In this research we have studied the roles and effects of ENSO atmospheric and oceanic phenomenon on seasonal rainfall fluctuations using multivariate ENSO index (MEI) in Eastern Azerbaijan Province. The results of applying Pearson analysis indicate positive correlation between MEI and precipitation in the stations under study, and among the seasons, the fall season has been showing significant correlation while in other seasons it was not the case. This is an indicative of the increase of autumn precipitation during the occurrence of El Niño (positive and warm phase in ENSO phenomenon), and on the contrary the precipitation reduction during the La Niña phase (cold and negative phase). Among the stations the maximum correlation of autumn precipitation with the MEI exists in Sarab Station and its minimum is in Tasooj Station. The calculated correlation coefficient rates between precipitation and MEI specify the effects of latitude on the amount of affectation from ENSO, implying that in Eastern Azerbaijan the correlation rates increase from east to the west and from north to south, the maximum of which can be seen in Sarab Station.

The various atmospheric circulation patterns are caused the different conditions of weather; for example, the ftequency changes of occurrence of atmospheric circulation patterns weather types are caused the precipitation patterns variations, therefore, studies on weather types can used as a criterion for analysis of precipitation patterns variations. Precipitation variability is one of the important factors which control natural and economical systems. This effect is more significant in arid and semi-arid regions such as Iran. This paper, studied relation between circulation patterns and ENSO index. In order to classification of circulation patterns, the data of 500hpa geopotential height and sea level pressure were taken from NCEP data center at the statistical period of 1961-2003. For classification of daily weather types, it is used principle component analysis and clustering method. Finally, 8 weather types were recognized for Iran on winter season time. In order to recognition of relation between frequency of various weather types and warm and cold phases of ENSO, the monthly data provided from NCEP and then frequency of weather types were calculated in warm, cold, and neutral phases. Conclusions reveal that Mediterranean low-pressure, South polar low-pressure, Eastern high-pressure, Northern high-pressure and Eastern European high-pressure and also joining Siberian high-pressure with the European high-pressure in the El Nino phase have more frequencies, Whereas occurrence frequencies of the Siberian high –pressure and central high-pressure systems are more at the La Nina periods.

The effect of the El Southern - o n ~ Ni Oscillation (ENSO) phenomenon on winter rainfall in Iran was explored for the period 1951-1995. The interactions between this phenomenon, aloft wind in Tehran and the rainfall were also investigated. Positive and significant (at 1% level) correlations between the Troup Southern Oscillation Index (SOI) and February rainfall data were found for Bandaranzali and Noushahr located over the western half portion of the Caspian sea coastal strip. In February, the aloft wind velocity was observed in association with SOI. It was found that, in January, an increase (decrease) in wind velocity (500 to 200 hPa levels), generally, corresponds with less (more) than usual rainfall over the eastern half of the Caspian sea shores. The velocity data (in February) are also exhibited a meaningful relationship with the corresponding rainfall in various parts of the country. On a seasonal scale, winter rainfall in Iran tends to be slightly more (less) than normal for the episodes that SOI is positive (negative). Compared to the warm ENSO phase, the SOI-rainfall relationships were found to be stronger during cold periods. For most parts of the country, more (less) than usual winter rainfall has occurred during intense La a n ~ Ni (El o n ~ Ni ) events. Exceptional spells in which contrary effects of the ENSO events were observed were also identified.

IntroductionENSO is one of the most important teleconnection patterns in the southern Hemisphere, affecting the worldwide climate. This phenomenon happens with the appearance of a warm water current in the central and eastern tropical Pacific Ocean. walker first demonstrated in 1924 that air pressure between the eastern and western regions of the Pacific Ocean oscillates like a seesaw., El Nino is more than a sudden warm water current along the coast of Peru. Because it is able to increase the temperature of a vast realm of the tropical pacific and can change wind direction and ocean current. As a result, clematises don't consider El Nino a single phenomenon, the southern oscillation Index (SIO)Is used to indicate the status of southern Oscillations, representing the strength or weakness of the walker circulation. this index is calculated by measuring the pressure difference between Darwin, Australia and Tahiti in the eastern Pacific Ocean. MethodologyDogonbadan located in Kukillueh, we used average temperature and precipitation for 1985-2006, And the numerical data of ENSO index.  to evaluate the impact of El Nino on the climate of Dogonbadan, the warm (EL Nino) and cold (La Nino) periods of ENSO index were first identified using the numerical values. Subsequently, the effect of the El Niño event on the temperature and precipitation was studied by comparing the numerical values of the ENSO index with the temperature and precipitation data, and the results were analyzed graphically. Furthermore, the correlation between the Southern Oscillation Index and the temperature and precipitation was calculated and analyzed using Pearson's correlation coefficient. Resultsit can be observed that the ENSO index experienced significant fluctuations on a monthly scale., La Niña occurred in the years 1988, 1989, 1996, 1999, 2000, 2001, and 2006, while El Niño occurred in the years 1987, 1992, 1993, 1994, 1997, 1998, 2002, 2003, and 2005In some years, the Southern Oscillation Index was in a neutral state, and despite considerable fluctuations throughout a year, it cannot be considered as an occurrence of El Niño or La Niña, such as in the years 1985 and 1986.On an annual scale, the occurrence of the El Niño does not affect the increase or decrease of temperature. because in some years of El Niño occurrence, the temperature has a decreasing trend, while in other years it has an increasing trend. a comparison between the ENSO and the average monthly temperature, through calculating the Pearson correlation coefficient, does not show a significant relationship., it can also be said that on a monthly scale, the occurrence of the El Niño phenomenon does not have a significant effect on the temperature. Regarding the impact of El Niño on precipitation there is a significant relationship between the annual value of the Southern Oscillation Index and the total annual precipitation., there is a linear trend of increasing precipitation, which often coincides with the occurrence of El Niño, while a decrease in precipitation is seen during the occurrence of La Niña. The calculation of the Pearson correlation coefficient between the annual value of the ENSO index and the total annual rainfall reveals the influence of precipitation from the occurrence of the ENSO phenomenon. The inverse relationship between these two indicates a relative increase in precipitation during El Niño and a decrease La Niña DiscussionThe occurrence of ENSO can influence the climate of various regions of the globe by affecting Rossby waves, monsoon systems, ocean currents, and wind patterns.Considering the climatic situation of Iran and its location in the world's desert belt, which faces a lack of precipitation in most areas, along with the negative effects that periods of drought and excessive rainfall have on the country's water resources and consequently their direct impact on agricultural production and people's livelihoods, examining the effects of ENSO on the climate of the country seems important. Given this significance, this research analyzed the effects of this phenomenon on the climate ConclusionThe results indicated that on an annual scale, the linear trend of temperature has been decreasing; however, no significant correlation with El Niño and La Niña events was found. On a monthly scale, a comparison between the ENSO index and average monthly temperature through Pearson correlation coefficient calculation did not show a significant relationship between these two variables. Therefore, the influence of El Niño events on the temperature city is very minimal. Unlike temperature, the impact of El Niño on precipitation showed a linear increasing trend, generally with an increase in precipitation coinciding with the occurrence of El Niño and a decrease during La Niña events. There is a good correlation between the annual ENSO index and the total annual precipitation at the Dogonbedan station, indicating the influence of precipitation from the occurrence of the ENSO phenomenon. Based on research conducted by other researchers, the effect of ENSO on climatic elements, especially temperature and precipitation in the country, has been somewhat different.

