With a 36 per cent deficit, India recorded the driest August since 1901. August receives 254.9 mm of rainfall, accounting for around 30 per cent of the precipitation during the monsoon season. The actual rainfall recorded in August was 162.7 mm.
After excess rainfall in July, the Southwest Monsoon played truant for most of August which witnessed 20 break days, from Aug 6-17, Aug 21-22 and Aug 26-31.
India recorded a rainfall deficit of 25 per cent in August 2005; 24.6 per cent in 1965; 24.4 per cent in 1920; 24.1 per cent in 2009 and 24 per cent deficit in 1913, according to the IMD data.
The primary reasons for below-normal rainfall in August are El Nino and the unfavourable phase of the Madden-Julian Oscillation (MJO). El Nino is generally associated with the weakening monsoon winds and dry weather in India.
India Meteorological Department (IMD) chief Mrutyunjay Mohapatra said September was likely to witness normal rainfall in the range of 91-109 per cent of the long period average of 167.9 mm.
Madden-Julian Oscillation (MJO)
• The Madden-Julian Oscillation is a large-scale intraseasonal atmospheric disturbance originating in tropical Africa and travelling eastwards. It is like a pulse or wave lasting about 30 to 60 days.
• The MJO was first discovered in the early 1970s by Dr. Roland Madden and Dr. Paul Julian of the American National Centre for Atmospheric Research (NCAR), when they were studying tropical wind and pressure patterns. They observed regular oscillations in winds between Singapore and Canton Island in the west central equatorial Pacific.
• The MJO consists of two cycles. One is the enhanced rainfall (or convective) phase and the other is the suppressed rainfall phase. Each cycle lasts approximately 30-60 days and there are eight phases.
What is El Nino and La Nina?
• El Nino and La Nina events are a natural part of the global climate system. They occur when the Pacific Ocean and the atmosphere above it change from their neutral (‘normal’) state for several seasons.
• El Nino, which is the warming of the waters in the Pacific Ocean near South America, is generally associated with the weakening of monsoon winds and dry weather in India.
•La Nina, which is the opposite of El Nino, typically brings good rainfall during the monsoon season.
• These changes in the Pacific Ocean and its overlying atmosphere occur in a cycle known as the El Nino–Southern Oscillation (ENSO).
• The term ‘El Nino’ translates from Spanish as ‘the boy-child’. Peruvian fishermen originally used the term to describe the appearance, around Christmas, of a warm ocean current off the South American coast. It is now the commonly accepted term to describe the warming of the central and eastern tropical Pacific Ocean. ‘La Nina’ translates as ‘girl-child’ and is the opposite ENSO phase to El Nino.
