89th American Meteorological Society Annual Meeting

Tuesday, 13 January 2009: 9:30 AM
Observed characteristics of the urban heat island during the harmattan and monsoon in Akure, Nigeria
Room 124B (Phoenix Convention Center)
Ahmed Balogun, Univ. of Leeds, Leeds, United Kingdom; and I. A. Balogun, A. A. Abatan, and E. A. Adefisan
Poster PDF (1.7 MB)
All major reviews of urban climate research have pointed to the fact that there are few studies on the urban micro climate and urban climatology of tropical regions, and this is particularly so for sub-Saharan Africa. Many of these few studies also remain unpublished or have been published in less accessible media. This paper reports results from studies investigating the variation of air temperature across a humid tropical city, Akure in south-western Nigeria. The paper focuses on the description of temperature measurements during the harmattan (dry) and monsoon (wet) seasons of 1997. The characteristics of the urban heat island (UHI) in Akure have been assessed using a network of seven thermographs and six mercury-in-glass hygrometers during the dry and wet seasons respectively. The UHI has been found to occur throughout the day and night with the highest intensity occurring during the day, reaching 6.8C and 4.3C in the dry and wet seasons respectively. The pattern of the contours of the temperature distribution of the Akure UHI deviates from the simple idealized concentric structure around the thermal centre, mainly because of the location of the central business district (CBD), meteorological factors and local geographical features. Relatively warm regions extend over the CBD in the south and cooler regions are located in the more vegetated northeast and northwest directions. Also of interest is the influence of Ala River that tends to split the temperature distribution into two distinct heat and cool islands during the cooler parts of the day in the dry season. This pattern is less evident during the wet season. In the humid tropical climate of Akure, the UHI is detrimental, and its effect can be valuated in terms of decreased human comfort and increased costs of air conditioning and refrigeration. These setbacks can be mitigated by climate sensitive urban planning, informed by an in-depth understanding of the UHI in the city. As part of contributions to achieving this goal for Akure, this available UHI data have been reanalyzed in more detail than hitherto. Also the direction for future research to reassess the UHI in Akure will be discussed.

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