Review of urban climate research in (sub)tropical regions

Over the last 50 years the developing world, much of which is located in (sub)tropical regions, has seen a dramatic growth of its urban population associated with serious degradation of environmental quality. The total number of (sub)tropical urban climate studies, however; is still small (<20% of all urban climate studies). The available work is further biased towards descriptive studies rather than process work that seeks to indicate the physical climatology of (sub)tropical cities. The available results allow for a preliminary comparison with data from temperate latitudes. Urban heat island (UHI) intensities are generally lower compared to those of temperate cities with comparable population and show a seasonal variation with lower (higher) intensities during the wet (dry) season. (Sub)tropical population-based relations may exist but insufficient appropriate data is available to confirm a logarithmic relationship or systematic differences between different climate types. The (sub)tropical energy balance studies are biased towards dry, clear sky conditions. The amount of net radiation dissipated by sensible heat during daytime is about 40% which is similar to values observed in (sub)urban areas of cities located in temperate climates. Energy partitioning is modulated by water availability and higher percentage of vegetation promotes latent heat flux at the expense of surface heat storage. The apparent strong influence of vegetation and water availability on the energy partitioning irrespective of the climate type, suggests vegetation to be an effective means to reduce heat. storage uptake during daytime and hence has the potential to effectively mitigate the nocturnal heat island. It is important to ensure that the rapidly expanding cities of the developing world incorporate climatological concerns in their design to provide a better living and working environment for a large segment of the world's inhabitants. Copyright (c) 2007 Royal Meteorological Society.