  Trend analysis of meteorological parameters (temperature, pressure, and
relative humidity) as well as calculated refractivity, equivalent potential
temperature (EPT) for a pseudo-adiabatic process, and field strength in
Calabar, Southern Nigeria has been analyzed using Mann-Kendall trend test and
Sens slope estimator. Data of the meteorological parameters were obtained from
the Nigerian Meteorological Agency (NiMet) in Calabar for 14 years (2005 -
2018). Results show that the maximum and average temperature, atmospheric
pressure, refractivity, EPT and field strength all exhibited a positive Kendall
Z value with 2.52, 0.33, 3.83, 0.77, 0.44 and 3.18 respectively which indicated
an increasing trend over time, with only maximum temperature, atmospheric
pressure and field strength showing a significant increase at 5% (0.05) level
of significance, since their calculated p-values (0.012, 0.0001, and 0.001)
were less than 0.05. The relative humidity and minimum ambient temperature
showed a decrease in trend over time as they both had a negative Kendall Z
values (-0.11 and -1.09 respectively), however, together with the average
ambient temperature and refractivity, their trend was not significant 5% level
of significance since their calculated p-values were all more than 0.05. Linear
regression, correlation and partial differentiation showed that relative
humidity has the most effect on the changes in seasonal refractivity and an
indirect relationship with field strength variability. The relationship between
EPT and refractivity has been discovered to be very strong and positive.
Descriptive statistics has been used to portray the seasonal and annual trend
of all parameters.
