Western Disturbances
Recently an intense thunderstorm caused by Western Disturbances (WD), claimed over 64 lives in Rajasthan, MP, Gujrat, Bihar, and Maharashtra.
How are Western Disturbances caused?
1) It originates in the Mediterranean Sea and the Caspian Sea.
2) During winter season due to the intrusion of cold air from polar regions in the European region, the warmer air with high moisture ( system) ascends in the upper atmosphere.
3) Through Westerlies winds, the low-pressure system flows from west to east.
4) They travel through Iran, Iraq, Afghanistan, Pakistan and enters India.
6) It is blocked by the Himalayas and causes precipitation in forms of snow in mountainous areas and rainfall in low-areas.
Why is it called as Western Disturbances?
1) It originates in the West. So, Western.
2) It is a weather system which distorts the existing conditions and passes through. So, Disturbance.
Which way does WD impact India?
1) From November to March, it causes most of the winter and pre-monsoon rains in North-Western India.
2) It causes snowfall in Uttarakhand, Sikkim and Arunachal Pradesh Himalayan region.
3) Average of 4-5 WD is formed during winter season and rainfall varies during every WD.
4) It is estimated that 5-10% of the total annual rainfall is from WD.
5) Weak WD are associated with crop failure and water problems and strong WD can help residents, farmers and government avoid many of the problems associated with water scarcity.
6) Sometimes helps in the activation of monsoon in certain parts of North-Western India.
7) WD is much beneficial to Rabi Crops.
What are the issues associated with WD?
Since WD are not high-intensity weather system, they are usually not associated with disasters, but in recent past, it is observed that this beneficial weather phenomenon is increasingly becoming disaster especially during summer and monsoon seasons.
Some of the associated disasters are:
1) Cloudburst in Leh, 2010.
2) Kashmir floods in September 2014.
3) Uttarakhand floods in 2013.
Many believe that erratic rainfall may occur due to the interaction between WD and summer monsoon. But conclusive evidence is not available to support this.
Where lies the solution?
1) The availability of data on WD is low.
2) There is no official end to end tracking of WD, unlike tropical cyclones.
3) WD needs to be studied in much more details.
4) In the age of global warming and drastic climate change are becoming all too common, studying WD is crucial.
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