Variability in Latent Heat Flux over the Tropical Pacific in Association with Recent Two ENSO Events

This paper analyzed the variations of latent heat flux (LHF) over the tropical Pacific in the period 1978-1988 by using COADS (Comprehensive Ocean and Atmospheric Data Set). It has been founded that the interannual variabili ty of LHF exhibits strong ENSO signal, with the significant increasing LHF during the recent two warm events, i.e., 1982 / 83 and 1986 / 87 and decreasing LHF in the cold episodes. However the longitudinal distribution of the LHF departures varies from event to event. In the eastern Pacific, the specific humidity difference at air-sea interface (qs -qa) makes a dominant contribution to the interannual variability of LHF ( r = 0.73 ), while in the western Pacific the surface wind speed, W and the qs - qa make nearly equal contribution to that of LHF.

STUDY OF A COMPREHENSIVE MONITORING INDEX FOR TWO TYPES OF ENSO EVENTS

Some recent studies presented two existing types of ENSO events, one is the Eastern-Pacific(EP) type and the other the Central-Pacific(CP) type. This study examined the monitoring ability of several current operational ENSO indices. The results indicated that a single index could not distinguish the EP and CP in the historical ENSO events during 1950-2009. The Nio 3 index may only be suitable for monitoring the EP-type ENSO, while the Nio 4 index works only for the CP-type ENSO. In order to capture the occurrence of ENSO events and distinguish the type, we considered a new monitoring index group using Nio 3 and Nio 4 indices. Further analysis confirmed that this index group can monitor different types of historical ENSO events with different spatial distribution of sea surface temperature. It has a good performance in determining the characteristics of the ENSO events, including peak intensity, onset,decay, and mature phase.

RELATION BETWEEN SUMMER TYPHOON FREQUENCY ANOMALIES IN WEST PACIFIC AND ENSO EVENTS AND THE ANOMALOUS ATMOSPHERIC CIRCULATION CHARACTERISTICS

By using data of serially numbered typhoons in northwestem Pacific and NOAA OLR data and NCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between the calendar years with more （or fewer） summer typhoons and ENSO events, we compared the composites of OLR eigenvectors and tropical summer wind fields during E1 Nino and La Nino events with more or fewer than normal summer typhoons, respectively. The results show that, in summer, without remarkable systematic anomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation will dominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise, when systematic anomalies of Australia High appear during the El Nino events, circulation anomalies in the South Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of La Nina events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewer typhoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in westem Pacific and the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and compares the source locations and ranges of more （fewer） typhoons in the events of El Nino and La Nino, respectively.

A Further Study on an Extended Nonlinear Ocean-Atmosphere Coupled Hydrodynamic Characteristic System and the Abrupt Feature of ENSO Events

An extended ocean-atmosphere coupled characteristic system including thermodynamic physical processes in ocean mixed layer is formulated in order to describe SST explicitly and remove possible limitation of ocean-atmosphere coupling assumption in hydrodynamic ENSO models. It is revealed that there is a kind of abrupt nonlinear characteristic behaviour, which relates to rapid onset and intermittency of El Nino events, on the second order slow time scale due to the nonlinear interaction between a linear unstable low-frequency primary eigen component of ocean-atmosphere coupled Kelvin wave and its higher order harmonic components under a strong ocean-atmosphere coupling background. And, on the other hand, there is a kind of finite amplitude nonlinear characteristic behaviour on the second order slow time scale due to the nonlinear interaction between the linear unstable primary eigen component and its higher order harmonic components under a weak ocean-atmosphere coupling background in this model system.

Abnormality of the monsoon wind in the sea area along the southeasterncoast of China and the response of the northern areaof the South China Sea during the ENSO events

-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.

AN ANALYSIS ON LARGE-SCALE AIR-SEA INTERACTIVE LINKAGES BETWEEN THE TROPICAL INDIAN OCEAN AND THE PACIFIC OCEAN DURING ENSO EVENTS

By utilizing a 3-D atmospheric circulation resolving method, the authors studied the air-sea interactive linkages between the tropical Indian Ocean and the Pacific Ocean in 1979-2008 E1 Nifio-Southern Oscillation （ENSO） events. Their findings showed that evident 3-D gear-coupling characteristics existed in the 1979-2008 ENSO events. Their resolving analyses also suggested that the general circulation showed stronger and wider sinking motions over the eastern Indian Ocean-western Pacific during the mature phase of 1979-2008 ENSO events, compared with the vertical velocities from the U.S. National Centers for Enviornmental Prediction （NCEP） reanalysis data. With their 3-D analysis method, the vertical velocity was resolved by two components, i.e. zonal and meridional components. It was found that the zonal component of the vertical velocities showed a strong sinking motion while the meridional components showed an upward motion during the prevailing phases of the ENSO events. In the tropics, the zonal component of the vertical velocities was found greater than the meridional component, reflecting the dominant characteristics of the vertical velocity, and the overall outcomes showed a strong sinking motion, although the two components also partially offset each other in the processes. Compared with the vertical velocities from NCEP reanalysis, the vertical motions calculated with the 3-D resolving analysis method demonstrate some advantages.

