TITLE:
The Influence of Local Rainy and Dry Seasons on the Diurnal Temperature Range in Nigeria
AUTHORS:
Stanley I. Echebima, Andrew A. Obafemi
KEYWORDS:
Dry Season, Rainy Season, Harmattan Period, Primary and Secondary Axes of a Graph
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.13 No.2,
April
30,
2023
ABSTRACT: This study analyzed the impact of the local dry and
rainy seasons on diurnal temperature range (DTR), for each major climatic zone
of Nigeria namely the tropical monsoon, tropical savannah and semi-arid, using
meteorological data from thirteen observation stations for the period 1981 to
2021. DTR was computed from the difference of minimum temperature from maximum
temperature and yearly and forty one years’ monthly averages of DTR and
rainfall were computed and plotted in different graphs. The overall results
from each climatic zone showed that DTR fluctuates with the seasons and there
is an inverse relationship between DTR and rainfall whereby the value of DTR
decreases as the rainy season approaches but increases as the rainy season
departs ushering in the dry season or conversely DTR increases as the dry
season approaches and decreases as the dry season departs ushering-in the rainy
season. Secondly, the average yearly patterns of rainfall and DTR are roughly
and oppositely shaped parabolas where the peak value of rainfall is
diametrically opposite to the trough value of DTR and the least or nil volume
of rainfall corresponds to the highest value of DTR. Thirdly, due to the yearly
seasonal cycle of dry and rainy seasons in Nigeria coupled with the inverse relationship
between DTR and Rainfall, the seasonal plot of DTR and rainfall is also cyclic
in pattern with DTR cycle lagging 180 degrees with the rainfall cycle and the
intersection of the two cycles represents the departure of one season and onset
of another season while each half-cycle represents either the dry or rainy
season. Fourthly, the dependence of DTR on any season at hand in Nigeria makes
DTR season-forcing. This fourth result is underpinned by a result that showed
that the 1981 and 2021 patterns of DTR and 1981 and 2021 patterns of rainfall
when compared were similar, the differences were in the volume of rainfall
which was due to climate change that has taken place over the four decades and
which also impacted DTR since DTR varies inversely with rainfall. Finally and
notwithstanding the common grounds of the results stated above, the result
further showed that each climatic zone of Nigeria reacts differently to the
local and global climate changes leading to the magnitude of DTR and the volume
of rainfall being different across climatic zones, with rainfall volume and
duration decreasing towards the arid North from the Coastal South while
contrariwise DTR increases towards the arid North from the Coastal South.