India is expected to witness a ‘near normal’ monsoon this year, according to the India Meteorological Department (IMD). This forecast gives hope to the agriculture sector as well-distributed rainfall will benefit crops. However, there are also indications of a significant probability for the monsoon falling in the ‘below normal’ category.
Monsoon Forecasts
IMD stated that the monsoon rainfall forecast is at 96% of the Long Period Average (LPA), which equates to about 89 cm. This value is based on a 50-year average of India’s monsoon rains and is classified as “near normal.” Rainfall that falls in the range of 90%-96% of the LPA is considered ‘below normal’.
Despite the IMD’s forecast, private agency Skymet projected a below-average monsoon in 2019 due to the possibility of El Nino. Recently, US weather agencies forecasted a 60% chance of El Nino occurring this summer season.
Understanding El Nino
The term El Nino refers to a warming in the Pacific Ocean. A rise in temperature greater than 1 degree Celsius for three consecutive months is considered a ‘strong’ El Nino and poses a threat to the monsoon. Currently, the El Nino condition is rated as weak with a temperature rise of only 0.9 C.
Under ‘normal’ conditions, the west tropical Pacific is warmer than its eastern basin. This area is associated with cloudiness and rainfall. During El Nino years, the warmth shifts to Central and East Tropical Pacific along with cloudiness and rainfall. El Nino has been found to impact almost half the world, causing droughts and floods.
Unfortunately, no direct correlation has been established yet between the ENSO events and the monsoons.
The Influence of Other Factors
Apart from El Nino, several other factors can influence the monsoon. These include the location of warming in the Pacific, the progressive heating of the land, and the extent of Himalayan/Eurasian snow cover. Warmer subcontinent temperatures can intensify monsoon circulation and result in more rain.
| Factor | Description |
|---|---|
| Location of Warming | Position of warm areas in the Pacific can impact monsoon patterns |
| Progressive Heating | Heating of land during April-May-June affects monsoon |
| Snow Cover | Less snow means a warmer subcontinent, leading to more intense rains |
Indian Ocean Dipole (IOD)
Another factor that could help neutralize the potential negative impact from El Nino is a positive Indian Ocean Dipole (IOD). The IOD refers to a phenomenon of warming in the western Arabian ocean. A positive IOD, where the western parts of the Indian Ocean are warmer than the east, can push rain-bearing clouds over India.
El Nino Related Acronyms and Their Significance
There are other terms related to El Nino: Southern Oscillation Index (SOI) and ENSO (El Nino Southern Oscillation). The SOI provides an indication of the development and intensity of El Nino or La Nina based on atmospheric pressure differences between the South Pacific Ocean and Australia. Sustained positive SOI values indicate La Nina conditions while negative values suggest El Nino conditions.
On the other hand, ENSO refers to the oscillation between El Nino and La Nina that shifts irregularly every two to seven years. This shift disrupts temperature, precipitation, and wind patterns in the tropics, triggering global side effects.