Summer Monsoon Onset Progression and Predictability over Different Monsoon Regions

Monsoons are important sources of precipitation for many areas around the world including tropical, subtropical and semi-arid regions. The purpose of this work is to compare the speed of progression of the monsoon onset over several monsoon regions around the globe and determine the predictability of monsoon onsets over late-start locations compared to early-start locations within the same monsoon region.

In this project, using daily Modern Era Retrospective Reanalysis version 2 (MERRA-2) data from 1980 to 2016, we create an objective monsoon onset and withdrawal identification based on the frequency of days in which precipitation and high precipitable water occur simultaneously. Within each monsoon region we identify locations where the monsoon starts early and locations of successively later starts. The speed in km/day at which the monsoon progresses through these locations is calculated.

The mean, interannual variability and change of onset and onset speed will be compared between monsoon regions. A conditional onset predictability will also be explored by correlating the onset at late-start locations to early-start locations. Comparison to other teleconnection indices that have shown relation to monsoon onset will also be explored.