El Nino Episodes Research Articles

A Review Paper on El Nino

El Nino episodes are major climatic disruptions that occur every 2 to 8 years and originate in the equatorial Pacific Ocean. From the coastlines of Peru and Ecuador to the middle of the equatorial Pacific Ocean, unusually warm waters at the ocean surface mark the developed phase of El Nino. The reason of this occurrence is a peculiar lessening of the westward blowing trade winds, which enables warm surface waters to reverse their course eastward. El Nino's climatic effects are increasing throughout the globe, and this may have a variety of consequences on regional weather. It is linked to a broad range of changes in the climate system, and it has the potential to have significant socio-economic consequences in the infrastructure, agricultural, health, and energy sectors. Despite the fact that El Nino occurs in the tropical Pacific, it has an effect on worldwide climate and weather events such as drought, floods, and tropical storms. The usual state in the equatorial Pacific has altered because of increased greenhouse gas emissions, which has resulted in changes in the El Nino Southern Oscillation (ENSO). ENSO fluctuations will continue to exist and affect global climate conditions in the future decades and millennia, we can be certain. As a result, both scientists and the public rely on predicting and understanding ENSO conditions. The occurrence of El Nino and its effect on world climate and socio-economic status have been researched and discussed in this article.

Spatial and temporal variability of satellite sea surface temperature in the Makassar Strait and the Java Sea

Sea surface temperature (SST) data obtained from the Aqua-MODIS satellite from 2002 to 2012 were analyzed to determine the spatial and temporal variability in the key region of small pelagic fisheries between Makassar Strait and the Java Sea. Results of the Empirical Orthogonal Function (EOF) analysis show that the characteristics of this region are described by 60% based on the greatest contribution value respectively. The largest contribution of 52% shows that the SSTs in this region is warm. A strong indicator of these conditions appears in the east through the southern part of Kalimantan Island while the weak indicator is in the south to western part of Sulawesi Island. The temporal variation shows that the annual oscillation is dominant in this area where maximum SSTs occurs in the first transitional monsoon (April), while the minimum occurs in the southeast monsoon period (August). The influence of southeast monsoon formats the minimum SSTs area in the south of South Sulawesi that is generated by parallel wind-driven induces to the coast and the divergent current close to the coast. Due to inter-annual variability, minimum SSTs occurs before the El Nino episode whereas the maximum occurs before the La Nina event.

Study the rainfall variability and impact of El Nino episode on rainfall and crop productivity at Parbhani

The weekly rainfall data for 36 years (1981-2016) recorded at Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani were analyzed for mean seasonal, weekly rainfall and also weekly rainfall probabilities. The mean seasonal rainfall was 796 mm, received in 38 rainy days. The seasonal rainfall indicated that there is 53% chance of receiving less than 700 mm with variable intensities and 36% chance of getting more than normal rainfall and 11% chance of seasonal rainfall, in between 700 mm to 800 mm. The mean weekly rainfall during crop season was 45.8 mm with a CV of 116%. Highest mean weekly rainfall was recorded 71.8 mm with SD (95.3) and CV (132.7%) in 30th MW. Sowing of Kharif crops should be undertaken during 24th MW to 27th MW. Significant and positive correlation between yield and rainfall was observed for Soybean, Pigeonpea, Black gram, Green gram and rice. The predictability of productivity of crops using seasonal rainfall is 10-20% variation in productivity for all the crops at the Centre. The El Nino episode was negatively influencing Southwest monsoon and annual rainfall as well as rainfall during the months of July and September. El Nino episodes exhibit more negative influence on productivity of all the crops except rice crop. Among the different categories of El Nino, weak events exerted more negative impact on productivity of short duration crops (i.e., sorghum, soybean and Black gram) as compared to moderate and strong El Nino events.

