PANAJI
Goa's unusually prolonged dry spells during the first two months of this year's southwest monsoon may offer a glimpse into what the future holds, as scientists have warned that climate change is likely to make the Indian summer monsoon increasingly erratic with longer rainless periods punctuated by short bursts of intense rainfall.
The warning comes from a new study by scientists from the Centre for Atmospheric Sciences and Climate Studies (TROPIC), which projects a significant increase in prolonged "break spells"- extended periods of little or no rainfall during the southwest monsoon across India in the coming decades, particularly during July and August, the peak monsoon months.
The study estimates that the occurrence of long break spells lasting more than seven days could rise by 50 per cent during 2021-2040, 62 per cent during 2041-2060, and 75 per cent by 2081-2100 compared to the historical period.
The findings resonate with Goa's monsoon this year, which has been marked by prolonged dry spells, an unusual pattern for a State that traditionally receives fairly continuous rainfall during June and July. The State is currently facing over 32 per cent rainfall deficit.
Using a multi-model ensemble of five of the best-performing Global Climate Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) under the SSP2-4.5 emissions scenario, the researchers assessed future changes in active and break phases of the Indian summer monsoon driven by the Monsoon Intraseasonal Oscillation (MISO) and the movement of the monsoon trough across central India.
At the same time, short active spells-periods of rainfall lasting less than seven days-are also projected to become more frequent, increasing by 27 per cent in the near term, 33 per cent by the mid-century, and 60 per cent by the end of the century.
As per the researchers, the changing pattern suggests that future monsoons will increasingly be characterised by alternating episodes of prolonged dry weather and short-lived but intense rainfall instead of sustained, evenly distributed precipitation.
The study further found that rainfall associated with MISO is expected to become stronger. The contribution of MISO-driven rainfall to the overall Indian Summer Monsoon Rainfall is projected to increase from 4.08 dB during the historical period to 6.67 dB by the mid-century, while rainfall generated by synoptic-scale weather systems is expected to increase from 3.7 dB to 5.38 dB.
