south-west monsoon Current Affairs - 2019
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The Indian Meteorological Department said that the retreat of monsoon that was delayed by more than a month is to happen by October 10, 2019. The monsoon this year was 110% of Long Period Average (LPA) with above average precipitation. The LPA between 1961 and 2010 was 88 centimeters.
The retreat of monsoon is set to be the most delayed in 60 years. The delay ravaged Bihar raising death toll to 100. UP and Bihar were the worst affected states due to the delay. Hospitals, schools and health care facilities were hampered in the states due to heavy rains. Failure of desilting of lakes, ponds and rivers in the states were the main reason behind floods.
The unusual events that caused the shift
Monsoon usually starts retreating from west Rajasthan from September 1. However, this time the retrieval began on September 16. The reasons behind the late retrieval include
- Easterly winds – This year they were still blowing in upper latitudes.
The Easterly winds originate from sub tropical high-pressure belt of northern hemisphere. They blow towards south Equatorial Low 0 Pressure area. They shift to lower latitudes causing the retreat of monsoon.
By the end of September, the low-pressure trough of Ganga plains moves southwards in response to the southward march of the sun. (The sun in the months of August – September shifts from Summer Solstice to Autumnal Equinox). This causes the shift of easterly winds.
- Monsoon Trough remained south of its usual position because of successive low pressure in the Bay of Bengal. The number of such low pressure were more than usual this year.
The axis of monsoon trough during the retreating period usually extends between Punjab in the west and West Bengal in the East. However, this year the axis shifted over northern plains causing rains in Bihar and Uttar Pradesh. Monsoon trough is the confluence of winds.
- The break in period of the monsoon began late during August. It usually breaks in July.
During the break in period the monsoon trough shifts towards north bringing rainfall to the north eastern states and Himalayan states. During this period the rest of the country remains dry. This failed to happen this year.
The above factors led to the unusual and untimely rainfall in central India and in southern states.
Tags: Climate Change • Disaster • Floods • heavy rains • India floods
The IMD (Indian Meteorological Department) said that India received 10% above average monsoon rains in 2019. It is the highest in 25 years.
States like Maharashtra, Rajasthan, Karnataka received 35% more rainfall than the normal. It is the highest recorded rains in the history of these states.
Heavy rains damaged the summer sown crops like pulses, soybean and cotton that were close to harvest.
What caused heavy rains?
The monsoon begins in June and ends by September. However, this year it delayed its retreat. This caused increased rainfall that led to floods. Climatologists believe that climate change is the main reason for the increased floods. However, anthropogenic activities are hastening climate change and resulting in disasters.
Extreme climate in India
India has been experiencing extreme weather conditions in several parts of the country. In July the GoI said that 2,400 people were killed in 2018 due to extremities of the weather.
Deficiency of rains in June
By the end of June, India was 33% monsoon rain deficit. In the past 146 years whenever deficit rainfall in June has been more than 30% it either led to below normal monsoon or drought. Never in the history of India, it has received above average monsoon as it has happened this year.
Significance of South West Monsoon
- It brings rain to all parts of the country except Tamil Nadu, Andhra Pradesh and Telangana between June and September
- The monsoon helps farmers expand areas under winter – sown crops like rice, wheat, chick peas, rapeseed.
Floods created havocs in most parts of the country this monsoon. According to Central Water Commission that monitors dams and flood levels around 25 stations crossed the HFL – Highest Flood Level till August 2019. The rivers Warna and Krishna in Maharashtra and Karnataka crossed the HFL. The levels were the greatest of those in the past.
Kerala and monsoon
Till August Kerala was under seasonal rainfall deficit of 27%. However, between August 1 and August 7 it received 368% more rainfall than normal that led to floods. Again, after August 13, the state faced seasonal rainfall deficit. This season around 100 were killed in Kerala and more than a lakh displaced.
What made June month dry?
The South West monsoon that sets on June 1 delayed and began on June 9. After being set, the monsoon progressed as Cyclone Vayu. The cyclone disrupted the regular trade winds that are the carriers of the monsoon. This arrested the monsoon in Kerala, Karnataka and Tamil Nadu till June 21. The warming of Indian Ocean decreased the temperature difference between the land and sea. The disturbance in the trigger of monsoon is also a reason for their delay.