摘要：This study characterizes Global Navigation Satellite System amplitude scintillation over Dakar (14.75°N, 17.45°W, magnitude latitude: 5.88°N), Senegal. The data, which we arranged on daily and monthly scales, cover 14 months: September–November 2012; February–December 2013; and January–February 2014. The data were further binned into three levels of scintillation using the S4 index: weak (0.3 ≤ S4 < 0.4), moderate (0.4 ≤ S4 < 0.7), and intense (S4 ≥ 0.7), over varying elevation angles (10°, 20°, and 30°). Daily occurrences of scintillation were most frequent around 22–02 LT. On a month-by-month basis, October recorded the highest occurrences of scintillations, while June recorded the least. Furthermore, contrary to Akala et al. (2014, 2015) who earlier reported January as off season for scintillation occurrences at some sites in Africa, namely, Lagos (Central West Africa), Nairobi, and Kampala (East Africa), the current study recorded some scintillation occurrences at Dakar (far west of West Africa) in January. It therefore implies that longitudinal variations do exist in the climatology of ionospheric scintillations over Africa. Consequently, detailed understanding of the climatology and daily distributions of ionospheric scintillations over equatorial Africa, which is our key objective in this study (from the perspective of Dakar), is the basic requirement for developing robust physics-based scintillation models for the African equatorial region. Finally, we noted that the conventional adoption of high-elevation masking angles during scintillation data processing, with a view to suppressing multipath effects usually hid important ionospheric-induced scintillation data.
