Temporal and spatial variations of ground surface visibility during Harmattan season in North-Eastern Nigeria

Abstract

Ground surface visibility during Harmattan season over the years has impeded road and air transportations, causing numerous infectious diseases in West African sub region. Surface degraded visibility is one of the prominent climatic parameters that define Harmattan season in the region. The presence of dust in the atmosphere brought by the North east trade winds during the Harmattan season plays a vital role in absorbing and scattering solar radiation. The degraded visibility has various effects on low temperature and relative humidity experienced during the season. The study assessed the temporal and spatial variations of surface visibility in Northeastern Nigeria during the Harmattan season with the aim of ascertaining its variability, patterns and trends in the last three decades. Descriptive statistics of mean, standard deviation, coefficient of variation, and time series analysis with ArcGIS10.3 was used in assessing the temporal and spatial variations of surface visibility from 1984–2014 in six synoptic stations of Northeastern Nigeria. The findings show that surface visibility varied both temporally and spatially over the years. The pattern of visibility in the last three decades has shown rising trends with above mean variations dominating the entire distributions in all the six synoptic stations of the study area.

Keywords

• harmattan season
• visibility
• trade wind
• inter tropical discontinuity