Southwest monsoon season in Kerala expected around June 4; 80% chance of El Niño event in May-June-July
At least 78 per cent of total districts across India were facing arid conditions, according to the aridity anomaly outlook index for May 11-17 issued by India Meteorological Department (IMD).
Only 116 of about 691 districts mapped on the index were non-arid, while 539 were facing different degrees of aridity — mild, moderate and severe. The data for the remaining 36 districts was not available.
Aridity anomaly outlook index for May 11-17, 2023
On May 16, the IMD predicted that the southwest monsoon season would set in over Kerala three days later, by June 4. The usual onset date is June 1. The weather agency also gave a model error of +/- four days, meaning the onset could be as late as June 8.
This forecast comes when the spectre of an El Niño event looms in the equatorial Pacific Ocean, which could have a huge impact on the onset and the distribution of rainfall during the season.
The aridity anomaly index refers to the water stress a growing plant suffers due to a shortage of available moisture (both rainfall and soil moisture). An anomaly from a normal value would thus signify the water shortage from a long-term climatic value.
Normal values of this index for successive weeks are worked out for different agroclimatic zones of the country.
Every week the actual aridity at different places is computed from the weekly total rainfall and antecedent soil moisture conditions. The difference between the actual aridity for the week and the normal aridity comes out to be the anomaly.
A negative or a zero value of this anomaly would imply that, as compared to the normal, the place had experienced less arid/drought conditions.
A positive value would indicate that the place had experienced more arid/drought conditions than the average. This positive value is classified into three categories of mild, moderate and severe arid conditions.
In states like Uttar Pradesh, Madhya Pradesh, Gujarat, Rajasthan, Haryana, Punjab, Jharkhand, Andhra Pradesh, Telangana, Assam and Chhattisgarh, almost all the districts were under either mild or moderate arid conditions.
Meanwhile, around 46 districts faced ‘severe’ arid conditions. These were mostly in Odisha and West Bengal.
The index monitors agricultural drought, a situation when rainfall and soil moisture is inadequate to support healthy crop growth till maturity, causing crop stress.
This analysis indicates qualitative retardation in plant growth and, thus, poor yields. Indirectly, this may also be helpful for irrigation scheduling, the amount and the time at which the plant badly needs the water.
This could cause damage to summer crops, which are grown in the Indian subcontinent between Rabi (winter) and Kharif (monsoon) crops. The sowing for crops like pulses, oilseeds and nutritional cereals starts in the last week of February or first week of March and these crops are harvested by May-June.
Meanwhile, there is more than 80 per cent chance of the development of an El Niño event in the equatorial Pacific Ocean in May-June-July, according to the National Oceanic and Atmospheric Administration (NOAA) of the United States. This chance increases to close to 90 per cent for the June-July-August period.
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