Abstract
The local temperature is one of the major climatic elements to record the changes in the atmospheric environment brought about by industrialization, increasing population and massive urbanization. The present study deals with the annual and seasonal temperature trends and anomalies for maximum, minimum and mean temperatures of the four meteorological stations of the National Capital Region (NCR) of India namely Safdarjung, Palam, Gurgaon and Rohtak for the past few decades and their association with the development through urbanization processes. The annual mean maximum temperature did not show any specific trend; however a consistent increasing trend was seen in the annual mean minimum temperatures indicating an overall warming trend over the NCR especially after 1990. This warming trend is contrary to the cooling trend observed by earlier studies till 1980’s in various other cities of India including Delhi. However, the temperature trends in annual mean minimum temperatures reported in various countries (USA, Turkey, Italy, etc.) across the world showed warming trends to be associated to the urbanization process of the cities also. The current warming trends in temperature in the NCR Delhi based on the annual mean minimum temperatures have thus been supported by the trends in other parts of the world and could be utilized to infer the development process in this region. The urbanization pattern within Delhi is reflected by the trends of differences in annual mean minimum temperature of the two stations within the city namely Safdarjung and Palam. The significance of the warming trends of the annual minimum temperature for the urban heat island effect is also discussed.
Highlights
Urban Heat Island (UHI) is considered as one of the major problems in the 21st century posed to human beings as a result of industrialization and urbanization [1]
The temperature trends in annual mean minimum temperatures reported in various countries (USA, Turkey, Italy, etc.) across the world showed warming trends to be associated to the urbanization process of the cities
The current warming trends in temperature in the National Capital Region (NCR) Delhi based on the annual mean minimum temperatures have been supported by the trends in other parts of the world and could be utilized to infer the development process in this region
Summary
Urban Heat Island (UHI) is considered as one of the major problems in the 21st century posed to human beings as a result of industrialization and urbanization [1]. Industrialization and urbanization improves our material lives and comfort; many problems are induced by these processes such as urban heat islands, global warming, air pollution, etc. It is believed that air pollutants, in particular aerosols, can absorb and re- radiate long wave radiation and inhibit the corresponding radiative surface cooling producing a pseudo-green house effect that may contribute towards the urban heat island effect [1]. Kadioglu [9] studied the surface air temperature trends in Turkey and concluded that night time temperatures have a comparatively significant increase while day time temperatures remain unchanged over the study area. Cayan and Douglas [10] studied the urban influences on surface temperatures in the South Western United States for the period 1930-1980 and concluded that urban warming appears to be predominantly a night time phenomenon, with minimum tem-
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