Impact Of El Research Articles

The impact of phenomena El Niño and La Niña and other environmental factors on episodes of acute diarrhoea disease in the population of Aguascalientes, Mexico: a case study

Abstract. Acute diarrhoea diseases (ADDs) are one of the major health problems in Aguascalientes, Mexico. Due to the risk of significant increases of ADDs in the hot season, it has been necessary to determine the weather conditions that might lead to escalating ADD events. The effects of El Niño and La Niña phenomena on the morbidity rate of ADD (MRADD) in the State of Aguascalientes were determined during the period of 2000–2010. The MRADD was calculated from cases reported by the State Health Department. The Oceanic Niño Index (ONI) was obtained from the US National Oceanic and Atmospheric Administration. The impact of El Niño and La Niña on the MRADD was determined using the Pearson correlation coefficient and analysis of variance (ANOVA). The results gave a significant inverse correlation between El Niño phenomenon and MRADD (r = −0.55, P = 0.001), but a correlation was not observed on the La Niña phenomenon (r = −0.022, P = 0.888). Field data showed significant inverse influence of El Niño on MRADD for the years 2000–2010.

Response of CO<sub>2</sub> and H<sub>2</sub>O fluxes in a mountainous tropical rainforest in equatorial Indonesia to El Niño events

Abstract. The possible impact of El Niño–Southern Oscillation (ENSO) events on the main components of CO2 and H2O fluxes between the tropical rainforest and the atmosphere is investigated. The fluxes were continuously measured in an old-growth mountainous tropical rainforest in Central Sulawesi in Indonesia using the eddy covariance method for the period from January 2004 to June 2008. During this period, two episodes of El Niño and one episode of La Niña were observed. All these ENSO episodes had moderate intensity and were of the central Pacific type. The temporal variability analysis of the main meteorological parameters and components of CO2 and H2O exchange showed a high sensitivity of evapotranspiration (ET) and gross primary production (GPP) of the tropical rainforest to meteorological variations caused by both El Niño and La Niña episodes. Incoming solar radiation is the main governing factor that is responsible for ET and GPP variability. Ecosystem respiration (RE) dynamics depend mainly on the air temperature changes and are almost insensitive to ENSO. Changes in precipitation due to moderate ENSO events did not have any notable effect on ET and GPP, mainly because of sufficient soil moisture conditions even in periods of an anomalous reduction in precipitation in the region.

Impacts of El Niño Southern Oscillation and Indian Ocean Dipole on dengue incidence in Bangladesh.

Dengue dynamics are driven by complex interactions between hosts, vectors and viruses that are influenced by environmental and climatic factors. Several studies examined the role of El Niño Southern Oscillation (ENSO) in dengue incidence. However, the role of Indian Ocean Dipole (IOD), a coupled ocean atmosphere phenomenon in the Indian Ocean, which controls the summer monsoon rainfall in the Indian region, remains unexplored. Here, we examined the effects of ENSO and IOD on dengue incidence in Bangladesh. According to the wavelet coherence analysis, there was a very weak association between ENSO, IOD and dengue incidence, but a highly significant coherence between dengue incidence and local climate variables (temperature and rainfall). However, a distributed lag nonlinear model (DLNM) revealed that the association between dengue incidence and ENSO or IOD were comparatively stronger after adjustment for local climate variables, seasonality and trend. The estimated effects were nonlinear for both ENSO and IOD with higher relative risks at higher ENSO and IOD. The weak association between ENSO, IOD and dengue incidence might be driven by the stronger effects of local climate variables such as temperature and rainfall. Further research is required to disentangle these effects.

Impacts of El Niño Occurrence during Summer Season on Rice Crop Yield and Rice Blast Disease in Iwate Prefecture

Impacts of El Niño Occurrence during Summer Season on Rice Crop Yield and Rice Blast Disease in Iwate Prefecture

Seasonal Tropical Cyclone Predictions Using Optimized Combinations of ENSO Regions: Application to the Coral Sea Basin

