Thermal inversion is a big factor behind the sudden spike in dense smog. New Delhi: Since Wednesday morning, north India has been covered in a thick blanket of smog, leading to low visibility, a drop in temperature and the air quality deteriorating to the ‘Severe’ category. Air quality remained a concern all over the Indo-Gangetic Plains (IGP), with satellite images showing the alarming scale of the smog cover over northwest India including Delhi and its adjoining areas. Punjab, Haryana, Uttar Pradesh, Delhi, parts of north Rajasthan, Himachal Pradesh and Uttarakhand, are covered with smog. Hiren Jethwa, an aerosol remote sensing scientist at NASA Goddard Space Flight Center, shared the satellite images, detailing the extent of the smog covering the IGP, the reasons behind the dense smog in November, and how the farmers in Punjab are evading NASA satellites by burning crops late afternoon. Early morning satellite images reveal IGP engulfed in smog. Delhi AQI in severe category. Urban heat island effect over Delhi. Farm fires in Pujab appear to have passed peak burning phase, but …