Trend and Change-Point Detection Analyses of Rainfall and Temperature Over the Awash River Basin of Ethiopia

Awash River basin (ARB) as a system is in a state of continuous change that requires successive studies to discern the changes or trends of climatic elements through time due to climate change/variability, and other socio-economical developmental activities in the basin. The livelihood of communities in the ARB is primarily based on rainfall-dependent agriculture. Effects of rainfall anomalies such as reduction of agricultural productivity, water scarcity, and food insecurity are becoming more prevalent in this area. In recent years, ARB experienced more frequent and intense spatio-temporal rainfall anomalies, which make the shift and trend analyses of rainfall associated with sea surface temperature crucial in providing guidance to improve agricultural productivity. Change-point detection tests (Pettit’s, the von Neumann ratio (VNR), Buishand’s range (BR) and standard normal homogeneity (SNH)) and Mann-Kendall (MK) trend analysis of rainfall and temperature data from 29 meteorological stations in the ARB were carried out from 1986 to 2016. A significant increasing trend of annual and seasonal temperature was found. The temperature change-points for the annual and major rainy season (MRS) were detected in 2001, while for the minor rainy season (mRS) in 1997. A significant decreasing trend, shift, and high variability of rainfall were detected in the downstream part of the ARB. The BR and SNH results showed that the mRS rainfall change-point was in 1998, with a subsequent mean annual decrease of 52.5 mm. The increase (decrease) of rainfall in the annual and MRS was attributable to La Nina (El Nino) events. The significant decreasing trend and change-point of rainfall in the mRS was attributable to the steady warming of the Indian and Atlantic Oceans, local warming, and La Nina events. With this knowledge of the current trends and change-point for rainfall and temperature in the ARB, it is therefore essential that appropriate integrated water management and water-harvesting technologies are established, especially in the downstream areas. Moreover, early detection of El Nino episodes would provide invaluable warning of impending rainfall anomalies in the ARB and would enable better preparations to mitigate its negative effects.

Water supply and effective rainfall impacts on major crops across irrigated areas of Punjab, Pakistan

An integrated approach is developed to assess major crops water productivity (CWP) in relation to water supply across the irrigated areas of Punjab province in central Pakistan during 1982–2015. The role of precipitation (effective rainfall) in term of add on to water supply and impacts on wheat yield is also studied. The water supply from canals displayed a significant declining trend for Rabi season (wheat mainly) during 1996−2015. Crop water productivity for harvestable area (CWPA) has decreased; however, it has increased in case of production (CWPP) and yield (CWPY). The role of tube wells is analyzed to assess the improved CWP even under decreased canal water supply. Contribution of water supply through effective rainfall showed a significant add on of 7.6 mm to 291.8 mm to water supply and 0.48 kg ha−1 mm−1 to 8.19 kg ha−1 mm−1 towards CWPY during the studied 34-year period. The precipitation (effective rainfall) contribute water supply of 10.6 mm (6.64 mm), 23.4 mm (14.6 mm), and 25.5 mm (16.0 mm) for January, February, and March, respectively. Average canal water supply for irrigation is observed to be 254.9 mm against irrigation need of 418.6 mm with a deficit of 39.1%, across irrigated areas. The multiple regression models are developed with seasonal predictive capacity for wheat harvestable area and yields with an explained variability of ~ 81% and ~ 78%, respectively. A decrease in temporal satellite-based weekly composite NDVI profile during 1986, 1992, 1994, 1997, 2002, and 2010 corresponded to El Nino episodes, since negative phases of ENSO are known to cause droughts across Punjab province. The synthesized information calls for a more comprehensive management of declining canal water supply for sustainable major crops water productivity such as wheat which is a staple food crop.

English

English

Atmospheric Rivers Contribution to the Snow Accumulation Over the Southern Andes (26.5° S–37.5° S)

Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) AFB180004 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1171032 11151009

ENSO-driven CO2 efflux variability and the role of the upwelling region on the carbon exchange in the Northern Humboldt Current System

