PRE-MONSOON SEASON IN INDIA

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Context

India is again undergoing a huge deficit in pre-monsoon rainfall this year - India Meteorological Department (IMD) data has shown.

IMD Findings

Large parts of Punjab, Haryana, Uttar Pradesh, Bihar, Gujarat and North East India have received no rain at all in March 2022.
The hill regions of India including Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh have recorded ‘Deficient’ or ‘Large Deficient’ rains.
Districts such as Poonch, Leh, Tehri Garhwal, West Sikkim, South Sikkim, East Kameng and East Siang recorded ‘deficient’ rainfall in the hills.
Baramulla, Nainital, North Sikkim, East Sikkim), Tawang, Papum Pare and Upper Siang recorded ‘normal’ rainfall in the hills.
The low amount of rainfall this pre-monsoon is similar to 2019. The low pre-monsoon (March to May) rainfall that year was the lowest in the last five years and second lowest in last 65 years.

Pre Monsoon Season in India

As the sun shifts northward towards the Tropic of Cancer after the Vernal Equinox, the whole India experiences an increase in temperature and marks the commencement of Pre-monsoon season.
Pre-monsoon is from March to May.
The term Mango showers is used to describe the occurrence of pre-monsoon rainfall. Sometimes, these rains are referred to generically as ‘April rains’ or ‘Summer showers’.
They are notable across much of South and Southeast Asia, including India, and Cambodia.
In southern Asia, these rains greatly influence human activities because of the control the rains have on crops that are culturally significant like mangoes and coffee.
These rains normally occur from March to April, although their arrival is often difficult to predict. Their intensity can range from light showers to heavy and persistent thunderstorms.
In India, the mango showers occur as the result of thunderstorm development over the Bay of Bengal.
They are also known as 'Kaal Baisakhi' in Bengal, as Bordoisila in Assam and as Cherry Blossom showers or Coffee Showers in Karnataka.
Towards the close of the summer season, pre-monsoon showers are common, especially in Kerala, Karnataka and parts of Tamil Nadu in India. They help in the early ripening of mangoes and are hence often referred to as "Mango showers."

Conditions fuelling the pre monsoon showers

From March the temperatures in the north India rise as the vertical rays of the Sun reach the Tropic of Cancer.
April is considered the hottest month for the western and southern regions of the country. For most of North India, May is the hottest month. Temperatures of northwest India sometimes reaches 50 °C and higher.
Another striking feature of summer is the Loo (hot wind).
Strong, hot, and dry wind known as the loo blows in from the west during the daytime, with very high temperatures, in some cases up to around 45 °C.
Isolated pockets of north and west Rajasthan sometimes reaches 50 °C also.
The atmospheric pressure is low all over the country due to high temperatures. Since the sun goes gradually towards the north (summer solstice), the Inter Tropical Convergence Zone (ITCZ) begins to move towards the north.
The general direction of winds is from the north-west and west in north-western India.

Andhis and little rainfall

In the months of May and June, the high temperature in north-western India builds a steep pressure gradient leading to strong winds.
These strong dust storms result from the convective phenomenon and their intensity increases in the afternoon.
These are locally known as Andhis, which are short-lived thunderstorms, which move like a solid wall of sand and dust.
These weather activities bring little rainfall and give much-needed relief from the heat.
Dust storms in the evening are very common during May in Punjab, Haryana, Eastern Rajasthan, and Uttar Pradesh.

Kal Baisakhi or "Nor'westers"

Immense pre-monsoon squall-line thunderstorms, known locally as Kal Baisakhi or "Nor'westers", commonly associated with hailstorm and very strong winds, occurs in east India.
During this time Odisha, West Bengal, Assam, Bihar, Chhattisgarh, Jharkhand, Bangladesh and North-Eastern states of India are affected by violent thunderstorms. They cause considerable damage to life and property.
Effects- Kalbaishakhi brings destruction by uprooting trees due to gale-winds and waterlogging roads due to heavy rainfall. It often damages crop by hailstorms. However it is extremely helpful for kharif crops like jute, paddy, etc.

Tea Showers, Mango Showers and Cherry Blossoms

In the south, thunderstorms occur in Kerala and adjoining parts of Karnataka and Tamil Nadu, particularly in the evenings and nights. These pre-monsoonal showers are called by various names.
Tea showers in Assam (they are good for tea, jute, and rice). Mango showers in Kerala and coastal areas of Karnataka as they help in the early ripening of mangoes. Cherry Blossoms/Coffee showers in Kerala and nearby areas (good for coffee plantations).