Presentation Title

An Objective Definition for Onset and Withdrawal of the West African Monsoon

Faculty Mentor

Simona Bordoni

Start Date

18-11-2017 11:15 AM

End Date

18-11-2017 11:30 AM

Location

9-279

Session

Physical Sciences 1

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Accurate definition of the onset and withdrawal of the seasonal monsoon in West Africa is important for agriculture and water management in the region. Though several methods exist for defining the onset and withdrawal, most are threshold-based methods that may result in a false onset when short-lived weather systems bring rain to the region before the real monsoon onset. This project utilizes a method for more objective definition of the monsoon using change point detection (CHP). This method has previously been shown to correctly characterize the South Asian summer monsoon (SASM) and may be useful for defining onset and withdrawal of other monsoons as well. We successfully demonstrate that our method is objective and robust, making it unsusceptible to false and ambiguous onsets in the West African region and well capturing the transition in wind and precipitation patterns that occur at monsoon onset.

Summary of research results to be presented

Our CHP (change point) definition of West African monsoon onset and withdrawal accurately corresponds to transitions between positive and negative net precipitation, or positive and negative moisture flux convergence over a relatively large region representative of the monsoon. The method is robust and defines unambiguous onsets as the time when precipitation increases significantly over Western Africa. We find that extending our region of interest to incorporate larger amounts of precipitation and a larger area do not considerably shift onset and withdrawal days. Additionally, small spikes in precipitation before the true onset do not lead to false onset definitions.

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Nov 18th, 11:15 AM Nov 18th, 11:30 AM

An Objective Definition for Onset and Withdrawal of the West African Monsoon

9-279

Accurate definition of the onset and withdrawal of the seasonal monsoon in West Africa is important for agriculture and water management in the region. Though several methods exist for defining the onset and withdrawal, most are threshold-based methods that may result in a false onset when short-lived weather systems bring rain to the region before the real monsoon onset. This project utilizes a method for more objective definition of the monsoon using change point detection (CHP). This method has previously been shown to correctly characterize the South Asian summer monsoon (SASM) and may be useful for defining onset and withdrawal of other monsoons as well. We successfully demonstrate that our method is objective and robust, making it unsusceptible to false and ambiguous onsets in the West African region and well capturing the transition in wind and precipitation patterns that occur at monsoon onset.