Abstract This study examines combining ENSO sea surface temperature (SST) regions for seasonal prediction of Coral Sea tropical cyclone (TC) frequency. The Coral Sea averages ~4 TCs per season, but is characterized by strong interannual variability, with 1–9 TCs per season, over the period 1977–2012. A wavelet analysis confirms that ENSO is a key contributor to Coral Sea TC count (TCC) variability. Motivated by the impact of El Niño Modoki on regional climate anomalies, a suite of 38 linear models is constructed and assessed on its ability to predict Coral Sea seasonal TCC. Seasonal predictions of TCC are generated by a leave-one-out cross validation (LOOCV). An important finding is that models made up of multiple tropical Pacific SST regions, such as those that comprise the El Niño Modoki Index (EMI) or the Trans-Niño Index (TNI), perform considerably better than models comprising only single regions, such as Niño-3.4 or Niño-4. Moreover, enhanced (suppressed) TC activity is expected in the Coral Sea when the central Pacific is anomalously cool (warm) and the eastern and western Pacific are anomalously warm (cool) during austral winter. The best cross-validated model has persistent and statistically significantly high correlations with TCC (r > 0.5) at lead times of ~6 months prior to the mean onset of the Coral Sea TC season, whereas correlations based heavily on the widely used Niño-3.4 region are not statistically significant or meaningful (r = 0.09) for the same lead times. Of the 38 models assessed, several optimized forms of the EMI and of the TNI perform best.

Impacts of El Niño Southern Oscillation on the global yields of major crops.

The monitoring and prediction of climate-induced variations in crop yields, production and export prices in major food-producing regions have become important to enable national governments in import-dependent countries to ensure supplies of affordable food for consumers. Although the El Niño/Southern Oscillation (ENSO) often affects seasonal temperature and precipitation, and thus crop yields in many regions, the overall impacts of ENSO on global yields are uncertain. Here we present a global map of the impacts of ENSO on the yields of major crops and quantify its impacts on their global-mean yield anomalies. Results show that El Niño likely improves the global-mean soybean yield by 2.1-5.4% but appears to change the yields of maize, rice and wheat by -4.3 to +0.8%. The global-mean yields of all four crops during La Niña years tend to be below normal (-4.5 to 0.0%). Our findings highlight the importance of ENSO to global crop production.

Change of the wintertime SSTA variability over the West Pacific after the mid‐1980s: Effect of the increasing El Niño Modoki

AbstractFrom 1949 to 2010, the EOF 1 of sea surface temperature anomalies (SSTA) over the West Pacific (WP) in the boreal winter shows a clear increase during the 1980s, which is associated with the increase in global SSTA. It is found that the characteristics of WP SSTA are different since the mid‐1980s. Before the mid‐1980s, the first EOF presents a dipole pattern associated with El Niño. After the mid‐1980s, EOF1 of WP SSTA captures a uniform SSTA variability over WP and is related to El Niño Modoki. Meanwhile, the dipole SSTA pattern captured by EOF2 is associated with the canonical El Niño. The generation of these two different SSTA patterns might be attributed to the different atmospheric responses to El Niño and El Niño Modoki. The impact of El Niño Modoki over the WP SSTA is significantly enhanced along with the increased occurrences of El Niño Modoki. The increasing intensity of WP SSTA variability has a similar period with that of El Niño Modoki. During El Niño Modoki, the central Pacific SSTA has a leading impact on the development of the WP SSTA by a Rossby wave response. July(0) to October(0) is suggested as a crucial period for the development of WP SSTA during El Niño Modoki. The increased wind speed and evaporation might be responsible for the formation of WP SSTA. After the negative SSTA established, the suppressed convection would counteract the impact of evaporation anomaly and prevent the decreasing of WP SSTA.

Impacts of fire emissions and transport pathways on the interannual variation of CO in the tropical upper troposphere

Abstract. This study investigates the impacts of fire emission, convection, various climate conditions and transport pathways on the interannual variation of carbon monoxide (CO) in the tropical upper troposphere (UT), by evaluating the field correlation between these fields using multi-satellite observations and principle component analysis, and the transport pathway auto-identification method developed in our previous study. The rotated empirical orthogonal function (REOF) and singular value decomposition (SVD) methods are used to identify the dominant modes of CO interannual variation in the tropical UT and to study the coupled relationship between UT CO and its governing factors. Both REOF and SVD results confirm that Indonesia is the most significant land region that affects the interannual variation of CO in the tropical UT, and El Niño–Southern Oscillation (ENSO) is the dominant climate condition that affects the relationships between surface CO emission, convection and UT CO. In addition, our results also show that the impact of El Niño on the anomalous CO pattern in the tropical UT varies strongly, primarily due to different anomalous emission and convection patterns associated with different El Niño events. In contrast, the anomalous CO pattern in the tropical UT during La Niña period appears to be less variable among different events. Transport pathway analysis suggests that the average CO transported by the "local convection" pathway (ΔCOlocal) accounts for the differences of UT CO between different ENSO phases over the tropical continents during biomass burning season. ΔCOlocal is generally higher over Indonesia–Australia and lower over South America during El Niño years than during La Niña years. The other pathway ("advection within the lower troposphere followed by convective vertical transport") occurs more frequently over the west-central Pacific during El Niño years than during La Niña years, which may account for the UT CO differences over this region between different ENSO phases.

