The role of teleconnections and solar activity on the discharge of tropical river systems within the Niger basin

Olusola, Adeyemi; Ogunjo, Samuel; Olusegun, Christiana

doi:10.1007/s10661-023-11073-4

Cited by 2 publications

(2 citation statements)

References 42 publications

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“…In a similar approach, the connection between large-scale oscillations revealed weak relationships using nonlinear approaches [24]. The influence of external connections, such as teleconnections and solar activity, has been explored using a nonlinear causality approach [27]. Exploring these nonlinear connections at different timescales allows for an investigation of the role of solar activity on the ionosphere-radio signal relationship.…”

Section: Introductionmentioning

confidence: 99%

Complexity and Nonlinear Dependence of Ionospheric Electron Content and Doppler Frequency Shifts in Propagating HF Radio Signals within Equatorial Regions

Akerele,

Rabiu,

Ogunjo

et al. 2024

Atmosphere

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The abundance of ions within the ionosphere makes it an important region for both long range and satellite communication systems. However, characterizing the complexity in the ionosphere within the equatorial region of Abuja, with geographic coordinates of 8.99° N and 7.39° E and a geomagnetic latitude of −1.60, and Lagos, with geographic coordinates of 3.27° E and 6.48° N and a dip latitude of −1.72°, is a challenging and daunting task due to the intrinsic and external forces involved. In this study, chaos theory was applied on data from both an HF Doppler sounding system and the Global Navigation Satellite System (GNSS) for the characterization of the ionosphere over these two tropical locations during 2020–2021 with respect to the quality of high-frequency radio signals between the two locations. Our results suggest that the ionosphere at the two locations is chaotic, with its largest Lyapunov exponent values being greater than 0 (0.011≤λ≤0.041) and its correlation dimension being in the range of 1.388≤D2≤1.775. Furthermore, it was revealed that there exists a negative correlation between the state of the ionosphere and signal quality at the two locations. Using transfer entropy, it was confirmed that the ionosphere interfered more with signals during 2020, a year of lower solar activity (sunspot number, 8.8) compared to 2021 (sunspot number, 29.6). On a monthly scale, the influence of the ionosphere on signal quality was found to be complicated. The results obtained in this study will be useful in communication systems design, modelling, and prediction.

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Section: Introductionmentioning

confidence: 99%

Complexity and Nonlinear Dependence of Ionospheric Electron Content and Doppler Frequency Shifts in Propagating HF Radio Signals within Equatorial Regions

Akerele,

Rabiu,

Ogunjo

et al. 2024

Atmosphere

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“…Rivers play a critical role in nations’ climate and socio‐economic development, especially in West Africa (Ogunjo et al ., 2022a; Olusola et al . 2023). Rivers are essential parameters of the hydrological cycle as they contribute to the total precipitable water column.…”

Section: Introductionmentioning

confidence: 99%

Multidecadal trend analysis of hydrological drought along River Niger using the Streamflow Drought Index

Ogunjo

Olusola

Durowoju

2023

Singap J Trop Geogr

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Droughts affect human well‐being and the economy of countries across the world. Understanding the long‐term evolution of droughts within a particular region will help in drought mitigation and adaptation plans, thereby reducing drought impact on the environment. This study examined the multidecadal trends in hydrological droughts at two stations along River Niger using 3‐month, 6‐month, and annual time scales. Hydrological drought events were identified using the streamflow drought index (SDI) between 1915 and 1990 based on the Theil‐Sen slope and Mann‐Kendall approaches. Across the timescales, extreme and severe droughts occurred in 1982/84 and 1983/84 with ‐2 ≤ Sd < ‐1.5. On an annual scale, the results from the annual SDI further showed that the 7th and 8th decades (1971−1990) recorded more drought events of varying degrees ranging from mild to extreme drought in both stations than in other decades. The last two decades (7th and 8th) further revealed the most extended hydrological drought duration from 1974/75 to 1988/89 for Baro and from 1979/80 to 1988/89 for Lokoja. The highest severity recorded at Baro was ‐15.56 and ‐14.26 at Lokoja. The prolonged duration of drought events across the stations and their associated yearly intensities suggests that more proactive measures are needed to ameliorate the hydrological drought impact in the study area.

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The role of teleconnections and solar activity on the discharge of tropical river systems within the Niger basin

Cited by 2 publications

References 42 publications

Complexity and Nonlinear Dependence of Ionospheric Electron Content and Doppler Frequency Shifts in Propagating HF Radio Signals within Equatorial Regions

Complexity and Nonlinear Dependence of Ionospheric Electron Content and Doppler Frequency Shifts in Propagating HF Radio Signals within Equatorial Regions

Multidecadal trend analysis of hydrological drought along River Niger using the Streamflow Drought Index

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