exhibits considerable interannual and interdecadal variabilities. After eliminating the linear trend, the NEWD anomalies show distinct seasonal patterns. The NEWD anomalies are characterized by a "dipole" mode with opposite phases between northern and southern China in spring and autumn, a "tri-pole" mode with opposite phases between Yangtze River valley and southern and northern China in summer, and a "monopole" mode with the same phase over most of China in winter. The relationship of the NEWD anomalies in China with the SST anomalies in Indian and Pacific Oceans is found to be mainly dependent on the ENSO, and associated atmospheric circulation anomaly patterns for the ENSO's impact on the NEWD in China are identified.

Numerical Simulation of the Relationships between the 1998 Yangtze River Valley Floods and SST Anomalies

With the IAP/LASG GOALS model, the relationships between the floods in the Yangtze River valley arid sea surface temperature anomalies (SSTA) in the Pacific and Indian Oceans in 1998 have been studied. The results show that the model can reproduce the heavy rainfall over the Yangtze River valley in the sum-mer of 1998 forced by global observational sea surface temperatures (SST). The model can also reproduce the observed principal features of the subtropical high anomalies over the western Pacific. The experiments with the observed SST in different ocean areas and different periods have been made. By comparing the ef-fects of SSTA of different ocean areas on the floods, it is found that the SSTA in the Indian Ocean are a ma-jor contributor to the floods, and the results also show that the SSTA in the Indian Ocean and the western Pacific have a much closer relationship with the strong anomalies of the subtropical high over the western Pacific than the SSTA in other concerned areas. The study also indicates that the floods and subtropical high anomalies in the summer of 1998 are more controlled by the simultaneous summertime SSTA than by SSTA in the preceding winter and spring seasons.

Influences of two types of El Ni?o event on the Northwest Pacific and tropical Indian Ocean SST anomalies

Based on the Had ISST1 and NCEP datasets,we investigated the influences of the central Pacific El Ni?o event(CP-EL)and eastern Pacific El Ni?o event(EP-EL)on the Sea Surface Temperature(SST)anomalies of the Tropical Indian Ocean.Considering the remote ef fect of Indian Ocean warming,we also discussed the anticyclone anomalies over the Northwest Pacific,which is very important for the South China precipitation and East Asian climate.Results show that during the El Ni?o developing year of EP-EL,cold SST anomalies appear and intensify in the east of tropical Indian Ocean.At the end of that autumn,all the cold SST anomaly events lead to the Indian Ocean Dipole(IOD)events.Basin uniform warm SST anomalies exist in the Indian Ocean in the whole summer of EL decaying year for both CP-and EP-ELs.However,considering the statistical significance,more significant warm SST anomalies only appear in the North Indian Ocean among the June and August of EP-EL decaying year.For further research,EP-EL accompany with Indian Ocean Basin Warming(EPI-EL)and CP El Ni?o accompany with Indian Ocean Basin Warming(CPI-EL)events are classified.With the remote ef fects of Indian Ocean SST anomalies,the EPI-and CPI-ELs contribute quite differently to the Northwest Pacific.For the EPI-EL developing year,large-scale warm SST anomalies arise in the North Indian Ocean in May,and persist to the autumn of the El Ni?o decaying year.However,for the CPI-EL,weak warm SST anomalies in the North Indian Ocean maintain to the El Ni?o decaying spring.Because of these different SST anomalies in the North Indian Ocean,distinct zonal SST gradient,atmospheric anticyclone and precipitation anomalies emerge over the Northwest Pacific in the El Ni?o decaying years.Specifically,the large-scale North Indian Ocean warm SST anomalies during the EPI-EL decaying years,can persist to summer and force anomalous updrafts and rainfall over the North Indian Ocean.The atmospheric heating caused by this precipitation anomaly emulates atmospheric Kelvin waves accompanied by low level easterly anomalies over the Northwest Pacific.As a result,a zonal SST gradient with a warm anomaly in the west and a cold anomaly in the east of Northwest Pacific is generated locally.Furthermore,the atmospheric anticyclone and precipitation anomalies over the Northwest Pacific are strengthened again in the decaying summer of EPI-EL.Af fected by the local WindEvaporation-SST(WES)positive feedback,the suppressed East Asian summer rainfall then persists to the late autumn during EPI-EL decaying year,which is much longer than that of CPI-EL.

PRELIMINARY DISCUSSIONS OF BASIC CLIMATIC CHARACTERISTICS OF PRECIPITATION DURING RAINING SEASONS IN REGIONS SOUTH OF CHANGJIANG RIVER AND ITS RELATIONSHIP WITH SST ANOMALIES

Basic climatic characteristics are analyzed concerning the precipitation anomalies in raining seasons over regions south of the Changjiang River (the Yangtze). It finds that the regions are the earliest in eastern China where raining seasons begin and end. Precipitation there tends to decrease over the past 50 years. Waters bounded by 9(S -1(S, 121(E - 129(E are the key zones of SST anomalies that affect the precipitation in these regions over May ~ July in preceding years. Long-term air-sea interactions make it possible for preceding SST anomalies to affect the general circulation that come afterwards, causing precipitation anomalies in the raining seasons in regions south of the Changjiang River in subsequent years.

