Ground-based airglow imager reveals drastic shift in monsoon rainfall pattern over Maharashtra

Scientists of  the Indian Institute of Geomagnetism (IIG) have found a significant alteration in the monsoon rainfall pattern over Kolhapur, Maharashtra. Utilising data from ground-based airglow imagers, the research sheds light on a climatic shift during the pre-monsoon months of March to May, spanning from 2016 to 2020.

Clouds, often overlooked factors in Earth's climate dynamics, have been identified as one of the key players in this transformation. Their influence on the atmosphere, through scattering incoming solar radiation and regulating outgoing long-wave radiation, is pivotal. According to the study, the intricate interplay of cloud parameters, including height, thickness, size distribution, and spatial-temporal distribution, brings about nonlinear effects on the climate.

According to the Ministry of Science and technology’s official statement scientists repurposed all sky imager data, conventionally used for upper atmospheric studies, to trace cloud movements over Kolhapur (16.8° N, 74.2° E). This unexplored application of cloudy sky data has unveiled information previously deemed irrelevant for airglow research.

The high spatial resolution of the all sky imager enabled a precise comparison with INSAT data of 10 km resolution, the statement stated. Over the period of 2016 to 2020, during the crucial pre-monsoon months, the researchers calculated cloud motion vectors, cloud coverage percentages, and the direction of cloud movement.

Surprisingly, the study reveals a significant slowdown in cloud speed in 2017, with speeds averaging ‘10±3 m s–1’, contrasting sharply with other years where speeds exceeded ‘15±3 m s–1’. Intriguingly, the clouds exhibited a consistent south-westerly movement, aligning with the winds originating from the Arabian Sea, due to Kolhapur's proximity to this massive body of water.

As per the Ministry, the research has unearthed a pivotal trend: the cloud propagation direction is progressively veering southward as the year advances. This shift is most pronounced in March and April, suggesting a potential linkage to larger climatic transformations. The implications of this shift are profound, potentially imprinting alterations in the region's rainfall behaviour.