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