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According to reports and charts meteorological phenomenon El Niño is close to Iran, but the question is, El Niño phenomenon in Iran is likely to achieve? What are the consequences?

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    $\begingroup$ @Mohsen_Kh.: It would be helpful if you could post links to the reports & charts you mention in your question. $\endgroup$
    – Fred
    Nov 7, 2015 at 7:40

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A very quick and general answer, if anyone wants to get more specific, feel free:

the question is, El Niño phenomenon in Iran is likely to achieve? What are the consequences?

Iran's been through several El Nino's, so its not like this year you'll see things you've never seen before. I mean, you could. There's always a chance of record breaking weather, but have a look at El Nino's and how often they occur, here and more numerical and monthly specifics here.

If we assume this year will be a strong El Nino, then look back at weather in Iran in winter 97-98 through Summer 1998, and Winter 82-83 into 1983. Those were the 2 most recent big El Ninos.

I found this article from last month. You probably have better access to local updates than I do, but it seems that frost and flooding are the primary concerns. As Gordon Stranger points out, that's not a guarantee, only an increased chance that it happens.

El Niño is close to Iran

El Nino is in the Pacific Ocean. The El Nino effect is all over the globe, so it's, in a sense, close to everywhere on earth. Here's a kind of cool picture of the effects of the 1982-83 El Nino. Those were just the effects for that one year, and no two El Nino's will affect the globe in the same way, though they can have some similar patterns.

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Source

However, you should be afraid of the possible occurrence of El Niño in Iran?

When I first read this, I thought you were suggesting that he be afraid, but reading it again, I think what you're asking is whether you should be afraid.

El Nino probably isn't something to be afraid of cause there's no guarantee the effects will be bad where you are. It's silly to worry about a 30% increased chance of something happening - which is basically what this is.

If you live in a flood prone area try to prepare for flood. Have food and drinking water on hand, maybe sandbags to put in-front of your doorway - which might help for a smaller flood. If you're a farmer, as much as possible, try to prepare for Frost. Fear isn't helpful, but planning ahead for possible bad weather events is always a good idea.

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Although the El Nino phenomenon is primarily a Pacific Ocean phenomenon, affecting circum-Pacific countries the most, it occurs on such an enormous scale that it has knock-on affects around the world. These are difficult to generalize, but a rough idea can be gleaned from the map of global El Nino effects in such pages as: http://www.circleofblue.org/waternews/2015/world/el-nino-droughts-take-toll-in-africa-asia-and-the-pacific/ Bear in mind that there are other co-variables of ocean and atmospheric circulation that operate upon time scales varying from years to decades. These can either amplify or negate the extra-Pacific El Nino effects. Therefore the specific effects for any given year require modelling with atmosphere-Ocean-coupled global climatic models. Also consider that the outputs from all AOGCMs don't all agree, so it is necessary to consider a consensus from several outputs before drawing firm conclusions. Yet another consideration is that computer simulations do not give equal weighting to different parameters. So, as far as Iran is concerned, the modelled El Nino effects are likely to be very reliable for temperature, but wildly unreliable for rainfall. If you are concerned about rainfall in Iran my advice is to run a correlation analysis between the two variables: historic El-Nino-Southern Oscillation (ENSO) signal index (available on internet), and historic rainfall. Try this for monthly, seasonal and/or annual data. If the correlation coefficient is high, say >0.70, use this relationship to adjust the normal expected rainfall in Iran. Attach as much credence to this as to any forward projections from any AOGCM. Rainfall analysis is not what AOGCMs were designed for.

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  • $\begingroup$ However, you should be afraid of the possible occurrence of El Niño in Iran? $\endgroup$
    – Mohsen Kh.
    Nov 7, 2015 at 10:00
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In addition to the other two answers this article Relation between Rainfall and El Nino in Iran evaluates the relation between quantum of rainfall in Iran during El Nino years. The study concludes that an increase of rainfall is seen across the Iranian plateau during El Nino years and a decrease of rainfall is seen across coastal areas. On the whole El Nino years are beneficial for Iran. The author does perform a correlation study using Pearson's method and conclude a meaningful relationship does exist at the 0.01 significance level. Considering Iran's geography and arid lands this would suggest a more careful management of water resources and ensure the rainfall is harvested through watershed management.

The following study confirms the above findings On the relationship between ENSO and autumn rainfall in Iran and reports that El Nino episodes produce greater rainfall than La Nina episodes. The regions that benefited the most are the southern foothills of Alborz mountains, northwestern districts and central areas. Sources of moisture appear to be the Mediterranean Sea, Black Sea, Persian Gulf and the Red Sea. There is no evidence to suggest that the Pacific Ocean and Indian Ocean are sources of moisture.

In addition the following study Effects of El Nino Southern Oscillation on the Discharge of Kor River in Iran conclude that efforts need to be directed at flood and drought predictability.

In average, El Nino caused increased discharge by 15% at Chamriz station and 20% at Dehkadeh-Sefid station. The time of maximum impact was found in the months of February and March of the El Nino year. It can be expected that the results obtained in the present study will help to understand the variations of river discharge due to El Nino which in turn will help water managers, dam operators, and policy makers in water resources planning and management as well as flood and drought forecasting and mitigation.

In Synoptic Climatology of Precipitation in Iran authors conclude that upper level disturbances are responsible for over fifty percent of rainfall. If it is indeed the case rainfall maxima during El Nino years are experienced in February and March in Iran then these maybe due to Western Disturbances Western Disturbances. These are basically upper level systems (500 hPa and above) and the following study describes the dynamics of winter precipitation episodes over Iran as well Numerical study of western disturbances over western Himalayas using mesoscale model

Here is a recent review of Winter Western Disturbances and their multi annual variations. Multi-annual variations in winter westerly disturbance activity affecting the Himalaya. These authors confirm the same sources of moisture.

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  • $\begingroup$ I wouldn't regard a correlation coefficient of 0.01 as 'meaningful'! $\endgroup$ Nov 9, 2015 at 9:41
  • $\begingroup$ The 0.01 is the significance level - numberwatch.co.uk/significance.htm $\endgroup$
    – user1066
    Nov 9, 2015 at 9:51

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