Why in news? Monsoon Mayhem Claims Lives in North India includes Rains, Flooding Continue Across Himachal, Uttarakhand, Delhi, UP states

Highlights:

• IMD attributed confirmed that flooding situation is a result of rare phenomenon that is of the interaction of two climatic factors has led to incessant heavy rain across large swathes of north India

What is the rare interaction ?

• According to Indian Meteorological Department (IMD) heavy rain in parts of Himachal Pradesh and Uttarakhand is due to the interaction of the monsoonal winds with the western disturbance that has created a trough above Himachal Pradesh with low-pressure area lies over northeast Rajasthan and neighbouring regions.
• Situations are part of the Indian monsoon, the interaction remains rare.

What are the western disturbances and monsoonal winds ?

Western Disturbances

• It refers to an extratropical storm or a low-pressure system originates in the Mediterranean region, and travel eastward across the Middle East and Iran
• It has a substantial influence on the weather in northern India, as they approach, cause the northwestern regions of the country to experience cloud cover, rainfall, and sometimes snowfall in the higher altitudes of the Himalayan region.

Monsoonal Winds

• It refer to the seasonal wind patterns that prevail in the Indian subcontinent, bringing about the Indian Monsoon. The Southwest Monsoon and the Northeast Monsoon make up these winds that bring essential rainfall during the summer and winter in India.

Rainfall Deficiency 

• Southern states such as Karnataka, Kerala, Telangana, Jharkhand, and Bihar and northeastern states such as Assam, Tripura, Mizoram, Meghalaya, etc are still facing a rain-deficient monsoon season

What   preparations are needed for the situation ?

Structural Methods

• Storage reservoirs moderate the flood peak by storing water during high-flow periods and releasing it after they have subsided
• Need to encourage tanks and ponds are traditional means of water conservation in India that aid in groundwater recharge

Non-Structural Methods

• A forecasting and warning system provides a priori estimate of approaching floods so that people and movable assets are relocated to safer places in time
• Early mapping of floods spots at various level and Flood zoning is also important
• Defences such as levees, bunds, reservoirs, and weirs are used to prevent rivers from bursting their banks.
• De- synchronising peak flows from tributaries

What are the factors that influence the monsoon in India  ?

• Climate change : With global warming, a warm and humid atmosphere acts like a steroid for the weather. wildfires thus far this year have burned over three-times the normal area and have also emitted about three times as much carbon dioxide.
• Instabilities in the atmosphere: The instabilities in the atmosphere that drive convection are not strong enough to drive large-scale rainfall during the pre-monsoon season.
• Western disturbances : Rainfall this pre-monsoon was above normal due to a combination of the warm Arabian Sea and an unusually high number of western disturbances. As a result, soils were left moister than normal, which in turn affected the evolution of the monsoon.
• Atlantic Nino: The entire Atlantic Ocean has been warmer. While the so-called Atlantic Niño, with a warm tropical Atlantic, generally tends to suppress monsoon rainfall, it is not clear what the impacts are when the entire Atlantic is as warm as it has been this year.
• Geographical location :Disuniform terrain and heterogeneous land-use patterns are the likely culprits. The strongest winds that occur in the upper atmosphere can spontaneously break into clockwise and anticlockwise patterns, especially when they run into mountainous terrain, such as the Himalaya.
• Wind circulation: Strong clockwise winds, with air flowing out from the centre, in the upper atmosphere demand an anticlockwise circulation near the surface, in order to feed the upper-level outflow. Such a convergence near the surface can drive excess rainfall.
• El Niño and La Nina: They are the events are associated with weak monsoons and lower than average rainfall. The La Niña has the opposite effect to the El Niño and is responsible for stronger monsoons and above-average rainfall.
• Local features : Some parts of the mountain chain are amplifying global warming, leading to rapid local warming. Irregular weather patterns during the monsoon superpose on these local features as a result of the winds expanding or compressing as they race up and down the narrow valleys. The results can be cloudbursts, heavy rains or even heatwaves depending on the local flow patterns.