CLIMATE ANOMALY RECORDED IN GULIYA ICE CORE AND ENSO EVENTS

Examination of ENSO events and the accumulated precipitation and δ^(18)O values recorded in the Guliya ice core,China,shows that the relationship between the occurrence of ENSO events and the precipitation anomaly in Guliya is significant.In the years of El Nino events,the anomalies of precipitation and δ^(18)O values in the Guliya ice core were negative anomalies,that is,the ENSO events are related to the deficit of precipitation as well as low temperature in the western China.

Interannual variations in the length of day and ENSO events in 1982-1983 and 1997-1998

The length of day series during the period of 1962.0-2000.0, the atmospheric angular momentum and the Southern Oscillation Index are adopted to analyze the relationships among the EN-SO events that have occurred since 1960, the changes in the length of day and the atmospheric angular momentum. Attention is particularly given to the different effects of the 1982-1983 and 1997-1998 ENSO events on the variations of Earth rotation. The synthetic excitation effects of multi-scale atmospheric oscillations on the anomalous variations of the interannual rates of Earth rotation are revealed by means of the time-frequency spectrum of the wavelet transform.

Impacts of ENSO on the Welfare of Rural Residents in China: A Stochastic CGE Model Assessment

ENSO-driven extreme weather events such as droughts and floods can cause significant damage to agricultural production and different intensities of ENSO events make uncertain changes to rural residents'welfare in different regions.To emphasize this uncertainty,the stochastic CGE model is constructed by imbedding a stochastic parameter into the production module to analyze the impacts of ENSO on the welfare of rural residents in various regions of China and the volatility of uncertain ENSO events on the welfare of residents.The role of agricultural technology in improving welfare stability and transfer payments in reducing welfare losses from ENSO are also examined.The results show that weak ENSO events have little effect on the welfare of rural residents while strong ENSO events cause the welfare of rural residents a significant decline,and the largest decrease appears separately in the southwest region and the smallest one in the northeast.The uncertainty of ENSO events seriously affects the stability of the welfare of the residents,with the average fluctuation level of 200%in the change of the rural residents'welfare in all regions under El Ni o.Technically improving the anti-risk ability of agriculture can effectively reduce the fluctuation of residents'welfare.Besides,if the government increases the transfer payment to the rural resident for disaster relief,the welfare would increase,and the higher the payment,the greater the improvement of the welfare.

Two Opposite Extreme Events in Seasonal Mean Winter Rainfall over East China during the Past Three Decades

In this study,the extremes of winter seasonal mean precipitation have been investigated by using daily precipitation data from 91 stations in East China,the National Centers for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR） monthly reanalysis,and sea surface temperature data from the Hadley Centre for 1979-2007.The largest anomalous rainfall amount was observed in regions south of the Yangtze River.In the most recent three decades,extreme events in the seasonal mean winter precipitation occurred in 1985 and 1997.Because it was influenced mainly by a La Ni（n）a event,the precipitation in 1985 showed a deficit following a stronger winter monsoon.The rainfall amount in 1997 was influenced by E1 Ni（n）o and was significantly larger than normal with a weaker winter monsoon.Both the circulation anomalies and wave energy dispersions during the winters of 1985 and 1997 differed significantly.In 1985,the North Atlantic Oscillation anomalously excited the Eurasian-Pacific teleconnection and circumglobal teleconnection phenomena.Consequently,Rossby wave energy propagated along the north and south branches of the westerlies,strengthening the East Asian trough along with a stronger winter monsoon,which facilitated the wintertime dry extreme in East China.In 1997,however,Rossby wave energy propagated from low latitudes northeastward into the southern part of China,resulting in a weaker winter monsoon and the wettest winter.The results of this study will be helpful for future monitoring and prediction of extreme winter rainfall events in East China.

