CHARACTERISTICS OF 10-DAY MEAN SURFACE SENSIBLE HEAT FLUX VARIATIONS IN THE SCS MONSOON REGION AND POSSIBLE CONNECTIONS WITH THE SCS SUMMER MONSOON ONSET

The time and space variations of the ten-day mean surface sensible heat flux have been analyzed in this paper based on the data of NCEP/NCAR from January of 1979 to December of 1995 in the South China Sea(SCS)monsoon region.It is found that large variations of the surface sensible heat flux standard deviations exist in the northwestern Indochina Peninsula and the Indian Peninsula regions,and their locations and strength change significantly during the onset period of SCS monsoon.The negative deviations appear evidently earlier in the Indocbina Peninsula than in the Indian Peninsula but the deviation strength in the Indian Peninsula is stronger than that in the Indochina Peninsula.The appearance of the zonal negative mean deviations in the southern part of the Indochina Peninsula corresponds to the date of the SCS summer monsoon onset,while the occurrence of the deviation decrease corresponds to the date of the South Asian monsoon onset. The sensible heat flux increases dekad by dekad before the onset of the summer monsoon in the Indian Peninsula and the Indochina Peninsula and decreases after the monsoon onset.Therefore, the surface sensible heat flux changes in the Indochina and the Indian Peninsula regions maybe have some connections with the SCS monsoon onset and the Indian monsoon onset,and the Indochina Peninsula maybe becomes the sensitive or key region to the SCS monsoon onset and the land maybe plays an important role in triggering summer monsoon onset.

NUMERICAL SIMULATION EXPERIMENTS OF THE IMPACTS OF LOCAL LAND-SEA THERMODYNAMIC CONTRASTS ON THE SCS SUMMER MONSOON ONSET

The important effects of local land-sea thermodynamic contrast between the South China Sea (SCS) and Indochina Peninsula on SCS summer monsoon onset are preliminarily studied by using two sets of SSTA tests and two ideal tests in s-p regional climate model. The result shows that warm SST in the SCS in winter and spring is favorable for the formation of monsoon circulation throughout all levels of the atmosphere over the sea, which hastens the onset of SCS summer monsoon. The effects of cold SST are generally the opposite. The local land-sea contrast in the SCS is one of the possible reasons for SCS summer monsoon onset. Superposed upon large-scale land-sea thermodynamic differences, it facilitates the formation of out-breaking onset characteristics of SCS summer monsoon in the SCS area.

BASIC CLIMATOLOGICAL FEATURES OF AIR-SEA HEAT EXCHANGES IN THE SOUTH CHINA SEA (SCS) REGION AND THEIR RELATIONS WITH THE SCS MONSOONS

By using the NCEP reanalysis data set in 1979-1995, the fluxes of the latent heat, the sensible heat and the net long-wave radiation in the South China Sea (SCS) are expanded by means of EOF in order to discuss the basic climatological features in the SCS. The detailed analysis shows that the air-sea heat exchanges in different SCS regions have different seasonal variations. The middle and the north of the SCS are the high value regions of the air-sea heat exchanges during the winter and the summer monsoon periods, respectively, the seasonal variations of air-sea heat exchanges in the south of the SCS are small. In addition, the proportions of different components in the total air-sea heat exchanges have different seasonal variations in different regions. The results show that the SCS monsoon and the air-sea heat exchanges in the SCS region are the accompaniments of each other, the great difference of the sensible heat flux between the Indochina Peninsula and the SCS before the SCS summer monsoon onset may be one of the triggers of the latter. There maintains a high value center of the sensible heat flux before the 13th dekad, its disappearing time consists with that of the summer monsoon onset. It means that as far as the SCS local conditions are concerned, the northwest of the Indochina Peninsula is probably a sensitive region to the SCS summer monsoon onset and the land may play a leading role in the SCS summer monsoon onset.

