Mixing Heights (Inversion Layer Heights) Over Delhi

Delhi experiences extremes in climate – very hot summers and cold winters. It is a landlocked city, and hence cannot rely on breeze from the sea to carry away pollutants. A characteristic of these extremes is that the inversion layer is high in summer, but significantly lower in winter. What this means is that, emissions in winter are more concentrated because they cannot get distributed high into the atmosphere. As the graph below shows, on average mixing layer heights are almost twice as high in summer months as compared to winter. Winds are also much lower strength in winter, and hence any pollution that is created tends to stay for longer.

Role of meteorology in the seasonality of air pollution in Delhi

Mixing layer height (inversion layer height) over Delhi for the next three days, based on simulations from WRF meteorological system

 
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