Global warming coupled with changes arising out of an evolving El Nino may have combined to cause the heavy spells of unseasonal rain which have devastated crops in many parts of India since late February, a leading meteorologist has said.
India received nearly double its average rainfall this March, making it the wettest March in 48 years, and the second wettest since record-keeping began in the country. Rains and hailstorms have continued into April, compounding crop losses in many states across north and central India.
M Rajeevan, director of Pune’s Indian Institute of Tropical Meteorology, said western disturbances (WDs), that cause rains in India in winter and spring, were deeper and extended more southward than usual in March this year.
“This southward extension caused excess rains over central India (in addition to north India). In this way, the winter precipitation was anomalous,” the meteorologist said. The frequency of WDs also increased. While March usually sees five-six WDs, this year there were eight. The average for April is five WDs. This year, however, there have been three already and another would arrive by April 15.
The unusual WD pattern, said Rajeevan, was due to “large scale anomalies in the mid-latitude circulation patterns”. There could be two possible reasons for this, he said. “One could be the large scale circulation anomalies associated with warming over the Pacific region. An El Nino event is growing over the Pacific region. In most El Nino years, we find this kind of more frequent mid-latitude systems and deep troughs moving across the Indian region”.
The second reason could be melting of Arctic Sea ice. “The Arctic Sea ice is melting due to global warming. This causes abnormal warming of the Arctic region, but forces the mid-latitude region towards south causing the mid-latitude jet stream shifting southwards. This can cause abnormal wetter winter season with extreme precipitation over Europe. Recent research shows this is happening during the recent years,” Rajeevan said.
