HYDROCLIMATIC TELECONNECTION BETWEEN METEOROLOGICAL VARIABLES AND LARGE-SCALE ATMOSPHERIC CIRCULATION PATTERNS OVER UPPER BLUE NILE, ETHIOPIA

AYNALEM, ASAYE

dc.contributor.author	AYNALEM, ASAYE
dc.date.accessioned	2021-08-07T08:05:33Z
dc.date.available	2021-08-07T08:05:33Z
dc.date.issued	2021-08-07
dc.identifier.uri	http://ir.bdu.edu.et/handle/123456789/12314
dc.description.abstract	Precipitation over the Upper Blue Nile Basin (UBNB) contributes most of the annual rainfall in Ethiopia and plays an important role in agriculture and thus the economy. In this study we applied various wavelet analysis methods to explore possible in uences of large-scale climatic patterns on monthly precipitation by taking 20 Raingauge stations across the UBNB for the last 32 years (1987-2018) and their teleconnections to three prominent climate indices namely; Ni~no4, Indian Ocean Dipole (IOD) and Indian Summer Monsoon Index (ISMI). Rainfall Anomaly Index (RAI) is calculated using precipitation data to identify the dry and wet periods. Then the temporal patterns of precipitation are detected by wavelet and global coherence. Subsequently, wavelet coherence (WTC) between precipitation and oceanic indices (ENSO, IOD, ISMI) is applied to identify the dominant driving factors causing precipitation variability. The WTC results reveals a common dominant oscillation at 8-16 months for all stations over UBNB. The results suggest that ENSO has dominant coherence at 8-16 months periodicity during 1991-1994, 19992002 and 2005-2009, whereas IOD have noticeable e ects at 4-8 months time scales. ISMI is also responsible for the variability of summer precipitation with the e ective periods of 4-6 months over the basin. Meanwhile, partial wavelet coherence analysis (PWCA) is used to investigate the standalone relationship between the climate indices and precipitation after removing the e ect of interdependency. Finally, the spatial variation of summer (June to September) precipitation during the incidence of IOD and ENSO years conclude that the co-occurring of La Ni~na and positive IOD brings excess precipitation via the modulation of monsoon rainfall while El Ni~no and negative IOD phases cause rainfall de cit over the entire basin.	en_US
dc.language.iso	en_US	en_US
dc.subject	Physics	en_US
dc.title	HYDROCLIMATIC TELECONNECTION BETWEEN METEOROLOGICAL VARIABLES AND LARGE-SCALE ATMOSPHERIC CIRCULATION PATTERNS OVER UPPER BLUE NILE, ETHIOPIA	en_US
dc.type	Thesis	en_US