A web fire-mapper brought out by the NASA (National Aeronautics and Space Administration of the US) shows the extent of crop burning undertaken in North-West India to prepare farms for the rabi crop.

Crop burning has been widely thought of as one of the principal contributors to the suffocating envelope of smog that settles over the national capital and neigbourhood with the advent of winter.

Biggest culprit

The NASA firemap shows Punjab as the biggest culprit in terms of the extent of land where crop burning has been undertaken during the last seven days.

Except fringes along the eastern corridor, in north-central and south-west regions, crop burning has spread across its entire geography as also into the inter-state border separating contiguous Haryana.

To a lesser extent, Uttar Pradesh, Haryana, and Madhya Pradesh too have resorted to the practice.

Prevailing easterly to south-easterly winds have ensured that the smoke waft towards Delhi and neighbourhood.

The national capital region could do well with either a blast of dry westerly winds or well-endowed ‘western disturbances’ (periodical low-pressure waves) which trigger seasonal showers.

The dry winds would blow away the smog and its contents, while the winter-time precipitation heralded by western disturbances will wash down the smog.

Western disturbance

But Delhi would need to wait until the next week for relief on either front. For now, the winds are light north-westerly and would stay as such for the next three days.

This doesn’t help. Winter brings into play the typical ‘sinking motion’ of air that makes the latter sit over ground with its baggage of seasonal pollutants.

This is quite unlike in summer when the sun heats up the environment, air becomes warmer and lighter (signalling lower pressure that aids cloud formation and rain), rises and spreads out.

Judging from the India Met Department (IMD) projections, a ‘suitably-endowed’ western disturbance would arrive over North-West India triggering snow in the hills and thundershowers over the plains.

Thundershowers next week

Western disturbances originate from the Mediterranean, travel east across Iraq, Iran, Afghanistan and Pakistan before crossing the Rajasthan-Gujarat border into North-West India.

These disturbances are responsible for setting the tone for the winter weather over the country — ranging from being warm, wet or foggy to seasonal cold, chill or frost.

Warm western disturbances mean they carry moisture mopped up from the North Arabian Sea, which is precipitated over the hills and plains of North-West India.

A disturbance of this type is expected to bring rain/thundershowers to Delhi and its neighbourhood next week, promising to clean up the atmosphere.

Seasonal rains/thundershowers are keenly awaited also by farmers of the region.

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