Unseasonal rain brings best air quality for Mumbai in 2 months

The air quality index (AQI) on Monday was 76, falling under the satisfactory category, according to the System of Air Quality Weather Forecasting and Research (SAFAR).

Sporadic spells of light showers in the city and suburbs between Sunday and Monday not only led to the coldest day this season but also helped disperse pollutants making it the best air quality since October 19.

Mumbai witnesses sudden change in weather accompanied with drizzle. (Satyabrata Tripathy/HT Photo)

The air quality index (AQI) on Monday was 76, falling under the satisfactory category, according to the System of Air Quality Weather Forecasting and Research (SAFAR).

The last time Mumbai recorded an AQI lower than this was 68 (satisfactory) on October 19 and thereafter the AQI started rising. It was 90 (satisfactory) on October 20 and fluctuated between the poor and moderate categories up till Diwali (November 14). The AQI remained in the moderate category through rest of November with isolated spikes (on a few days) with poor AQI. However, after almost two months, light showers over the past four days improved the air quality.

Mumbai witnessed intermittent spells of light showers between Sunday night and Monday morning allowing a marginal drop in minimum temperatures and considerable drop in maximum temperatures leading to cool conditions. Between 11.30 pm Sunday and 8.30 am Monday, the Santacruz weather observatory, representative of the suburbs and Mumbai, recorded 4.8 mm rain while 13.8 mm was recorded at Colaba weather station, representative of south Mumbai. Between 8.30 am and 5.30 pm Monday, 6.2 mm rain was recorded in south Mumbai and 1.1 mm in the suburbs. Maximum rain between Sunday and Monday was recorded at Kandivali at 18.6 mm followed by Colaba and Mazgaon 8.4 mm.

This allowed the maximum temperature to drop to 26.9 degrees Celsius, 5.4 degree Celsius below normal in the suburbs, which is the lowest this season and second lowest for the month in 9 years. The lowest maximum temperature over the past decade was recorded on December 6, 2017, at 23.6 degrees Celsius. On Monday, south Mumbai recorded the maximum temperature at 27 degrees Celsius, 4.5 degree Celsius below normal. On Sunday the maximum temperature was 27.6 and 27.4 degree Celsius in the suburbs and south Mumbai respectively.

The minimum temperature fell marginally from previous days to 22 degrees Celsius, both in the suburbs and in south Mumbai, which was above normal. Mulund, Kandivali, and Powai had the lowest minimum temperatures in the city below 20 degrees Celsius.

The weather bureau predicted the possibility of light rain for Tuesday as well. “Mumbai Metropolitan Region (MMR) received light to moderate intermittent overnight showers that continued on Monday morning. Satellite images had indicated heavy cloud cover over north Konkan region,” said KS Hosalikar, deputy director-general, western region, India Meteorological Department (IMD).

Showers are expected till Wednesday, according to the IMD, due to the confluence of northwesterly (coming from western disturbance over north) and southeasterly winds (coming from a low-pressure system over the Arabian Sea) extending over northwest India.

“December rain is not routine for Mumbai but showers led to traffic snarls, poor visibility, moist and wet conditions through the city,” said Hosalikar. He highlighted that weather radar images on Monday had shown a cloud patch all the way from Raigad (Navi Mumbai, Alibag, Panvel), over MMR (Mumbai, Thane, Palghar), and Nashik. Meanwhile, apart from Mumbai, Nashik recorded 9.8 mm rain, Harnai 4.4 mm, Thane 4.2 mm, and Mahabaleshwar 2.2 mm.