Numerical simulation of influence of the anomalies of theCentral-eastern Equatorial Pacific SST and Arctic seaice cover in summer on the atmospheric circulation

A series of numerical experiments have been conducted with a perpetual July, nine-level general circulation spectral model to determine the effect of variation of the Arctic sea ice cover extent and the joint effect of anomalies of both the Arctic sea ice cover and the Central-eastern Equatorial Pacific sea surface temperature on the summer general circulation. Results show that the two factors,anomalously large extent of the Arctic sea ice cover and anomalously warm sea surface temperature over the Central-eastern Equatorial Pacific Ocean, play substantially the equal role in the effect on the summer general circulation, and either of them can notably induce the atmospheric anomalies. The main dynamical processes determining the effect of the Arctic sea ice and the equatorial SST anomalies are associated with two leading teleconnection patterns, i. e. the Asia North/American and Eurasian patterns observed in atmosphere. The results presented in this paper again prove that the general circulation is fundamentally motivated by the non-uniform heating between the equator and the pole on the rotating earth.

Numerical Simulation of the Relationships hetween the 1998Yangtze River Valley Floods and SST Anomalies

With the IAP/ LASG GOALS model, the relationships between the floods in the Yangtze River valley and sea surface temperature anomalies (SSTA) in the Pacific and Indian Oceans in 1998 have been studied. The results show that the model can reproduce the heavy rainfall over the Yangtze River valley in the sum mer of 1998 forced by global observational sea surface temperatures (SST). The model can also reproduce the observed principal features of the subtropical high anomalies over the western Pacific. The experiments with the observed SST in different ocean areas and different periods have been made. By comparing the ef fects of SSTA of different ocean areas on the floods, it is found that the SSTA in the Indian Ocean are a ma jor contributor to the floods, and the results also show that the SSTA in the Indian Ocean and the western Pacific have a much closer relationship with the strong anomalies of the subtropical high over the western Pacific than the SSTA in other concerned areas. The study also indicates that the floods and subtropical high anomalies in the summer of 1998 are more controlled by the simultaneous summertime SSTA than by SSTA in the preceding winter and spring seasons.

Model Study on the Interannual Variability of Asian Winter Monsoon and Its Influence

The interannual variation of Asian winter (NE) monsoon and its influence is studied using the long-term integration of Max-Plank Institute ECHAM3(T42 L19) model. The simulation well reproduces the main features of the climatological mean Asian winter monsoon and shows pronounced difference of atmospheric circulation between strong and weak winter monsoon and for the consecutive seasons to follow. Most striking is the appearance and persistence of an anomalous cyclonic flow over the western Pacific and enhanced Walker circulation for strong winter monsoon in agreement with the observation. The contrast in summer rainfall patterns of both East China and India can also be discerned in the simulation. Comparison of three sets of experiments with different SST shows that the forcing from the anomalies of global SST makes a major contribution to the interannual variability of Asiao winter monsoon and, in particular, to the interseasonal persistence of the salient features of circulation. The SSTA over the tropical western Pacific also plays an important part of its own in modulating the Walker circulation and the extratropical flow patterns. The apparent effect of strong NE monsoon is to enhance the convection over the tropical western Pacific. This effect, on the one hand, leads to a strengthening of SE trades to the east and extra westerly flow to the west, thus favorable to maintaining a specific pattern of SSTA. On the other hand, the thermal forcing associated with the SSTA acts to strengthen the extratropical flow pattern which is, in turn, conducive to stronger monsoon activity. The result seems to suggest a certain self-sustained regime in the air-sea system, which is characterized by two related interactions, namely the air-sea and tropical-extratropical interactions with intermittent outburst of NE cold surge as linkage. There is a connection between the strength of the Asian winter monsoon and the precipitation over China in the following summer. Links between these two variabilities are mainly through SST anomalies but snow over Asia is a contributing factor as well.

Enhanced correlation between ENSO and western North Pacific monsoon during boreal summer around the 1990s

The correlation between summertime Nino3.4 index and western North Pacific(WNP)summer monsoon index has strikingly enhanced since the early 1990 s,with nonsignificant correlation before the early1990 s but significant correlation afterward.This observed interdecadal change around the 1990 s may be associated with more frequent occurrences of central Pacific(CP)El Nino and the interdecadal changes in ENSO-associated SST anomalies.During the post-1990 s period(the pre-1990 s period),highly noticeable tropical Atlantic(Indian)Ocean SST anomalies tend to co-occur with the summertime Nino3.4 SST anomalies.The concurrent tropical Atlantic(Indian)Ocean SST anomalies could constructively reinforce(destructively mitigate)the WNP monsoon circulation anomalies induced by the summertime Nino3.4 SST,thus boosting(muting)the correlation between summertime Nino3.4 SST and WNP monsoon.In addition,the faster decaying pace of preceding-winter El Nino after the 1990 s,which may have been mainly induced by the influences from the spring tropical North Atlantic SST anomalies,could also have contributed to the enhanced correlation between the summertime Nino3.4 index and WNP monsoon.These results suggest that the enhanced influences from the tropical Atlantic SST may have triggered the intensified correlation between summertime ENSO and WNP monsoon since the early 1990 s.

