Development Of Urban Heat Island Research Articles

Urban heat island development in medium and large urban areas in Mexico

Urban heat island development in medium and large urban areas in Mexico

Canyon geometry and the nocturnal urban heat island: Comparison of scale model and field observations

AbstractA simple hardware scale model is used to simulate nocturnal cooling rates for rural and urban environments under calm and cloudless conditions. Comparison with field observations gathered under similar conditions shows the model capable of reproducing many of the features of the temporal development of urban heat islands and the long‐wave radiative exchange in urban canyons. The model is used to investigate the roles played by rural/urban differences in geometry and thermal admittance. The results of the experiments show that canyon geometry in the central portion of a city (as measured by the sky view factor) is a relevant variable in producing nocturnal urban heat islands due to its role in regulating long‐wave radiative heat loss. It is also demonstrated that this measure is central to the relationship between city size and heat island intensity. The importance of canyon geometry as a feature of urban design is discussed. Thermal admittance differences can also produce realistic heat island features but their magnitude requires quantification in the field.

The influence of atmospheric stability and the urban heat island on urban-rural wind speed differences

Mean hourly wind speed data for several sites in and near London were examined to determine the relative effects of the seasonal and diurnal variation of atmospheric stability and the urban heat island on urban-rural wind speed differences. A “critical” wind speed exists below which urban wind speeds are faster, and above which urban speeds are slower, than rural wind speeds. When regional wind speeds are high, the frictional effect of the city surface is the dominant factor, but under conditions of light regional airflow, strong rural atmospheric stability and intense urban heat island development, the more unstable city atmosphere allows a greater flux of momentum to the surface, thus maintaining higher wind speeds within the city.

On the mean year, or the solar variation of the barometer, in the climate of London

Global warming and climate change are two indispensable phenomena that cannot be overlooked. These can be inferred to the unrelenting rise in surface temperature globally. Unplanned and speedy urbanization is one of the foremost causes of surface temperature rise as it alters the landscape. Urbanization defines the socio-economic value of city and management but if inadvertent, it can lead to serious insinuations on environmental parameters. As a result of globalization and industrialization, a sheer increase in population was observed due to migration, improved health facilities, better job opportunities and superior living standards. It is necessary to inculcate the demand of these rising urban dwellers in the form of infrastructure, energy, clean air and water. As a result of this, landscape restructuring befalls that can be understood by conversion of green or open spaces into concrete structures. This alters the surface properties causing changes in latent and sensible heat flux leading to increased surface temperature as well as ambient air temperatures. With clustered urban spaces and decrease in vegetation cover and water that acts as sinks, the temperature of urban region shoots more than nearby rural areas leading to the development of urban heat islands. These parameters are directly and indirectly related to air pollution, increased summer days, energy requirement, heat-related diseases, emission of GHGs (greenhouse gases). The communication focuses on the recent challenges and criticism faced by developing Indian cities with very minimum landscape to house burgeoning population, immediate strategies and action-plan required to tackle increasing temperatures and mitigate negative environmental impacts and effects on human beings. The study is an attempt to establish a relationship between surface temperature and land use pattern for Kolkata Metropolitan Area. Study also deals with the estimation of various temperature indices for defining and understanding the variation in surface temperature precisely. Application of these results will help in developing necessary policy measures and sustainable actions that are required to reduce anthropogenic effects on urban and natural environment.