Wind speed has declined across the country and this has major implications on air pollution,Dr Gufran Beig,programme director of Indias first System for Air Forecasting and Research (SAFAR),told Newsline. Scientists A K Jaswal and A L Koppar have found that dip in wind speed had led to a decline in the number of good visibility days in the urban areas as pollutants remained suspended in the air. Meteorological factors like wind,humidity,cloud cover,rain and temperature affect pollution,the scientists said,adding that the rate at which pollutants are converted into other pollutants is determined by availability of sunlight and the presence or absence of clouds. We analysed data across 170 stations between 1961 and 2008,and our study showed that the average wind speed dropped from 9.7 kmph in 1961 to 5 kmph in 2008,with a 9.2 per cent decline in annual average wind speed per decade, said Jaswal,scientist at the National Data Centre of Indian Meteorological Department,who coordinated the study. There has been a 49 per cent drop in the near-surface wind speeds over the past 50 years,he said. Global warming,urban heat islands,urbanisation,unplanned changes in land-use patterns and deforestation have been linked to falling wind speeds. Wind plays an important role in dispersion of aerosol particles. If there are no surface winds,a layer of haze forms near the ground and continues to build as long as the atmospheric stagnation persists. Experts like Beig have raised concerns over such dips in wind speed,especially as pollutants do not get dispersed but remain concentrated,thereby adding to the rising air pollution levels.
