Research on the Relationship of ENSO and the Frequency of Extreme Precipitation Events in China

Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.

The Influence of El Ni?o on MJO over the Equatorial Pacific

In this paper, the influence of E1 Nino event on the Madden-Julian Oscillation （MJO） over the equatorial Pacific is stud- ied by using reanalysis data and relevant numerical simulation results. It is clearly shown that E1 Nino can reduce the intensity of MJO. The kinetic energy of MJO over the equatorial Pacific is stronger before the occurrence of the E1 Nino event, but it is reduced rapidly after E1 v event outbreak, and the weakened MJO even can continue to the next summer. The convection over the cen- tral-western Pacific is weakened in E1 Nino winter. The positive anomalous OLR over the central-western Pacific has opposite variation in E1 Nino winter comparing to the non-ENSO cases. The vertical structure of MJO also affected by E1 Nino event, so the opposite direction features of the geopotential height and the zonal wind in upper and lower level troposphere for the MJO are not remarkable in the E1 Nino winter and tend to be barotropic features. El Nino event also has an influence on the eastward propa- gation of the MJO too. During E1 Nino winter, the eastward propagation of the MJO is not so regular and unanimous and there exists some eastward propagation, which is faster than that in non-ENSO case. Dynamic analyses suggest that positive SSTA （El Nino case） affects the atmospheric thickness over the equatorial Pacific and then the excited atmospheric wave-CISK mode is weakened, so that the intensity of MJO is reduced; the combining of the barotropic unstable mode in the atmosphere excited by external forcing （SSTA） and the original MJO may be an important reason for the MJO vertical structure tending to be barotropic during the E1 Nino.

A Long Lasting and Extensive Drought Event over China in 1876-1878

Between 1876 and 1878 a large-scale drought occurred in China. This is a major meteorological disaster and an extreme climate event despite the cold climate at the end of the Little Ice Age. In this paper the dynamic evolution of the occurrence and development of the drought is reproduced on the basis of historical literature records. These were used to calculate the yearly numbers of drought-hit counties and to determine the spatial distribution in addition with concomitant famine, locust plague and pestilence epidemic for each of the three years. The persistent drought disaster spread over 13 provinces with its center in Shaanxi, Henan and Shanxi provinces, where the continuous non-soaking rain period exceeded 340 days. Conclusively, it is more severe than the worst drought （1928-1930） in the 20th century. This drought disaster of 1876-1878 took place in the descending phase of the 11th sunspot activity period and the start of the 12th period. It also happened during a spell of frequent E1 Nino events and corresponds with an extremely strong E1 Nino.

Distinguished Effects of Interannual Salinity Variability on the Development of the Central-Pacific El Ni o Events

El Nio events in the central equatorial Pacific (CP) are gaining increased attention,due to their increasing intensity within the global warming context.Various physical processes have been identified in the climate system that can be responsible for the modulation of El Nio,especially the effects of interannual salinity variability.In this work,a comprehensive data analysis is performed to illustrate the effects of interannual salinity variability using surface and subsurface salinity fields from the Met Office ENSEMBLES (EN3) quality controlled ocean dataset.It is demonstrated that during the developing phase of an El Nio event,a negative sea surface salinity (SSS) anomaly in the western-central basin acts to freshen the mixed layer (ML),decrease oceanic density in the upper ocean,and stabilize the upper layers.These related oceanic processes tend to reduce the vertical mixing and entrainment of subsurface water at the base of the ML,which further enhances the warm sea surface temperature (SST) anomalies associated with the El Nio event.However,the effects of interannually variable salinity are much more significant during the CP-El Nio than during the eastern Pacific (EP) El Nio,indicating that the salinity effect might be an important contributor to the development of CP-El Nio events.

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.

