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Fogged out

Foggy conditions during winters in Delhi have increased drastically over the past decade. Meteorological data for December and January in 1983 shows the average clear visibility during the day in the capital was 5:07 hours. This decreased to 10 minutes in 2005. Duration of dense fog rose from half an hour per day in the early 1980s to two-three hours in 2003.

During cold weather when the relative humidity touches 100 per cent the moisture in the air begins to saturate around particulate matter like dust and pollutants. These particles inflate on absorbing moisture and create haze or fog. The India Meteorological Department (IMD) has come up with only partial explanations for the increased incidence of fog. The phenomenon is attributed to a high rate of humidity and an increase in particulate matter from pollution.

R K Jenamani, director of the IMD centre at the Delhi airport, has correlated pollution, humidity and temperature in a paper titled

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