RELATIONSHIPS BETWEEN AUTUMN INDIAN OCEAN DIPOLE MODE AND THE STRENGTH OF SCS SUMMER MONSOON

Based on 1948 - 2004 monthly Reynolds Sea Surface Temperature （SST） and NCEP/NCAR atmospheric reanalysis data, the relationships between autumn Indian Ocean Dipole Mode （IODM） and the strength of South China Sea （SCS） Summer Monsoon are investigated through the EOF and smooth correlation methods. The results are as the following. （1） There are two dominant modes of autumn SSTA over the tropical Indian Ocean. They are the uniformly signed basin-wide mode （USBM） and Indian Ocean dipole mode （IODM）, respectively. The SSTA associated with USBM are prevailing deeadal to interdecadal variability characterized by a unanimous pattern, while the IODM mainly represents interannual variability of SSTA. （2） When positive （negative） IODM exists over the tropical Indian Ocean during the preceding fall, the SCS summer monsoon will be weak （strong）. The negative correlation between the interannual variability of IODM and that of SCS summer monsoon is significant during the warm phase of long-term trend but insignificant during the cool phase. （3） When the SCS summer monsoon is strong （weak）, the IODM will be in its positive （negative） phase during the following fall season. The positive correlation between the interannual variability of SCS summer monsoon and that of IODM is significant during both the warm and cool phase of the long-term trend, but insignificant during the transition between the two phases.

Analysis of the Characteristics of 30-60 Day Low-Frequency Oscillation over Asia during 1998 SCSMEX

The wavelet analysis is performed of the mid- and low-latitude circulation index at 850 hPa over East Asia, the East Asian monsoon index and the precipitation over the middle and lower reaches of the Yangtze River during 1998 South China Sea Monsoon Experiment (SCSMEX) from May to August. Analysis shows that distinct 30-60 day low-frequency oscillation (LFO) exists in all of the above elements during the experiment period. Analysis of low-frequency wind field at 850 hPa from May to August with 5 days interval is performed in this Paper. Analysis results reveal that: (l ) A low-frequency monsoon circulation system over East Asia, characterized by distinct 30-60 day low-frequency oscillation, exists over 100°-150°E of East Asian area from the middle and eastern parts of China continent and the South China Sea to the western Pacific in both the Northern and Southern Hemisphere. The activity of East Asian monsoon is mainly affected by the low-frequency systems in it; (2) All of the tropical monsoon onset over the South China Sea in the fifth pentad of May, the beginning of the Meiyu period and heavy rainfall over the middle and lower reaches of the Yangtze River in mid-June and the heavy rainfall after mid-July are related to the activity of low-frequency cyclone belt over the region, whereas the torrential rainfall over the upper reaches of the Yangtze River in August is associated with the westward propagation of low-frequency anticyclone into the mainland; (3) There are two sources of low-frequency oscillation system over East Asia during SCSMEX. i.e. the equatorial South China Sea (SCS) and mid-high latitudes of the middle Pacific in the Northern Hemisphere. The low-frequency system over SCS propagates northward while that in mid-high latitudes mainly propagates from northeast to southwest. Both of the heavy rainfall over the middle and lower reaches of the Yangtze River in June and July are associated with the northward propagation of the above-mentioned SCS low-frequency systems from the tropical region and the southwestward propagation from mid-high latitudes respectively and their convergence in the middle and lower reaches of the Yangtze River; (4) There are two activities of low-frequency cyclone and anticyclone belt each in the East Asian monsoon system during May to August. However the activity of these low-frequency circulation systems is not clearly relevant to the low-frequency circulation system in the indian monsoon system. This means that the low-frequency circulation systems in indian monsoon and East Asian monsoon are independent of each other. The concept previously put forward by Chinese scholars that the East Asian monsoon circulation system (EAMCS) is relatively independent monsoon circulation system is testified once more in the summer 1998.

Mechanism of Thermal Features over the Indo-China Peninsula and Possible Effects on the Onset of the South China Sea Monsoon

