Climate Change

In 5 graphs: How Monsoon 2021 is turning out to be an unusual one

Officially, it is still a normal monsoon but deficit level has been rising since July

By DTE Staff
Published: Thursday 26 August 2021
Photo: Wikimedia Commons
Photo: Wikimedia Commons Photo: Wikimedia Commons

The southwest monsoon is a key economic factor as close to 60 per cent of Indian farmers are dependent on rainwater for cultivation currently and monsoon-dependent agriculture employs more than 50 per cent of the Indian workforce. But the monsoon of 2021 has been unusual in many ways.

It has been marked by a long break; fewer low pressures in the Bay of Bengal, reducing rain events; a sudden increase in rainfall, leading to a surplus for a few weeks; and finally, consistently deficit rainfall.

Large areas are flooded. But more than one-third of districts are currently reporting deficit rainfall. “The southwest monsoon, one of the most stable weather systems on the planet, has gone for a toss in 2021,” reported Down To Earth July 12.  

Here are the key trends on the progress of the monsoon as it enters its last month of the season (June-September):

From the week beginning July 14, the monsoon has been reporting a deficit from the normal average. It has been the sixth consecutive week (ending August 25, 2021) that the monsoon has been deficit. On August 25, the India Meteorological Department (IMD) said the monsoon was deficit by 10 per cent.

According to the IMD, a rainfall deficit below 19 per cent is considered normal. So, the current level is officially well within the normal range.

The general trend since the week beginning July 14 is that of rise in the deficit level. This week, there was a deficit of five per cent and it continued for the next two weeks. The deficit level has gone up to 10 per cent on the week ending August 25, from six per cent in the week beginning August 11.

Photo: IMD. Green represents actual rainfall and blue represents normal

East and Northeast India have been reporting lower-than-average rainfall since the week obeginning July 7, 2021. In the next seven weeks, this deficit has consistently, rather dramatically, increased till the week ending August 25. The monsoon was deficit by 11 per cent at the end of this week.

Northwest India is an unusual case of the monsoon. It became largely deficit till August 25, from largely surplus in the beginning of the season. Till the week ending June 30, it had a surplus of 14 per cent.

In the week ending June 2, the region had a surplus of 226 per cent that was preceded by heavy rainfall and also resulted in a sporadic flood-like situation. Since the week ending July 7, the region has been reporting deficit rainfall. In the week ending August 25, the monsoon was deficit by 12 per cent.

The South Peninsula is the only region that has been reporting a surplus consistently. At the end of June, it had a surplus of 4 per cent; this increased to 22 per cent in July and currently stands at three per cent. 

Like Northwest India, the Central India region also had a surplus monsoon to begin with, but currently has a deficit of 13 per cent. By June end, it had a surplus of 17 per cent; by July-end, the surplus level came down to two per cent; and it has been a deficit across August.

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