Utjecaj zimskog ENSO- a na oborinu u području Indijskog oceana

master's thesis

• Title (english): Impact of winter ENSO on rainfall in the Indian Ocean
• Author: Tomislav Harambašić
• Mentor: Ivana Herceg Bulić (mentor)
• Committee member: Ivana Herceg Bulić (predsjednik povjerenstva)
• Committee member: Maja Telišman Prtenjak (član povjerenstva)
• Committee member: Ivica Sović (član povjerenstva)
• Committee member: Željko Večenaj (član povjerenstva)
• Committee member: Josip Stipčević (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geophysics); Zagreb
• Defense date and country: 2019-09-27, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geophysics; Meteorology and Climatology

Abstract

El Niño - Južna oscilacija je atmosfersko-oceanski fenomen koji se javlja u području tropskog Pacifika i snažan je generator klimatske varijabilnosti na Zemlji. U ovom diplomskom radu promatran je njegov utjecaj na Indijski ocean, s naglaskom na oborinu. Meteorološka polja simulirana su numeričkim modelom SPEEDY, a radi veće pouzdanosti rezultata napravljena je ansambl analiza. Također je provedena i analiza empirijskih ortogonalnih funkcija koja je dala bolji uvid u značajnost dobivenih rezultata povezanosti ENSO-a i oborine nad Indijskim oceanom. Analizirana su tri različita eksperimenta, svaki je rezultat ansambl analize od 35 numeričkih simulacija, a međusobno se razlikuju po duljini prinudnog djelovanja u tropskom Pacifiku. Eksperimenti su definirani tako da CTL predstavlja kontrolni eksperiment s forsiranjem na donjoj granici putem površinskih temperatura mora (SST) tijekom cijele simulacije. Eksperiment JFM ima zadano forsiranje na donjoj granici putem SST-a samo tijekom zime (od siječnja do ožujka), dok je u eksperimentu ONDJFM ono duljeg trajanja (od listopada do ožujka). Ovako definirani eksperimenti omogućili su proučavanje utjecaja duljine trajanja prinudnog djelovanja mora tijekom jako zimskih događaja ENSO-a na atmosferska zbivanja u području Indijskog oceana. Rezultati ovog rada pokazali su da utjecaj ENSO-a na oborinu u Indijskom oceanu nije jednostavna funkcija duljine prinudnog djelovanja, već je ona posljedica složenih procesa međudjelovanja atmosfere i mora. Oni uključuju izravnog djelovanja ENSO-a (putem procesa u atmosferi) te neizravnog (vremenski produljenog) djelovanja putem generiranja anomalija SST-a u Indijskom oceanu. Analiza pomoću funkcija EOF pokazala je da se određeni dio varijabilnosti oborine u području Indijskog oceana može pripisati utjecaju zimskog djelovanja ENSO-a, što je posebno izraženo u anomalijama zimske oborine.

Abstract (english)

El Niño - Southern Oscillation is an atmospheric-oceanic phenomenon that occurs in the tropical Pacific and is a powerful generator of climate variability on Earth. This graduate thesis explores its impact on the Indian Ocean, with an emphasis on precipitation. Meteorological fields were simulated using the numerical model SPEEDY, and for the sake of greater reliability of the results an ensemble analysis was made. An analysis of the empirical orthogonal functions was also performed, which gave a better insight into the significance of the obtained results of the connection between ENSO and precipitation over the Indian Ocean. Three diferent experiments were analysed, each one a result of an ensemble analysis of 35 numerical simulations differing in the forcing length in the tropical Pacific. The experiments were defined such that CTL represents a control experiment with forcing at the lower boundary via surface sea temperatures (SST) throughout the simulation. The JFM experiment has the same forcing at the lower boundary via the SST, but only during the winter (January to March), whereas in the ONDJFM experiment it has a longer duration (from October to March). The experiments thus defined have made it possible to study the effect of the length of the SST forcing during winter ENSO events on atmospheric events in the Indian Ocean. The results of this paper shown that the impact ENSO has on the precipitation in the Indian Ocean is not a simple function of the forcing length, but rather is a consequence of the complex processes of the interaction between the atmosphere and the sea. These include the direct ffect of the ENSO (via atmospheric processes) and the indirect (time-lengthened) ffect by generating SST anomalies in the Indian Ocean. Analysis using EOF showed that some of the variability of precipitation in the Indian Ocean area can be attributed to the impact of winter ENSO activity, which is especially pronounced in winter precipitation anomalies.

• Keywords: ENSO; oborina nad Indijskim oceanom
• Keywords (english): ENSO; precipitation over the Indian Ocean
• Language: croatian
• URN:NBN: urn:nbn:hr:217:391680
• Study programme: Title: Graduate university study pf Physics - Geophysics; specializations in: Seismology and Physics of the Earth's Interior, Meteorology and Physical Oceanography; Course: Meteorology and Physical Oceanography; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra fizike – geofizike (magistar/magistra fizike – geofizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-10-02 13:49:56