Oceans and the monsoon

Please read the complete article as it explains several concepts in geography

http://www.thehindu.com/opinion/op-ed/article2142488.ece


Summary

·         1.5 moths before monsoon, central bay of bengal(BoB) warms up leading to increased evopration of surface water and formation of dense clouds

·         These clouds precipitate giving rise to pre monsoon rains in KL and TN, myanmar and south east asia

·         This rain also cools down waters of BoB

·         Meanwhile waters of arabian sea heats up and clouds build up near equator and move north leading to onset of monsoon in KL

·         Factors determining onset off monsoon

o   Temperature of oceans north and south of equator

§  If northern waters cooler than south, then delayed monsoons

·         Factors determining cloud formation

o   Sea surface temperature

§  Has to be above 28 deg Celsius, for higher chances of cloud formation

§  Gradients in temperature across ocean surface

·         The 2009 monsoon flop reasons

o   Since monsoon clouds form near equator and have to move north towards India, they need warm waters for northward movement

o   In 2009, BoB was colder than usual while eastern equatorial indian ocean was warmer leading to delayed monsoon

BoB vs arabian sea

·         BoB is less saline than arabian sea coz , it receives more rainfall and river water discharge

·         As a result BoB has lesser surface water at top than arabian sea

·         Upwelling is a phenomenon when the colder water at bottom rises up and replaces the warmer surface water

o   Upwelling is more in arabian sea than BoB

·         Less saline water heats up and cools rapidly

o   rApid changes in sea surface temperature can build up atmospheric pressure gradient giving rise to cyclones