Role of antropogenic and natural drivers in estimation of urban heat island

Abstract

Thermal anomalies in cities (urban heat island) caused by man-made processes should be distinguished from natural microclimatic heterogeneities in the temperature field. Significant spatial variability in the thermal characteristics occurs even in flat terrain with small changes in elevation. It develops due to unequal conditions for the drainage and accumulation of cold air in different forms of relief or between areas with different properties of the underlying surface. Natural microclimatic temperature variations cannot be ignored in studies of the technogenic impact on the thermal regime of terrain as they are comparable and even exceed the values of urban heat island intensities of world largest cities and megacities. For example, many West Siberian cities were built on the uplands to avoid the risk of flooding and construction on water-saturated soils. These places were originally warmer than surrounding wetlands because cold air drainage and drier soil. Anthropogenic activity increased the temperature contrast that existed earlier. The urban heat island intensity would be unjustifiably overstated if positive temperature anomaly in cities were considered having solely anthropogenic origin. Correct estimation of the urban heat intensity can only be obtained through temperature comparison in urban and rural areas under similar microclimatic conditions.