In what ways do human beings modify the composition of the urban atmosphere? How do such atmospheric modifications affect the nature of precipitation in urban areas?

monoxide is toxic gas produced by incomplete combustion of fossil fuel like coal and petroleum. Carbon dioxide is the most common gaseous pollutant, which is a very efficient heat absorber and is responsible for a remarkable increase in atmosphere temperature.Improvement in transport leads to heavy traffic for transport of agricultural produce, manufactured goods and raw materials. Innovation of vehicles and increasing capita income cause the mass production of car. Rising car owernship with the use of diesel oil which produce the exhaust fumes which are the great source of CO, SO2, NO, NO2 and compound of lead. In Tokyo, automobile exhaust is estimated to account for 67% of the total amount of nitrogen oxides.Construction activities and open burning contribute ashes, cement particulate, dust and fine clay to the atmospheres.Power stations, incinerators and burning of coal and oil emit CO2 and SO2.Deforestation for expanding population increasing lumbering activities and ranching as well as recreation by the mean of burning release large quantity of carbon dioxide once trapped in the biomass and the amount of oxygen is reduced.With the increasing industrial activities, air pollution is produced. Gases in the atmosphere are altered. There may be three to seven times more dust particles in urban areas than in rural area. Urban areas may have up to 200 times sulphur dioxide and 10 time more nitrogen oxides and 10 times more hydrocarbons, and twice as much as carbon dioxide.The modification of compositional atmosphere affect nature of precipitation in urban areas. There is more frequent convection rainfall and acid rain.The pollutants are good heat absorbers. Temperatures in urban areas are higher than in rural areas. The heat island effect means the degree of warning diminishes slowly outward from the city center, through suburbs and then decreases markedly at the city periphery. High temperature promotes the upward movement of unstable air. Pollutants provide density of condensation nuclei for cloud formation and rainfall formation. The mean annual precipitation and the number of days with less than 5mm of rainfall are both 10% greater in urban areas.In areas with serious air pollution, acid rain may form. The two main sources involved in the formation of acid rain are sulphur dioxide and nitrous oxides. These two pollutants are produced during burning of fossil fuels in power stations, heavy industry and vehicle exhausts. Both SO2 and nitrous oxides are transformed in the atmosphere into acids, i.e., sulphuric acid and nitric acid. These pollutants are absorbed by water droplets in the atmosphere and fall to the ground in rain. The acid rain over most of northwest Europe has a pH value of between 4 and 5 with even lower values occurring during acid mists. The lowest even recorded being 2.4. The acid rain causes ecological, medical, economic problems in our living environment. An increase in level of water acidity caused by the direct fall of acid rain on lake and river surfaces and the through flow and overland flow leads to the death of fish and plant life. Forest may be destroyed because of the nutrients are washed away and replaced by manganese and aluminum which are harmful to root growth. In time, trees become less resistant to drought and disease. Birds dusk, grebes are affected because of their reliance on food from acidified watercourses and lake. The effect of acid rain pass along the food chain and human beings are at risk.Acid rain is also dangerous to human health. In the USA, SO2 is recognized as the major causes of lung disease after active and passive smoking. Acid and polluted smog produces severe health problem for many people.There is also economic cost because of the fall in crop yields. In Poland, the costs of acid damage are equivalent to 10% of the country's GVP. In Canada, sugar production has reduced and the timber growth has also declined markedly.The sulphuric acid also causes corrosion of metal and limestone, and chemical weathering to man-made structure, i.e. buildings.In conclusion, human activities manipulate the natural environment and modify the composition of atmosphere. Pollutants increase and acid rain become more likely to occur. In return, the living environment is affected.