<p>Cold waves have impacted northern India since the last week of December, with heavy rains contributing to a sharp drop in temperature. <a href="https://www.deccanherald.com/tags/imd">Indian Meteorological Department (IMD)</a> has predicted the weather will continue in the new year, with dense smog and fog reducing visibility and affecting travel. Heavy snowfall has blanketed northern parts. IMD issued yellow alerts and warned travellers to be prepared for road, rail and air transport disruptions.</p>.<p>Winter rains in north Indian plains are caused by western disturbances, which originate from the low-pressure system formed in the Mediterranean and then travel eastwards across the country. In the Indian subcontinent, the Himalayas block these disturbances, causing widespread rains in the northwestern plains and snow in the west of the Himalayas. </p>.<p>Further, northeast trade winds prevailing in India bring dry weather to most regions, including the peninsula, which experiences less defined cold weather due to the moderating influence of the seas. At the same time, retreating monsoons cause rainfall on the Tamil Nadu coast.</p>.Over 12 lakh destitute cows protected in 7,696 shelters amid cold wave: Uttar Pradesh government.<p>World Meteorological Organization (WMO) has said 2024 was the warmest year on record based on global average temperature. It has breached a 1.45-degree Celsius average rise above the pre-industrial temperature recorded in 2023. Indian Meteorological Department (IMD) also came up with a report on 1st January 2025 that 2024 was the warmest year since 1901, breaching the Indian record 2016 by 11 degrees Celsius. The sea surface temperatures have risen relatively high during November and December.</p>.<p>The warm and moist air over the ocean's surface moves above it, leaving less air near it and thus creating a low-pressure area. High-pressure air in the surrounding area pushes in the low pressure already developed, and the new air also becomes warm and moist and rises. So long as warm air continues to rise, the surrounding air swirls in to take its place. The warm and moist air rises and cools off, and the formation of clouds takes place. </p>.<p>Storms originating from seas are natural phenomena caused by violent atmospheric disturbances on land and sea. They are formed when the centre of low pressure develops with a high-pressure system around them. These storms develop between 50 and 300 N latitudes in the northern hemisphere and south of the Tropic of Cancer. If the wind velocity is less than 60 km per hour, the storm is a tropical depression; if it is between 60 and 120 km per hour, it is a tropical storm; and if it is more than 120 km per hour, it is a tropical cyclone. </p>.<p>Western disturbances are low-pressure systems bringing snow and rain in the monsoon winter season across Pakistan and northwest India, contributing 5 to 10 per cent of annual rainfall in the region. They are helpful to wheat crops grown in the season. As against cyclonic storms occurring in the tropical region south of the Tropic of Cancer, western disturbances develop in the mid-latitude region and north of the Tropic of Cancer.</p>.<p>These are low-pressure systems embedded in the western winds from west to east. The low pressure formed over the Mediterranean travels over Iran, Iraq, Afghanistan, and Pakistan and enters the northwest region of India. These disturbances eventually come up against the Himalayas and get blocked, causing moisture to get trapped and precipitation in rain and snow.</p>.<p>Easing the pollution?</p>.<p>Since the western disturbances have arrived, the region is locked in a cycle of fog, heavy showers, drizzle and low clouds. Before the arrival of western disturbances, the Delhi NCR region annually grapples with severe pollution due to several anthropogenic activities. During November and December, when vertical air circulation ceases, a high concentration of PM 2.5 is reported in the region, leading to the Air Quality Index (AQI) registering an inferior and severe category. </p>.<p>The leading causes of high pollution have been the transport sector, industrial emissions, biomass burning, road dust, residential emissions, brick kilns, and stubble burning in the states surrounding Delhi. So long as the dry winter prevails, the pollution in the region is a significant health hazard for humans, especially children and old persons.</p>.<p>Currently, the weather has caused a big relief from pollution. AQI has improved, and the suspension of activities like schools, construction works, movement of vehicles, etc., has been eased. The planners and the policymakers in the government sector would not have to scratch their heads for cloud bursts. IMD has already predicted slightly more rainfall than normal rains for January 2025, especially in north India; thus, cold wave conditions will likely persist.</p>.<p>Pollution is a more significant health hazard than cold-wave conditions. The annual cycle of pollution in Delhi NCR is a bigger worry, and authorities have failed to find a workable solution. The only feasible solution is to entirely phase out fossil fuel burning and wholly depend on renewable energy. </p>.<p><em>(The author is a retired principal chief conservator of forests, Karnataka)</em></p>
