The onset and cessation of the “long rains” in eastern Africa and their interannual variability

Camberlin, Pierre; Okoola, Raphael E.

doi:10.1007/s00704-002-0721-5

Cited by 150 publications

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“…While naming the seasons may be confusing, the period known as the short rains generally receives more rain and is known to be more reliable than the period known as the long rains (Camberlin and Okoola, 2003; Rao and Okwach, 2005; Karanja, 2006). Consequently, the season of short rains is more important for agricultural activities in the area.…”

Section: Discussionmentioning

confidence: 99%

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

et al. 2017

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Climate variability is the major risk to agricultural production in semi-arid agroecosystems and the key challenge to sustain farm livelihoods for the 500 million people who inhabit these areas worldwide. Short-season grain legumes have great potential to address this challenge and help to design more resilient and productive farming systems. However, grain legumes display a great diversity and differ widely in growth, development, and resource use efficiency. Three contrasting short season grain legumes common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet] were selected to assess their agricultural potential with respect to climate variability and change along the Machakos-Makueni transect in semi-arid Eastern Kenya. This was undertaken using measured data [a water response trial conducted during 2012/13 and 2013/14 in Machakos, Kenya] and simulated data using the Agricultural Production System sIMulator (APSIM). The APSIM crop model was calibrated and validated to simulate growth and development of short-season grain legumes in semi-arid environments. Water use efficiency (WUE) was used as indicator to quantify the production potential. The major traits of adaptation include early flowering and pod and seed set before the onset of terminal drought. Early phenology together with adapted canopy architecture allowed more optimal water use and greater partitioning of dry matter into seed (higher harvest index). While common bean followed a comparatively conservative strategy of minimizing water loss through crop transpiration, the very short development time and compact growth habit limited grain yield to rarely exceed 1,000 kg ha−1. An advantage of this strategy was relatively stable yields independent of in-crop rainfall or season length across the Machakos-Makueni transect. The growth habit of cowpea in contrast minimized water loss through soil evaporation with rapid ground cover and dry matter production, reaching very high grain yields at high potential sites (3,000 kg ha−1) but being highly susceptible to in-season drought. Lablab seemed to be best adapted to dry environments. Its canopy architecture appeared to be best in compromising between the investment in biomass as a prerequisite to accumulate grain yield by minimizing water loss through soil evaporation and crop transpiration. This lead to grain yields of up to 2,000 kg ha−1 at high potential sites and >1,000 kg ha−1 at low potential sites. The variance of observed and simulated WUE was high and no clear dependency on total rainfall alone was observed for all three short-season grain legumes, highlighting that pattern of water use is also important in determining final WUEbiomass and WUEgrain. Mean WUEgrain was lowest for cowpea (1.5–3.5 kggrain ha−1 mm−1) and highest for lablab (5–7 kggrain ha−1 mm−1) reflecting the high susceptibility to drought of cowpea and the good adaptation to dry environments of lablab. Results highlight that, based on specific morphological, phonological, and phys...

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Section: Discussionmentioning

confidence: 99%

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

et al. 2017

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“…Equatorial rainfall region variability in the three rainy seasons (e.g. Camberlin and Okoola, 2003;Hastenrath et al, 2010;Diro et al, 2011;Omondi et al, 2012Omondi et al, , 2013Williams et al, 2012;Manatsa et al, 2014). At least part of the correlation between the summer and equatorial rainfall regions can be accounted for the fact that there is a strong correlation between the JAS season and the OND season (0.79 for the summer rainfall region and 0.66 for the equatorial rainfall region).…”

Section: Summer Rainfall Regionmentioning

confidence: 99%

An analysis of recent rainfall conditions in eastern Africa

Nicholson

2015

Int. J. Climatol.

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This article examines recent rainfall conditions in two sectors of eastern Africa, the summer rainfall region and the equatorial rainfall region with rainy seasons in the boreal spring and boreal autumn. The analysis covers the years 1998–2014 and is carried out using TRMM 3B43 Version 7 rainfall estimates. In both regions, extensive periods of anomalously low rainfall and prolonged drought have prevailed since roughly 2008. Prior to that time, only three periods of drought are noteworthy 1998/1999, 2000, and 2005. The post‐2008 drought conditions were interrupted by floods in both regions in February 2010 and in several years in the equatorial region. This rapid alternation between extremes creates additional hardships on the population. Two notable results emerge from this analysis. One is the tendency for similar trends in interannual variability in both regions, despite vastly different rainfall regimes. The other is the persistence of recent droughts through several rainy seasons. The implication of these results is that one or more factors in interannual variability is operative in all seasons. This could account for the common trends in the equatorial and summer rainfall regions.

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“…While the East African short rains (the terms "short rains" and "long rains" are used to broadly describe a typically bimodal rainfall season across East Africa; the seasonal cycle of rainfall has notable regional variations and differing terms to describe them) have been studied extensively, exhibiting a robust relationship with El Niño-Southern Oscillation (ENSO) on the seasonal to interannual time scale [Mason and Goddard, 2001], climate scientists have focused considerably less attention on the long rains season. Attempts to link interannual variability of the long rains to large scale climate patterns such as ENSO and tropical Atlantic or Indian Ocean sea surface temperatures (SSTs) have met with limited success [Camberlin and Philippon, 2002;Indeje et al, 2000] or revealed relationships that only apply to the early, or late, stages of the season [Camberlin and Philippon, 2002;Camberlin and Okoola, 2003]. On longer timescales, total precipitation received during the long rains season has been reported to be in decline in recent decades [e.g., Williams and Funk, 2011].…”

Section: Introductionmentioning

confidence: 99%

A recent and abrupt decline in the East African long rains

Lyon¹,

DeWitt²

2012

Geophysical Research Letters

371

308

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The successive failure of the East African short rains (typically October‐December) and subsequent long rains (March‐May) in 2010–11 plunged much of the region into severe drought, impacting millions of people and triggering a humanitarian crisis. While poor short rains in 2010 were generally anticipated given linkages with La Niña, the subsequent long rains do not exhibit similar predictability. Here we show the long rains failure in boreal spring of 2011 is consistent with a recurrent large‐scale precipitation pattern that followed their abrupt decline around 1999. Using observations and climate model simulations, we show the abrupt decline in long rains precipitation is linked to similarly abrupt changes in sea surface temperatures, predominately in the tropical Pacific basin.

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The onset and cessation of the “long rains” in eastern Africa and their interannual variability

Cited by 150 publications

References 0 publications

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

An analysis of recent rainfall conditions in eastern Africa

A recent and abrupt decline in the East African long rains

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