[01] David Edokpa, Department of Geography and Environmental Management, Rivers State University, Port Harcourt, Nigeria. [02] Peace Nwaerema, Department of Geography and Environmental Management, University of Port Harcourt, Port Harcourt, Nigeria.

This study examined the boundary layer turbulence pattern and the heat index in the lower atmosphere of the coastal city of Port Harcourt using Richardson number (Ri) technique and temperature-humidity index equation. Six years surface data (2011-2016) from Era-Interim Platform were used for this study. The study was conducted for the period of October-December 2016 when the black soot emission from illegal petroleum crude refining was noticed across the atmospheric boundary layer of Port Harcourt. Mean turbulence within the surface layer (10-50m) height was between 0.27-0.52. This indicates a weak mechanical turbulence since all the values were greater than the Richardson critical (R_ic) value of 0.25. Generally, Ri values for the study area at the surface layer were less than 1 while Ri values at the mid layer (50-100m) were greater than 1 indicating laminar condition. The heat index analysis shows that the extreme caution and danger levels constituted about 85% which could generate heat stroke for the city dwellers especially the elderly persons. Study results revealed that the heat island during the night is enhanced within the hours 00:00-03:00 hours. The weak Ri values of mechanical origin shows that the enhanced heat island mostly experienced during the night periods will not be diluted easily and faster. This enhanced heat island is due to the positive radiation forcing of the emitted black soot, the humid atmosphere as well as the very stable atmospheric condition of Port Harcourt. These lower atmospheric factors reduce the strength of the winds in modifying the heat island. In order to mitigate the increased heat island in the city mostly at night, policy makers should ensure that anthropogenic emission releases are reduced from sources to avoid air pollutants build-up. Also, the greater Port Harcourt plan that proposes the decongestion of the city’s increasing population should be adopted to create opportunity for adequate expansion thereby reducing concentration of business hubs around the long-standing city center.

Turbulence, Heat Index, Port Harcourt, Black Soot, Richardson Number, Atmosphere

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