Heat Wave

Heat Wave

Subject: Geography

Context: In spite of rise of above 3-5 degree Celsius the IMD ruled out heat wave conditions over North-West India due to calming influence of a cooler western disturbance.

Concept:

• Afresh western disturbance as a trough lay over South Afghanistan and adjoining South-west Pakistan on Thursday evening accompanied by an offspring cyclonic circulation over Central Pakistan and adjoining West Rajasthan which makes it an active weather system.

About heat wave

• A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India.
• Heat Waves typically occur between March and June, and in some rare cases even extend till July.
• Urban heat island effects, deforestation, global warming leading to higher daily peak temperature etc. are major causes of heat waves.
• The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, dehydration, heat cramps, heat exhaustion and/or heat stroke and sometimes resulting in death.
• Children, the elderly and those with pre-existing morbidities are particularly vulnerable.

IMD defines Heat Waves as:

1. Heat Wave need not be considered till maximum temperature of a station reaches at least 40°C for Plains and at least 30°C for Hilly regions
2. When normal maximum temperature of a station is less than or equal to 40°C Heat Wave Departure from normal is 5°C to 6°C Severe Heat Wave Departure from normal is 7°C or more
3. When normal maximum temperature of a station is more than 40°C Heat Wave Departure from normal is 4°C to 5°C Severe Heat Wave Departure from normal is 6°C or more
4. When actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heat waves should be declared.