Impacts of canonical and Modoki El Niño on tropical Atlantic SST

AbstractThe impacts of canonical and Modoki El Niño on tropical Atlantic sea surface temperature (SST) are quantified using composite analysis. Results show that El Niño Modoki fails to produce significant warming in the tropical Atlantic, in contrast to the well known warming following canonical El Niño events. El Niño Modoki instead induces significant cooling in the northeastern tropical Atlantic and near‐neutral conditions elsewhere in the tropical Atlantic. It is shown that the difference in SST response stems primarily from a much stronger Pacific/North American (PNA) teleconnection pattern and stronger atmospheric Kelvin wave response during canonical events compared to Modoki. The stronger PNA pattern and Kelvin waves during canonical events generate anomalously weak surface winds in the tropical North Atlantic, driving anomalously weak evaporative cooling and warmer SSTs. Past research has shown significant decadal variability in the frequency of noncanonical El Niños relative to canonical events. If such variability continues, it is likely that the impact of El Niño on tropical Atlantic SST will also fluctuate from one decade to the next.

The Impact of El Niño/Southern Oscillation on Hydrology and Rice Productivity in the Cauvery Basin, India: Application of the Soil and Water Assessment Tool

This study was performed to further understanding of the variations in hydrology and rice crop productivity during different El Niño/Southern Oscillation (ENSO) events in the Cauvery River Basin of Tamil Nadu, India using the Soil and Water Assessment Tool (SWAT). The entire Cauvery Basin was divided into 301 sub-basins and further subdivided into 3,601 Hydrological Response Units (HRU). Based on the National Oceanic and Atmospheric Administration (NOAA) official website, information on El Niño (1972, 1982, 1987, 1991, 1997, 2002 and 2004) and La Niña (1970, 1971, 1973, 1974, 1975, 1988, 1998, 1999 and 2000) years were obtained. The SWAT model was continuously run from 1970 to 2008, and a composite for El Niño, La Niña and normal years was constructed to understand their influence on hydrology and rice crop productivity in the study area. From the analysis, it was clear that an El Niño episode is correlated with rainfall, hydrology and rice productivity in the Cauvery river basin. The validation of the SWAT model indicated the capability of SWAT to accurately predict stream flow and rice productivity. It was evident from the investigation that the quantum of rainfall was more during El Niño years with high inter-annual rainfall variability (809.3mm to 2,366mm) compared with La Niña and normal years. As a result, the soil water recharge, including percolation and soil water availability in the surface layers, was increased in the El Niño years. Simulated rice productivity over 39 years in the Cauvery Basin ranged between 1,137 and 7,865kgha−1 with a mean productivity of 3,955kgha−1. The coefficient of variation in rice productivity was higher during La Niña (21.4%) years compared with El Niño (14.7%) and normal years (14.6%). The mean rice productivity was increased in both El Niño and normal years, indicating the possibility of higher yields than those in La Niña years. An analysis of the hydrological data and rice productivity showed that the risk of failure was low during El Niño years compared with normal or La Niña years. This behavior could be utilized for forecasting rice crop productivity under different ENSO conditions and can provide information for policy makers when deciding on water allocation and import / export policies.

Statistical analysis of Indian rainfall and rice productivity anomalies over the last decades

ABSTRACTMonsoon fluctuations have a reflective influence on rice productivity, which is the main foodgrain in India. The impact of El Niño on spatial variability of summer monsoon rainfall and thereby kharif rice productivity was analysed for the period 1974–2009. It was clear from the analysis that the delayed onset of monsoon along with El Niño has varied influences on rice productivity over different rice growing states as well as over India. Out of eight El Niño years, 6 years received deficit rainfall during monsoon season. But, the quantity of deficit varies from −20.3% in 2002 to −5.5% in 1991. The monthly distribution of monsoon rainfall shows higher frequency of deficit occurred during July and September. Interestingly, all El Niño years, except in 1997, September received deficit in rainfall which indicate the early withdrawal of monsoon. During 8 moderate and strong El Niño years, 5 years the kharif rice productivity falls below the technological trend ranging by between −4.3% in 1986 and −13.8% in 2002 over India. There exists a wide spatial variability of normalized kharif rice productivity anomaly during moderate El Niño event, with a maximum of −21.9% over Gujarat followed by −15.9% at Maharashtra. However, during the strong El Niño event, there is a maximum of −14.2% at Bihar to −6.6% over Maharashtra. The correlation between normalized monthly rainfall anomaly and rice productivity anomaly during the El Niño years indicated that July rainfall contributed 71% of the variations in rice productivity. Analysis of El Niño impact on spatial rice productivity may be useful for formulating farm‐level site specific management planning and policy decisions.