Impacts of the Two Types of El Ni?o on Pacific Tropical Cyclone Activity

It is well known that Tropical cyclone （TC） activities over the Pacific are affected by E1 Nino events. In most studies El Nifio phenomena have been separated into east Pacific warming （EPW） and central Pacific wanning （CPW） based on the location of maximum SST anomaly. Since these two kinds of El Nino have different impacts on Pacific tropical cyclone activities, this study investigates different features of TC activities and the genesis potential index （GPI） during EPW years and CPW years. Four eontrib- nting factors, i.e., the low-level absolute vorticity, the relative humidity, the potential intensity and the vertical wind shear, are exam- ined to determine which factors are most important in causing the anomalous TC activities. Our results show that during EPW years in July-August （JA-0）, TC activities are more frequent with stronger intensity over the Western North Pacific （WNP） and Eastern North Pacific （ENP）. The maximum anomaly center of TC activities then drifts eastward siguifieantly in September-October （SO-0）. However, centers of anomalous TC activity barely change from JA-0 to SO-0 during CPW years. In January-February-March （JFM-1） of the decaying years of warming events, TC frequency and intensity both have positive anomaly over the South Pacific, The anoma- lies in EPW years have larger amplitude and wider spatial distribution than those in CPW years. These anomalous activities of TC are associated with GPI anomaly and the key factors affecting GPI anomaly for each ocean basin are quite different.

The first meteorological observations at a tropical high elevation site:Antisana,1846

Antisana is a stratovolcano with an associated glacier located in the Ecuadorian Andes. Dr Aguirre made meteorological readings every day, at every hour from sunrise to sunset, from December 1845 to December 1846, at Antisana using a meteorological station at 4060 mamsl （meters above mean sea level）. Unfortunately, only the monthly average data have been preserved. These meteorological data are here studied and compared with the closest modern stations for monthly values of temperature, rainfall, and pressure. According to these comparisons, the year 1846 was rainy and cold in comparison with the current climate. Moreover, these observations have been useful to help resolve a debate about a possible E1Nifio event in 1846 with the high precipitation in Antisana and Quito in 1846 discarding the occurrence of an E1 Nifio event. The probable occurrence of a La Nifia event is discussed. These data are the earliest known systematic instrumental meteorological observations taken at above 4000 mamsl.

Distribution of the tropical Pacific surface zonal wind anomaly and its relation with two types of El Nio

E1 Nino events with an eastern Pacific pattern （EP） and central Pacific pattern （CP） were first separated using rotated empirical orthogonal functions （REOF）. Lead/lag regression and rotated singular value decomposition （RSVD） analyses were then carried out to study the relation between the surface zonal wind （SZW） anomalies and sea surface temperature （SST） anomalies in the tropical Pacific. A possible physical process for the CP E1 Nifio was proposed. For the EP E1 Nino, strong westerly anomalies that spread eastward continuously produce an anomalous ocean zonal convergence zone （ZCZ） centered on about 165°W. This SZW anomaly pattern favors poleward and eastward Sverdrup transport at the equator. For the CP E1Nino, westerly anomalies and the ZCZ are mainly confined to the western Pacific, and easterly anomalies blow in the eastern Pacific. This SZW anomaly pattern restrains poleward and eastward Sverdrup transport at the equator; however, there is an eastward Sverdrup transport at about 5°N, which favors the wanning of the north-eastern tropical Pacific. It is found that the slowness of eastward propagation of subsurface warm water （partly from the downwelling caused by Ekman convergence and the ZCZ） is due to the slowdown of the undercurrent in the central basin, and vertical advection in the central Pacific may be important in the formation and disappearance of the CP E1 Nifio.