Abstract The role played by El Nino-Southern Oscillation (ENSO) on modulating the oceanic carbon outflux in the Northern Humboldt Current System (NHCS) is assessed with the use of outputs from a coupled physical-biogeochemical hindcast which permits to evaluate the interannual variability of the surface seawater partial pressure of carbon dioxide, hereinafter pCO 2 s w , and reconstruct associated air-sea CO2 fluxes from 1998 through 2015 at monthly timescales. In addition, surface dissolved inorganic carbon (DIC) concentrations were inferred from a recent neural network methodology prescribed with the same outputs of the biogeochemistry hindcast. Results show a large spatiotemporal variability of the CO2 exchange to nine El Nino and La Nina episodes throughout the period of analysis. Within the coastal and equatorial upwelling region, that variability results from combined ENSO-driven ΔpCO2 (pCO 2 s w - pCO 2 a i r ) and wind speed variations, although the latter in a minor proportion during ENSO peaks. Specifically, it is found that the weak CO2 source behavior during an average El Nino episode is mainly caused by a weakening of ΔpCO2 which is partially compensated by more efficient CO2 exchange at the air-sea interface due to the strengthening of the upwelling-favorable winds. Conversely, the relatively strong CO2 source behavior during an average La Nina episode results from more efficient upwelling which brings colder but CO2-rich waters to the surface, therefore, increasing pCO 2 s w and the associated CO2 efflux. Moreover, it is estimated that during an average La Nina episode, 3.3 million metric tons of carbon is additionally emitted contributing to the atmospheric CO2 accumulation. In contrast, during an average El Nino episode, the total amount of carbon retained is about 24.7 million metric tons of carbon that normally would have been lost to the atmosphere as CO2, rendering the NHCS a key region for the global atmospheric carbon budget.

The effect of the equatorial Pacific cold SST bias on simulated ENSO teleconnections to the North Pacific and California

Precipitation in California is modulated by variability in the tropical Pacific associated with El Nino/Southern Oscillation (ENSO): more rainfall is expected during El Nino episodes, and reduced rainfall during La Nina. It has been suggested that besides the shape and location of the sea surface temperature (SST) anomaly this remote connection depends on the strength and location of the atmospheric convection response in the tropical Pacific. Here we show in a perturbed physics ensemble of the Kiel Climate Model and CMIP5 models that due to a cold equatorial SST bias many climate models are in a La Nina-like mean state, resulting in a too westward position of the rising branch of the Pacific Walker Circulation. This in turn results in a convective response along the equator during ENSO events that is too far west in comparison to observations. This effect of the equatorial cold SST bias is not restricted to the tropics, moreover it leads to a too westward SLP response in the North Pacific and too westward precipitation response that does not reach California. Further we show that climate models with a reduced equatorial cold SST bias have a more realistic representation of the spatial asymmetry of the teleconnections between El Nino and La Nina.

Seasonal and Inter-annual Variation of Evapotranspiration in Amazonia Based on Precipitation, River Discharge and Gravity Anomaly Data

We analyzed seasonal and spatial variations of evapotranspiration (ET) for five Amazon sub-basins and their response to the 2015/16 El Nino episode using a recently developed water-budget approach. ET varied typically between ~7 and 10 cm/month with exception of the Xingu basin for which it varied between 10 and 15 cm/month. Outstanding features of ET seasonality are (i) generally weak seasonality, (ii) two ET peaks for the two very wet catchments Solimoes and Negro, with one occurring during the wet season and one during the drier season, and (iii) a steady increase of ET during the second half of the dry season for the three drier catchments (Madeira, Tapajos, Xingu). Peak ET occurs during the first half of the wet season consistent with leaf flush occurring before the onset of the wet season. With regards to inter-annual variation, we found firstly that for the Solimoes and Madeira catchments the period with large positive wet season anomalies (2012–2015) is associated with negative ET anomalies, and negative SIF (solar induced fluorescence) anomalies. Furthermore, we found negative ET of several cm/months and SIF (up to 50%) anomalies for most of the Amazon basin during the 2015/16 El Nino event suggesting down-regulation of productivity as a main factor of positive carbon flux anomalies during anomalously hot and dry conditions. These results are of interest in view of predicted warmer and more erratic future climate conditions.

Near-future tropical cyclone predictions in the western North Pacific: fewer tropical storms but more typhoons

This study presents forecasts of near-future tropical cyclone (TC) activities over the western North Pacific (WNP) using a TC track-pattern-based prediction model in conjunction with long-term free-run simulations from the National Centers for Environmental Prediction Climate Forecast System. The prediction shows that the East Asian coastal area will be affected by fewer TC landfalls. However, the number of stronger TC landfalls may increase in the near future (2016–2030) compared to the present-day period (2002–2015). The potential candidates for modulating the near-future TC activity are three large-scale climate variability: El Nino–Southern Oscillation (ENSO), the North Pacific sea surface temperature (NPSST) variation, and basin-wide warming of the Pacific. More frequent El Nino episodes in the near future may contribute to the activation of TC formations in the far-eastern tropical ocean, which generates a favorable influence on TC intensification due to longer distances and development periods over the ocean. NPSST variations have contrasting effects, i.e., they have unfavorable effects on TC genesis due to weak vorticity, while creating favorable conditions for TC intensification by providing more humid environments in the subtropics. The impact of overall Pacific warming on the changes in TC activities is low compared to that of the other two factors. Our results physically demonstrate the contributions of three WNP sea surface temperature variability on near-future TC activity, emphasizing the critical roles of ENSO and NPSST rather than the near-term warming effect.

