Rainfall variability and the influence of El Niño-Southern Oscillation in the coastal savannah agroecological zone of Ghana

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Ankrah, Johnson (Author) Other; Monteiro, Ana (Author) FLUP; Madureira, Helena (Author) FLUP

Journal

Title: Theoretical and Applied Climatology

Serial No. Art. 342 Vol. 156

ISSN: 0177-798X

Publisher: Springer Nature

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Scopus

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ProQuest

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DOI: 10.1007/s00704-025-05571-3

Abstract (EN): This study analysed rainfall variability and the influence of the El Niño-Southern Oscillation (ENSO) in the coastal savannah agroecological zone of Ghana. Daily rainfall and ENSO data from 1981 to 2021 were used. The standardized rainfall anomaly index (SRAI), cumulative departure index (CDI), individual seasonality index ( ), rainfall anomaly index (RAI), coefficient of variation (CV), one-way analysis of variance, inverse distance weighting interpolation, and the R-Instat software (version 0.70) were the methods applied. The results revealed more wet years in both the annual and major season rainfall across the zone, and the opposite is true for the minor season rainfall. More above-average rainfall was observed across the zone for the major season than the minor and annual. The mean individual seasonality index identified values between 0.66 and 0.72, indicating that rainfall distribution across the zone is seasonal. Both the major and minor season rainfall amounts and rainy days increased from the Central region to the Volta region. The CV for major season rainfall ranged from 17 to 22%, and the minor season ranged from 36 to 46%. The onset of rains for the major season was similar across the zone and occurred in the 1st week of April (day 92 of the year), while the cessation varied between the 4th week of July (day 183) and the last 4.4286 week (4 weeks and 3 days) of July (day 212). The corresponding onset for the minor season also appeared to be similar across the study location and occurred in the 1st week of September (with range from days 245 to 249, and a similar cessation, which occurred in the 1st week of November (day 306) across the zone. The length of the minor and major rainy seasons ranged from 57 to 61 days and 91 to 120 days, respectively. No significant difference in total annual rainfall was observed for the different ENSO phases. The variation in total annual rainfall explained by the different ENSO phases was small, between 1% and 12%. The La Niña phase was associated with greater mean annual rainfall and had greater influence on the major season rainfall than the other two phases. The greater rainfall variability could affect several livelihood opportunities and can be addressed by improving the irrigation systems in the zone.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 25