431 The Cooling of the Arabian Sea Induces a Major Change in Monsoon Dynamics

Tuesday, 9 January 2018
Exhibit Hall 3 (ACC) (Austin, Texas)
Robert L. Grossman, Univ. of Colorado, Boulder, CO

I contend that the Indian Monsoon experiences a dramatic synoptic change shortly after the cooling of the Arabian Sea; a result of large scale air-sea interaction due to advection of the cool Somali Current and upwelling due to the enhancement of southerly currents along the west coast of India.

The onset period of the monsoon can be characterized as a two cell, regionally-locked Walker circulation with deep convective uplift over the warm Bay of Bengal and coastal/mid-ocean deep convective uplift over the warm eastern Arabian Sea. Downward motion would be, respectively, central India and the western Arabian Sea/coastal Saudi Arabia.

With the cooling of the Arabian Sea below 28.5C the off-shore convection over the E. Arabian Sea diminishes commencing the establishment of the fully developed monsoon and changes the monsoon circulation over India to a one-celled Walker circulation with uplift over the still warm Bay of Bengal and downward motion over the cooler Arabian Sea. This change should have an emphatic influence on the climatic pattern of the monsoon, including the way westerly momentum is injected into the Tropical Easterly Jet by deep convection.

Using the INSAT geostationary satellite's water vapor channel imagery from the IMD archive for 2016/7 and NOAA reanalysis output, I intend to show this dramatic change in monsoon circulation in hopes of initiating a further exploration of the change.

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