Scientists have developed an isotopic technique that can more precisely predict the withdrawal date of the southwest monsoon and the onset date of the northeast monsoon. Scientists from Pune’s Indian Institute of Tropical Meteorology (IITM) published a paper in the international journal ‘Water resources research’ of the American Geophysical Union on August 15 this year.
The paper titled ‘Modulation of the precipitation isotopes by the dynamic and thermodynamic variables of the atmosphere in southern parts of India’ proposes a new technique that can more precisely predict the withdrawal date of the southwest monsoon and the onset of the northeast monsoon.
Scientists emphasised that the isotopic technique can more precisely predict the date of onset of northeast monsoon according to which agriculture practices like ploughing and sowing are dependent in the southern peninsular parts of India.
Supriyo Chakraborty, senior scientist at IITM and author of the paper, said that the paper is crucial as a prediction of withdrawal date is less precise compared to monsoon onset date as withdrawal of southwest monsoon and onset of the northeast monsoon is a gradual process.
“Onset date prediction is relatively easy as the climatological conditions change drastically. But for the southwest monsoon when it is withdrawing, the northeast monsoon is advancing. Unlike the monsoon onset, the meteorological conditions during the withdrawal phase change slowly, as a result, a precise estimation of the withdrawal date becomes difficult,” he said.
{{/usCountry}}“Onset date prediction is relatively easy as the climatological conditions change drastically. But for the southwest monsoon when it is withdrawing, the northeast monsoon is advancing. Unlike the monsoon onset, the meteorological conditions during the withdrawal phase change slowly, as a result, a precise estimation of the withdrawal date becomes difficult,” he said.
{{/usCountry}}“Monsoon spreads for four months, from June to September, approximately for 120 days. Meteorologists want to know how long the monsoon season continues in a given year and how it varies from year to year. Hence a better prediction of the monsoon withdrawal date is also essential for academic purposes,” he said.
He added that the isotopic technique may be potentially useful in accurately predicting the withdrawal of southwest monsoon and the onset of northeast monsoon season.
“Monsoon circulation is south-westerly during the summer and north-easterly during the winter. These two opposing circulation regimes cause isotopic seasonality in south peninsular India. Meteorological parameters such as rainfall, wind speed, etc., display sharp changes during the summer monsoon onset in early June. But they change rather slowly during the transition from summer to winter monsoon season around late September–early October. As a result, the estimation of the summer monsoon withdrawal date may have considerable uncertainty. It is proposed that applying the isotopic technique may be potentially helpful in reducing such an uncertainty,” said Chakraborty.