Bangalore: The Indian subcontinent is currently at the end of a prolonged heat wave lasting nearly six weeks, resulting in the hottest March and April on record for the region. During this time, the temperature in Indian cities rose by more than 45 °C, while place in pakistan went above 47 °C.
The persistence of the heat wave is linked to the pressure conditions created by the ongoing La Nia event, which formed in the winter of 2021 for the second year in a row. La Nia is an oceanic phenomenon that moves warm waters from the western US towards East Asia. Pacific, and in turn also affects the jet stream.
Jet streams are bands of powerful winds that circle the globe at different latitudes, affecting global weather.
The formation of a ridge in the subtropical jet stream over India resulted in a high pressure area that trapped heat within the subcontinent, creating a persistent heat wave.
While heat waves are common at this time of year and peak in May, the ongoing heat wave was first announced as early as March 11.
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What is heat wave?
The India Meteorological Department (IMD) defines a heat wave as a condition when the mean maximum temperature exceeds 45 °C, or if the temperature is 4.5 °-6.4 °C above normal for at least two consecutive days. be more.
A severe heat wave, meanwhile, is a condition when the average temperature exceeds 47 °C, or an increase of more than 6.4 °C above normal, is recorded in two consecutive days.
In many parts of the country, there was an outbreak of severe heat in this season.
Every summer, a low pressure build-up over India draws high pressure winds from the Arabian Sea, producing the monsoon. However, the subtropical jet stream flowing over the northern part of India developed a ridge or crest. This meant that the warm air above the ground was boxed in on all sides by the high pressure of the jet stream, resulting in the formation of a ‘heat dome’. The resulting overall high pressure area prevents other winds from being pulled into the subcontinent.
Within the heat dome, the jet stream moves the air from west to east, but this air sinks back as it heats up, causing a heat wave.
Experts believe the discrepancy was likely initiated by itself. persistent La Nia conditionsWhich continues to affect the weather in some parts of the world.
La Nia produces a pattern of low pressure over the Indian subcontinent, leading to cold winters. This climate pattern tends to end after winter, but has continued for two consecutive years this year, leading to other disturbances such as the formation of rarefied. cyclone in march,
All of these conditions, being pulled down by the warming Arctic’s currents, led to heat-wave conditions for about two months. land surface temperature, which under normal conditions consistently measures much higher than atmospheric temperature, 60 degree celsius exceeded In some parts of the country over the weekend.
wet bulb temperature
The presence or absence of moisture plays a major role in how a heat wave affects life on Earth.
In arid regions, increased evaporation and dryness lead to fires. Over in the first three months of this year only 1,00,000 wildfires were recorded in Uttarakhand, Chhattisgarh, Rajasthan, Madhya Pradesh, Odisha, Karnataka and Tamil Nadu.
An increase in mercury also leads to dehydration and heat stroke, which can be fatal If not treated
In more humid areas, such as the eastern coastal states, heat and humidity make for an even more deadly combination. When the humidity is too high, the human body is unable to cool itself by sweating, which leads to overheating and physical damage.
Metrics that measure such conditions are called wet bulb temperature (WBT), which is measured by placing a wet cloth over the thermometer and passing air through it, or by using a wet thermometer in the shade and evaporating the water. Wet bulb temperatures are always lower than regular or dry bulb temperatures in the same location due to humidity.
A wet bulb temperature of 32 °C is considered the limit for the ability to perform outdoor activities, and a wet bulb temperature of over 35 °C can cause death if exposed to prolonged exposure.
(Edited by Amritansh Arora)
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