Analysis of rainfall variability over Tanzania in late austral summer

Based on site-observation data,NCEP–NCAR reanalysis data,and Climatic Research Unit gridded data,the rainfall variability over Tanzania during late austral summer(January–March,JFM)was analyzed for the period 1961–2011.Further,the associated atmospheric circulation and SST anomalies(SSTAs)were explored to understand the mechanisms of dry-and wet-year cases based on an interannual time scale.The correlation,Morlet wavelet power spectrum,and composite analysis methods were employed.The results showed that the JFM standardized rainfall anomaly time series exhibited significant time scales of variability at interannual(2–8 years)and quasidecadal(8–12 years).During dry years,anomalous anticyclonic northeasterly flow originating from western tropical Indian and southeast trades from the Indian Ocean to the southeast were associated with subsiding dry air,which resulted in suppression of rainfall as observed.In the typical wet-year cases,meanwhile,anomalous westerlies from the tropical and southeast Atlantic were strengthened over the Congo basin,delivering more precipitation to the region.Significant correlation was exhibited over the western tropical and southeast Indian Ocean,as well as the southeast and tropical Atlantic Ocean.These SSTA patterns favored atmospheric general circulation anomalies that were closely related to JFM rainfall over Tanzania.

Summer Persistence Barrier of Sea Surface Temperature Anomalies in the Central Western North Pacific

The persistence barrier of sea surface temperature anomalies （SSTAs） in the North Pacific was investigated and compared with the ENSO spring persistence barrier. The results show that SSTAs in the central western North Pacific （CWNP） have a persistence barrier in summer： the persistence of SSTAs in the CWNP shows a significant decline in summer regardless of the starting month. Mechanisms of the summer persistence barrier in the CWNP are different from those of the spring persistence barrier of SSTAs in the central and eastern equatorial Pacific. The phase locking of SSTAs to the annual cycle does not explain the CWNP summer persistence barrier. Remote ENSO forcing has little linear influence on the CWNP summer persistence barrier, compared with local upper-ocean process and atmospheric forcing in the North Pacific. Starting in wintertime, SSTAs extend down to the deep winter mixed layer then become sequestered beneath the shallow summer mixed layer, which is decoupled from the surface layer. Thus, wintertime SSTAs do not persist through the following summer. Starting in summertime, persistence of summer SSTAs until autumn can be explained by the atmospheric forcing through a positive SSTAs-cloud/radiation feedback mechanism because the shallow summertime mixed layer is decoupled from the temperature anomalies at depth, then the following autumnwinter-spring, SSTAs persist. Thus, summer SSTAs in the CWNP have a long persistence, showing a significant decline in the following summer. In this way, SSTAs in the CWNP show a persistence barrier in summer regardless of the starting month.

Causes of seasonal sea level anomalies in the coastal region of the East China Sea

Based on the analysis of sea level, air temperature, sea surface temperature（SST）, air pressure and wind data during 1980-2013, the causes of seasonal sea level anomalies in the coastal region of the East China Sea（ECS） are investigated. The research results show：（1） sea level along the coastal region of the ECS takes on strong seasonal variation. The annual range is 30-45 cm, larger in the north than in the south. From north to south, the phase of sea level changes from 140° to 231°, with a difference of nearly 3 months.（2） Monthly mean sea level（MSL）anomalies often occur from August to next February along the coast region of the ECS. The number of sea level anomalies is at most from January to February and from August to October, showing a growing trend in recent years.（3） Anomalous wind field is an important factor to affect the sea level variation in the coastal region of the ECS. Monthly MSL anomaly is closely related to wind field anomaly and air pressure field anomaly. Wind-driven current is essentially consistent with sea surface height. In August 2012, the sea surface heights at the coastal stations driven by wind field have contributed 50%-80% of MSL anomalies.（4） The annual variations for sea level,SST and air temperature along the coastal region of the ECS are mainly caused by solar radiation with a period of12 months. But the correlation coefficients of sea level anomalies with SST anomalies and air temperature anomalies are all less than 0.1.（5） Seasonal sea level variations contain the long-term trends and all kinds of periodic changes. Sea level oscillations vary in different seasons in the coastal region of the ECS. In winter and spring, the oscillation of 4-7 a related to El Ni？o is stronger and its amplitude exceeds 2 cm. In summer and autumn, the oscillations of 2-3 a and quasi 9 a are most significant, and their amplitudes also exceed 2 cm. The height of sea level is lifted up when the different oscillations superposed. On the other hand, the height of sea level is fallen down.