Contrasting meteorological structure of intra‐seasonal wet and dry spells in Zimbabwe

Matarira, C. H.; Jury, Mark R.

doi:10.1002/joc.3370120205

Cited by 35 publications

(19 citation statements)

References 20 publications

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“…A similar low level anomaly pattern was also found for El Niño years by Goddard & Graham (1999). These pat- 1980 1982 1984 1986 1988 1990 Northwest ( 1980 1982 1984 1986 19901992 199419982002 1980 1982 1984 1986 19901992 199419982002 Year 1980 1982 1984 1986 19901992 199419982002 Year a c d b [49][50][51][52][53][54][55][56][57][58][59][60][61][62] 2006 terns reflect the high-pressure anomaly that extends from Australia during the El Niño mature phase (Kiladis & Mo 1998, Reason et al 2000 and suggest that the ascending branch of the Walker circulation is shifted offshore, consistent with the warm SST anomalies that develop in the tropical SW Indian Ocean (not shown). The velocity potential anomalies for DJF (Fig.…”

supporting

confidence: 76%

Interannual variability in dry and wet spell characteristics over Zambia

Hachigonta¹,

Reason²

2006

Clim. Res.

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We studied the variability of dry and wet spell frequency over Zambia during the core of the rainy season (December to February, DJF), and associated circulation anomalies. Zambia's large rural population depends critically on rain-fed agriculture; in general, the southern part of Zambia is prone to a high number of dry spells during DJF, and to wet spells of short duration, while the northern regions of the country more typically have a large number of wet spells during DJF, which can lead to flooding. Good rainfall over southern Zambia is typically associated with low level convergence of moisture emanating from the tropical southeast Atlantic Ocean and the tropical western Indian Ocean. During seasons with increased numbers of dry spells over Zambia, low level easterly anomalies typically exist over Zambia, thereby reducing moisture from the tropical southeast Atlantic. Seasons with reduced dry spell frequency and more wet spells tend to be characterised by low level westerly anomalies over southern Angola and western Zambia. Furthermore, DJF seasons occurring during the mature phase of El Niño (La Niña) events tend to show above (below) average dry spell frequency. All El Niño seasons during the period of study showed reduced frequency of wet spells over Zambia, but not all La Niña events were associated with above average wet spell frequency. In fact, wet spell frequency over Zambia during several neutral seasons was greater than that observed during some La Niña events. A relatively strong relationship between anomalies in dry spell frequency and Niño 3.4 sea surface temperature (SST) was found. Relationships with Indian Ocean SST anomalies were also explored, but these were weaker than those found for Niño 3.4 SST. KEY WORDS: Dry spell frequency · Zambia · ENSO · Interannual variability Resale or republication not permitted without written consent of the publisherClim Res 32: [49][50][51][52][53][54][55][56][57][58][59][60][61][62] 2006 mer rainy seasons over each southern African country (such as Zambia) are issued based on the outputs from SST(sea surface temperature)-regional rainfall regression models and General Circulation Model (GCM) products obtained from the South African Weather Service, the UK Meteorological Office, the European Centre for Medium-Range Weather Forecasts and the International Research Institute. However, the need by user groups for information about onset dates and dry/wet spells needs to be specifically addressed, particularly for regions depending on predominantly rain-fed subsistence agriculture such as Zambia. Thus, Zambia and the southern African region urgently need more tailor-made applications-oriented seasonal forecasts (e.g. Klopper 1999, Johnston et al. 2004.However, improved forecasting relies on better understanding of the climate variability of the region and on assessing what rainy season characteristics might have some predictability. Possible relationships between large-scale climate modes or identifiable regional circulation anomalies and dry and w...

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supporting

confidence: 76%

Interannual variability in dry and wet spell characteristics over Zambia

Hachigonta¹,

Reason²

2006

Clim. Res.

