Inter- and Intra-annual precipitation variability and associated relationships to ENSO and the IOD in southern Africa

Abstract

Precipitation variability at inter-and intra-annual scales may influence land-use management decisions in semi-arid savannas worldwide, and in particular, over the Kavango-Zambezi Transfrontier Conservation Area (KAZA) in southern Africa. Over KAZA, spatiotemporal precipitation variability forced by the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) is important to local and regional-scale decisions for planting, livestock grazing, and wildlife migration patterns. We investigate the annual water year (October-September) and early rainy season [October-November-December (OND)] precipitation patterns during 60 years before and after a 1970s shift in the global ocean-atmosphere system for this region in southern Africa.The coincidence of the number of wet (upper tercile) and dry (lower tercile) years and OND seasons during the various phases of ENSO and IOD are compared prior to (1950-1975) and after (1980-2008 the 1970s climate shift over KAZA. Since the 1970s climate shift, KAZA has been significantly drier and observed fewer wet years and OND seasons. ENSO is the dominant forcing of precipitation differences over southern Africa before and after the 1970s climate shift, with IOD playing a secondary role. However, when ENSO and IOD phases are analysed simultaneously, El Niño and positive IOD events are significantly related to dry periods.The forcing of atmospheric circulation over southern Africa before and after the 1970s climate shift during El Niño and La Niña events is significantly different. Prior to the 1970s climate shift, atmospheric circulation during El Niño (La Niña) favoured strong (weak) precipitation increases (decreases). Afterward the 1970s climate shift, atmospheric circulation during La Niña (El Niño) favoured strong (weak) precipitation decreases (increases). The shifting nature of climate modes, especially ENSO, and respective influence on rainfall variability for southern Africa is important to understand to better inform seasonal climate forecasts to improve operational decision-making for land-use and water management decisions in semi-arid savanna regions.

Interannual Hydroclimatic Variability of the Lake Mweru Basin, Zambia

“…However only seven of the 67 stations returned significant correlations between annual precipitation and the MEI. This weak, spatially patchy, negative association matches that identified for early season (Oct, Nov, Dec) precipitation [34] and may arise from the basin's position between two established poles of association with ENSO [20,24,34]. Significant associations between OND precipitation and the DMI occurred mainly in the northeastern part of the basin [34].…”

“…The nature and strength of the linkage between ENSO and East African precipitation undergoes interdecadal change governed by atmosphere-ocean exchanges over the Indian Ocean [21][22][23][24][25][26][27]. The Indian Ocean Dipole (IOD) and the Southern Indian Ocean Dipole (SIOD) have been proposed to represent these interactions [24,[28][29][30][31][32][33][34].…”

Análise Da Tendência Temporal Da Precipitação Pluviométrica Interanual E Intra-Anual No Semiárido Pernambucano

“…Evidências científicas de que a mudança global prevê um cenário de aumento nos eventos climáticos extremos acrescentou à análise espacial da precipitação uma importância ainda maior devido à necessidade de compreender a grande variabilidade da precipitação regional intra e interanual (GAUGHAN et al, 2016).…”

“…Trabalhos como o de Gaughan et al (2016) sobre a variação de precipitação nas escalas inter e intra-anuais em savanas semiáridas alertam para a relação entre as variações atípicas do clima e sua relação com fenômenos como a Oscilação Sul de El Niño (ENOS) e o Dipolo do Oceano Índico (IOD).…”

A Smart Irrigation Tool to Determine the Effects of ENSO on Water Requirements for Tomato Production in Mozambique

“…Since growers cannot modify the weather conditions by modifying the microenvironment (e.g., cultivation under high tunnels) to avoid its variability, they have to understand how the variability occurs to benefit from it and to minimize its negative effects [9]. The El Niño-Southern Oscillation is the main phenomenon influencing climate variability around the world [9][10][11][12][13] and in Mozambique [3,14,15]. In Mozambique, the warm phase of ENSO (El Niño) is related to drier and warmer conditions in most parts of the country from December to May, while the cold phase of ENSO (La Niña) has the opposite effects during the same period [16].…”