Does El Niño play an early signal role for the south-flood north-drought pattern over eastern China?

Reconstructed hydroclimatic spatial patterns from historical documents, the chronology of El Nino events since 1525, Meiyu (a unique rainy season dominated by the East Asian summer monsoon in eastern China) series since 1736, and a 1000-year control simulation using the Community Earth System Model were used to analyze the occurrence of anomalous summer precipitation patterns over eastern China with El Nino events. The results show that the frequency of the south-flood north-drought during 1525–2005 was significantly higher during El Nino episodes. Specifically, the occurrences of the triple pattern with floods in the Yangtze River Valley but droughts in its north and south (FYRDNS) as well as the dipole pattern with floods in the south but droughts in the north (FSDN) divided by the Yangtze River both increased in El Nino developing years, while the occurrence of FSDN increased in El Nino decaying years. Among 44 severe and extreme Meiyu events over the middle and lower reaches of the Yangtze River in 1736–2016, 75% of events occurred during El Nino episodes. Especially, 80% of extreme Meiyu events occurred in El Nino decaying years. The 1000-year control simulation captured well the reconstructed triple pattern of FYRDNS in developing years and the dipole pattern of FSDN in decaying years, with more noticeable precipitation anomalies for developing years of very strong and extremely strong El Nino events. These results implicated that the El Nino is likely an early signal for the occurrence of the south-flood north-drought over eastern China.

Simulation of synoptic features during summer monsoon onset over GWB, India, with CFSv2 coupled model: skill and bias assessment

The aim of this study is to examine the skill of climate forecast system version 2 (CFSv2) in simulating the synoptic features of Bay of Bengal (BOB) branch of summer monsoon (SM) during the onset over Gangetic West Bengal (GWB), India. Precise prediction of the onset time and the synoptic features associated with the onset is a major challenge in SM study. Better understanding of the synoptic and intra-seasonal variability during the propagation along with the mean simulation of monsoon features is crucial, especially for the operational models. The earlier studies focused mainly on the mean simulation of SM during June–September (JJAS) period. However, the main objective of the present study is to improve the understanding of CFSv2 model biases in simulating the synoptic features during the propagation of BOB branch of SM system till the onset over GWB. The skill of the coupled model is estimated for the years 2011 to 2015 with tropospheric temperature (TT), sea surface temperature (SST), mean sea level pressure (MSLP), winds at 850 and 500 hPa pressure levels, and rainfall rate (RR). The result shows that the observed characteristics are simulated, reasonably well, by CFSv2 model with quite high reliability unlike other coupled models. The CFSv2 has been able to simulate the position/variation during the onset; however, the model has not been able to estimate the intensity in some occasions. The gradients of pressure and SST have been slightly overestimated by the model. The model has not been able to simulate the winds at 850 and 500 hPa pressure levels in some occasions. The CFSv2 model in simulating the features during propagation of BOB branch of SM system shows disparity from observation in some occasions during 2011 to 2015. The result also reveals that the model biases remain unaltered during El Nino episode of 2011.

Amplifying effect of ENSO on heat waves in China

This paper investigates the impacts of the El Nino Southern Oscillation (ENSO) on various aspects of heat waves (HWs), including frequency, duration, and magnitude, over China during 1961–2014. Results show that El Nino (La Nina) significantly amplifies (weakens) the HW activities in most areas of China. Such influences are particularly strong in southern China. HW activities are enhanced (weakened) during the summers following mature El Nino (La Nina) episodes, with increased (reduced) occurrence of HW events and number of HW days, as well as prolonged (shortened) duration and elevated (decreased) amplitude of such events. These amplifying effects are substantially stronger for severe HWs (i.e., hottest and longest episodes) than for those events of average duration and intensity. Diagnosis by compositing reanalysis data over ENSO events indicates that the atmospheric circulation during the summers following El Nino is characterized by anomalous rising motion over the tropical central Pacific and Indian Oceans, and sinking motion over the western North Pacific (WNP). The anomalous subsidence over the WNP is accompanied by reduced precipitation and condensational heating, as well as anomalous anticyclonic flows in the lower troposphere. El Nino also induces a stronger South Asian high, which can strengthen the WNP anticyclone and subtropical high. These changes provide a favorable environment for the occurrence and sustenance of HWs in China. Analogous arguments apply to changes with the opposite polarity in association with La Nina events.

