Cool Harmattan Episodes in the Northwestern Region of Nigeria (1961 – 2020)

Abstract

This study examined cool harmattan episodes in the Northwestern Region of Nigeria from 1961 to 2020). Over a period of 60 years, monthly minimum temperatures of the harmattan seasons (November to February) were collected and analyzed for five (5) selected stations: Kaduna, Kano, Gusau, Katsina, and Sokoto. The study concentrated on evaluating sub-periods occurrences of cool harmattan events in the study area. Specifically, the analysis encompassed the 1961-1990 and 1991-2020 sub-periods, respectively. A Standard Anomaly Index (SAI) was employed in this study to assess cool harmattan episodes (CHEs) during the harmattan seasons. The categorization of the index was adapted from a similar study conducted in the same geographic region, which established SAI thresholds for various levels of harmattan intensity. However, that study specifically concentrated on severe cold harmattan events, whereas the present study extends the application of the SAI to examine cool harmattan episodes (CHEs). Findings revealed that stations such as Kano, Katsina and Sokoto experienced an increase in CHEs during the most recent sub-period (1991-2020) compared to the earlier sub-period (1961-1990). In contrast, stions like Kaduna and Gusau saw a decline in CHEs during the latter sub-period (1991-2020) compared to the former or first sub-period (1961-1990). The cause of the decline in CHEs in these stations (Kaduna & Gusau) may be associated with the issue of climate change. The study recommends that further research is needed to better understand the underlying factors influencing the regional differences and to inform targeted climate adaptation measures.