In the Aridity Anomaly Outlook (AAO) for July 2022, the Indian Meteorological Department (IMD) reported that at least 85% of districts in the country experience dry weather.
How does the Aridity Anomaly Outlook Index work?
The index tracks agricultural drought, which occurs when precipitation and soil moisture are insufficient to maintain healthy crop development until maturity, resulting in crop stress. A deviation from the usual value indicates a water deficit in certain regions, which might directly impact agricultural production. The India Meteorological Department (IMD) designed it.
- Water balance is taken into account in a real-time drought index.
- The Aridity Index (AI) is calculated weekly or biweekly.
- The actual aridity for each period is matched to the expected aridity for that period.
- Moisture excess is shown by negative values, whereas positive values indicate moisture stress.
Factors that are taken into Consideration
- Actual evapotranspiration and computed potential evapotranspiration, which need wind, temperature, and solar radiation values, are the parameters.
- Actual evapotranspiration is the amount of water eliminated from a surface due to transpiration and evaporation.
- The greatest feasible or achievable evapotranspiration for a specific crop owing to evaporation and transpiration is referred to as potential evapotranspiration.
- Drought damages agriculture, particularly in the tropics, where distinct wet and dry seasons are part of the climatic regime.
- This approach may evaluate both the winter and summer cropping seasons.
- It is estimated that only 63 of 756 districts are not arid, and the remaining 660 experience varying degrees of aridity (mild, moderate, and severe).
- A total of 196 districts are experiencing severe dryness, with 65 located in Uttar Pradesh (highest).
- Bihar has the second-highest number of dry districts (33) behind Rajasthan. The region also has a 45% rainfall deficit.
- Maharashtra, Rajasthan, Madhya Pradesh, Haryana, Delhi, Jammu and Kashmir, Telangana, Jharkhand, Andhra Pradesh, Punjab, West Bengal, Karnataka, and Tamil Nadu are among the other States affected by severe aridity.’
- The SPI on the DEWS platform also shows that there has been a persistent rainfall shortfall in these locations over the previous six months.
- Arid conditions have influenced current Kharif sowing, as the area seeded under various Kharif crops as of July 2022 was 13.26 million hectares smaller than at a similar time in 2021.
What is the Standardised Precipitation Index (SPI)?
- The SPI is frequently used for describing meteorological dryness over many periods.
- The SPI is intimately tied to soil moisture on short durations and can be linked to underground water and reservoir storage on longer timelines.
- The SPI on the Drought Early Warning System (DEWS), an authentic drought monitoring platform operated by the Indian Institute of Technology, Gandhinagar (IIT-G), reveals a six-month rainfall deficiency in these places.
- Bihar, UP, Jharkhand, West Bengal, and portions of the North East are experiencing severe drought, and agriculture in these areas may suffer as a result.
Indian Meteorological Department (IMD)
- IMD was founded in 1875.
- It functions as a department under the Ministry of Earth Sciences.
- It is the primary agency in meteorological monitoring, forecasts, and seismology.