Coldwave

When an abnormally cold influx of air reaches the middle or lower latitudes, usually it is known as a cold wave. When dense, cold air comes out of its source regions in northern Canada or northern Asia, it forms cold waves in the Northern Hemisphere. The “wave” in cold waves is evident in the upper-air flow (the Jetstream), which is generally amplified into a strong ridge-trough pattern during a major cold outbreak. The deviation from the norm is how meteorologists measure cold waves.

Whenever the minimum or night-time temperature significantly decreases, a cold wave is declared. The India Meteorological Department’s criteria for a cold wave in the plains is that “the minimum temperature should be 10 degrees or lower and the departure from normal minimum temperature 4.5 degrees or less for 2 consecutive days”.

Causes: 

Cold wave conditions take place during the winter months when the cold air mass from higher latitudes sweeps over the region. Cold wave conditions also develop if the temperature falls rapidly, much below normal. A foggy day can prevent the day from warming and make it easier for cold wave conditions to persist. Clear sky conditions during the night further facilitate the lowering of temperature by unobstructed radiation cooling.

Effects:

• Cold waves may cause extreme thermal stress to the human body, which may lead to devastating impacts on human health and well-being.
• The probability and severity of health disorders increase progressively if the thermal stress is persistent.
• The impact of consecutive days of extreme cold will be quite significant on human health, livestock, agriculture and industrial production as well.

Cold waves can occur and be severe depending on a number of factors, including the climate and geography of the area. The weaker segments of society who cannot afford to defend themselves from the elements are frequently made easy prey by extreme weather. The best way to prevent illnesses during a cold wave is to stay indoors for short periods of time.