Determining rainy season onset and retreat over Nigeria from precipitation amount and number of rainy days

Odekunle, Theophilus O.

doi:10.1007/s00704-005-0166-8

Cited by 75 publications

(68 citation statements)

References 6 publications

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“…Retreat is more abrupt as it takes only 8 pentads compared to 12 for onset. This rapid retreat was also observed in neighbouring Nigeria (Ayoade, 1974;Odekunle, 2006). Earliest onset is in zone 1, south of the study domain, on the 16th pentad of the year (17th-21st March), followed by zone 2 four pentads (20 days) later, and latest onset, close to 2 months (11 pentads) after zone 1, is in the northernmost stations (Table III(a)).…”

Section: Comparative Study Of Mean Onset and Retreat Dates And Lengthsupporting

confidence: 77%

Onset, retreat and length of the rainy season over Cameroon

Guenang

Kamga

2012

Atmospheric Science Letters

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Observed precipitation from 24 stations in Cameroon during 1962-1993 were used to study onset, retreat and length of the rainy season. Results were compared to control simulations by four IPCC 4AR AOGCMs. CSIRO-mk3.5 and MPI-echam5 AOGCMs best captured onset, retreat and duration of the rainy season. Projections for 2082-2098 under the SRES A2 emission scenario were also analysed. For that period, onset dates are expected to be later by 1 pentad or more than in the current climate and retreat by less than half a pentad in zones 1 and 2. This will lead to a slight decrease in the duration of the rainy season. The situation is reverse in zone 3, where the season will be longer.

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Section: Comparative Study Of Mean Onset and Retreat Dates And Lengthsupporting

confidence: 77%

Onset, retreat and length of the rainy season over Cameroon

Guenang

Kamga

2012

Atmospheric Science Letters

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“…These methods do not help clarify the relationship between the onset of the growing and precipitation seasons, when the seasons are not entirely synchronised. Cumulative % precipitation (Ilesanmi, 1972) is the most widely used indicator of the onset and cessation of the precipitation season independent of other climatic and vegetation factors (Adejuwon et al, 1990;Adejuwon and Odekunle, 2006;Odekunle, 2006). In this method, daily % precipitation data are processed to generate 5-day means.…”

Section: Onset Cessation and Duration Of The Precipitation Seasonmentioning

confidence: 99%

Relating seasonal dynamics of enhanced vegetation index to the recycling of water in two endorheic river basins in north-west China

Matin

Bourque

2015

Hydrol. Earth Syst. Sci.

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Abstract. This study associates the dynamics of enhanced vegetation index in lowland desert oases to the recycling of water in two endorheic (hydrologically closed) river basins in Gansu Province, north-west China, along a gradient of elevation zones and land cover types. Each river basin was subdivided into four elevation zones representative of (i) oasis plains and foothills, and (ii) low-, (iii) mid-, and (iv) highmountain elevations. Comparison of monthly vegetation phenology with precipitation and snowmelt dynamics within the same basins over a 10-year period (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009) suggested that the onset of the precipitation season (cumulative % precipitation > 7-8 %) in the mountains, typically in late April to early May, was triggered by the greening of vegetation and increased production of water vapour at the base of the mountains. Seasonal evolution of in-mountain precipitation correlated fairly well with the temporal variation in oasisvegetation coverage and phenology characterised by monthly enhanced vegetation index, yielding coefficients of determination of 0.65 and 0.85 for the two basins. Convergent cross-mapping of related time series indicated bi-directional causality (feedback) between the two variables. Comparisons between same-zone monthly precipitation amounts and enhanced vegetation index provided weaker correlations. Start of the growing season in the oases was shown to coincide with favourable spring warming and discharge of meltwater from low-to mid-elevations of the Qilian Mountains (zones 1 and 2) in mid-to-late March. In terms of plant requirement for water, mid-seasonal development of oasis vegetation was seen to be controlled to a greater extent by the production of rain in the mountains. Comparison of water volumes associated with in-basin production of rainfall and snowmelt with that associated with evaporation seemed to suggest that about 90 % of the available liquid water (i.e. mostly in the form of direct rainfall and snowmelt in the mountains) was recycled locally.

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“…In Nigeria, rain falls in different months of the year at different places, as the rain belt appears to follow the relative northward and southward movements of the sun [5]. In this situation of a marked seasonal rainfall regime, variability of the onset and cessation of rain is highly significant, and its estimation and prediction are necessary [6].…”

Section: Introductionmentioning

confidence: 99%

Analysis of onset and cessation of rainfall in southwest nigeria: food security impact of of variability in the length of growing season

Sobowale¹,

Sajo²,

Ayodele³

2016

HAE

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The analysis of onset and cessation of rainfall for selected locations in South west Nigeria was carried out using daily meteorological data for five synoptic stations (Ikeja, Abeokuta, Ondo, Ibadan and Osogbo) in the region. The FAO Rainfall-Evapotranspiration model was used to elucidate the length of growing season and the impact of climate change on climatic variables and agricultural productivity. Results revealed that the wet season lasts from March to November within the period (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014). The onset and cessation dates varied across the five locations that were considered; Ibadan and Ondo had an early onset of rain while Ondo and Oshogbo had a late cessation, while other stations considered had similar onset and cessation days. The length of the growing season range from 219 -228 days within the region, this suggests the types of crops that can be supported by the rain fed cropping system predominantly practiced in the region and the number of growing cycles that can be accommodated. The study also revealed that weekly analysis of data gave better result than monthly analysis, while daily analysis did not lead to any useful results. The results are of inestimable value for the planning, organization and execution of agricultural activities in the region and in areas of similar climate around the world.

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Determining rainy season onset and retreat over Nigeria from precipitation amount and number of rainy days

Cited by 75 publications

References 6 publications

Onset, retreat and length of the rainy season over Cameroon

Onset, retreat and length of the rainy season over Cameroon

Relating seasonal dynamics of enhanced vegetation index to the recycling of water in two endorheic river basins in north-west China

Analysis of onset and cessation of rainfall in southwest nigeria: food security impact of of variability in the length of growing season

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