Sea surface temperature anomalies in the South China Sea during mature phase of ENSO

Based on the 18-year （1993-2010） National Centers for Environmental Prediction optimum interpolation sea surface temperature （SST） and simple ocean data assimilation datasets, this study investigated the patterns of the SST anomalies （SSTAs） that occurred in the South China Sea （SCS） during the mature phase of the E1 Nifio/Southem Oscillation. The most dominant characteristic was that of the out- of-phase variation between southwestern and northeastern parts of the SCS, which was influenced primarily by the net surface heat flux and by horizontal thermal advection. The negative SSTA in the northeastern SCS was caused mainly by the loss of heat to the atmosphere and because of the cold-water advection from the western Pacific through the Luzon Strait during E1 Nifio episodes. Conversely, it was found that the anomalous large-scale atmospheric circulation and weakened western boundary current during E1 Nifio episodes led to the development of the positive SSTA in the southwestern SCS.

Animal Radioecology in the Exclusion Zone Since the Chernobyl Catastrophe

We review 20 year long investigations by the Schmalhausen Institute of Zoology on radioecological and ecological consequences of the Chernobyl catastrophe for wild animals in the Exclusion Zone （EZ） around the nuclear plant. Using previous observations on bird migrations through Ukraine, we assessed the 137^Cs and 90^Sr carry-out with migrants from the EZ. In addition, we selected animal species as standard indicators of the state of the environment to map ： 1 ） contamination of vertebrates with 137^Cs in the EZ and 2） beta-activity of mollusc shells indicating 90^Sr, in the whole Dnieper drainage area, in the Kiev Administrative Region, and in the EZ. We revealed regular seasonal and long-term trends, relative radionuclide accumulation by different species, transfer and accumulation factors, and used these measurements to diminish the enormous variation and complexity of the data. Secondary ecological changes in forest, devastated by direct irradiation, were caused by the crash of trophic chains and an outbreak of insect pests on dead or sick trees. Ninety-nine percent of the EZ area was not affected directly by irradiation. Ecological changes in this area have been caused by evacuation of the public, cessation of agriculture and forest management, and decontamination on a large scale. After initial changes, animal density and distribution have been stabilized at a limit restricted by natural resources, predators and poachers. A herd of Przewalski horses was successfully introduced into the EZ years ago. We renewed the protected state of nature reserved sites, which existed before, and proposed to expand the area of nature reservation.

再讀新羅月城垓子2號木簡——與中國出土古代行政文書的比較研究

雖然以往學界有不少關於新羅月城垓子2號木簡的研究成果,但甚少與中國出土行政文書資料的比較研究。本文擬針對這一缺憾,立足於與中國出土行政文書的比較,對月城垓子2號木簡进行重新釋讀和研究。月城垓子2號木簡的内容、用語和書寫方式準確反映了當時東亞地區廣泛實行的文書行政程序及其文書用語和格式。通過新的釋讀和研究,可以復原2號木簡所記録的有關購買紙張的行政程序如下:1)上級下達了定期購買紙張的命令。2)下級負責官吏依據上級命令,啓動按照一定的價格購買特定種類紙張的相關準備工作。3)負責官吏請求上級批准,以完成紙張購買。4)製作這些内容的文書後,題寫文書製作者的職位及簽名。2號木簡即是按照行政文書格式對這些行政程序的記録:第一面是向收件人即上級報告的内容;第二面爲業務負責人的具體準備措施;第三面是請求上級許可的内容;第四面爲文書製作者的職位和簽名。由於每一面需要準確寫入的内容有不同的規定和要求,所以各面所書寫的字數不一樣,末端的留白也不一樣。因此,月城垓子2號木簡可以説是反映當時嚴格遵守相關規定的文書行政程序和文書格式的實物。

Optimal Precursor Perturbations of El Ni?o in the Zebiak-Cane Model for Different Cost Functions