<p>Cold waves have impacted northern India since the last week of December, with heavy rains contributing to a sharp drop in temperature. <a href="https://www.deccanherald.com/tags/imd">Indian Meteorological Department (IMD)</a> has predicted the weather will continue in the new year, with dense smog and fog reducing visibility and affecting travel. Heavy snowfall has blanketed northern parts. IMD issued yellow alerts and warned travellers to be prepared for road, rail and air transport disruptions.</p>.<p>Winter rains in north Indian plains are caused by western disturbances, which originate from the low-pressure system formed in the Mediterranean and then travel eastwards across the country. In the Indian subcontinent, the Himalayas block these disturbances, causing widespread rains in the northwestern plains and snow in the west of the Himalayas. </p>.<p>Further, northeast trade winds prevailing in India bring dry weather to most regions, including the peninsula, which experiences less defined cold weather due to the moderating influence of the seas. At the same time, retreating monsoons cause rainfall on the Tamil Nadu coast.</p>.Over 12 lakh destitute cows protected in 7,696 shelters amid cold wave: Uttar Pradesh government.<p>World Meteorological Organization (WMO) has said 2024 was the warmest year on record based on global average temperature. It has breached a 1.45-degree Celsius average rise above the pre-industrial temperature recorded in 2023. Indian Meteorological Department (IMD) also came up with a report on 1st January 2025 that 2024 was the warmest year since 1901, breaching the Indian record 2016 by 11 degrees Celsius. The sea surface temperatures have risen relatively high during November and December.</p>.<p>The warm and moist air over the ocean's surface moves above it, leaving less air near it and thus creating a low-pressure area. High-pressure air in the surrounding area pushes in the low pressure already developed, and the new air also becomes warm and moist and rises. So long as warm air continues to rise, the surrounding air swirls in to take its place. The warm and moist air rises and cools off, and the formation of clouds takes place. </p>.<p>Storms originating from seas are natural phenomena caused by violent atmospheric disturbances on land and sea. They are formed when the centre of low pressure develops with a high-pressure system around them. These storms develop between 50 and 300 N latitudes in the northern hemisphere and south of the Tropic of Cancer. If the wind velocity is less than 60 km per hour, the storm is a tropical depression; if it is between 60 and 120 km per hour, it is a tropical storm; and if it is more than 120 km per hour, it is a tropical cyclone. </p>.<p>Western disturbances are low-pressure systems bringing snow and rain in the monsoon winter season across Pakistan and northwest India, contributing 5 to 10 per cent of annual rainfall in the region. They are helpful to wheat crops grown in the season. As against cyclonic storms occurring in the tropical region south of the Tropic of Cancer, western disturbances develop in the mid-latitude region and north of the Tropic of Cancer.</p>.<p>These are low-pressure systems embedded in the western winds from west to east. The low pressure formed over the Mediterranean travels over Iran, Iraq, Afghanistan, and Pakistan and enters the northwest region of India. These disturbances eventually come up against the Himalayas and get blocked, causing moisture to get trapped and precipitation in rain and snow.</p>.<p>Easing the pollution?</p>.<p>Since the western disturbances have arrived, the region is locked in a cycle of fog, heavy showers, drizzle and low clouds. Before the arrival of western disturbances, the Delhi NCR region annually grapples with severe pollution due to several anthropogenic activities. During November and December, when vertical air circulation ceases, a high concentration of PM 2.5 is reported in the region, leading to the Air Quality Index (AQI) registering an inferior and severe category. </p>.<p>The leading causes of high pollution have been the transport sector, industrial emissions, biomass burning, road dust, residential emissions, brick kilns, and stubble burning in the states surrounding Delhi. So long as the dry winter prevails, the pollution in the region is a significant health hazard for humans, especially children and old persons.</p>.<p>Currently, the weather has caused a big relief from pollution. AQI has improved, and the suspension of activities like schools, construction works, movement of vehicles, etc., has been eased. The planners and the policymakers in the government sector would not have to scratch their heads for cloud bursts. IMD has already predicted slightly more rainfall than normal rains for January 2025, especially in north India; thus, cold wave conditions will likely persist.</p>.<p>Pollution is a more significant health hazard than cold-wave conditions. The annual cycle of pollution in Delhi NCR is a bigger worry, and authorities have failed to find a workable solution. The only feasible solution is to entirely phase out fossil fuel burning and wholly depend on renewable energy. </p>.<p><em>(The author is a retired principal chief conservator of forests, Karnataka)</em></p>