As the minimum temperature in January hovered around 4°C in the city, the residents of Delhi said they felt a lot colder during the mornings and evenings than it really was. Meteorologists explain this as wind chill factor.
The India Meteorological Department (IMD) or the Met department announced in 2016 that information about wind chill would be released this winter, but the plan seems to be stalled for now. Wind chill factor is the perceived decrease in air temperature felt by the body on exposed skin due to the flow of air.
“It is not such a serious issue here in this region. Our focus is to bring out cold day and cold wave forecasts,” Dr M Mohapatra, a scientist at the IMD said.
The IMD started releasing summer and winter forecasts with heat and cold wave warnings only last summer.
The forecasts include minimum and maximum temperatures and wind speeds but not wind chill factor, which is a derived product, explained IMD scientists. The two things that determine wind chill are temperature and wind speed. Strong winds aggravate the loss of warmth from exposed skin. The higher the wind speed, the cooler you would feel.
The face is generally the most exposed part of the human body, so wind chill calculations usually also take into account the average height of the population.
“The factors that impact wind chill are many and they are very localised. Narrow alleys between buildings where winds are stronger can feel colder. Even if you calculate the wind chill for a neighbourhood, for example, Safdarjung, you cannot generalise it to all of Delhi,” said IMD’s director general, Dr Kanduri Jayaram Ramesh.
Although, the IMD is hoping to launch an app to disseminate weather information and also crowdsource data from the public by this monsoon season, the priority for the department is getting high-resolution data about temperatures and wind speeds and secondary products like wind chill don’t figure high on the department’s priority list.
Mohapatra insisted that it is more important for western countries, where temperatures regularly fall below freezing, to provide this data. Meteorological agencies in countries like Canada and the US are proactive about providing wind chill information.
According to the US National Weather Service calculator if the temperature is 6° and there is a wind blowing at a speed of 5km/ hour the actual temperature feels like 5°C. If winds are blowing at 10 km/ hour the experienced temperature falls to 4°C.