What makes protracted El Niño to last longer than canonical El Niño?

Behavior and teleconnections associated with canonical El Nino (~ 18–24 months; CE) and protracted El Nino (> greater than 3 years; PE) events are revisited in the present study. A careful look at seasonal mean of SST anomalies averaged over Nino3.4 region for the period 1980–2010 shows that El Nino episodes in the boreal winter of 1991 and 2002 do not turn into La Nina as CE events (1982–1983, 1986–1988, 1997–1998, 2009–2010). Unlike phase transition in canonical cases of El Nino followed by a neutral or La Nina event, El Nino episodes in the years 1991 and 2002 continued as weak El Nino for another 3 years. A typical signature of CE events in the tropical Indian Ocean (IO) is basin-wide warming, whereas in the case of PE events, warming remains highly localized and relatively weaker in magnitude. PE events are found to be associated with almost no subsurface ocean propagation in the equatorial Pacific Ocean (PO). PE events are linked to more frequent westerly wind bursts (WWBs) of weaker intensity and smaller timespan compared to CE cases. Strong IO warming during CE events generates easterlies in the equatorial western PO, which extend further towards the eastern PO as upwelling Kelvin waves. This upwelling Kelvin waves shoals thermocline through Ekman divergence and cools the sea surface temperature (SST) during the decay phase of El Nino. During PE cases, localized IO warming is incapable of generating significant atmospheric response in the form of easterlies and therefore frequent WWBs help in maintaining positive SST anomalies in the eastern PO.

The [OI] 557.7-nm Airglow Emission during El Niño/La Niña Extreme Events in Solar Cycles 23–24

Variations in airglow in the 555.7 nm atomic oxygen line and the ONI index of the El Nino Southern Oscillation (ENSO) phenomenon in 1997–2017 are analyzed. A correlation between these parameters is revealed. During the prolonged La Nina episode of 1999–2001, the 557.7-nm emission depression was observed, whereas in the extreme El Nino episode of 2015–2016, the 557.7-nm emission increased. A possible effect of the ENSO phenomenon on the airglow is considered. A tentative conclusion is drawn that longterm and interannual variations in the 557.7-nm emission intensity can result from the joint effect of solar activity and changes in the global atmospheric circulation.

北日本（噴火湾）におけるエルニーニョに起因すると推定される低温期に関する考察

北日本（噴火湾）におけるエルニーニョに起因すると推定される低温期に関する考察

Understanding Water Systems Resilience Problems in Tanzania

The world’s biggest devastation is currently due to disasters; their consequences range from deaths and physical damages of infrastructures to environmental, ecological and economic losses. Water systems are critical infrastructures and are recurrently affected by the impacts of disasters. In Tanzania, these events play a part in infrastructures failures; the country has experienced 266 different disasters contributing to 13,288 deaths, 57,556 injuries, and damages valued at 465.79 million USD for the period from 1900 to 2016. Water systems, in particular, are a subject of exposure to disasters, their resilience has been tested and has shown different responses. Of concern is the El Nino episodes of 1992-1993 and 1997-1998 which had significant impacts nationwide regarding economic losses, power blackout and rationing, widespread water-related diseases, infrastructure destructions and others. As such, different studies have investigated water-related issues, but little is known about their resilience to disasters. This paper uses literature to examine the problems and improvement measures of water systems resilience at a global scale and the case of Tanzania. The findings show that aging infrastructures, systems interdependency, unbalanced investment, limited community involvement, rapid population growth and urbanization, regular changes of the water ministry and others affect the resilience of water systems. On the other hand, acceleration of assets replacement, preparedness, installation of alternative power supply, community involvement, policies and plans enforcement, and balanced investment and others would improve their resilience. However, further studies are required to measure the resilience across all dimensions systematically.

