A massive plume of sulphur dioxide (SO₂) and volcanic ash drifting thousands of kilometres from Ethiopia’s Hayli Gubbi volcano briefly reached Delhi’s upper atmosphere late Monday night, but according to air quality and meteorology experts, the intrusion did not significantly worsen the city’s surface pollution levels. Delhi’s Air Quality Index (AQI) stayed firmly in the ‘very poor’ category, driven mostly by its usual winter pollutants rather than the ash plume.
The volcanic eruption—Ethiopia’s first from this volcano in nearly 12,000 years—sent shockwaves through global aviation systems, prompting flight cancellations, diversions, and advisories by India’s Directorate General of Civil Aviation (DGCA). While the plume’s presence over north India generated public concern, scientific assessments indicate that the ash arrived at high altitudes, far above where Delhi’s day-to-day pollution accumulates.
Volcanic Plume Passes Over Delhi at 35,000–45,000 Feet
IMD and global Volcanic Ash Advisory Centres (VAAC) tracking confirmed that the plume passed over Delhi’s airspace around 11 pm Monday to 1 am Tuesday, travelling rapidly across northern India at speeds of 100–120 km/hr.
Key details:
- Altitude of plume: 35,000–45,000 feet
- Duration over Delhi: Around 2 hours
- Main composition: Sulphur dioxide, minor volcanic ash
- Movement direction: From Ethiopia → Arabian Sea → Rajasthan → Delhi → Uttarakhand/Nepal
Experts say this height prevented the plume from descending into Delhi’s boundary layer.
“This event occurred far above the levels at which urban pollutants accumulate,” explained independent meteorologist Ashwary Tiwari (IndiaMetSky). “While isolated ash particles were observed at the surface, the plume’s altitude made its impact negligible for Delhi’s AQI.”
Delhi’s AQI Sees No Major Spike
Delhi’s AQI was 370 (‘very poor’) at 11 pm, and 362 at 9 am Tuesday, showing:
- No drastic deterioration due to volcanic ash
- Pollution remained driven by local emissions + winter inversion
HT’s analysis of real-time station data found only slight fluctuations in PM2.5 and SO₂ levels at some locations, not enough to alter overall AQI.
Station-Wise Pollution Behaviour
📍 Mandir Marg
- PM2.5:
- 173 µg/m³ at 11 pm → 185 at midnight → 218 at 2 am
- SO₂:
- 41.3 µg/m³ at 11 pm → 61.8 at midnight → 61 at 1 am
- Standards:
- PM2.5 safe limit: 60 µg/m³
- SO₂ safe limit: 80 µg/m³
📍 Anand Vihar
- PM2.5 rose from 328 → 382 → 367 µg/m³
- SO₂ increased marginally from 9.2 → 12.9 µg/m³
📍 Punjabi Bagh
- PM2.5: 306 → 345 µg/m³
- SO₂ dipped slightly (27.6 → 21.2 µg/m³)
Experts observed no consistent trend linking these changes with the volcanic intrusion.
Why the Ash Did Not Affect Delhi’s Surface Air
Three scientific reasons explain the negligible impact:
1️⃣ High-altitude flow
Volcanic ash travelled in the upper troposphere and lower stratosphere, never mixing downward into Delhi’s cold, trapped surface layer.
2️⃣ Rapid movement
The plume moved at extreme speeds, limiting any chance of deposition.
3️⃣ Stable boundary layer in Delhi
Winter inversion over Delhi prevents upward or downward mixing, locking local pollutants near ground level but blocking external intrusions.
Impact on Flights and Aviation Systems
The ash plume had more impact on aviation than on ground pollution.
DGCA issued a detailed advisory asking airlines to:
- Avoid affected regions
- Alter altitudes
- Adjust fuel planning
- Prepare for diversions
Airlines that issued advisories:
- IndiGo – monitoring drift toward India
- Air India – stated no flights were impacted yet
- Akasa Air – evaluating international advisories
- SpiceJet – warned passengers traveling to/from Dubai
Mumbai Airport also alerted passengers that disruptions may occur.
Flight cancellations and rerouting began across multiple international routes as the ash cloud advanced toward the northwest and parts of north India.
Volcanic Plume Drifts Over Rajasthan and North India
Before touching Delhi’s upper atmosphere, the ash cloud crossed:
- South Arabian Sea
- Parts of Oman and Yemen
- Pakistan airspace
- Entered Rajasthan around 6:30 pm Monday
- Moved into NCR night onwards
The plume is now travelling toward the Himalayas, Nepal, and the UP Terai belt, where scientists say SO₂ levels may temporarily rise.
