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El Niño

El Niño is certainly one of the recently quite frequently used terms, sometimes a little bit hated or at least leaving us with some uncertainty or concern. It refers to the phenomenon of temperature fluctuations of surface water masses in the Pacific Ocean, especially in its central and eastern part and all the way to the coast of South America. By definition, the change in the temperature of the surface water should be at least 0.5 degrees Celsius and as expected, it should last at least three months. In the past it occurred every two to seven years and lasted from about nine months to two years. It is usually associated with the established area of high pressure over the western Pacific (Indonesia, Australia) and with an area of low pressure over the eastern part of the Pacific Ocean.

We need to clarify that ocean currents have a decisive influence on the course of weather on Earth by channeling either hot or cold water masses. Since they are slow and long lasting, the weather behaves for a longer period like on "dictation" patterns of ocean currents. In fact, it would be better to say that a permanent ocean currents shape weather patterns around the Earth. And when it comes to random changes in the sea currents, the weather starts behaving "unusually". So, the change in water temperature in the eastern and central Pacific Ocean influences the weather events also elsewhere on Earth, at some places more, elsewhere less. Weather events on our planet are connected and if there is something in the Pacific that alters the pattern of air flow, this may affects other parts of the Earth as well.

El Niño brings warm sea water in the area west of the Pacific coast of South America. Therefore, during the time of El Niño it rains in the deserts of the west side of South America as well in North America, where there was no rain for many years. Summers in this area are usually much more wet and rainy, on the other hand in the territory of Australia or Indonesia there is a drought. As we often say, "crazy", unusual weather. By the way, a very similar but less pronounced phenomenon is being »active« also in the Atlantic.

According to measurements by NASA it seems that this year's El Niño is very similar to the one from years 1997-98, which was the strongest ever. And if you compare the current with the strongest ever, we could indicate that the Pacific could start cooling down slowly at this point.

Of course we cannot be sure about that for couple of weeks until our presumptions are confirmed by measurements. But there is still something we need to be aware of and that is the year 2015 was globally the warmest in the last 135 years. So it was not only the El Niño who has caused the warming. And even if the Pacific starts slowly cooling down, or lets say with other words - if towards South America colder water will start to flow again, the warming may be delayed due to the impact of a warmer climate and this would lead to the result that El Niño may take a little longer. However, weather patterns triggered by El Niño might retain quite likely till the end of spring or even till the beginning of the summer, eventhougt the single phenomenon of El Niño will not be active any longer at that time.

Weather conditions at the time of Matevž Lenarčič world flight will therefore probably be a little more demanding, or let say better, less predictable, as if he would be flying at the time when there was not impact of the El Niño. A result of everything written above, it would have not been any difference if we move the take off of the world flight, for example, to one month further into the spring. Either way is not possible to forecast in advance the approximate behaving of the weather. And even during the El Niño being present, with some luck we could have quite predictable conditions, or with bad luck also worst conditions than expected even without influencing of El Niño. It is all about which weather phenomenon may be more likely or less likely.

Andrej Velkavrh

El Niño

Eden od zadnje čase zelo pogosto uporabljanih izrazov, pa tudi malo osovraženih ali vsaj negotovost vzbujajočih, je gotovo El Nino. To je pojav nihanja temperature površinske vodne mase v Tihem oceanu, predvsem v njegovem osrednjem in vzhodnem delu, vse do obal Južne Amerike. Po definiciji naj bi bila sprememba v temperaturi površinske vode vsaj 0,5 stopinje C in naj bi trajala vsaj tri mesece. V preteklosti se je pojavljal vsakih dve do sedem let in trajal od okoli devet mesecev pa tudi do dveh let. Običajno je povezan z ustaljenim območjem visokega zračnega tlaka nad zahodnim Pacifikom (Indonezijo, Avstralijo) in območjem nizkega zračnega tlaka nad vzhodnim delom Tihega oceana.

Pojasniti je potrebno, da morski tokovi z usmerjanjem bodisi toplih ali pa hladnih vodnih mas odločilno vplivajo na potek vremena na Zemlji. Ker so počasni in dolgo trajajo, se vreme zato dlje časa obnaša »po nareku« vzorcev teh morskih tokov. Pravzaprav bi bilo bolje reči, da stalni morski tokovi sooblikujejo vremenske vzorce po Zemlji. In kadar pride do občasnih sprememb v morskih tokovih, se tudi vreme obnaša »neobičajno«. Tako sprememba temperature vode v vzhodnem in osrednjem delu Tihega oceana vpliva tudi na vremenska dogajanja drugod na Zemlji, ponekod bolj, drugod manj. Vremensko dogajanje na našem planetu je namreč povezano in če se na območju Pacifika spremeni vzorec zračnih tokov, to vpliva tudi na druge dele Zemlje.

El Nino prinaša toplo morsko vodo na območje zahodno od tihomorskih obal južne Amerike. Zato v času El Nina dežuje v puščavah zahodne južne, pa tudi severne Amerike, kjer sicer tudi več let ni dežja. Poletja na tem območju so takrat bolj mokra, na drugi strani, na območju Avstralije, Indonezije in še kje, pa vlada suša. Skratka »zmešano«, neobičajno vreme. Mimogrede, podoben, a manj izrazit pojav, je tudi na Atlantiku.

Po meritvah NASE izgleda, da je letošnji El Nino podoben tistemu iz let 1997-98, ki je bil najmočnejši doslej. In če ga primerjamo s tistim, bi lahko sklepali, da se bo začel Pacifik prav v tem času počasi ohlajevati. O tem seveda še nekaj tednov ne moremo biti prepričani, dokler nam te domneve ne potrdijo meritve. Je pa še nekaj, na kar moramo biti pozorni. Leto 2015 je bilo globalno najtoplejše v zadnjih 135 letih. Torej ni bil samo El Nino tisti, ki je povzročil otoplitev. In tudi če se začne Pacifik počasi spet ohlajati, oz. da bo proti Južni Ameriki spet začela dotekati hladnejša voda, se bo otoplitev lahko zavlekla zaradi vpliva toplejšega ozračja in tako bi El Nino lahko trajal nekoliko dlje. Ali drugače povedano, vremenski vzorci, ki jih je sprožil El Nino, se bodo še zadržali, dokaj verjetno tja do konca pomladi ali do začetka poletja, pa čeprav bo sam pojav El Nino že ponehal.

Vremenske razmere na letu Matevža Lenarčiča bodo zato verjetno nekoliko zahtevnejše, ali bolje, manj predvidljive, kot če bi letel v času, ko ni čutiti vpliva El Nina. A zaradi zgoraj povedanega ne bi bilo nič bolje, če bi let premaknili, recimo, za en mesec v pomlad. Tako ali tako se ne da vnaprej napovedati približnega poteka vremena. In tudi v času El Nina bi z nekaj sreče lahko imeli na poti kar predvidljive razmere, z malo smole pa seveda slabše od pričakovanih tudi brez El Nina. Gre le za to, ali je kakšen vremenski pojav verjetnejši ali manj verjeten.

Andrej Velkavrh