The northern part of the country, including the national
capital, is experiencing a severe cold wave.
Winter can be divided as either wet or dry winter.
Wet winter, or early winter, is characterized by fall in
temperature along with high humidity. In cold weather, high humidity levels
will make one feel colder.
The body cools itself by sweating. During summers, when
the humidity is low, sweat evaporates easily and cools the body because the
process of evaporation requires thermal (heat) energy. But, when humidity is
high in summers, evaporation rate is reduced. The resulting limited evaporation
in hot and humid conditions is not enough to cool the body. And, therefore,
high humidity in hot weather makes one feel sticky and warmer. This combined
effect of temperature and relative humidity is called heat index, which is
experienced as the felt air temperature.
In winter, the cold air (low temperature) with high relative
humidity "feels" colder. This is because the insulating effect of
clothes decrease as the humidity rises. The moisture in the atmosphere is
captured on the clothing, even though the clothes
do not appear wet and results in greater heat loss from the body.
Another factor to be considered during winters is the
sun. Cold days are more likely to be overcast, which reduces the amount of
direct sunlight reaching the surface; whereas, on
a dry sunny day, the body is warmed by radiant heating from the sun.
Fog and smog are common during wet winter.
Whenever the humidity is high, air movement is less and
temperature is low, fog is the automatic result. It occurs when water droplets
are suspended in the air.
When the level of pollutants is high in the atmosphere,
the pollutants get mixed into the fog. This is called smog. Therefore, smog is
the combination of smoke and fog and it further reduces the visibility. The
smoke includes toxic emissions from vehicles and industries, dust and open
burning of crops.
Dry winter, or late winter is characterized by absence of
fog, smog and presence of chilly airy winds. Cold and dry air generally feels
warmer than cold and humid air at the same temperature.
Dr KK Aggarwal
Padma
Shri Awardee
President Elect Confederation of Medical Associations in Asia and
Oceania (CMAAO)
Group
Editor-in-Chief IJCP Publications
President
Heart Care Foundation of India
Past National President IMA
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