Odisha, Jharkhand, Bihar, eastern UP, Assam may not get sufficient rainfall
Barring Odisha, Bihar, Jharkhand, north-Chhattisgarh, eastern Uttar Pradesh, Meghalaya and Assam, India will probably experience normal monsoon rainfall this year as La Nina or El Nino weather conditions, which impact rain patterns, are likely to be absent.
The India Meteorological Department (IMD) on Friday predicted overall “normal” monsoon rainfall at 98 per cent of the Long Period Average (LPA), which has a model error of plus and minus 5 per cent during the June-September period across the country. The LPA of the monsoon is 88 centimetres.
Rainfall between 96-104 per cent of the LPA is considered normal. The IMD said the probability of the 2021 monsoon being “normal” was 40% while there was 21% chance of it being “above normal”.
While releasing the first Long Range Forecast for the four-month rainfall period from June to September, M Rajeevan, secretary of the Ministry of Earth Sciences, said, quantitatively, the monsoon seasonal rainfall is likely to be 98% of the LPA with a model error of +/- 5 per cent.
“It is really good news for the country and will help India have a good agriculture output,” he said.
The news augurs well for an economy battered due to the coronavirus pandemic. Large parts of the country rely on the four-month rainfall season for agriculture and also for filling reservoirs.
The ‘normal’ rainfall means good acreage of Kharif crops (paddy, pulses, oilseeds, and coarse cereals), and adequate water storage in major water bodies across the countries for the next crop season. Better water storage also helps (winter sown) crops, bringing the entire crop year in bumper output phase.
This is the first time the IMD has adopted the most advanced and comprehensive system to arrive at its forecast, keeping in view demands from different users and government authorities for forecasts of the spatial distribution of seasonal rainfall along with the regionally averaged rainfall forecasts for better regional level planning of activities.
For this specific purpose, Office of Climate Research & Services, IMD, Pune has developed a Multi-Model Ensemble (MME) forecasting system based on coupled global climate models (CGCMs) from different global climate prediction and research centres including the Monsoon Mission CFS (MMCFS) being used by IMD. According to Rajeevan, the IMD will also issue month-wise forecasts during the next four months.
The La Nina and El Nino factors major influences on the Indian monsoon. The former is associated with the cooling of the Pacific waters and brings good rainfall while the latter is linked to the heating of Pacific waters and could lead to deficient precipitation. “There are less chances of formation of an El Nino,” Rajeevan said. He said in the recent years, the year after La Nina has usually seen a normal rainfall season. The Indian Dipole is another major influence on the outcome of the monsoon. A negative IOD is associated with the heating of the Indian Ocean waters and a positive IOD is linked to the cooling of Indian Ocean waters.
The latest global model forecast indicates that neutral ENSO (El Nino Southern Oscillation) conditions are likely to continue over the equatorial Pacific and negative IOD conditions are likely to develop over the Indian Ocean during the ensuing monsoon season, IMD Director General M Mohapatra said. “La-Nina is favoured through March-May with 80 per cent chances of a transition to ENSO-neutral in April-June 2021 and continuing through the fall of 2021,” Rajeevan said, implying these conditions are favourable for a good rainfall season.
The IMD’s forecast shows that the 2021 monsoon will be the third consecutive year (2019-2021) of good rainfall. India had earlier three consecutive years of rainfall in 1996,1997 and 1998.
However, several experts say that ‘below-normal rains in East and North-East India are not always harmful as the quantum of rains in these parts and also the daily average is higher than other regions of the country.
Recently, private weather forecasting agency, Skymet had also said that the southwest monsoon in 2021 is likely to be ‘normal’ at 103 per cent of the LPA. The Skymet Weather had completely ruled out the possibility of 2021 being the ‘drought’ year, the IMD’s forecast on Friday mentioned 14 percent probability of the ‘deficient’ (drought) monsoon. If both the two forecasts come true, it would mean that for the third consecutive year India will have a normal to above-normal rainfall during the monsoon months. In 2020, actual rainfall across India was 109 percent of LPA, while in 2019, it was 110 per cent of the LPA.