Monsoon leaves city with 38% rain deficit
Over-A-Week Delay For Just 3rd Time In 9 Yrs
New Delhi: The monsoon officially retreated from the capital on Thursday — 10 days later than “normal”. Delhi recorded an overall rain deficit of 38%, data from the meteorlogical department showed. This is also only the third time since 2010 that the monsoon retreat has been delayed beyond September 30.
In both 2018 and 2017, the monsoon officially started retreating from Delhi on September 30, whereas it was delayed by over a week in 2016 (October 7). The delay was the longest in 2013, when the retreat was declared on October 17.
Delhi recorded 404.1mm of rainfall this season — well beMonsoon
retreat in Delhi on Usual date for retreat low the normal of 648.9mm. “There has been an overall rain deficit of over 200mm this monsoon season. This makes it a deficit of 38% and, despite a prolonged monsoon, not much recovery happened in September,” an official said. In fact, Delhi recorded a rain deficit in all four months of June, July, August and September. The monsoon reached Delhi a week late this year (July 5) against the normal date of June 29, meaning there was an 83% rain deficit that month alone. Only 11.2mm of rainfall was recorded against a normal of 65.5mm.
In July, 210.4mm was received compared with a normal of 276.1mm (24% deficit) and, in August, 119.6mm was recorded against an expected 247.4mm (52% deficit). In September, Delhi received 74.1mm of rainfall as compared with a normal of 125.1mm (41% deficit).
Kuldeep Srivastava, scientist at IMD, said following the retreat, northwesterly winds were affecting Delhi now, with stubble burning likely to play a part in the air quality. An anti-cyclonic formation over Rajasthan may also influence Delhi in the coming days.
Delhi’s maximum temperature on Thursday was recorded at 33.9 degrees Celsius, while the minimum was 20.7 degrees Celsius. Humidity levels oscillated between %36 and 93% in the last 24 hours. The regional meteorological department has forecast “hazy” conditions in the morning for the next few days with the maximum and minimum temperatures likely to hover around 34° and 21° C, respectively.
Since 2010, this is the second
most delayed retreat after 2013
The dip in air quality is due to a change in wind direction to northwesterly, influence of stubble burning and local emissions getting trapped after effigy burning. Wind speeds also low
CPCB wrote to state pollution control boards and other government agencies on Thursday, asking them to take appropriate measures to control dust and pollution.
In letters sent to the municipal bodies in Delhi and NCR states as well as other agencies, CPCB asked for weekly action taken reports to be submitted and called for precautions to be taken during construction activities, particularly with dust, C&D waste and open burning.
Among the agencies contacted by CPCB were NHAI, DMRC, CPWD, NBCCIL, PWD, DDA, DSIIDCL New Delhi, Ghaziabad Development Authority, Noida and Greater Noida authorities.
A SAFAR bulletin said, “The southwest monsoon has started to retreat now. Wind speeds continue to be slow and variable with predominant direction from the west. Under these conditions, air quality is
predicted to deteriorate further. Indications of increased fire activity during the last 48 hours are visible from satellite imagery and a further deterioration of AQI is expected for the next two days.”
AQI is classified as “poor” at reading between 201 and 300. It is below the “very poor” (301-400) and “severe” (401-500) zones while being worse than “moderate” (101200), “satisfactory” (51-100) and “good” (below 50) levels.
The last time Delhi had air quality in the “poor” zone was on July 14, when it touched an AQI of 235. Following that, a prolonged monsoon largely helped Delhi keep the AQI below 200. In fact, Delhi recorded two “good” air days in August while experiencing the cleanest September in the last nine years, according to CPCB data. SAFAR, however, said a late withdrawal of the monsoon was bad for Delhi’s air quality.
“The late monsoon withdrawal is not good for air quality in north India. During the third to fourth week of October, the temperature will also start to cool. The anticyclone, which persists as part of the withdrawal, associated with clear skies and sinking motion will mean significantly calm surface winds. Both these conditions will lead to stagnant weather conditions (low wind speeds and descending air), which favours rapid fine particulate matter formation and accumulation of pollutants,” said SAFAR.
On Wedneday, EPCA chairman Bhure Lal also wrote to NCR states, asking them to prepare for “very poor” and “severe” air under the GRAP from October 15. Air quality was likely to deteriorate from October 12 onwards, he said.
“EPCA has been advised by the task force on GRAP, which is chaired by the member secretary of the CPCB that the coming period, beginning October 12, 2019, is projected to have adverse weather conditions, which exacerbate the potential for pollution,” said Lal.