Effect of urbanization on some key atmospheric parameters: a study over north east India

Long-term behavior of atmosphere in terms of temperature, pressure, humidity, cloud cover, precipitation etc defines climate of a specific area. Urban areas are characterized by high density of human created structures viz., high buildings, roads etc and high concentration of population. Urban climate is greatly influenced by human activity. Due to human activity, the temperature of any urban area in general is higher than the surroundings and hence they behave as heat islands. The building materials are non-reflective, concrete road surfaces have high thermal capacity and hence absorb heat during day-time which is slowly released at night thereby increasing the temperature. Presence of factories and increased car use within the city causes pollution which creates smog and forms a pollution dome. This pollution dome allows short-wave insolation to enter, but traps outgoing long-wave terrestrial radiation, therefore increasing the amount of heat retained. These urban heat islands can have effect on pressure, humidity, cloud cover and hence precipitation over the region as a whole. In this piece of work, we have examined the trends in relative humidity, cloud cover and precipitation pattern over northeastern region of India during last two decades and tried to see their correlation with rapid urbanization in the region. It is observed that the rapid urbanization has led to substantial irregularities in precipitation pattern and cloud cover over the region.