The“Spring Predictability Barrier” Phenomenon of ENSO Predictions Generated with the FGOALS-g Model

Using the sea surface temperature （SST） predicted for the equatorial Pacific Ocean by the Flexible Global Ocean-Atmosphere-Land System Model-gamil （FGOALS-g）, an analysis of the prediction errors was performed for the seasonally dependent predictability of SST anomalies both for neutral years and for the growth/decay phase of El Nino/La Nina events. The study results indicated that for the SST predictions relating to the growth phase and the decay phase of El Nino events, the prediction errors have a seasonally dependent evolution. The largest increase in errors occurred in the spring season, which indicates that a prominent spring predictability barrier （SPB） occurs during an El Nino-Southern Oscillation （ENSO） warming episode. Furthermore, the SPB associated with the growth-phase prediction is more prominent than that associated with the decay-phase prediction. However, for the neutral years and for the growth and decay phases of La Nifia events, the SPB phenomenon was less prominent. These results indicate that the SPB phenomenon depends extensively on the ENSO events themselves. In particular, the SPB depends on the phases of the ENSO events. These results may provide useful knowledge for improving ENSO forecasting.

Antarctic sea ice and ENSO event

The characteristic low-frequency oscillation of the sea surface temperature anomaly (SSTA) of ENSO related regions, Nino 1 + 2, Nino 3, Nino 4 and Nino West, and the Southern Oscillation index (SOI) is analyzed with the method of maximum entropy spectrum. Antarctic sea ice is divided into 4 regions, i. e. East Antarctic is Region Ⅰ (0°-120° E), the region dominated by Ross Sea ice is Region Ⅱ (120° E-120° W), the region dominated by Ross Sea ice is Region Ⅲ (120° W-0°), and the whole Antarctic sea ice area is Region Ⅳ. Also, the month-to-month correlation series of the sea ice with ENSO from contemporary to 5-years lag is calculated. The optimum correlation period is selected from the series. The characteristics and the rules obtained are as follows.1. There are a common 4-years main period of the SSTA of Ninos 1 + 2,3 and 4, a rather strong 4-years secondary period and a quasi-8-years main period of that of Nino West. There are also 1. 5 and 2 to 3-years secondary periods of that of all 4 Nino regions.2. As another indicator of El Nino, the SOI represents the feature of the atmosphere in low latitude area, having a quasi-5-years main period; it also has secondary periods, 1, 1. 5 and 2 to 3 years, among them, the 2 to 3-years one is prominent.3. There is a close relationship between Antarctic sea ice and ENSO event. In the long-range correlation from contemporary up to 60 months of the SSTA in Ninos 1 + 2,3 and 4 and Antarctic sea ice area index, or the time series of 16 correlation coefficients made of each one of the 4 sea ice regions with that of the 4 Nino regions, there is a prominent common characteristic that all correlations are negative from contemporary to 34-months lag of the SSTA of the 4 Nino regions behind Antarctic sea ice, the optimum correlation periods with the confidences equal to or more than 5 % , 1 % lagging in 13-19, 24-34 month are the most. The correlations of sea ice in Regions Ⅱ , Ⅲ and W with the SSTA of Ninos 3 and 4 are the strongest. The correlation of the sea ice in Region Ⅰ with Nino West in 4 - 5-years lag becomes a very strong positive one. The correlations of the sea ice in Regions Ⅱ and Ⅲ with Ninos 1 + 2, 3 and 4 become strong positive ones during the quasi-4-years lag. The variation of the correlation series of the SOI and the 4 sea ice regions is the opposite of that of the 4 Nino regions. The correlations with the sea ice in Regions Ⅱ , Ⅲ and Ⅳ are strong, with the strong positive correlations of 6, 10 and 24-months lag being the optimum correlation periods. And the strong negative correlation period is 40-months lag.4. The characteristic variation of the correlation time series reflects the low-frequency oscillation feature of Antarctic sea ice and ENSO. In the periodic variation, the correlation becomes the strongest when the ice and ENSO are inresonance. Specifically,the Antarctic sea ice influences ENSO most in an earlier period of its own variation. Moreover, it is also related with the period of variation of ENSO itself, i. e. the correlation of sea ice and ENSO gets the best in a period lag of ENSO its own variation.

NUMERICAL MODELING STUDY OF EFFECTS OF EASTERN PACIFIC WARM POOL ON ENSO

In this study, sensitivity experiments were conducted with the Zebiak-Cane ocean-atmosphere coupled model forced by the wind stress anomaly from the U.S. National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data to study the impacts of eastern Pacific warm pool on the formation and development of ENSO events. The effects of climatological mean sea surface temperature of the warm pool on forecast skill during the ENSO events of 1982-1999 are more considerable that those of climatological mean meridional winds and ocean currents. The forecast skill for the 1997/1998 E1 Nifio event is characterized by sensitivity to climatological mean sea surface temperature and anomalies of northerly winds and currents. The forecast skill is found insensitive to climatological mean northerly meridional winds and currents.

