Hazy winter

Print edition : December 09, 2016

Connaught Place, New Delhi, a bird's-eye view on November 5. Photo: Altaf Qadri/AP

Fig 1: Mean wind speeds and direction (during November 1-6) at about 1 km height. The small arrows in the plots indicate the direction of wind motion. Photo: NASA

Pic. 1: Distribution of fires on November 2, 2016, based on data from the VIIRS instrument aboard satellite Suomi-NPP. Each of the small coloured squares (25 km × 25 km) on the map indicates the number of fires detected. The dark red squares have between 1 and 5 fire detections (within the 25 km × 25 km area), while the yellow areas represent up to 25 fire detections. Photo: NASA

Pic. 2: Suomi-NPP satellite image of smoke spread on November 6, 2016, showing fires originating from sources in the north, north-west, west-north-west, including regions in Pakistan. The red dots indicate the distribution fires on the basis of data from VIIRS instrument, which have been overlaid on the image. Photo: NASA

Pic. 3: Smoke spread on November 6, 2015, showing the emissions being steered towards the west over Rajasthan unlike (compare with Pic. 2) this year where it is seen spreading all across the Indo-Gangetic plain. The big white blob in the image is fog in that region on that day. Photo: NASA

Fig. 2: Temporal variability in the number of fire detections in Punjab and Haryana during September-November 2004-14 based on MODIS instrument on-board the NASA satellite Aqua at 1 km resolution. Photo: NRSC, Hyderabad/Current Science, Noiv. 25, 2015

Fig 3: Wind Rose Diagram: The figures show how wind speed and direction were distributed during the days indicated. The colour shading scale on the left of the plots indicates the wind speeds and the circles indicate different percentage shares of the total time for each speed and direction. Photo: SAFAR/Indian Institute of Tropical Meteorology, Pune

Fig. 4: PM2.5 concentration levels during October 20-November 6. The plot also shows temperature, horizontal surface wind speeds on each day and the categories of air quality index in which the values fall. Photo: NAAQS

Table 1: Though it may seem that firecracker bursting was less this year, pollution on the single day of Deepavali was higher than last year. Photo: Central Pollution Control Board

An unusual confluence of factors caused unprecedented pollution and smog in the Delhi region soon after Deepavali, and experts warn of a similar episode in the days to come.
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