Inversion Explained

In general, temperature drops with altitude. The rate of decrease, known as the Environmental Lapse Rate (ELR), depends on atmospheric conditions and the composition of air (water vapour, carbon dioxide, dust). On average, the atmosphere cools by 6°C every 1000 m.

A parcel of warm air which is forced upwards by the normal process of convection cools as it gains altitude. If the rate of cooling of that parcel is lower than the prevailing ELR, the air rises even higher. Such a phenomenon is common in summer and helps air pollution from metropolitan areas to rise and dissipate. The air either gets diluted or is blown away by winds of the upper atmosphere.