Indian scientists decode Himalayan air motions to sharpen monsoon prediction models

Accurate prediction of the Indian monsoon is vital for crop planning, reservoir management, disaster preparedness, and air-quality assessment across the region.

A team of Indian scientists has made a major breakthrough in understanding how vertical air motion over the Himalayas shapes the Indian monsoon—South Asia’s most critical climate system and a lifeline for millions of people dependent on rainfall for agriculture, water security, and livelihoods.

Accurate prediction of the Indian monsoon is vital for crop planning, reservoir management, disaster preparedness, and air-quality assessment across the region. While scientists have long studied horizontal winds, vertical air movement—especially over the complex Himalayan terrain—has remained poorly understood due to the lack of direct, long-term observations.

Addressing this gap, researchers from the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science & Technology (DST), Nainital, in collaboration with the Space Physics Laboratory (SPL) of ISRO, Thiruvananthapuram, conducted the first direct, high-resolution measurements of vertical air motion during the Asian Summer Monsoon (ASM) over the central Himalayas.

The study focused on the Asian Summer Monsoon Anticyclone (ASMA)—a massive, persistent circulation system that dominates the upper atmosphere over South Asia during monsoon months and plays a crucial role in transporting heat, moisture, pollutants, and greenhouse gases.

Cutting-edge observations over the Himalayas

To achieve this, scientists used an indigenously developed Stratosphere–Troposphere (ST) radar installed at ARIES, Nainital. Over a period of two years, the radar was continuously pointed upward, collecting thousands of hours of data under all-weather conditions. This advanced system enabled researchers to directly observe extremely faint vertical air motions—down to 5 centimetres per second—with unprecedented accuracy.

Until now, studies of vertical motion in this region relied mainly on indirect methods such as weather balloons or satellite data, which cannot fully capture fine-scale, long-term variability in rugged mountainous terrain. The radar-based observations filled this critical knowledge gap.

Key discoveries

The researchers identified a persistent downward-moving air layer between 10 and 11 kilometres altitude during monsoon months—a previously unobserved feature. This discovery reveals a distinct zone of descending air in the upper troposphere, indicating that vertical circulation within the ASMA is far more complex than earlier models suggested.

The findings show:

• Alternating regions of rising and sinking air within the monsoon anticyclone

• Strong variability in vertical air motion in the lower and middle troposphere

• A relatively steady upward flow above 12 km, largely unchanged across monsoon months

Together, these patterns point to a “two-step” vertical transport process, in which air rises from the lower troposphere and is gradually transferred toward the stratosphere through layered circulation pathways.

Implications for weather, climate, and air quality

The research, published in the journal Earth and Space Science by the American Geophysical Union (AGU), has far-reaching implications. By improving scientific understanding of vertical airflow over the Himalayas, the findings can:

• Enhance monsoon forecasting accuracy

• Strengthen early-warning systems for floods and extreme rainfall

• Improve climate and atmospheric circulation models

• Support better assessment of pollutant and greenhouse gas transport

• Aid air-quality management and climate change mitigation strategies

Understanding how air ascends and descends within the Asian Summer Monsoon Anticyclone is particularly important for tracking how pollutants and climate-forcing gases are redistributed across South Asia and into the upper atmosphere.

The study represents a significant step forward in monsoon science and demonstrates India’s growing capability in advanced atmospheric observations using indigenous technology.