The thermal characteristics during the South China Sea (SCS) summer monsoon onset period near the Indo-China Peninsula are analyzed by using the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from 1 May to 31 August 1998 and the NCEP/ NCAR pentad-mean reanalysis data from January 1980 to December 1995. The possible relationships between the anomaly of thermal features near the Indo-China Peninsula and the SCS monsoon onset are investigated, and the mechanism causing the SCS summer monsoon onset is also discussed. Results from the 1998 SCSMEX reanalysis data show that there exists a strong persistent surface sensible heating near the Indo-China Peninsula prior to the SCS monsoon onset, which has apparent low frequency oscillation features. This sensible healing leads lo a warmer center in the lower atmosphere near the Indo-China Peninsula and strong local horizontal temperature and geopotential height gradients which are favorable to strengthening the southwest wind over the Indo-China Peninsula. It is also found that stronger convergent winds at lower levels and stronger divergent winds at high levels appear, which provide a favorable configuration for the development of vertical motion, enhancement of precipitation, and onset of the SCS monsoon. These results can be verified by analysis of the multi-year mean data. Additionally, it is found that the temperature at 850 hPa increases more rapidly over the Indo-China Peninsula than the South China Sea prior to the SCS monsoon onset, which leads to a strengthening of the temperature difference between the Indo-China Peninsula and the South China Sea. Moreover, results from the analysis of the longitudinal temperature and geopotential height differences show that the eastern retreat of the subtropical high over the Indo-China Peninsula during the period of SCS monsoon onset is associated with the temperature increase over the Indo-China Peninsula and the eastern extension of low trough over the Bay of Bengal.

Main Features of Regional Circulation Variation during Onset of the South China Sea Monsoon in 1998

In this work, the National Center for Environmental Prediction/ National Center for Atmospheic Research (NCEP/ NCAR) global daily–mean reanalysis data are used to diagnose the features of the local circulation variation during the South China Sea (SCS) monsoon in 1998. It is found that by taking the appearance of southwest wind in lower layers and east wind in upper layers as the sign of the monsoon onset, the SCS monsoon starts on May 25 in 1998, which is later than that in normal years. The formation of the SCS monsoon is not a simple propagation of southwest monsoon in the north—south direction, but a process in which the southwest wind starts first over the north of the SCS, withdraws southward, and then propagates from south to north again. During this process, both meteorological elements and circulation fields change significantly. The outbreak of the SCS monsoon is the result of the seasonal variation of the height in lower and upper layers. The air rounding the Tibetan Plateau might be one of the dynamic reasons that make the summer monsoon start over the SCS at first. At the different stages of the monsoon, the vertical circulations as well as the lower and the upper layer divergence fields undergo evident temporal and regional changes. The SCS monsoon has the 60–day, 20–30–day and 8–15–day low frequency oscillations (LFOs), and dominant scale changes at the different stages of monsoon. The monsoon onset is related to the superimposition of the amplitudes of LFOs with different scales. Key words SCS monsoon - Circulation variation - Regional climate - LFO Sponsored by the National Key Project of Fundamental Research SCSMEX

Strong/Weak Summer Monsoon Activity over the South China Sea and Atmospheric Intraseasonal Oscillation

The circulation pattern corresponding to the strong / weak summer monsoon in the South China Sea (SCS) region and the associated characteristics of the abnormal rainfall in Eastern China have been studied by using the NECP reanalysis data and precipitation data in China. The results show that the climate variations in China caused by the strong / weak summer monsoon are completely different (even in opposite phase). The analyses of atmospheric intraseasonal oscillation (ISO) activity showed that the atmospheric ISO at 850 hPa near the SCS region is strong (weak) corresponding to the strong (weak) SCS summer monsoon. And the analyses of the circulation pattern of the atmospheric ISO showed that the strong / weak SCS summer monsoon circulation (200 hPa and 850 hPa) result mainly from abnormal atmospheric ISO. This study also reveals that the atmospheric ISO variability in the South China Sea region is usually at opposite phase with one in the Jiang-huai River basin. For example, strong (weak) atmospheric ISO in the SCS region corresponds to the weak (strong) atmospheric ISO in the Jiang-huai River basin. As to the intensity of atmospheric ISO, it is generally exhibits the local exciting characteristics, the longitudinal propagation is weak. Key words The SCS summer monsoon - Atmospheric intraseasonal oscillation - Circulation pattern This was supported by National Key Basic Science Program in China (G1998040903) and State Key Project-SCSMEX.