North-Central Pacific Tropical Cyclones: Impacts of El Niño–Southern Oscillation and the Madden–Julian Oscillation

Abstract Both El Niño–Southern Oscillation (ENSO) and the Madden–Julian oscillation (MJO) have been documented in previous research to impact tropical cyclone (TC) activity around the globe. This study examines the relationship of each mode individually along with a combined index on tropical cyclone activity in the north-central Pacific. Approximately twice as many tropical cyclones form in the north-central Pacific in El Niño years compared with La Niña years. These differences are attributed to a variety of factors, including warmer sea surface temperatures, lower sea level pressures, increased midlevel moisture, and anomalous midlevel ascent in El Niño years. When the convectively enhanced phase of the MJO is located over the eastern and central tropical Pacific, the north-central Pacific tends to have more tropical cyclone activity, likely because of reduced vertical wind shear, lower sea level pressures, and increased vertical motion. The convectively enhanced phase of the MJO is also responsible for most of the TCs that undergo rapid intensification in the north-central Pacific. A combined MJO–ENSO index that is primarily associated with anomalous rising motion over the tropical eastern Pacific has an even stronger relationship with north-central Pacific TCs, as well as rapid intensification, than either individually.

Reexamining El Niño and Cholera in Peru: A Climate Affairs Approach

Abstract In the 1990s Peru experienced the first cholera epidemic after almost a century. The source of emergence was initially attributed to a cargo ship, but later there was evidence of an El Niño association. It was hypothesized that marine ecosystem changes associated with El Niño led to the propagation of V. cholerae along the coast of Peru, which in turn initiated the onset of the epidemic in 1991. Earlier studies supported this explanation by demonstrating a relationship between elevated temperatures and increased cholera incidence in Peru; however, other aspects of El Niño–Southern Oscillation (ENSO) and their potential impacts on cholera were not investigated. Therefore, this study examines the relationship between El Niño and cholera in Peru from a holistic view of the ENSO cycle. A “climate affairs” approach is employed as a conceptual framework to incorporate ENSO’s multidimensional nature and to generate new hypotheses about the ENSO and cholera association in Peru. The findings reveal that ENSO may have been linked to the cholera epidemic through multiple pathways, including rainfall extremes, La Niña, and social vulnerability, with impacts depending on the geography of teleconnections within Peru. When the definition of an ENSO event is examined, cholera appears to have emerged either during ENSO neutral or La Niña conditions. Furthermore, the analysis herein suggests that the impact of El Niño arrived much later, possibly resulting in heightened transmission in the austral summer of 1992. In conclusion, a modified hypothesis with these new insights on cholera emergence and transmission in Peru is presented.

The effect of ENSO on rainfall characteristics in the tropical peatland areas of Central Kalimantan, Indonesia

The effect of the El Niño Southern Oscillation (ENSO) on rainfall characteristics in the tropical peatland areas of Central Kalimantan, Indonesia, is demonstrated. This research used rainfall data collected between 1978 and 2008. The results suggest a relationship between ENSO events and the trend in rainfall observed in the study area. Further analyses show that El Niño events have a stronger effect on the rainfall compared to La Niña events. El Niño events were also correlated to the increase in the number of days with less than 1 mm of rainfall in the dry season. The analysis reveals that the impact of El Niño events on rainfall in dry seasons is intensifying annually. Furthermore, ENSO events are not the only factors affecting rainfall trends in the observed area. Other factors, such as deforestation, may also affect the trend. Editor Z.W. Kundzewicz Citation Susilo, G.E., Yamamoto, K., Imai, T., Ishii, Y., Fukami, H., and Sekine, M., 2013. The effect of ENSO on rainfall characteristics in the tropical peatland areas of Central Kalimantan, Indonesia. Hydrological Sciences Journal, 58 (3), 539–548.

