New Delhi: The national capital’s air quality improved on Wednesday due to a favourable wind speed with the 24-hour average air quality index (AQI) reading 237 at 4 pm. Neighbouring Faridabad (188), Ghaziabad (229), Greater Noida (154), Gurgaon (185) and Noida (186) also recorded an improvement in their air quality.Also Read - Delhi Pollution: Govt Extends Bans on Truck Entry Till Further Orders

An AQI between zero and 50 is considered ‘good’, 51 and 100 ‘satisfactory’, 101 and 200 ‘moderate’, 201 and 300 ‘poor’, 301 and 400 ‘very poor’, and 401 and 500 ‘severe’. The Ministry of Earth Sciences’ air quality forecast agency SAFAR said the improvement in the air quality was “higher than expected, implying that (air pollution) control measures are yielding results”. Also Read - Air Pollution Latest Update: Air Quality Panel Orders Immediate Closure of Industries in NCR For Not Using Cleaner Fuels

Moderate wind speed is likely to increase ventilation over the next four days, it said. However, a gradual decrease in temperatures will lead to a drop in the mixing height — the vertical height in which pollutants are suspended in the air — in the coming days, it said. Also Read - Air Pollution Causes Irreversible Damage to The Eyes

The mixing height reduces on cold days with calm wind speed. Mahesh Palawat, Vice President (Meteorology and Climate Change), Skymet Weather, said moderate wind speed will help improve the air quality further.

Cold northwesterly wind will commence from Friday after a Western Disturbance affecting the hilly region recedes, causing the minimum temperature to drop by two to three degrees Celsius, he said. Delhi recorded a minimum temperature of 10.1 degrees Celsius, a notch more than normal. The maximum temperature settled at 24 degrees Celsius. The minimum temperature is likely to drop by two to three degrees Celsius over the next three to four days, the Met office said.