Peculiar Temporal Structure of the South China Sea Summer Monsoon

Beijing located at the junction of four major components of the Asian-Australia monsoon system (the Indian, the western North Pacific, the East Asian subtropical, and the Indonesian-Australian monsoons), the monsoon climate over the South China Sea (SCS) exhibits some unique features. Evidences are presented in this paper to reveal and document the following distinctive features in the temporal structure of the SCS summer monsoon: (1) pronounced monsoon singularities in the lower tropospheric monsoon flows which include the pre-onset and withdrawal easterly surges and the southwesterly monsoon bursts at Julian pentad 34-35 (June 15-24) and pentad 46-47 (August 14-23); (2) four prominent subseasonal cycles (alternative occurrences of climatological active and break monsoons); (3) considerably larger year-to-year variations in convective activity on intraseasonal time scale compared to those over the Bay of Bengal and the Philippine Sea; (4) the redness of the climatological mean spectrum of precipitation/deep convection on synoptic to intraseasonal time scales in the central SCS; (5) a remarkable asymmetry in the seasonal transitions between summer and winter monsoons and an extremely abrupt mid-May transition (the outburst of monsoon rain and the sudden switch in the lower troposphere winds from an easterly to a westerly regime); (6) the bi-modal interannual variation of summer monsoon onset (normal and delayed modes). In addition, the monsoon rainfall displays enormous east-west gradient over the central SCS. Possible causes for these features are discussed. A number of specific science questions concerning some of the peculiar features are raised for the forthcoming SCS monsoon experiment to address.

Response of the South China Sea summer monsoon onset to air-sea heat fluxes over the Indian Ocean

We objectively define the onset date of the South China Sea (SCS) summer monsoon, after having evaluated previous studies and considered various factors. Then, interannual and interdecadal characteristics of the SCS summer monsoon onset are analyzed. In addition, we calculate air-sea heat fluxes over the Indian Ocean using the advanced method of CORARE3.0, based on satellite remote sensing data. The onset variation cycle has remarkable interdecadal variability with cycles of 16 a and 28 a. Correlation analysis between air-sea heat fluxes in the Indian Ocean and the SCS summer monsoon indicates that there is a remarkable lag correlation between them. This result has important implications for prediction of the SCS summer monsoon, and provides a scientific basis for further study of the onset process of this monsoon and its prediction. Based on these results, a linear regression equation is obtained to predict the onset date of the monsoon in 2011 and 2012. The forecast is that the onset date of 2011 will be normal or 1 pentad earlier than the normal year, while the onset date in 2012 will be 1-2 pentads later.

The influence of 30~60 d oscillation on the development of the South China Sea summer monsoon

Using the National Center for Enviromental Prediction/National Center for Atmospheric Research (NCEP/NCAR)reanalysis data and NOAA satellite-observed outgoing long-wave radiation (OLR) data, the development of theSouth China Sea (SCS) summer monsoon and intraseasonal (30~60 d) oscillation (ISO) have been examined. Theresults show that there exists obvious interannual variability of intraseasonal oscillaiton. Using the 16 a time series offiltered OLR averaged over the SCS, an index is defined to define onset events over the SCS on the ISO time scales.Of the 16 a examined here, 10 shows a strong ISO signal in the onset of monsoon convection over the SCS. In thesecases, the ISO initially suppresses the seasonal development of southwesterly and cyclonic circulation over the SCSbefore the ISO onset. As the ISO propagates northeastward, the low frequency cyclonic circulation anomaly occursin the SCS and the low frequency southwesterly wind and convection over here dramatically intensify. The northeastprogression of the ISO anomaleis plays a role in the initial suppression and then acceleration of the seasonal cycle ofthe SCS summer monsoon.

THE INFLUENCE OF SOUTH CHINA SEA SUMMER MONSOON ON THE RAINSTORM ASSOCIATED WITH THE LANDFALLING STRONG TROPICAL STORM BILIS (0604)

Bilis (0604) is a strong tropical storm that sustained over land for a long time, bringing torrential rain. With conventional observation data, radar data and infrared satellite imagery, Mesoscale Convective Systems (MCSs) are found to form and develop successively, which cause torrential rain. Then numerical simulation is conducted using MM5 to simulate a 66-h post-landfall process. The simulated distribution and intensity of precipitation match the observation well. With the simulated result, the characteristics and process of MCS development are analyzed with the finding that the convergence of the tropical depression and South China Sea (SCS) summer monsoon over The south of China causes the formation of a mesoscale vortex, mesoscale convergence center and mesoscale convergence line, which are favorable to the development and sustaining of the MCSs. A sensitivity experiment indicates that the SCS summer monsoon transports unstable energy and water vapor continuously, which is of vital importance to rainstorms.

