Scientists estimate turbulence parameters over central Himalayas

For the first time, scientists have been able to estimate the air turbulence parameters in the lower troposphere over the central Himalayan region, which is likely to make weather predictions more accurate and help prevent air traffic disasters.

The study by scientists at the Aryabhatta Research Institute of Observational Sciences (ARIES), which works under the government’s Department of Science and Technology (DST), has been published in Radio Science journal.

While the turbulence parameters for southern India are known earlier, the same over the Himalayan region were not known, and hence some approximate values were used by modellers for calculations and forecasts.

“They have now been found to be much higher over the Himalayan region. Now modellers will be able to update these values in their existing models. This will help in improving weather predictions. Also, precise knowledge on turbulence over this region will help in safe air traffic movements,” a statement by the Department of Science and Technology (DST) said.

The researchers have calculated the magnitude of refractive index structure (Cn2), a constant that represents the strength of the atmospheric turbulence, using observations from their Stratosphere Troposphere Radar (S T Radar).

The study, led by Aditya Jaiswal, a PhD student at ARIES, Nainital, and ARIES faculties DV Phani Kumar, S Bhattacharjee, and Manish Naja has found that the refractive index structure constant (Cn2) is as large as 10-14 m-2/3.

Such large values at the lower altitudes are due to the mountain wave activities and presence of low-level clouds.

“Proper and timely information of the higher values of the atmospheric turbulence parameters and understanding of time and space distribution of turbulence structure in the troposphere could help improve performance of numerical weather prediction and climate models,” the study stated.

“It is also important to model clear-air turbulence as that would aid in limiting the air traffic disasters, particularly over the complex mountainous regions,” it added.

Low levels of cloud are generated in a mountainous region with complex topography. Because of this, stable air in this region is set into oscillations known as mountain waves and lee waves.

Characterisation of turbulence in the mountainous region is vital to understand the dynamics of mountain-induced wave disturbances and other related phenomena, which have a crucial role in modulating the general circulation wind patterns.