An investigation was conducted to detect the change-point years in the Southern Oscillation Index (SOI) and precipitation time series in Iran for the period 1951-1999 (49 years). Due to the unavailability of data, the record length of the precipitation time series was not consistent for all stations, varying from 34 to 49 years. The Pettitt-Mann-Whitney and Mann- Whitney-Wilcoxon tests were applied to determine the significance of the detected changes. The difference in SOI and precipitation amounts for the period before and after the change years was investigated. The coincidence of change-point years in the SOI time series and precipitation data was explored to evaluate the possible forcing effects of the El Nino-Southern Oscillation (ENSO) phenomenon on the suppression or enhancement of Iran’s hydrological cycle. The results indicated that the mid 1970s are the most probable change-point years in the time series of Southern Oscillation Index (SOI) data. The frequency and intensity of El Nino events have increased since then. Consistent with this finding, precipitation data from both south-western and northern parts of Iran have also shown significant change years in or around the mid 1970s. Compared to the period before 1975, annual precipitation over most of the studied regions has increased. This increase was found to be more considerable in southern rather than northern districts. Seasonal precipitation amounts in southern regions have generally increased during autumn and winter and decreased in spring. On the other hand, for northern regions, precipitation has increased during summer and autumn and decreased throughout winter and spring. The most enhanced portions of the hydrological cycle in the southern and northern regions were centred on March and May, respectively.

Background and Objective: Malaria is a disease affecting 300–500 million people in tropical and subtropical regions and causes approximately 2.7 million deaths annually. Currently, no vaccine protects against malaria and resistance to anti-malaria drugs such as chloroquine is increasing and spreading geographically. Moreover, anti-malarial drugs are expensive and often unaffordable to low-income populations. A better understanding of the relationship between the El Nino Southern Oscillation (ENSO), the climatic anomalies it engenders, and malaria epidemic could help mitigate the world-wide increase in incidence of this mosquito transmitted disease. There is evidence of a relationship between climate variability and the transmission of mosquito-transmitted diseases. Therefore, in this study we intended to analyze the relationship between ENSO events and annual malaria occurrence (AMO) in Iran to assess the possibility of using ENSO forecasts for improving malaria control.Martials and Methods: Two types of data were used: The data of annual malaria incidence in Iran were collected from the national and international reports of malaria occurrence in Iran; the annual malaria occurrence data for 38 years (1974- 2013) were collected from related sources. ENSO is a cyclic phenomenon, which its frequency is 2 to 7 years (i.e., irregular) and is the second strongest natural driver of climate variability, the first being normal seasonal variability. This oscillation has two different phases: a warm episode known as El Nino; and a cold episode called La Niña, where warm and cold refer to the direction of departure from average of the equatorial Pacific Sea surface temperature (SST), a fundamental indicator of the ENSO state. The Pearson correlation analysis at 0.95 confident level (P-value=0.05) on monthly timescale was used in order to understand the relationship between ENSO and annual malaria occurrence in Iran. The 2-tailed independent parametric T-test was used knowing that whether there is a significant difference between the La Nina years occurrence and El Nino years occurrence.Results: The results indicated that a slight negative association could be detected between ENSO and annual Malaria occurrence in Iran. Our finding showed that the detected correlation between monthly ENSO and annual malaria occurrence is statistically significant only in months October and May while no significant relationship between ENSO and AMO at 0.95 confident level was found for other months.. The inverse relationship between ENSO and AMO means that the years having higher malaria occurrence coincides with the warm ENSO phases or EL Nino episode while the years having lower malaria occurrence coincides with the cool ENSO phases or La Nina episode. In El Nino episode, the annual occurrence of malaria is about 0.2 to 0.3 higher than La Niña episode years.Conclusion: The positive association between El Nino and rainfall of Iran resulted in higher occurrence of malaria by proliferation of Anopheles mosquito especially in southern and southeastern region of Iran.