Ahmedabad: Have you ever experienced a sudden, unexpected change in the weather? Like a heavy downpour when the forecast clearly predicted a dust storm that should have sent everything flying? On May 13 last year, Ahmedabad experienced a significant dust storm. Dust storms are not unusual in the city, a semi-arid region, particularly during the pre-monsoon season. However, this one was different, not only in its dust intensity but also because of the chain of events that led to the city receiving 19mm of rainfall.
A study by a team of Physical Research Laboratory (PRL) scientists led by Som Kumar Sharma, along with researchers from a few other institutes, examined this unexpected event in detail. They discovered how the dust particles acted as cloud condensation nuclei, leading to the formation of deep convective clouds and subsequent heavy rainfall.
“This highlights the crucial role of dust in modifying cloud microphysical properties and influencing precipitation patterns. This interaction between dust and clouds can result in intense precipitation events,” states the study published in the Jan 2025 edition of the journal, “Remote Sensing Applications: Society and Environment.”
Sharma, along with researchers D K Kamat, P Kumar, K N Kumar, Aniket, S Saha, and H Bencherif, meticulously studied data from ground-based ceilometer lidar and satellite data (INSAT-3D, MODIS, VIIRS, ERA5, Radiosonde) to observe how this dust storm was triggered by the outflow from two convective systems originating in southwest Gujarat and southeast Rajasthan.
This outflow, combined with a deepening thermal low core over Ahmedabad, generated strong near-surface winds that initiated the dust storm. The scientists noticed how the atmospheric boundary layer (ABL) — the lowest part of the atmosphere — experienced a dramatic transformation, with the mixed layer collapsing from 2.5km to just 250 metres due to the dust load. After the storm, the ABL remained shallower, peaking at 800 metres the following day. This led the dust storm to form deep convective clouds, extending up to 11km, resulting in 19mm of rainfall, with nearly 15mm falling within an hour.
The study highlights a critical issue: how extreme weather events can disrupt our usual weather predictions. By understanding how dust storms form and by observing similar phenomena in other regions, we can improve our weather forecasting capabilities. This is crucial, because these storms can have significant impacts on transportation, agriculture and human health.