In the last two weeks of monsoon, severe and devastating rainfall activity poured down in Central India, triggering dams spilling and floods. In such extreme conditions, it is crucial for everyone to know when the monsoon is expected to withdraw. However, Meteorological services currently forecast monsoon withdrawal only a few days in advance. “Niels Bohr once remarked ‘It's hard to make predictions, especially about the future’”, Elena Surovyatkina from PIK says. “It is indeed hard, but sometimes it is possible – when certain processes work by some rules and these rules are understood. We found that the monsoon withdraws from central India coincides with the decrease of daily average temperature in North Pakistan to the value in the Eastern Ghats."
Observations confirm the prediction based on the new methodology
The researchers predicted the monsoon withdrawal from the Eastern Ghats around October 5th on July 27, 2016. The prediction includes an estimation error of five days, which means the withdrawal date could be between October 1st and 10th.
After monsoonal withdrawal, the predictions can be compared with the observed withdrawal. “The Southwest monsoon has been withdrawing from the region of our forecast (the Eastern Ghats, grid point 20N, 80E) during several days. On October 10th, the relative humidity started to decrease, following the monsoon condition in the previous week (95 percent level). On October 11th-12th, the relative humidity passed below the 80 percent threshold, and a transition back to a monsoon state is nearly impossible (see PIK-Prediction Figure). Hence, the date of the start of monsoon withdrawal, October 10th, coincided within uncertainties with our forecast.” - said Elena Surovyatkina
These observations were confirmed by the data from the Indian Meteorological Department (see IMD maps): October 11-th - from 1 to 25 percent of meteorological stations in the area 75000 km2 around the region of our forecast reported only isolated rain; October 12-th -100 percent of meteorological stations reported 'No rain' in the region of our forecast, and also in all surrounding regions as well as in regions located across the subcontinent in the direction from the North Pakistan to the Bay of Bengal.
The team was able to correctly predict the onset and withdrawal dates of the Indian summer monsoon over the Eastern Ghats region in Central India for 40 and 70 days in advance respectively. “This has shown the strong potential of our new technique even for real predictions and not only retrospectively or hindcast"- says Jürgen Kurths, Chair of PIK’s research domain Transdisciplinary Concepts and Methods.
The monsoon timing is changing
In May 2016, India recorded its highest-ever temperature of 51C. The monsoon floods in Indian this year have also broken previous records. These weather-related mega-disasters such as heat waves and severe and devastating downpours are occurring under climate change.
"In the last several years, observational data show that the length of monsoon season increases due to the late withdrawal of monsoon that associates with climate change”, explains Veronika Stolbova. “This fact points out that nowadays it becomes harder to predict monsoon withdrawal based on the historical data. Our method makes possible a long-range forecasting based on observations only."
“Predicting monsoon withdrawal is instrumental for sustaining agriculture and improving water management”, adds Bodo Bookhagen from Potsdam University. - The improved prediction scheme allows to plan with water resources more accurately.”
Future plans
The scientists found that the IMD Maps of Advance and Withdrawal of Southwest Monsoon across India based on long history of inaccurate monsoon timing have to be reconsidered. “In the future, we are going to extend a region of our forecast to Telangana where we have well-established scientific collaborations with Indian scientists and authorities”, adds Elena Surovyatkina. “We also plan to collaborate with IIT Madras for predicting floods in Chennai. We stand ready to launch negotiations with other states for improving the monsoon timing in other regions of India.”
Moreover, the researchers intend to develop a scheme of reasonable distribution of meteorological stations over the Indian subcontinent to improve observational data in most significant areas. “In particular, in North Pakistan the number of meteorological stations there is quite low”, says Surovyatkina. “That means a misinformation on weather conditions in North Pakistan can affect life and prosperity of about billion inhabitants in North and Central India as well.”
See also:
Successful early forecasting of Indian Monsoon
https://www.pik-potsdam.de/news/in-short/early-forecasting-of-indian-monsoon-is-successful?set_language=en
Indian monsoon: novel approach allows early forecasting:
https://www.pik-potsdam.de/news/press-releases/indian-monsoon-novel-approach-allows-early-forecasting?set_language=en