ANALYSIS OF LOW-FREQUENCY OSCILLATIONS FOR THE SOUTH CHINA SEA SUMMER MONSOON IN 1998

With NCEP/NCAR reanalysis daily data and SST for 1998, the paper investigates the features of summer monsoon low-frequency oscillation (LFO) over the South China Sea (SCS). Results show that SCS summer monsoon onset is enhanced because of its LFO. Low-frequency (LF) low-level convergence (divergence) region of SCS is in the LF positive (negative) rainfall area. LFO of the SCS region migrates from south to north in the meridian and from west to east in zonal direction. LF divergence of SCS is vertically compensating to each other between high and low level.

CHARACTERISTICS OF ATMOSPHERIC HEAT SOURCE ASSOCIATED WITH THE SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA AND THE POSSIBLE MECHANISM RESPONSIBLE FOR ITS LATE OR EARLY ONSET

The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon onset is defined by the atmospheric heat source. Applying this criterion to the 15-year (1979 – 1993) mean field, the onset of the SCS summer monsoon is found to occur in the fourth pentad of May. And this criterion can also give reasonable results for the onset time of the SCS summer monsoon on a year-to-year basis. In addition, pretty high correlation has been found between the onset time of the SCS summer monsoon and the zonal mean vertically integrated heat source <Q1> at 40°S in April. The causes for the late or early onset of the SCS summer monsoon and the close relationship between the onset time and the zonal mean vertically integrated heat source <Q1> at 40 °S in April might be explained by the variations in intensity of the Hadley circulation.

The link between interannual variation of the South China Sea summer monsoon onset and summer precipitation in Shandong Province

Relationship between the onset date of South China Sea (SCS) summer monsoon and the summer rainfall in Shandong Province was examined by comprehensive analysis to establish a conceptual model of the link. If the summer monsoon occurs earlier, the 500 hPa level would induce the teleconnection of Eurasian pat- tern in the summer (June-August), which indicates that the western Pacific subtropical high is displaced north- ward further than usual, the Siberian high is intensified and the Okhotsk low is deepened. Under such circum- stance, Shandong, located in the west side of the subtropical high and in front of the mid-Siberia high, would be expected to have a wet summer because it is quite possible for cold and warm air to meet and interact with each other in Shandong. Statistical analysis revealed that the 500 hPa anomalies over Korea and Japan were sensitive to the SCS monsoon onset date and very important to precipitation in Shandong, and that the convective activi- ties over the deep water basin in the SCS in 24–26 pentads significantly influenced the position of the ridge line of the western Pacific subtropical high. These findings yielded better understanding of the causative mechanisms involved in the precipitation generation, so that the knowledge gained can possibly be applied for long-lead forecast.

OBSERVATIONAL STUDY OF AIR-SEA FLUXES DURING THE SCS SUMMER MONSOON IN 2000——FEATURES OF THERMAL BUDGET AT THE SEA SURFACE

This paper is devoted to the features of sea-surface heat budget during the active/break phases of the 2000 summer monsoon in the South-China Sea (SCS) by means of the observed air-sea heat fluxes and data from Xisha Weather Station and NCEP/NCAR in the same period.Results suggest that the primary factors affecting sea-surface thermal budget are solar shortwave penetrating radiation and latent heat flux.Regardless of their changes,however,the thermal gain is reduced or becomes net loss at the active stage and the thermal gain gets gradually increased in the weakening and lull periods:during the first emergence of southwest monsoon the net loss happens thanks to the dramatic diminution of penetrating radiation resulting from increased cloudiness and intense precipitation:while at the re-emergence of the wind.reduced net sea-surface thermal gain is attributed to the sharp increase in latent heat flux resulting from intense evaporation:owing to great thermal inertia of water the SST change lags behind that of heat budget over the sea surface, and the lagging is responsible for regulating the budget by affecting latent heat fluxes,which,in turn.has effect upon the change of the SST,thereby forming short-term oscillations that are in association with the active/break phases of the monsoons.Part of the conclusions have been borne out by the observational study based on 1998 and 2002 data.