A Diagnostic Analysis of Winter Atmospheric Circulation during the 1982-1983 ENSO Event

In this paper, the winter atmospheric circulation, the convection along the equator and their variations of 1982 and 1983 are investigated. It is suggested that there was a well organized three dimensional structure of anomalies of the atmospheric circulations during 1982 winter which may be related to the variations of the convection in the equatorial region.

The ENSO event and rice planthopper occurrence in China

The rice planthopper,including brown planthopper(Nilaparvata hugens Stal)and white—backed planthopper(Sogata furcifera Hor-vath),is one kind of tropical pests.They im-migrate with the southeast monsoon from low—latitude area into China at March of April.The global climatic anomaly especially the ElNi (?)o event and the Southern Oscillation(theENSO event)directly influence the rice plan-

Relationship between land cover and monsoon interannual variations in east Asia

Asian monsoon have multiple forms of variations such as seasonal variation, intra-seasonal variation, interannual variation, etc. The interannual variations have not only yearly variations but also variations among several years. In general, the yearly variations are described with winter temperature and summer precipitation, and the variations among several years are reflected by circulation of ENSO events. In this study, at first, we analyze the relationship between land cover and interannual monsoon variations represented by precipitation changes using Singular Value Decomposition method based on the time series precipitation data and 8km NOAA AVHRR NDVI data covering 1982 to 1993 in east Asia. Furthermore, after confirmation and reclassification of ENSO events which are recognized as the strong signal of several year monsoon variation, using the same time series NDVI data during 1982 to 1993 in east Asia, we make a Principle Component Analysis and analyzed the correlation of the 7th component eigenvectors and Southern Oscillation Index (SOI) that indicates the characteristic of ENSO events, and summed up the temporal-spatial distribution features of east Asian land cover’s inter-annual variations that are being driven by changes of ENSO events.

Comparison of nominal and standardized catch per unit effort data in quantifying habitat suitability of skipjack tuna in the equatorial Pacific Ocean

In the western and central Pacific Ocean,upper strata waters exhibit highly dynamic oceanographic features under ENSO variability.This has been proved to be responsible for the dynamic change of both abundance and zonal distribution of skipjack tuna(Katsuwonus pelamis).Although causality has been suggested by researchers using physical-biological interaction models,cumulative evidence needs to be obtained and the tenability of assertion needs to be tested from an ecological habitat perspective,based on fisheries data.For purse seine fishery,the use of catch per unit effort(CPUE)as an indication of the abundance is confusing because of technical improvements over the whole exploitation history and unbalanced individual fishing characteristic of vessels.It is particularly interesting to discriminate between habitat characteristics in comparative scenarios of CPUE application.This study identified habitat traits based on a series of oceanographic factors from a global ocean reanalysis model.A comparison was conducted between two habitat models based on unprocessed purse seine CPUE and standardized CPUE considering fishing characteristics.The results suggest that standardized CPUE could model the regular zonal shift of habitat compatible with the observed fishing efforts transfer,and achieved better prediction capacity than unprocessed CPUE.Furthermore,the habitat of skipjack tuna was also characterized and linked with surface and subsurface thermal environment,ocean current,dissolved oxygen,biotic environment,and ENSO variability.The monthly-averaged habitat suitable index,derived from the optimal habitat model prediction,showed a significant linear relationship with the southern oscillation index,which suggested that El Ni?o episodes eventually provide more preferable habitat for skipjack tuna under ENSO variability.

BIFURCATION OF THE NORTH EQUATORIAL CURRENT DERIVED FROM ALTIMETRY IN THE PACIFIC OCEAN

The gridded （1/3°＊1/3°） altimetry data from October 1992 through December 2004 were analyzed to study the seasonal and interannual variabilities of the bifurcation of the North Equatorial Current （NEC） at the surface in the western North Pacific Ocean. Calculations show that on annual average the bifurcation occurs at about 13.4°N at the surface. The geostrophic flow derived from Sea Surface Height （SSH） data shows that the southernmost latitude of the NEC bifurcation at the surface is about 12.9°N in June and the northernmost latitude is about 14.1°N in December. Correlation analyses between the bifurcation latitude and the Southern Oscillation Index （SOl） suggest that the bifurcation latitude is highly correlated with the E1 Nino/Southern Oscillation （ENSO） events. During the E1 Nino years the bifurcation of the NEC takes place at higher latitudes and vice versa.