Researchers develop algorithm to track shear lines

Filipino-led researchers have developed a physics-based algorithm to identify and track shear lines.

Shear lines are "kilometers-long bands of converging warm and cold air that are constantly shifting" and difficult to spot even via satellite, according to the study conducted by researchers from the Ateneo de Manila University, the Manila Observatory, Tokyo Metropolitan University, and the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA).

Analysis of decades of rainfall data linked to shear lines will help quantify their contribution to extreme rainfall during the Northeast Monsoon season and identify areas most at risk of heavy rain.

The study found that shear lines contributed up to 20% of all extreme rainfall days during the Northeast Monsoon season between 1979 and 2022, "with the greatest influence observed in November and December."

“There are no universally accepted thresholds for detecting shear lines, unlike cold fronts or tropical cyclones,” said lead researcher Lyndon Mark Olaguera, noting that shear lines form when cold fronts lose structure over warm ocean waters.

“The primary application of the algorithm is in weather forecasting and the development of early warning systems, but it can also be applied to climatological studies; the verification of numerical models, for example, assessing whether existing mathematical models can capture shear lines; the improvement of numerical weather prediction parameterizations, such as adjusting physical schemes if shear lines are not well represented; and the validation of forecast system performance,” he added.

The study was published in the Meteorological Society of Japan’s Scientific Online Letters on the Atmosphere (SOLA) in November 2025.—MCG/VBL, GMA Integrated News