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1981 -1990 and 1991 -2000 showed strong decline during the second decade with an average reduction of 5% per two decades. Despite the drastic decrease in S, the all India averaged surface maximum and minimum air temperatures have been increasing. But, the change in increase in maximum temperature from the first decade to second decade is only marginal under the present situation of drastic increase in greenhouse gas emissions, while the increase in minimum temperature has been doubled.

A negative electric discharge voltage generator (NAI Generator) was designed and used to investigate the possibility of reducing (neutralizing) fog, dhoop smoke, and vehicle smoke collected in closed glass containers. The experiment was carried out in a dark room, and two identical glass containers were used. Various sensitivity tests were carried out with fog and smoke. Light intensity was measured for each run as a function of time with and without a negative air ion generator. Negative air ions attach to particulate matter to enhance visibility. At a high negative ion emission rate, the particle mobility becomes sufficient so that particle migration results in their deposition on walls and other indoor surfaces. The performance characteristics of the negative electric discharge generator designed in this work, which produces uni-polar ions by corona discharge at a relatively high emission rate, were evaluated. This device, if operated continuously for six minutes, resulted in the removal of about 93% to 97% of the particles in the glass container, in addition to the natural decay effect. The rate of change of particle removal was higher for fog than for smoke. This study demonstrates that it is possible to neutralize and reduce the concentration of fog and smoke to a significant degree using negative air ions, resulting in increasing visibility in a closed chamber.

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Ground‐based observation of OClO, NO2, and O3 columns by differential UV‐Visible spectroscopy at twilight during the fall winter of 1993/94 at the sub‐Arctic station of Reykjavik (64°N, 23°W) are presented. Results show no direct evidence of ozone depletion during the period but significant amounts of OClO were observed in December and January when NO2 abundances were at the annual minimum. NO2 columns are found to be controlled by the hours of light available but highly modulated by the lower stratosphere temperature. OClO was observed outside the vortex as well, but only at times when NO2 was low.

High-energy radiations, such as alpha and beta particles or gamma radiation, ionize air molecules into pairs of positive ions and free electrons. The diurnal and seasonal variations of these air ions were measured for the first time at a rural monitoring station in Ramanandnagar (17°2'N, 74°E), India, and the urban tropical station in Pune (18°31'N, 73°55'E)

Twilight photometric technique has been used in order to demonstrate that the middle atmosphere can be perturbed by the presence of tiny particles delivered after an encounter with cometary dust trails like the one produced by 55P/Tempel‐Tuttle. The presence of meteoric dust in the atmosphere from the Leonid activity that occurred from 2001 to 2003 was detected by the twilight photometer operated at Pune (18.5°N, 73.9°E), India. The November 2001 and 2002 Leonid storms, and the 2003 November outburst, caused significant enhancements of dust from just above the mesopause to the lower stratosphere. The present study shows the formation of meteoric dust layers at mesospheric levels and their subsequent descent to lower altitudes. The enhanced stratospheric layers are observed 4 to 8 days after the peak meteor activity.

The air ions are continuously generated and destroyed by various processes in the atmosphere. Near the surface, the nature of ions is very complex and they show large variations in their physical properties. The attachment of small ions to the aerosol particles is depending on the mobility of air ions. High mobility air ions immediately are attached to the aerosol particles and settle down on the surface. In this study we report, about the air ion variation at different sites like Rural, Coastal, Mountain, Poultry farm and urban in the state of Maharashtra in India. The aim of this study is to understand the plausible distribution of air ions both diurnally and at different times in a day for long time (three years) and with various meteorological variables. The preliminary analysis of the data has reveled that negative air ions are observed to have attached to the aerosol particles and large aerosol particles are formed from small aerosol particles. Therefore uni-polarity factor observed to be below unity for coastal, mountain and rural site and about 2.8 at an urban site. However worst case is observed at the Poultry farm, where uni-polarity factor is 6.3, which is very harmful for human health. There is also effect of meteorological parameters on air ion concentration in the atmosphere.