Changing dependence of Zimbabwean rainfall variability on ENSO and the Indian Ocean dipole/zonal mode

Manatsa, Desmond; Matarira, C. H.

doi:10.1007/s00704-009-0114-0

Cited by 15 publications

(15 citation statements)

References 30 publications

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“…However, the presence of these significant and oppositely signed but similar correlation coefficients patterns for NESOR and SESOR in the Indo‐Pacific basin seem to stress that these rainfall anomalies are not only inversely related but strongly connected to the air sea coupling. Similar correlation structures to Figure 5(a) and (b) were obtained by Behera et al (2005) and Manatsa et al (2008) and Manatsa and Matarira (2009), when they studied the connection of the ‘short rains’ and Zimbabwe summer rainfall, respectively with the SSTs in the Indo‐Pacific basin. In both cases, relatively high correlation values are found in the tropical IO, with the highest values in the western part of the basin.…”

Section: Resultssupporting

confidence: 88%

“…The threshold for El Niño (positive (p) IODZM) and La Niña (negative (n) IODZM) event is positive and negative 0.7σ, respectively. This threshold value, although not standard, has been deliberately chosen as it is the level that has been shown to trigger anomalous rainfall events over southern Africa (Manatsa et al , 2008; Manatsa and Matarira, 2009). At the same time, these event phases match closely those that are widely used as proposed by Yamagata et al (2004).…”

Section: Datamentioning

confidence: 99%

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Relative impacts of ENSO and Indian Ocean dipole/zonal mode on east SADC rainfall

Manatsa

Matarira

Mukwada

2011

Intl Journal of Climatology

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ABSTRACT:The current paper is an observational study that investigates the October to December (OND) rainfall variability over the east Southern African Development Community (SADC) mainland region in relation to El Niño-Southern Oscillation (ENSO) and the Indian Ocean dipole zonal mode (IODZM) for the period 1950-1999. An empirical orthogonal function (EOF) analysis of OND rainfall field revealed that the north-south aligned areas of the eastern SADC are located in different covariability regions. This meridionally aligned dipole rainfall anomaly configuration is captured only in the dominant principal component (PC1), making it possible for the opposing rainfall anomalies of the two regions to have a common trigger. However, ENSO which is the standard attribute for regional rainfall variability failed dismally to adequately explain this dipole rainfall anomaly pattern. Instead, there appears to be consistent evidence through statistical techniques which strongly indicates the likelihood of the participation of only the positive IODZM phase events in the creation of the positive dipole rainfall phase (i.e. simultaneous floods over the northeast and droughts over the southeast of the SADC region). Since the negative IODZM phase events can hardly be linked to the reverse rainfall pattern, it implies that the positive and negative rainfall dipoles have fundamentally different causes. Thus, contrary to convectional knowledge, the ENSO association to this dipole rainfall anomaly pattern is by no means robust and could be symptomatic of the well-known ENSO-IODZM connection. Interestingly, however, when analysed over the 31-year overlapping segments, IODZM's once significant independent influence on this dipole rainfall seems to be diminishing gradually as from the early 1990s, whereas that of ENSO is correspondingly being reinforced.

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Section: Resultssupporting

confidence: 88%

Section: Datamentioning

confidence: 99%

Relative impacts of ENSO and Indian Ocean dipole/zonal mode on east SADC rainfall

Manatsa

Matarira

Mukwada

2011

Intl Journal of Climatology

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“…Faurismith station in the southern parts has the highest CV ranging from 50% to 69%. Other studies by Manatsa and Matarira (2009) in southern Africa (Zimbabwe) also showed high seasonal variability with an average of around 26%, which is lower than the figures obtained in this study. High variability of seasonal rainfall resulting to drought conditions affects mostly the resource-poor farmers in the rural areas, and thus local municipalities have to partner with researcher institutions, nongovernmental organizations, and private companies to implement measures to help the most vulnerable communities during seasons of low harvests (Moeletsi 2010).…”

Section: Wrsi For 120-day Maize Planted In Januarycontrasting

confidence: 85%

Assessment of agricultural drought using a simple water balance model in the Free State Province of South Africa

Moeletsi

Walker

2011

Theor Appl Climatol

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Water Requirement Satisfaction Index (WRSI) at three different probability levels (20%, 50%, and 80%) was used to quantify drought affecting rain-fed maize production in the Free State Province of South Africa based on climate data from 227 weather stations. Results showed high spatial variability in the suitability of different areas: the southern and southwestern localities are unsuitable due to high drought incidences; the northern, central, and western regions are marginally suitable; the eastern, northerneastern areas and a few patches in the northwest are highly suitable with relatively low drought severity. Proper choice of maize varieties to suit conditions at different localities is crucial. The Mann-Kendall test and coefficient of variation were further used to determine trends and temporal variability, respectively, in the WRSI, seasonal rainfall, and seasonal maize water requirements. Results of this analysis revealed no significant positive trends in the WRSI, no significant negative trends in seasonal rainfall, and no significant positive trends in maize water requirements, contradicting previous findings of increased drought severity. Seasonal rainfall and the WRSI showed high interseasonal variability, while seasonal maize water requirements showed low variability. In view of these observations, it is apparent that realignment of management practices is an overdue prerequisite for sustainable maize production.

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“…One explanation is the potential influence of other atmospheric circulation processes (e.g. low pressure systems and SSTs) (Nicholson and Selato, 2000;Usman and Reason, 2004;Hansingo and Reason, 2009;Manatsa and Matarira, 2009;Hoell et al, 2014). Specific to anomalous dry and wet spells, both annual and seasonally specific, there are various patterns that are highlighted across different parts of southern Africa.…”

Section: Introductionmentioning

confidence: 99%

“…Specific to anomalous dry and wet spells, both annual and seasonally specific, there are various patterns that are highlighted across different parts of southern Africa. For example, in Zimbabwe, Manatsa and Matarira (2009) highlight the influence of the IOD+ on unusually dry periods, and conclude that ENSO might have less to do with the country's rainfall variability. However, just north during the height of the Zambian rainy season (December-January-February), Hachigonta and Reason (2006), identify the strength of importance of ENSO phases on variable dry and wet spell frequencies with less influence shown in relation to associations to Indian Ocean SST anomalies.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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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.

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Changing dependence of Zimbabwean rainfall variability on ENSO and the Indian Ocean dipole/zonal mode

Cited by 15 publications

References 30 publications

Relative impacts of ENSO and Indian Ocean dipole/zonal mode on east SADC rainfall

Relative impacts of ENSO and Indian Ocean dipole/zonal mode on east SADC rainfall

Assessment of agricultural drought using a simple water balance model in the Free State Province of South Africa

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

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