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Will the current 'El Nino' trigger pockets of drought?
13 February 2007
In the 2005/06 marketing year some 10 million people were estimated to be vulnerable and to require humanitarian assistance in the SADC region. Given a 'satisfactory' regional food security situation in 2006/07 this figure fell to 3.1 million. The yet unknown numbers expected to require assistance in 2007/08 now seems likely to depend on a combination of systemic problems of regional poverty and underlying vulnerability and the unpredictable outcome of the developing 'mild to moderate' El Nino event forecast for the period February to June 20071.
Following on from the 10th Southern African Regional Outlook Forum statement (in September 2006), SADC Drought Monitoring Center (SADC-DMC) updated the initial seasonal outlook providing new information (in November) on the likely future rainfall and temperatures for the period December 2006 to February 2007. At that time, both the SADC-DMC seasonal outlook update2 and the SADC Food Security Update3 noted the potential hazard of the developing El Nino which is often associated with depressed rainfall in Southern Africa. These reports therefore highlighted increased chances of reduced rains in southern Angola, south western Zambia, Namibia, Botswana, western Zimbabwe, the bulk of South Africa, the western half of Swaziland, Lesotho and Madagascar. The latest (26-January-2007) SADC Agromet-update4 includes a summary of regional rainfall for 1 Sept to 20 January5 and a Water Requirement Satisfaction Index (WRSI)6 projected to end of season as at dekad 2 of January 2007 but makes no mention of the potential for drier and hotter conditions for the remaining agricultural season. However, in January 2007 both the International Research Institute (IRI)7 and the South African Weather Service (SAWS)8 have produced (January 2007) climate outlooks suggesting even higher probabilities for hotter and drier El Nino influenced conditions in the region.
Given assessed higher potential for typical (negative El Nino) effects9, and emerging evidence of pockets El Nino-like effects, we cannot be complacent. Depending upon location there is as much as 70-90 days left in the growing season. As history has shown, the effects of El Nino often only start to begin to be felt after January and (depending upon their severity) can have a nasty mid to late season impact on crops and related drought effects. We do not know whether the rains will simply switch off early in some locations and become a focus for some growing spheres of drought, or whether the rains will generally lighten over the region - but supply sufficient rain to carry most of the crops through to maturity? There is certainly the risk that areas of ‘average’ to ‘mediocre’ WRSI can be downgraded to ‘mediocre’, ‘poor’ and in some cases ‘failure’.
Given the uncertainty and the need to provide the best possible forecast information can we expect intensified monitoring to be put in place between now and June 2007? Given existing status reports and the forecasts are there already clear areas of possible drought risks and impacts emerging? If so, what are the most important likely impacts? Given what we know now, how might they be distributed and what can be done to improve links with policies and initiatives to reduce drought risk? These are questions that need to be addressed by SADC and national early warning and vulnerability assessment systems.
Footnotes:
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The inherent variability of the atmosphere (weather noise) and the lack of understanding of all of the components of the climate system require seasonal climate forecasts to be expressed probabilistically. Forecasts are made for three equi-probable categories of below-normal (dry conditions), near-normal (around the average), and above-normal (wet conditions). A probability is assigned to each category, indicating the chance of the particular category to occur during the target season. The most recent forecasts suggest that drier and hotter conditions are now more likely to occur. Source SAWS.
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http://www.nda.agric.za/docs/Cropsestimates/SADC%20Seasonal%20Outlook%20Nov%2006-Jan%2007.pdf
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http://www.sadc.int/english/fanr/food_security/Documents/fs_update/SADC%20Food%20Security%20Update%20-%20November%202006.pdf
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Food Security Early Warning System, Agromet-Updaqte 2006/2007 Agricultural Season Issue 05 Dekad 02 26-01-2007.
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“… Some areas have been consistently receiving low rainfall, while other have been receiving high amounts.”
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WRSI is a measure of the extent to which water requirement of a particular crop has been satisfied during the growing season. The USGS/FEWSNET figure appears to based on a projected to end of season position using normal rainfall data.
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http://iri.columbia.edu/climate/forecast/net_asmt/2007/jan2007/text/Africa.html
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http://www.weathersa.co.za/FcastProducts/LongRange/PDF/SeasonalForecast.pdf
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In Lesotho – the first two dekads of January witnessed dry weather conditions. … Due to high temperatures and suppressed rains, all summer crops have been experiencing water stress and this has negatively affected the development of maize and sorghum crops in most parts of the country. Crops in the western tip of Mafeteng, where it has been very dry and hot since the beginning of the current year are at risk of being permanently destroyed … and … rivers (Matabeleland - south western Zimbabwe) have not run this year and supply dams (with reference to the city of Bulawayo) are all falling rapidly, two are already dry and two have enough in them for another 4 or 5 months, leaving us with one dam for our total needs and that is unlikely to last the year unless we get late rains.
Image Credit: Manoocher Deghati/IRIN
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