Analysis of Rainfall Variability, Trends, and Anomalies in Gashaka-Gumti National Park, Nigeria (2002-2022)

Khalid Ibrahim Richifa; Bala Dogo; Asmau Mukhtar Ahmed; Auwal Farouk Abdussalam; Muhammad Sambo Ahmed; Aliyu Buba

doi:10.47514/kjg.2025.07.01.001

Authors

Khalid Ibrahim Richifa Kaduna State University
Bala Dogo Kaduna State University
Asmau Mukhtar Ahmed Kaduna State University https://orcid.org/0000-0001-6034-1163
Auwal Farouk Abdussalam Kaduna State University
Muhammad Sambo Ahmed Kaduna State University https://orcid.org/0009-0005-4402-4455
Aliyu Buba Kaduna State University

DOI:

https://doi.org/10.47514/kjg.2025.07.01.001

Keywords:

Gashaka-Gumti National Park, Rainfall anomaly index, Rainfall variability, Rainfall Trend

Abstract

Rainfall variability greatly influences vegetation distribution, growth, and density. This study analysed rainfall variability, trends, and the Rainfall Anomaly Index (RAI) in Gashaka Gumti National Park from 2002 to 2022, using annual average gridded rainfall data from the Climatic Research Unit (CRU_TS 4.07). The coefficient of variation (CV) was utilised to assess the rainfall data. The study employed the Modified Mann-Kendall Trend Test to evaluate trends, and the Rainfall Anomaly Index (RAI) was used to identify rainfall anomalies within Gashaka Gumti National Park. The results, with a CV of 25%, showed a mean rainfall of 1365 mm and a standard deviation of 148 mm. The modified Mann-Kendall trend test at a 95% confidence level produced a Z score of 0.507, a Kendall’s tau coefficient of 0.048, and a P-value of 0.613, along with Sen’s Slope estimate of 1.003. These outcomes indicate that the P-value exceeds the significance level of 0.05, suggesting no statistically significant trend. The analysis further shows that the variability in annual rainfall decreases over the period from 2002 to 2022. However, this decline did not show a statistically significant trend. The Rainfall Anomaly Index (RAI) results show wet RAI in 2002 and 2003 (+3.89 and +3.33) and dry RAI in 2008 and 2009 (-4.19 and -3.27). A severe dry RAI was recorded in 2011, with an RAI of -10.66. Additionally, 2012 and 2016 experienced notably wet RAI (+4.09 and +7.24), while 2015 showed a dry RAI of -4.23. This study recommends adopting an adaptive management framework based on rainfall anomaly patterns rather than long-term averages to enhance the ecological resilience of Gashaka Gumti National Park.

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Analysis of Rainfall Variability, Trends, and Anomalies in Gashaka-Gumti National Park, Nigeria (2002-2022)

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