IMPACTS OF SURFACE SENSIBLE HEAT FLUXES IN THE KEY AREAS OF THE TIBETAN PLATEAU ON INTERANNUAL VARIATION OF THE SCS SUMMER MONSOON INTENSITY

The impacts of the variations of surface heat fluxes over the Tibetan Plateau (TP) and surrounding areas on the interannual variation of the South China Sea (SCS) summer monsoon intensity is analyzed using the NCEP/NCAR reanalysis monthly sensible heat flux data from 1949 to 2000 and monthly mean wind and temperature field data from 1958 to 1997.The results show that there is a distinct interdecadal trend in sensible heat over the key areas of the TP and the SCS summer monsoon intensity as well as South Asia high intensity (SAHI),the transition occurs in late 1970s.The SCS summer monsoon intensity has a significant positive correlation with the variation of surface sensible heat fluxes over the northwestern part of the TP,while it has negative correlation with the surface sensible heat fluxes in the south of the TP.During the strong SCS summer monsoon year,the vertical ascending motion in the northwestern TP is strengthened,but in the southern TP it is weakened,and the position of the South Asian high is northward,while in the weak summer monsoon year,it is in the contrary.The SAHI is closely related to variation of surface heat fluxes over the TP and surrounding areas,and there exists a negative relationship between the SCS summer monsoon intensity and SAHI.

ABRUPT CHANGE IN ELEMENTS AROUND 1998 SCS SUMMER MONSOON ESTABLISHMENT WITH ANALYSIS OF ITS CHARACTERISTIC PROCESS

The latest dataset from the SCS(South China Sea)Monsoon Experiment is used to investigate the features of abrupt change in some meteorological elements before,during and after the summer monsoon's establishment in 1998 and explore its onset characteristic process.We have arrived at a preliminary conclusion that the 1998 Asian summer monsoon is established first in the SCS as early as May 23,which is representative of the earliest indicator of the conversion from a winter into a summer monsoon situation in Asia;the continued retreat eastward of the western Pacific subtropical high from the SCS region has direct effect on the SCS summer monsoon establishment because the withdrawal favors the release of unstable energy,responsible for the sudden onset of the monsoon.Our tentative investigation indicates that the eastward extension of the westerly and rainfall band from the equatorial Indian Ocean into the Indo-China Peninsula and the southward spreading of an active South-China stationary front,acting as the interaction between mid and low latitude systems,are likely to be the characteristic events contributing to the subtropical high's eastward retreating and the summer monsoon's onset over the SCS.

FEATURES OF VARIATION IN TOTAL,BAROTROPIC AND BAROCLINIC KINETIC ENERGY WITH THE MECHANISM EXPLORED AROUND THE 1998 SCS SUMMER MONSOON ONSET

This paper concerns atmospheric kinetic energy variation related to the onset of summer monsoon in May,1998 over the SCS (South China Sea).Results show that around the onset, noticeable conversion occurs in atmospheric total,barotropic and baroclinic kinetic energy (KE) at 300-1000 hPa;three days before the onset,total and barotropic KE are already growing markedly and baroclinic KE increases simultaneously with the onset:the monsoon's onset is associated closely to the meridional propagation of barotropic and baroclinic KE in the SCS region and study of equations of barotropie/baroclinic KE indicates that the net production term is the dominant factor for the change of the two forms of KE,the term of fluxes plays a part in weakening the energies and the conversion term is responsible for transforming barotropic into baroclinic KE.

NUMERICAL EXPERIMENT OF IMPACT OF SEA SURFACE TEMPERATURE IN SOUTH CHINA SEA AND WARM POOL/WEST PACIFIC ON EAST ASIAN SUMMER MONSOON

By using the NCAR CCM1 model, we have designed six sensitive experiments, which are increased and decreased SST (sea surface temperature) by 1℃ each in the SCS (South China Sea) and in the West Pacific warm pool, increased and decreased SST by 1℃ in the warm pool with increased SST by 1℃ in the SCS. All experiments are integrated from April to July. Comparing with the control experiment, we have analyzed the anomalies of the wind field at the upper and lower layers, the anomalies of the seasonal variability of the monsoon and precipitation for each experiment. In the result, we have found that the SST anomaly (SSTA) in the SCS greatly affects the seasonal variability of the SCS monsoon and precipitation in China, especially during the cold period of SST in the SCS. The impact of SSTA in the warm pool on SCS monsoon is also found. but is weak as compared to the effect of SST anomaly in the SCS. Besides, its impact on rainfall in China is uncertain.