South American Climatology and Impacts of El Niño in NCEP’s CFSR Data

Understanding regional climate variability is necessary in order to assess the impacts of climate change. Until recently, the best methods for evaluating regional climate variability were via observation networks and coarse-gridded reanalysis datasets. However, the recent development of high-resolution reanalysis datasets offers an opportunity to better evaluate the climatologically diverse continent of South America. This study compares NCEP’s CFS reanalysis dataset with NCEP’s coarser-resolution reanalysis II dataset to determine if CFS reanalysis improves our ability to represent the regional climate of South America. Our results show several regional differences between the CFSR and Re2 data, especially in areas of large topographical gradients. A comparison with the University of Delaware and TRMM precipitation datasets lends credence to some of these differences, such as heavier precipitation associated with anomalous 925 hPa westerlies over northwestern Peru and Ecuador during El Niño. However, our results also stress that caution is advised when using reanalysis data to assess regional climate variability, especially in areas of large topographical gradient such as the Andes. Our results establish a baseline to better study climate change, especially given the release of IPCC AR5 model simulations.

Variability in tropospheric carbon monoxide over an urban site in Southeast Asia

This paper analyses MOZAIC (Measurements of Ozone aboard Airbus in-service airCraft) measurements of carbon monoxide (CO) profiles over Bangkok to discuss the seasonality in vertical distribution during year 2005–2006. The mixing ratios of CO were enhanced in the lower troposphere being highest in winter followed by summer and wet seasons. During all the seasons, the mixing ratio of CO decreased rapidly and remained low in the middle troposphere. At higher altitudes (6–12 km), CO shows enhanced values particularly during wet and early winter seasons. The strong seasonality in CO was caused by the seasonal shift in the patterns of the long-range transport and biomass burning (BB) in South and Southeast Asia (S–SE Asia). Flow of cleaner air and negligible BB resulted in the lowest mixing ratio of CO in the wet season. In addition to anthropogenic influence, the long-range transport and BB caused the higher CO in the winter and summer seasons, respectively. Despite extensive local BB activities in Thailand during the summer season, the moderate levels of CO were attributed to the dilution due to flow of cleaner marine from the Indian and Pacific Oceans. We have also compared the observations with the Model for Ozone And Related Chemical Tracers (MOZART) simulations. Mostly the observations lie between the MOZART-2 and MOZART-4 simulations as they underestimate and overestimate the observed CO, respectively. In the middle and upper troposphere, both the observed and simulated mixing ratios of CO during September–November of year 2006 were higher by 15–30 ppbv compared to the same period of year 2005. Our analysis indicates the impact of El Niño induced extensive BB in Indonesia during the year 2006.

Impacts of El Niño-Southern Oscillation and local sea surface temperature on moisture source in Asian-Australian monsoon region in boreal summer

El Niño-Southern Oscillation (ENSO) and local sea surface temperature (SST) have been regarded as the important factors influencing the precipitation, evaporation and circulation over the Asian-Australian monsoon (AAM) region. The moisture source is determined directly by precipitation and evaporation. This present paper studies the impacts of ENSO and local SST on moisture source in the AAM region during boreal summer. Relative roles of ENSO and local SST are also discussed by using the singular value decomposition (SVD) and conditional SVD (CSVD) methods. The authors identify one major coupled mode between the interannual variations of apparent moisture sink (<Q2>) and SST for the period 1979–2008. Spatial structure of the major mode exhibits two key regions of moisture source, one over the western-central southern Indian Ocean (SIO) where <Q2> is negative, and the other over the northwest and north side of Australia, where <Q2> is positive. In the corresponding map of SST, negative values are also seen in the former region, but are positive in the latter region. The interannual variation of moisture source in the AAM region has an outstanding positive correlation with the local SST. Furthermore, ENSO also has a remarkable correlation with the principle component (PC) of the first empirical orthogonal function (EOF) mode of <Q2>. ENSO and local SST work cooperatively to determine the variations of moisture source in the AAM region.