Optimal precursor perturbations of El Nino in the Zebiak-Cane model were explored for three different cost functions. For the different characteristics of the eastern-Pacific （EP） El Nino and the central-Pacific （CP） El Nino, three cost functions were defined as the sea surface temperature anomaly （SSTA） evolutions at prediction time in the whole tropical Pacific, the Nino3 area, and the Nino4 area. For all three cost functions, there were two optimal precursors that developed into El Nino events, called Precursor Ⅰ and Precursor Ⅱ. For Precursor Ⅰ, the SSTA component consisted of an east-west （positive-negative） dipole spanning the entire tropical Pacific basin and the thermocline depth anomaly pattern exhibited a tendency of deepening for the whole of the equatorial Pacific. Precursor Ⅰ can develop into an EP-El Nino event, with the warmest SSTA occurring in the eastern tropical Pacific or into a mixed El Nino event that has features between EP-El Nino and CP-El Nino events. For Precursor Ⅱ, the thermocline deepened anomalously in the eastern equatorial Pacific and the amplitude of deepening was obviously larger than that of shoaling in the central and western equatorial Pacific. Precursor Ⅱ developed into a mixed El Nino event. Both the thermocline depth and wind anomaly played important roles in the development of Precursor Ⅰ and Precursor Ⅱ.

The Combined Effect of Initial Error and Model Error on ENSO Prediction Uncertainty Generated by the Zebiak-Cane Model

Initial errors and model errors are the source of prediction errors. In this study, the authors compute the conditional nonlinear optimal perturbation （CNOP）-type initial errors and nonlinear forcing singular vector （NFSV）- type tendency errors of the Zebiak-Cane model with respect to El Nifio events and analyze their combined effect on the prediction errors for E1 Nino events. The CNOP- type initial error （NFSV-type tendency error） represents the initial errors （model errors） that have the largest effect on prediction uncertainties for E1 Nifio events under the perfect model （perfect initial conditions） scenario. How- ever, when the CNOP-type initial errors and the NFSV- type tendency errors are simultaneously considered in the model, the prediction errors caused by them are not am- plified as the authors expected. Specifically, the predic- tion errors caused by the combined mode of CNOP-type initial errors and NFSV-type tendency errors are a little larger than those caused by the NFSV-type tendency er- rors. This fact emphasizes a need to investigate the opti- mal combined mode of initial errors and tendency errors that cause the largest prediction error for E1 Nifio events.

Sensitivity Difference in the Extratropical Atmosphere to Two Types of El Nio Events

A comparison of sensitivity in extratropical circulation in the Northern Hemisphere （NH） and Southern Hemisphere （SH） is conducted through observational analyses and diagnostic linear model experiments for two types of El Ni（n）o events,the traditional El Ni（n）o with the strongest warmth in the eastern tropical Pacific （EP El Ni（n）o） and the El Ni（n）o Modoki with the strongest warmth in the central tropical Pacific （CP El Ni（n）o）.It is shown that CP El Ni（n）o favors the occurrence of a negative-phase Northern Annular Mode （NAM）,while EP El Ni（n）o favors that of the Pacific-North American （PNA） pattern.In SH,both EP and CP El Ni（n）o induce a negative phase Southern Annular Mode （SAM）.However,the former has a greater amplitude,which is consistent with the stronger sea surface temperature （SST） warmth.The difference in the two types of El Ni（n）o events in NH may originate from the dependence of heating-induced extratropical response on the location of initial heating,which may be associated with activity of the stationary wave.In SH,the lack of sensitivity to the location of heating can be associated with weaker activity of the stationary wave therein.

Interannual variability of latent and sensible heat fluxes in the South China Sea

The South China Sea （SCS） is significantly influenced by El Nino and the Southern Oscillation （ENSO） through ENSO-driven atmospheric and oceanic changes. We analyzed measurements made from 1960 to 2004 to investigate the interannual variability of the latent and sensible heat fluxes over the SCS. Both the interannual variations of latent and sensible heat fluxes are closely related to ENSO events. The low-pass mean heat flux anomalies vary in a coherent manner with the low-pass mean Southern Oscillation Index （SOI）. Time lags between the heat flux anomalies and the SST anomalies were also studied. We found that latent heat flux anomalies have a minimum value around January of the year following El Nino events. During and after the mature phase of E1 Nino, a change of atmospheric circulation alters the local SCS near-surface humidity and the monsoon winds. During the mature phase of E1 Nino, the wind speed decreases over the entire sea, and the air-sea specific humidity difference anomalies decreases in the northern SCS and increases in the southern SCS. Thus, a combined effect of wind speed anomalies and air-sea specific humidity difference anomalies results in the latent heat flux anomalies attaining minimum levels around January of the year following an E1 Nino year.

