Increase in extreme wet and dry spells in South Asian monsoon: Stanford Study

Scientists of Stanford have identified a significant change in the patterns of extreme wet and dry events in central India. In their study they claimed that this change has increased the risk of drought and flood. The central India region is one of the most densely populated regions on the Earth. The study was published on 28 April 2014 in the journal Nature Climate Change.

This study is the result of the new collaboration between statisticians and climate scientists with a focus on utilizing statistical methods for analyzing rare geophysical events. The approach adopted for the study has revealed that in recent decades, the intensity of extremely wet spells and extremely dry spells has increased during South Asian Monsoon season.

The researchers found that though the average total rainfall during the monsoon season has declined, the variability of rainfall during the peak monsoon months has increased.

In particular, they observed increase in the intensity of wet spells and in the frequency of dry spells, which have a significant adverse impact on the region, especially on crop yield.

For example, during critical crop growth stages, too many days without rain can reduce yields or lead to crop failure and short periods of very heavy rainfall can create humanitarian disasters, such as in Mumbai in 2005.

They also found changes in the atmosphere such as winds and moisture that are likely responsible for the changes in wet and dry spells. The next step is to investigate what might be causing the changes in the atmosphere.

Since India is a complex region, the researchers want to be sure before pointing at global warming or any other cause heavier down and more frequent dry spells.

A new collaboration of Climate Scientists and Statisticians focused on utilizing statistical methods for analyzing rare geophysical events. The team compared rainfall data gathered by the Indian Meteorological Department (IMD) and other sources over a 60-year period.  They compared peak monsoon rainfall patterns during two time periods: from 1951 to 1980, and from 1981 to 2011.

About pattern of monsoon in India
The South Asian summer monsoon is an annual wind-driven weather pattern that is responsible for 85 percent of India's annual precipitation. It is vital for the agricultural sector of India.

The monsoon in India typically starts in southern India and moves across the subcontinent. The monsoon season starts in June and lasts through September. Rainfall extremes during the months of the monsoon period can be as important as how much total water is received.