Global Monsoon Onset and Retreat based on Precipitable

Water and Wind

By: Dimitri Ververelli

NASA Space Grant Symposium. Phoenix, AZ. April 18, 2009

Monsoon Study

• Multi-Regional climate phenomenon

• Multiple definitions of onset

• Problem: No definition that allows for operational use

• Objective: Create an operational definition primarily based on Zeng and Lu (2004)

NCEP Data

• From National Centers for Environmental Prediction (NCEP).

• Based on satellite and surface observations.• 1° X 1° resolution, 6 hourly, global• Data period: April 2000 – March 2001.• Precipitable water (total water vapor in a vertical

column) and 700 mb (10,000 ft) wind.

NPWI Based Onset

• A normalized precipitable water index (NPWI) is calculated.

• Onset and Retreat criterion is based on the Golden Ratio (0.618).

minmax

min

PWPW

PWPWNPWI

Thank You