Atmospheric Stability Pattern over Port Harcourt, Nigeria

Abstract

This study examined the atmospheric stability pattern over Port Harcourt in Nigeria from 2011-2015. Six hourly synoptic data retrieved from ECWMF Re-analysis Interim data set (Era-Interim) platform was used in the analysis. The Era-Interim platform provides a viable standard most especially for the exploration of temperature and wind speed data which are critical indicators of stability conditions. The widely and acceptably used Pasquill-Gifford stability technique was employed in assessing the stability variations. Results showed that very stable (class F) and neutral (class D) conditions occur during the early hours of dawn. While class D prevails from June to September, class F dominates from October to May. During the afternoon, slightly unstable condition (class C) exists and prevails from February to November. Stability class B was more dominant at sunset throughout the year while very unstable condition (class A) only prevails from December to January during noon time. The pattern of atmospheric stability conditions in the study area suggests that emissions will be restricted at ground level receptors during the early hours of dawn if emission sources are below inversion level. However, if the emission sources are above inversion level, dispersion will take place aloft. Emission dispersion during the day for elevated sources will not adversely affect close downwind receptors for most of the months due to the moderately unstable categories B-C dominant in the area as well as low wind speed. However, in December and January, vigorous mixing brings emissions to ground level at receptors close to emission sources due to the prevalent very unstable condition (class A) at moderate wind speed. The reverse will be the case for low level emission sources. Policy makers must ensure that pollution from industries within the study area are mitigated as well as keep potential emitters from being sited close to city areas.