On Thursday morning, humidity levels in the city peaked, hitting 98% in south Mumbai and 80% in the suburbs. Peaked moisture levels have high potential to hold pollutants, say experts.
According to the India Meteorological Department, the humidity in south Mumbai was almost 22% above normal. This dropped to 79% by evening. In the suburbs, the humidity fell from 80% in the morning to 55% in the evening. The humidity levels on Wednesday morning in south Mumbai and the suburbs was 87% and 77% respectively.
The minimum temperatures in the city too remained almost 3 degree Celsius above normal. The IMD recorded 26 degree Celsius at Colaba, 3.7 degree Celsius above normal and 23.4 degrees at Santacruz, a deviation of 3.3 degree Celsius. Weathermen said this could be due a day-to-day fluctuation. “There is no weather system which could affect the city so much, so this could be a result of a day-to-day fluctuation. The rain last weekend could have resulted in depositing moisture along the coastline,” said V K Rajeev, director, western region, IMD.
The high humidity levels also indicated that the air quality levels in the city took a hit as there was a thick haze in the sky on Thursday evening. According to System of Air Quality and Weather Forecasting and Research (SAFAR), Mumbai recorded an Air Quality Index (AQI) on 152 on Thursday. This is expected to worsen to 165 on Friday. AQI between 101 and 200 is acceptable for general public but moderate health concern for sensitive people.
AQI is measured for particulate matter (PM2.5 and PM10) – particles between 2.5 to 10 micrometers in size which get lodged into the respiratory system. “After the rain in Mumbai, there is lot of moisture in the air which is having high potential to hold the particles emitted from transport sector. That is the reason that PM levels are increasing in Mumbai. The wind is very calm and temperature is dropping,” said Gufran Beig, scientist, Indian Institute of Tropical Meteorology (IITM), Pune and project director, SAFAR.