Aridity Anomaly Outlook(AAO) Index: Some 85% districts in India now face arid conditions

Source: The post is based on the article “Aridity Anomaly Outlook(AAO) Index: Some 85% districts in India now face arid conditions” published in Down To Earth on 28th July 2022.

What is the News?

The Indian Meteorological Department(IMD) has released the Aridity Anomaly Outlook(AAO) Index. 

What is the Aridity Anomaly Outlook(AAO) Index?

Developed by: India Meteorological Department (IMD)

Purpose: The index monitors agricultural drought, a situation when rainfall and soil moisture are inadequate to support healthy crop growth till maturity, causing crop stress.

– An anomaly from the normal value signifies a water shortage in these districts that could directly impact agricultural activity.

The index is computed for weekly or two-week periods. For each period, the actual aridity for the period is compared to the normal aridity for that period.

– Negative values indicate a surplus of moisture while positive values indicate moisture stress.

Parameters used: Actual evapotranspiration and calculated potential evapotranspiration which requires temperature, wind and solar radiation values.

Note: Actual evapotranspiration is the quantity of water that is actually removed from a surface due to the processes of evaporation and transpiration.

— Potential evapotranspiration is the maximum attainable or achievable evapotranspiration for a given crop due to evaporation and transpiration.

Significance of this index: Impacts of drought on agriculture, especially in the tropics where defined wet and dry seasons are part of the climate regime.

Both winter and summer cropping seasons can also be assessed using this method.

What are the key findings of the index?

At least 85% of districts face arid conditions across India.

Some 196 districts are in the grip of a ‘severe’ degree of dryness and 65 of these are in Uttar Pradesh (highest).

Bihar had the second-highest number of districts (33) experiencing arid conditions. The state also has a high rainfall deficit of 45%.