A Beacon of Climate Data
At the southernmost point of Sri Lanka stands the Dondra Head Lighthouse, an octagonal brick tower that has been operational since March 1890. Designed by Sir James Nicholas Douglass, the 49-meter (161-foot) structure is the tallest lighthouse in the country. Its construction was an imperial project; the steel and bricks were imported from England, while granite came from quarries in Dalbeattie, Scotland, and Penryn, Cornwall. The lighthouse itself is a navigational aid, but its scientific contribution comes from the weather station established on its grounds.
Since 1889, this station has compiled a nearly uninterrupted record of meteorological data. Its location on Dondra Head is optimal for observing the atmospheric and oceanic systems that govern Sri Lanka's climate. The island experiences two distinct monsoon seasons: the Yala or southwest monsoon from May to October, and the Maha or northeast monsoon from December to March. The Dondra data provides a high-resolution, ground-truth account of these complex weather systems, recording daily measurements of rainfall, temperature, and wind. This long-term dataset is used by scientists studying climatic shifts over more than a century.
Decoding the Monsoon
The Dondra phenology station's records show that Sri Lanka's climate is changing. While global climate models predict general trends, they often fail to capture the local nuances of monsoon behavior. The Dondra data reveals specific shifts in the timing, intensity, and duration of the Yala and Maha monsoons. Scientists have observed a trend towards shorter, more intense bursts of rain replacing the steady, prolonged monsoons of the past. This increased variability leads to a greater risk of both flash floods and droughts, sometimes in the same season.
This detailed historical record is used for improving climate projections. The data from Dondra allows researchers to calibrate and test their models against real-world observations. For example, the records help in understanding the local impacts of large-scale climate drivers like the El Niño-Southern Oscillation, which can cause below-average rainfall during the northeast monsoon in El Niño years. By documenting more than 130 years of weather, this single station at the edge of the Indian Ocean provides a record of the mechanics of a changing climate.