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<p>This study aims to analyze the trends and future projections of four seasonal rainfall characteristics including onset day (OD), cessation day (CD), seasonal length (SL), and number of rainy days (RD) in Rwanda for long rain season (LR) of March–April–May and short rain season (SR) of September–October–November–December. Those indices are relevant for climate change adaptation and mitigation in planning at all sectoral levels. Gridded daily rainfall and temperature datasets were provided by Rwanda Meteorology Agency over 1983–2021. Trends of rainfall and magnitudes along with those of computed OD, CD, SL, RD time series were determined using the Modified Mann–Kendall test and Theil-Sen’s slope estimator. Changes in future projections over 2026–2060 and 2066–2100 under RCP2.6 and RCP8.5 emission scenarios relative to the observation period 1986–2020 were assessed using the CORDEX-CORE multimodel-ensemble (CORDEX-CORE-M-M-E). Results indicate that during the observation period (1983–2021) for LR, a statistically significant rate of increase in rainfall and RD is found in the Lake Kivu climate zone, the Central Temperate Highlands climate zone, the central part of the Central Plateau climate zone. For SR, a statistically significant rate of increase in rainfall and CD is found in all climate zones. This could explain a possible dependence of the amount of rainfall on RD in LR and on CD in SR in these localities. Changes are observed in projected ODs, SLs and RDs under RCP2.6 and RCP8.5 scenarios for both 2026–2060 and 2066–2100 during LR. Patterns of changes of OD vary spatially and the magnitudes of changes to early ODs as well as the magnitudes of increases in SL and RD are higher in the RCP2.6 scenario than in the RCP8.5 scenario. During SR, no significant changes in projected OD, CD, SL and RD are observed over the country in the two periods under both RCP2.6 and RCP8.5 scenarios. Results obtained from this study will help assist farmers, policy and decision-makers in making appropriate strategies.</p>

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Observed trends and future projections of seasonal rainfall onset, cessation, length, and rainy days in Rwanda

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  • 发表日期：

    2026年6月15日

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  • Ndakize Joseph Sebaziga,
  • Bonfils Safari,
  • Didier Ntwali,
  • Joshua Ndiwa Ngaina

摘要

This study aims to analyze the trends and future projections of four seasonal rainfall characteristics including onset day (OD), cessation day (CD), seasonal length (SL), and number of rainy days (RD) in Rwanda for long rain season (LR) of March–April–May and short rain season (SR) of September–October–November–December. Those indices are relevant for climate change adaptation and mitigation in planning at all sectoral levels. Gridded daily rainfall and temperature datasets were provided by Rwanda Meteorology Agency over 1983–2021. Trends of rainfall and magnitudes along with those of computed OD, CD, SL, RD time series were determined using the Modified Mann–Kendall test and Theil-Sen’s slope estimator. Changes in future projections over 2026–2060 and 2066–2100 under RCP2.6 and RCP8.5 emission scenarios relative to the observation period 1986–2020 were assessed using the CORDEX-CORE multimodel-ensemble (CORDEX-CORE-M-M-E). Results indicate that during the observation period (1983–2021) for LR, a statistically significant rate of increase in rainfall and RD is found in the Lake Kivu climate zone, the Central Temperate Highlands climate zone, the central part of the Central Plateau climate zone. For SR, a statistically significant rate of increase in rainfall and CD is found in all climate zones. This could explain a possible dependence of the amount of rainfall on RD in LR and on CD in SR in these localities. Changes are observed in projected ODs, SLs and RDs under RCP2.6 and RCP8.5 scenarios for both 2026–2060 and 2066–2100 during LR. Patterns of changes of OD vary spatially and the magnitudes of changes to early ODs as well as the magnitudes of increases in SL and RD are higher in the RCP2.6 scenario than in the RCP8.5 scenario. During SR, no significant changes in projected OD, CD, SL and RD are observed over the country in the two periods under both RCP2.6 and RCP8.5 scenarios. Results obtained from this study will help assist farmers, policy and decision-makers in making appropriate strategies.