Contribution of El Nino amplitude change to tropical Pacific precipitation decline in the late 1990s

Equatorial central Pacific precipitation experienced a prominent decline in the late 1990 s.This change was previously attributed to a La Nina-like mean sea surface temperature(SST)change in the Pacific Ocean associated with a phase switch of the Interdecadal Pacific Oscillation.Here,using a series of model experiments,the authors reveal that the El Nino-related interannual SST anomalies contributed largely to the precipitation decrease over the equatorial central Pacific.This El Nino SST effect was due to the change in the amplitude of El Nino events in the late 1990 s.The 1980-98 decade had more large-amplitude El Nino events than the 1999-2014 decade.The nonlinear precipitation response to SST anomalies resulted in a larger decadal mean precipitation in the 1980-98 decade than in the 1999-2014 decade.The results highlight the importance of El Nino amplitude change in future climate change related to global warming.

Subsurface temperature anomalies in the North Pacific Ocean associated with the ENSO cycle

Multi-year Simple Ocean Data Assimilation （SODA） and National Centers for Environmental Prediction （NCEP） datasets were used to investigate the leading patterns of subsurface ocean temperature anomalies （SOTA） and the corresponding atmospheric circulation structure in the Pacific Ocean （20°S-60°N）. In this paper, the evolution of North Pacific SOTA associated with El Nifio-southern oscillation （ENSO）, and their relationship with the overlying zonal/meridional atmospheric circulations were elucidated. The results indicate that： （1） there are two dominant modes for the interannual variability of the North Pacific SOTA. The primary mode is the dipole pattern of the central and western North Pacific SOTA associated with the leading mode of ENSO, and the second mode is the zonal pattern related to the second mode of ENSO. These two modes consist of the temporal-spatial variation of the SOTA in the North Pacific. （2） During the developing phase of the El Nifio event, positive （negative） SOTA appears in the western （central） portion of the North Pacific Ocean. During the mature and decaying phase of the E1 Nifio event, the western positive center and the central negative center continue to be maintained and enhanced. Meanwhile, the position of the western positive center slightly changes, and the central negative center moves eastward slowly. After the El Nifio event vanishes, the positive SOTA disappears, and the central negative SOTA becomes weak and remains in the northeastern Pacific Ocean. The results for La Nifia are generally the opposite. （3） During the El Nifio/La Nifia cycle, formation and evolution of the SOTA, with opposite signs in central and western North Pacific Ocean, resulted from vertical movement of the two northern branches of the Hadley Cell with opposite direction, as well as the positive feedback of the air-sea interaction induced by dynamic processes in the mid-latitudes. The former gives rise to the initial SOTA, and the latter intensifies SOTA. Under the forcing of these two processes, SOTA evolution is formed and sustained during the El Nino/La Nina events. Also discussed herein as background for the ENSO cycle are the possible connections among the West Pacific subtropical high, the strength of the Kuroshio near the East China Sea, the Kuroshio meanders south of Japan, the Aleutian Low, and cold advection in the central North Pacific Ocean.

