Western Disturbances

Western disturbances are low-pressure storms originating in the Mediterranean Sea and play a crucial role during India's winter season. Driven by the Westerly Jet Stream, they bring much-needed rain to the north, nurturing the rabi crop and clearing pollution. It also causes a extreme cold leading to hail storms, fog and smog in some cases. As climate change exacerbates, they are becoming unpredictable which has led to both losses and benefits for India.

The Westerly Jet Stream, a fast-moving air current present high in the atmosphere, acts like a highway for Western Disturbances.High Pressure forms around the Mediterranean and a low pressure builds over Northern India. The strong westerly winds of the jet stream catch the disturbances which are building over the Mediterranean and propel them towards India at high speeds. The Jet Stream collide with the Himalayas and split into two. The southern part of the Westerly Jet then intensifies due to rising /vertial air movements leading to increased cloud formation and rain.

"Western disturbances" are low-pressure extra- tropical storms which arrive in India from the West, originating in the Mediterranean region during Winter season. They are the source of scant rain outside of the monsoon season in India. They are brought by the Westerly Jet Stream and cause snowfall in the Himalayas and a chill in Northern India. They are important for the Rabi crop, however they can also damage the crop due to its intensity.

• Brought in by the Westerly Jet Stream: The Westerly Jet is a strong current of air at the upper troposphere (around 6-18 km above sea level). It blows throughout the globe (30-60° N and 30-60°S respectively) and brings the Western Disturbance to India. It arrives from the Weste and gets split by the Himalayan ranges. While the northern Branch goes to Tibet, it is the Southern Branch which rains over the Northern India along the 25° N latitude.
• Low Pressure System: they are hot pockets of air containing moisture picked up from the Mediterranean Sea and blows over Iraq, Iran & Pakistan collecting moisture again from the Gulf Region.
• Extra-tropical storms: as they develop beyond the tropic of Capricorn in the Mediterranean sea.
• Winter Season: Their full effect is felt during the months of January and February, however it starts arriving in mid December.
• Precipitation: Causing snowfall, cold waves, dense fog and even hail storms in Northern India and in the Himalayas.

Western Disturbance form an integral part of the Indian Cliamte system brining rain and relief during the winter season. It ripes the rabi crop and also helps with settling the pollution. However, there are challenges as well since climate change is making all things unpredictable. With this the intensity of the western disturbance is also varying with it waning and strengthening in some seasons. Both strong and weak western disturbance can be bad for the crop as discussed above. There is need to invest in improve forecast technology to be able to mitigate impact of the western disturbance and also tackle climate change to preserve the ecosystem. Under the National Action Plan on Climate Change (NAPCC), Government of India has formulated the National Mission for Sustainable Agriculture (NMSA) make agriculture more resilient to climate change. ‘National Innovations in Climate Resilient Agriculture’ (NICRA) was setup by the Ministry of Agriculture in 2011 for this purpose as well.