Climatic constraints for the maize-soybean system in the humid subtropical region of Argentina

The implementation of two summer crops in the same growing season is a possible alternative for land intensification in areas with a long frost-free period. The aim of this study was to analyse the strategy of land intensification through the implementation of the maize-soybean succession at two locations (Reconquista, 29°09′S 59°40′W and Las Brenas, 27°05′S 61°5′W) of the humid subtropical region of Argentina. CERES-Maize and CROPGRO-Soybean models were used to evaluate the impact of inter-annual variability of climate (36 years) of both locations on rain-fed grain yields of the following productive alternatives: (i) monoculture of maize, (ii) monoculture of soybean and (iii) the succession of a short-cycle maize followed by soybean as the second summer crop (maize-soybean system). The maize-soybean system was evaluated by the method of land equivalent ratio (LER), based on the sum of the relative grain yields of its components. The impact of the inter-annual variability of climate and of “El Nino” or “La Nina” episodes (El Nino Southern Oscillation phenomenon (ENSO)) on LER values was analysed. Simulated yields of maize monoculture (5687 kg ha−1; CV = 49.7% and 5637 kg ha−1; CV = 57.6% at Reconquista and Las Brenas, respectively) were higher than those of the short-cycle maize, especially at Las Brenas (5448 kg ha−1; CV = 49.3% and 2322 kg ha−1; CV = 33.9% at Reconquista and Las Brenas, respectively). Simulated yields of the soybean monoculture were higher (3588 kg ha−1; CV = 26.1% and 2883 kg ha−1; CV = 20.7% at Reconquista and Las Brenas, respectively) that those of the soybean as the second crop (2634 kg ha−1; CV = 38.1% and 2456 kg ha−1; CV = 32.9% at Reconquista and Las Brenas, respectively) at both locations. Average LERs were 1.69 (CV = 11.4%) at Reconquista and 1.41 (CV = 26.1%) at Las Brenas, and the inter-annual variability of LER was mainly determined by grain yields of (i) soybean as the second crop at Reconquista and (ii) maize monoculture at Las Brenas. Soil water content after maize harvest and rainfalls during reproductive period of soybean as the second crop conditioned LER values, but they were generally greater than 1. At Reconquista, LER values were not affected by the different episodes of ENSO phenomenon. By contrast, at Las Brenas, LER values were higher during La Nina episodes (1.48; CV = 26.6%) than during El Nino episodes (1.32; CV = 23.7%) mainly by their effects on grain yields of maize monoculture. Therefore, crop simulation models demonstrate the possibility to intensify land use (40–70%) at two locations of the humid subtropical region of Argentina, by the implementation of the maize-soybean system.

Variable and robust East Asian monsoon rainfall response to El Niño over the past 60 years (1957–2016)

Severe flooding occurred in southern and northern China during the summer of 2016 when the 2015 super El Nino decayed to a normal condition. However, the mean precipitation during summer (June–July-August) 2016 does not show significant anomalies, suggesting that—over East Asia (EA)—seasonal mean anomalies have limited value in representing hydrological hazards. Scrutinizing season-evolving precipitation anomalies associated with 16 El Nino episodes during 1957–2016 reveals that, over EA, the spatiotemporal patterns among the four categories of El Nino events are quite variable, due to a large range of variability in the intensity and evolution of El Nino events and remarkable subseasonal migration of the rainfall anomalies. The only robust seasonal signal is the dry anomalies over central North China during the El Nino developing summer. Distinguishing strong and weak El Nino impacts is important. Only strong El Nino events can persistently enhance EA subtropical frontal precipitation from the peak season of El Nino to the ensuing summer, by stimulating intense interaction between the anomalous western Pacific anticyclone (WPAC) and underlying dipolar sea surface temperature anomalies in the Indo-Pacific warm pool, thereby maintaining the WPAC and leading to a prolonged El Nino impact on EA. A weak El Nino may also enhance the post-El Nino summer rainfall over EA, but through a different physical process: the WPAC re-emerges as a forced response to the rapid cooling in the eastern Pacific. The results suggest that the skillful prediction of rainfall over continental EA requires the accurate prediction of not only the strength and evolution of El Nino, but also the subseasonal migration of EA rainfall anomalies.