Statistical Characteristics of ENSO Events in CMIP5 Models

By applying the historical-run outputs from 24 Coupled Model Intercomparison Project Phase 5(CMIP5) models and the NOAA Extended Reconstructed SST V3 b dataset(ERSST), the characteristics of different types of ENSO in the selected CMIP5 models, including cold-season-matured Eastern Pacific(C-EP) ENSO, warmseason-matured EP(W-EP) ENSO, cold-season-matured Central Pacific(C-CP) ENSO, and warm-season-matured CP(W-CP) ENSO, were examined in comparison with those in the ERSST dataset. The results showed that, in general, consistent with observations, EP ENSO events in most of the model runs were relatively much stronger than CP ENSO events, and cold-season-matured ENSO events were relatively much more frequent than warm-season-matured ENSO events for both EP and CP ENSO events. The composite amplitudes of ENSO events in most of the models were generally weaker than in observations, particularly for EP El Ni?o and CP La Ni?a. Moreover, most of the models successfully reproduced the amplitude asymmetries between El Ni?o and La Ni?a for cold-season-matured EP and CP ENSO events, exhibiting an average stronger/weaker EP El Ni?o/La Ni?a regime and a weaker/stronger CP El Ni?o/La Ni?a regime. Most of the models, however, failed to reproduce the observed regimes of stronger/weaker W-EP El Ni?o/ La Ni?a and weaker/stronger W-CP El Ni?o/La Ni?a.

The IOCAS intermediate coupled model(IOCAS ICM) and its real-time predictions of the 2015–2016 El Nio event

The tropical Pacific is currently experiencing an El Nifio event. Various coupled models with different degrees of complexity have been used to make real-time E1 Nifio predictions, but large uncertainties exist in the inten- sity forecast and are strongly model dependent. An intermediate coupled model （ICM） is used at the Institute of Oceanology, Chinese Academy of Sciences （IOCAS）, named the IOCAS ICM, to predict the sea surface temper- ature （SST） evolution in the tropical Pacific during the 2015-2016 E! Nifio event. One unique feature of the IOCAS ICM is the way in which the temperature of subsurface water entrained in the mixed layer （Te） is parameterized. Observed SST anomalies are only field that is utilized to initialize the coupled prediction using the IOCAS ICM. Examples are given of the model＇s ability to predict the SST conditions in a real-time manner. As is commonly evident in E1 Nifio- Southern Oscillation predictions using coupled models, large discrepancies occur between the observed and pre- dicted SST anomalies in spring 2015. Starting from early summer 2015, the model can realistically predict warming conditions. Thereafter, good predictions can be made through the summer and fall seasons of 2015. A transition to normal and cold conditions is predictecl to occur in rote spring 2016. Comparisons with other model predictions are made and factors influencing the prediction performance of the IOCAS ICM are also discussed.

Coral reefs in the South China Sea:Their response to and records on past environmental changes

This paper reviews both the recent and longer-term （Holocene） ecological history of coral reefs in the South China Sea （SCS）. （1） Local ecological monitoring since the 1960s shows that the coral reefs in the South China Sea have declined dramatically, reflecting the rapid decrease of living coral cover and the great loss of symbiotic zooxanthellae. Collectively, this has led to a significant decrease of annual CaCO3 production. Heavy anthropogenic activities and global warming are recognized as major triggers of the observed coral reef degradation. Observations show that the modern coral reefs in the SCS are a source of at- mospheric CO2 in summer. （2） Coral reefs of the SCS have been widely used to reveal longer-term environmental variations, including Holocene high-resolution sea surface temperature （SST） and abrupt climate events, millennial-scale E1 Nifio varia- tions, millennial- and centennial-scale sea level oscillations, strong and cyclic storm activities, East Asian monsoon intensities, variation in seawater pH, and recent seawater pollution. （3） Coral reefs of the southern SCS have experienced repeated epi- sodes of bleaching over the last 200 years due to high SST and intense E1 Nino events; coral reefs of the northern SCS suffered high levels of mortality during several abrupt winter cold-water bleaching events during the middle Holocene warm period. On average, recovery after the middle Holocene cold-bleaching took 20-30 years; recovery following other middle Holocene en- vironmental stresses took approximately 10-20 years. Such findings have significantly contributed to the understanding of the present ecological pressures faced by the coral reefs in the SCS, the histories of Holocene climate/environment changes, and the long-term models of coral reef responses to various past environmental changes.