New Delhi, April 23: Unofficial reports say 28 people have died of a heatwave in Orissa this April while the government has confirmed four deaths due to sunstroke. The numbers may be contested but it is clear that the heat is creating havoc.

While a heatwave is declared when the temperature is five degrees above normal, the state Met department’s advisory declared a “heatwave” only on one day this month.

The Met release says: “The recorded temperature at stations over Orissa indicate that the rise in temperature is about 2 to 3 degree Celsius above normal except in Angul, Sundergarh and Chandbali where it is about 4 degree Celsius above normal. Based on India Met Department (IMD) criteria, heat wave was realised only on one day, April 18, over North Orissa. Similar temperature trends have also been experienced in previous years.”

The release basically means that there is nothing unusual as far as temperatures go. A heatwave is meant to trigger certain administrative relief measures like an early closure of schools. However, news of deaths (unconfirmed as of now) in Orissa point to the fact that there may be dehydration and severe discomfort even when it is technically not a heatwave.

According to experts, humidity could be an element, especially in the coastal stations of Orissa, that is responsible for this trauma. And the measure that takes this into account is the heat index, still not taken seriously by the Met department.

Experts believe that the concept of heat index would be more helpful in this situation in gauging the “felt temperature” rather than the one captured on the thermometer. The heat index (HI) is an index that combines air temperature and humidity in an attempt to determine the human-perceived equivalent temperature—how hot it feels, termed the “felt air temperature”.

It is based on the principle that the human body normally cools itself by perspiration, or sweating, which evaporates and carries heat away from the body. However, when relative humidity is high, the evaporation rate is reduced. Heat removed from the body is at a lower rate causing it to retain more heat than it would in dry air.

High relative humidity retards evaporation, robbing the body of its ability to cool itself. “Yes it is an important parameter for us. We do calculate the heat index for coastal stations and then issue advisories saying that there will be some discomfort,” said S.C. Sahu, director, Orissa Met department, while acknowledging that better use can be made of the index. For example, the humidity in Bhubaneshwar was recorded at 50 per cent when the temperature was 40 degrees centigrade. The “felt temperature” would then be several degrees higher.

The index has been derived based on subjective descriptions of how hot subjects feel for a given temperature and humidity. For coastal areas, weather patterns are ideal to make use of the system that is commonly used in the United States.

The whole of last week, the northwesterly dry, hot winds are raising the temperature in the first half of the day when the wind direction is from the land to the sea but when the direction of the wind changes in the latter part of the day, the sea winds bring in moisture but are not strong enough to cool certain parts of the state.

They add to humidity levels, raising discomfiture that can be fatal. Another year that had seen high fatalities due to heat wave was in 2006 when temperature increased rapidly from the first week of April. The other coastal area to be affected was that of Andhra Pradesh. Warnings followed after hundreds of poor and vulnerable people succumbed to heat.

For now, following the news of these deaths, the revenue and disaster management department has swung into action: directives have been issued to wrap up classes by 10.30 a.m. and labourers have been barred from doing any physical work under the sun from 12 noon to 3 p.m.

Oral Rehydrated Salt packets have been distributed to all health centres and hospitals. Rs 6 crore has been sanctioned out of the Calamity Relief Fund for drinking water supply. The state government today demanded that the heatwave be declared a natural calamity and has sought adequate Central assistance from the National Calamity Fund. With only one day of official “heatwave”, they are unlikely to get any sympathy.

What is the heat index?

This is an index that combines air temperature and humidity in an attempt to determine the human-perceived equivalent temperature—how hot it feels, termed the “felt air temperature”

What is a heat wave?

It is when the temperature is five degrees above normal

Heat-related deaths in Orissa

1991: 91

2002: 41

2003: 67

2004: 43

2005: 53

1,400

People died in India in May 2003 as peak temperature touched 49 degrees Celsius in different parts of the country.

Europe (2003) 22,000-35,000 deaths

Chicago (1995) 700 deaths