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Register a new userEstimation of Radio Refractivity from a Decade Satellite Derived Meteorological Data for West Africa
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Added by
Oladiran Johnson Abimbola Dr
Publication date
2020
fields
Physics
and research's language is
English
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Radio refractivity, which is the bending of radio signal as it propagates through media, is very important in works involving terrestrial atmospheric electromagnetic propagation such as point-to-point microwave communication, terrestrial radio and television broadcast, mobile communication system, and so on. This study has focused on the West African region where it was found that the region has a refractivity which varies exponentially with height and from the coast towards the desert. Generally, refractivity gradient was found to range between -46.48 and -29.51 N-units/km (k-factor value of between 1.23 and 1.42) across the region, splitting the between sub- and super-refraction. The variation in refraction type was found to follow seasonal pattern across the West African region, with sub-refraction dominating during dry season and super-refraction dominating most part in the coastal area during the wet season.
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Drought poses a significant threat to the delicate economies in subsaharan Africa. This study investigates the influence of large scale ocean oscillation on drought in West Africa. Standardized Precipitation Index for the region was computed using monthly precipitation data from the Climate Research Unit during the period 1961 -1990. The impact of three ocean oscillation indices - Southern Ocean Index (SOI), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO) on drought over West Africa was investigated using linear correlation, co-integration test, mutual information and nonlinear synchronization methods. SOI showed predominantly positive correlation with drought over the region while PDO and NAO showed negative correlation. This was confirmed by the co-integration tests. The nonlinear test revealed more complex relationship between the indices and drought. PDO has lesser influence or contribute less to the drought in the coastal region compared to the Sahel region of West Africa.
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