Monsoon withdrawal leads to unfavourable conditions for air pollution dispersal
India Meteorological Department (IMD) scientist Vijay Soni said the wind speed reduced from Saturday evening and temperatures have also started falling
The monsoon withdrawal from northwest India has led to a calming of winds and a dip in temperatures, which are expected to result in unfavourable conditions for the dispersal of air pollution and a rise in its levels in Delhi.
India Meteorological Department (IMD) scientist Vijay Soni said the wind speed reduced from Saturday evening and temperatures have also started falling. “This is why we are also seeing a rise in air pollution levels. The winds are northwesterly and there are farm fires in Punjab and Haryana.”
He said farm fires are less in Haryana compared to last year. “We do not expect relief from these conditions till October 19 when wind direction is expected to become easterly temporarily. The ventilation index is too low for the dispersal of pollution,” said Soni.
The ventilation index on Sunday was around 4000 m2/s. A ventilation index lower than 6000 m2/s with an average wind speed of less than 10 kmph is unfavourable for the dispersion of pollutants.
Conditions are separately likely to become favourable for further withdrawal of the monsoon from more parts of Vidarbha, Chhattisgarh, Maharashtra, and Jharkhand, interior Odisha, and the rest of West Bengal during the next two days, IMD said on Monday.
A cyclonic circulation was lying over the southeast Arabian Sea and adjoining Kerala coast in lower tropospheric levels and a trough was running from this cyclonic circulation to the southwest Bay of Bengal.
A cyclonic circulation is again likely to form over the north Andaman Sea and neighbourhood around October 18. It would move west northwestwards towards the westcentral and adjoining southwest Bay of Bengal becoming low-pressure area around October 20.
Under the influence of these systems, widespread light/moderate rainfall with isolated heavy rain and thunderstorm/lightning is very likely in Tamil Nadu, Puducherry, Karaikal, Kerala, Mahe, South Interior Karnataka, and Lakshadweep until October 20.
Dry weather is likely in most parts of northwest and central India during this period.