Wednesday, August 18: Partly cloudy skies, high temperatures, poor air quality, high humidity, low wind speed and zero rain—the story of Delhi’s weather continues to remain unpleasant this week. However, in the second half of the week, a much-needed respite in the form of monsoon rains is very likely, says the national forecaster.
On Tuesday, the national capital witnessed a maximum temperature of 38°C—a whopping 4°C above normal. This trend of high daytime temperatures has been prevailing over Delhi since Sunday, August 15. On the other hand, the minimum temperature has stayed more or less constant for the past one week at the normal range of around 26-28°C. On Wednesday, the nighttime temperatures hit a low of 27.4°C, while the relative humidity stayed at 74% at 8.30 am.
Moreover, the air quality has continued to worsen, with some stations registering ‘very poor’ air qualities, with even ‘severe’ readings during some parts of the day. On Wednesday morning, the overall air quality remained moderate, with an average Air quality index (AQI) below 150.
Rains forecast this week
There is no possibility of rain will Wednesday, says the India Meteorological Department (IMD), as the seasonal surplus rainfall gradually reduces. So far, Delhi’s base station at Safdarjung has recorded more than 600 mm rainfall since June 1 as against the norm of 425 mm—42% excess. Unfortunately, more than 500 out of 600 mm was registered in July, while August—much like June—has remained dry.
As per forecasts, the next batch of monsoon showers may come back within a couple of days. As the western end of the monsoon trough gradually shifts southwards over the next two days, light to moderate rain is forecast for Delhi from Thursday, August 19, to Monday, August 23. The monsoon trough is an extended low-pressure area that drives monsoon rains across the country’s northern half.
As a result of the revival of monsoon rains, temperatures are set to fall drastically across Delhi-NCR this week. The rainfall intensity is expected to be maximum on Friday, August 20, and daytime temperatures may not breach 33°C from Friday to Sunday—five units below the current maximum.
Air quality remains poor
Overall, Delhi’s air quality was in the moderate category on Tuesday. However, the AQI in places like Anand Vihar (279) and Mundka (239) remained ‘very poor’ throughout Tuesday and even on Wednesday morning. Ballabhgarh—a city in Haryana that is part of the National Capital Region—remained the most polluted city in india on Tuesday, with a ‘poor’ AQI of 215.
In India, System of Air Quality Weather Forecasting and Research (SAFAR) and Central Pollution Control Board (CPCB) categorise AQIs between 101-200 as ‘moderate’, 201-300 as ‘poor’, 301-400 as ‘very poor’, and those above 400 as ‘severe’.
As per SAFAR, Delhi’s air quality has worsened due to the inflow of dust from the western states and polluted air from the west of Indo-Gangetic Plains. Moreover, re-suspension of dust from unpaved roads has also remained a cause of concern. The PM10—particulate matter of less than ten micrometer in size—has remained the lead pollutant, contributing about 80% of the pollution load.
SAFAR forecasts that the AQI may remain in the moderate category for the next two days. Suppose the national capital region receives substantial rainfall by Friday as forecast. In that case, the pollution load is likely to drop substantially, and the air quality may improve to satisfactory levels across Delhi 0ver the weekend.
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