Interannual variability of convective activity over the tropical Indian Ocean during the El Niño/La Niña events

Convection over the tropical Indian Ocean is important to the global and regional climate. This study presents the monthly climatology of convection, inferred from the outgoing longwave radiation (OLR), over the tropical Indian Ocean. We also examine the impact of El Niño/La Niña events on the convection pattern and how variations in convection over the domain influence the spatial rainfall distribution over India. We used 35 recent years (1974–2008) of satellite-derived OLR over the area, the occurrence of El Niño/La Niña events and high resolution grid point rainfall data over India. The most prominent feature of the annual cycle of OLR over the domain is the movements of convection from south-east to north and north-west during the winter to the summer monsoon season. This feature represents the movement of the inter-tropical convergence zone (ITCZ). The climatology of OLR during the winter months (December–February) over the domain is characterized by high subsidence over central India with a decrease of OLR values towards the north and south. Moderate convection is also seen over the Himalayan Range and the south-east Indian Ocean. In contrast, during the summer (June–September) the OLR pattern indicates deep convection along the monsoon trough and over central India, with subsidence over the extreme north-west desert region. The annual march of convection over the Arabian Sea and Bay of Bengal sector shows that the Arabian Sea has a limited role, compared to the Bay of Bengal, in the annual cycle of the convection over the tropical Indian Ocean. The composite OLR anomalies for the El Niño cases during the summer monsoon season show suppressed convection over all of India and moderate convection over the central equatorial Indian Ocean and over the northern part of the Bay of Bengal. Meanwhile in La Niña events the OLR pattern is nearly opposite to the El Niño case, with deep convection over entire Indian region and adjoining seas and subsidence over the northern Bay of Bengal and extreme north-west region. The spatial variability of the 1° × 1° summer monsoon rainfall data over India is also examined during El Niño/La Niña events. The results show that rainfall of the summer monsoon season over the southern peninsular of India and some parts of central India are badly affected during El Niño cases, while the region lying along the monsoon trough and the west coast of India have received good amounts of rainfall. This spatial seasonal summer monsoon rainfall distribution pattern seems to average out the influence of El Niño events on total summer monsoon rainfall over India. It seems that, in El Niño events, the convection pattern over the Bay of Bengal remains unaffected during summer monsoon months and thus this region plays an important role in giving good summer monsoon rainfall over the northern part of India, which dilutes the influence of El Niño on seasonal scale summer monsoon rainfall over India. These results are also confirmed by using a monthly bias-corrected OLR dataset.

The impact of El Niño on South American summer climate during different phases of the Pacific Decadal Oscillation

In austral summer, the observed El Nino (EN) events during warm Pacific Decadal Oscillation (PDO) phases (PDO(+)) exhibited large anomalous upper level wave patterns in response to larger Sea Surface Temperature (SST) anomalies in the Equatorial Pacific and Atlantic Oceans compared with SST anomalies in EN events during cold PDO phases (PDO(−)). The precipitation anomalies in PDO(+) EN are increased over Southeastern South America (SESA) associated with the intensification of the moisture flux convergence in this region. The PDO(−) EN events exhibit positive precipitation anomalies only over southern SESA, while negative anomalies were observed in the north. Downward motion and anomalous divergence over central eastern Brazil may have contributed to the weakening of the northwesterly moisture flux convergence associated with the South American Low Level Jet (SALLJ) over the subtropics. The extratropical cyclones showed higher frequency and lower central pressures in southern Brazil, Uruguay, northeastern Argentina, and Southwest Atlantic Ocean during the PDO(+) EN events compared with the PDO(−) EN events. Such increase in the frequency and intensity of cyclogenesis cases seems to be in accordance with the anomalous moisture flux convergence over the SESA and associated reduction in the Sea Level Pressure observed during PDO(+) EN events. In order to investigate the impact of a canonical El Nino event over South America under different PDO phases, two numerical experiments were done with an Atmospheric General Circulation Model. Global SST and ice sea fields average over years characterized by (a) PDO(+) and (b) PDO(−) were considered as climatologically fields, and a composite of anomalies of SST of all El Nino events observed in 1950–1999 was added in the region 20oS–20oN;120oW–175oW of both “climatologies.” The differences in experiments suggest that a canonical EN may produce significant different anomalous atmospheric patterns associated with distinct PDO climatologies. The more significant differences are simulated over extreme northern and eastern Brazil. Additional numerical experiments isolating the observed variability of SST over several oceanic basins during different PDO phases will be conducted to study their particular role on the South American climate.

Impact of El Niño Occurrence on Oil Palm Yield in Malaysia

The impact and occurrence of El Niño is being discussed in this paper in relation to particularly rainfall and the effects on oil palm yield. High rainfall could contribute to lower fruit set and bunch weight. Annual FFB yield was reduced in 1998 which was lower than that in previous years due to the occurrence of a severe El Niño event during that period. A continuously low rainfall (<100 mm) for more than two months will have significant effects on the palm yield. Keywords: El Niño, FFB yield, low rainfall.