POST TIME: 5 December, 2021 06:00:53 PM
Bay depression triggers drizzle in parts of Bangladesh; helps improve Dhaka’s air quality
UNB, Dhaka

Bay depression triggers drizzle in parts of Bangladesh; helps improve Dhaka’s air quality

Dhaka’s air quality showed a slight improvement on Sunday afternoon with the capital city ranking sixth worst in the Air Quality Index (AQI) due to rain triggered by depression in the Bay of Bengal.
Dhaka had an AQI score of 159 at 15:22 pm and its air quality was still classified as ‘unhealthy’.
Dhaka’s air quality usually turns unhealthy during winter and improves during monsoon.
India’s Delhi, Pakistan’s Lahore and China’s Chengdu occupied the top three spots respectively with scores of 187, 179 and 175.
An AQI between 101 and 200 is considered 'unhealthy', particularly for sensitive groups.
AQI, an index for reporting daily air quality, is used by government agencies to inform people how clean or polluted the air of a certain city is, and what associated health effects might be a concern for them.
In Bangladesh, the AQI is based on five criteria pollutants -- Particulate Matter (PM10 and PM2.5), NO2, CO, SO2 and Ozone.
Depression & drizzles 
Daylong drizzles disrupted normal life in the capital and some other parts of the country as cyclonic storm ‘Jawad’ weakened into a deep depression over the Bay of Bengal on Sunday.
“The Met office has recorded 1 mm rain in the city till 9 am on Sunday and light showers are likely to continue till Monday due to the deep depression,” metrologist  Hafizur Rahman told UNB. 
 The day started with a cloudy sky in the capital and people who stepped out of home in the morning without preparations to tackle rains suffered a lot.
Commuters had to wait for a long time to manage any transport to go to their respective destinations.
Traffic constables were seen too busy controlling traffic as drizzles caused traffic chaos in some areas in the morning.
According to a Met office bulletin, “Light to moderate rains or thunder showers accompanied by temporary gusty wind are likely to occur at most places over Khulna, Barishal, Chattogram and Dhaka divisions; and at many places over Rajshahi, Mymensingh and Sylhet divisions and at one or two places over Rangpur division with moderately heavy falls at isolated places over the country.”
Night temperature may remain nearly unchanged and day temperature may fall slightly over the country.
Signal 3 
The maritime ports of the country have been advised to hoist local cautionary signal number three as the deep depression over west-central bay and adjoining northwest bay moved north-northeast wards and lies over northwest bay and adjoining west-central bay.
It centred at 6 am on Sunday about 875 kms southwest of Chattogram port, 855 kms southwest of Cox's Bazar port, 695 kms south-southwest of Mongla port and 725 kms south-southwest of Payra port. 
It is likely to move further in a north-northeasterly direction and weaken gradually.
Maximum sustained wind speed within 48 kms of the deep depression centre is about 50 kph rising to 60 kph in gusts or squalls. The sea will remain rough near the centre of the deep depression.
Under the influence of the peripheral effect of the deep depression, deep convection is continuing over North Bay and adjoining coastal areas of Bangladesh.
Steep pressure gradient  
Rains or thundershowers with temporary gusty or squally wind speed of 40-50 kph is likely over North Bay and adjoining coastal areas of Bangladesh.
All fishing boats and trawlers over North Bay and deep sea have been advised to take shelter and remain in shelter till further notice.