Winter in the Western Himalayas fluctuates by 50% across the Atlantic Ocean between the Azores and Iceland

The amount of winter rain and snow in the western Himalayas can fluctuate by around 50% depending on the atmospheric pressure gradient across the Atlantic Ocean between the Azores and Iceland, according to a study led by the University of Reading.

Atlantic air changes supply to India

(Photo: AFP via Getty Images)

Scientists have spent decades trying to determine the origins of the relationship between the two places, according to ScienceDaily.

This new study adds to the body of knowledge that could lead to more accurate predictions of winter rainfall levels in India months in advance.

The results could be used to increase agricultural yields of essential crops like wheat and barley, as well as help manage the country’s vital water supply.

Dr Kieran Hunt, lead author of the study and tropical meteorology researcher at the University of Reading, said: “Although we are thousands of miles away, we know that pressure patterns over the Atlantic north have some impact on winter weather in the western Himalayas.”

However, scientists have spent years trying to figure out what this relationship is and how strong it is.

The correlation we discovered could be hugely beneficial for states and rural populations in northwest India who depend on winter rains and snow for food and water.

Watching the North Atlantic for any movement towards wetter or drier weather could be a lifeline in preparing for water shortages or flooding.

The new study, published in Climate Dynamics, examined the relationship between the North Atlantic Oscillation (NAO) and winter rainfall and snowfall in the western Himalayas.

The large difference between the high pressure in the Azores and the low pressure around Iceland pulls the North Atlantic jet stream north during a positive NAO phase.

The storms are brought to northwest India by additional disturbances in the subtropical jet.

According to the study, winter storms in the region were 20% more frequent and 7% more powerful during a positive phase of NAO than during a negative phase.

That jumped to 31% more frequent winter storms in places where they already happen often.

This resulted in an average of 40% more moisture carried by the subtropical jet, bringing 45% more rain and snow to the western Himalayas during the winter months when the NAO was positive.

Storms in northwest India are expected to hit regions such as Jammu and Kashmir, Punjab, Gujarat and southern Pakistan.

The study relied on data from the European Center for Medium-Range Weather Forecasts and other organizations, as well as rain gauge data from the Western Himalayan region provided by the Indian Meteorological Department, which lasted 70 years.

The authors found the highest link in NAO change over the 2-3 and 12-16 year cycles. Gradual changes in the NAO provide better forecasts of wetter or drier than average northwest India winter weather conditions up to three months in advance.

Apart from helping crops grown during the winter, the snow that falls on the Himalayas melts and feeds the rivers throughout the spring, making it an essential element for water security in India.

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Water supply and food in India

Rao Bahadur NS Joshi explores strategies for meeting projected 1971 needs in a booklet titled “Food and Irrigation Problems Affecting India in General and Bombay in Particular”, according to Nature.

It mainly deals with the engineering elements of irrigation which are supposed to be necessary; and, while the nutritional discussion is mainly in terms of area and tonnages grown, the need to improve diet is not overlooked.

A universal movement of food from surplus regions to “deficit” regions is impossible because of the great distances. According to the author, the solution is a significant expansion of irrigation; but in Bombay the type of dam and canal irrigation which has been so spectacularly successful in the river plain regions is not feasible.

The article can be considered a reasoned critique of canal irrigation. Bounding cropping can increase yields in steep locations, however, ideal crops for mountain farming are cereals of low nutritional value, which Bombay generally has in abundance; and profiling is incompatible with capture storage.

Consequently, the final answer for the province of Bombay is a massive increase in the number of tiny wells. The author recommends how these should be planned and financed, as well as how dams and water storage structures could be provided to make the most of all available water resources.

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