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“…Many researchers support this view in relation to southern African rainfall variability (Ropelewski and Halpert, 1989;Matarira, 1990;Reason et al, 2000;Makarau and Jury, 1997;Matarira and Jury, 1992). As a result, the recent development of seasonal forecasting techniques for southern Africa tend to rely heavily on ENSO-related predictability.…”

Section: Introductionmentioning

confidence: 99%

“…ENSO remote forcing of southern African rainfall is now recognized as not always being present and that, for sustained periods in the observed record, regional forcing has been much more important (Landman and Mason, 1999;Fauchereau et al, 2003). The 1991/1992El Niño and 1967/1968 La Niña episodes illustrate this degree of non-linearity in the ENSO-related climate anomalies over southern Africa (IPCC, 1998). In the former episode, southern Africa experienced the worst drought of the century.…”

Section: Introductionmentioning

confidence: 99%

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Manatsa

Chingombe

Matarira

2008

Intl Journal of Climatology

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A comparative study of the impact of the anomalous positive Indian Ocean SST gradient, referred to as the Indian Ocean Dipole/Zonal Mode (IODZM), and El Niño-Southern Oscillation (ENSO) on Zimbabwe seasonal rainfall variability for the period 1940-1999, is documented. Composite techniques together with simple and partial correlation analyses are employed to segregate the unique association related to IODZM/ENSO with respect to the Zimbabwe seasonal rainfall.The analysis reveals that the IODZM impact on the country's summer rainfall is overwhelming as compared to that of ENSO when the two are in competition. The IODZM influence remains high (significant above 99% confidence level), even after the influence of ENSO has been removed, while that of ENSO collapses to insignificance (even at 90% confidence level) when the IODZM contribution is eliminated. The relationship between ENSO and Zimbabwe seasonal rainfall seems to be sustained through El Niño occurring in the presence of positive IODZM events. However, when the co-occurring positive IODZM and El Niño events are removed from the analysis, it is apparently clear that ENSO has little to do with the country's rainfall variability. On the other hand, positive IODZM is mostly associated with the rainfall deficits, whether or not it co-occurs with El Niño. However, the co-occurrence of the two events does not necessarily suggest that El Niño influences droughts through the positive IODZM events. The El Niño event components during co-occurrence seem to be unrelated (at least linearly) to the droughts, while the positive IODZM events display a relatively strong relationship that is significant above the 95% confidence level. It thus becomes important to extend the study of this nature to cover the whole of southern Africa, so that the extent of the impact of the phenomena can be realized over the whole region.

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“…Tyson et al, 1975;Taljaard, 1986;Walker, 1990;Lindesay and Jury, 1991;Matarira and Jury, 1992;Levey and Jury, 1996;Mason and Jury, 1997;Landman and Mason, 1999;Reason and Mulenga, 1999;Cook et al, 2004). Since many countries in the region have a large rural population and tend to rely on rain-fed agriculture, southern Africa is vulnerable to the impacts of rainfall variability, posing challenges for food security and planning (Vogel and O'Brien, 2003).…”

Section: Introductionmentioning

confidence: 99%

Interannual variability in rainy season characteristics over the Limpopo region of southern Africa

Reason

Hachigonta

Phaladi³

2005

Int. J. Climatol.

109

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This study focuses on the interannual variability of dry spell frequencies, dry and wet spell characteristics and onset dates of the austral summer rainy season over the Limpopo region (22-25°S, 27-32°E) of northern South Africa. These characteristics of the rainy season are of considerable interest to farmers, water resource managers and other user groups. The Limpopo region supports a large rural population dependent on rain-fed agriculture as well as significant biodiversity, particularly in the Kruger National/Limpopo Transfrontier Park. It is also a region prone to devastating floods and droughts. Evidence is presented that summer dry spell frequency and onset date are related to ENSO via changes in regional circulation. Niño 3.4 sea surface temperature (SST) anomalies appear to show a robust relationship with dry spell frequency during the 1979-2002 period analysed. Anomalies in onset date of the rainy season during 1979-2002 appear to be inversely related to Niño 3.4 SST, with the relationship strengthening after 1986. These results suggest that there may be some predictability in these parameters, particularly in dry spell frequency during austral summer, based on existing skill in predicting tropical Pacific SST.

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Contrasting meteorological structure of intra‐seasonal wet and dry spells in Zimbabwe

Cited by 35 publications

References 20 publications

Interannual variability in dry and wet spell characteristics over Zambia

Interannual variability in dry and wet spell characteristics over Zambia

The impact of the positive Indian Ocean dipole on Zimbabwe droughts

Interannual variability in rainy season characteristics over the Limpopo region of southern Africa

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