Trajectory Calculations of Hydration/Dehydration in the Lower Stratosphere from Aura/MLS Water Vapor Measurements

Hydration/dehydration rates at 365 K isentrope are estimated by averaging the differences of two Aura MLS H2O measurements closely linked by two-day Lagrangian trajectories. Stratospheric dehydration mainly occurs in Northern Hemispheric winter over the tropical western Pacific, where seasonally averaged rates are collocated with regions of high deep convective activity and relative humidity (RH). The Madden-Julian Oscillation (MJO) modulates the tropical dehydration through the migration of deep convection. The dehydration rate over the western Pacific is strongest when the enhancement in deep convection migrates to about 160°E, and dehydration appears over the Indian Ocean when the convection is enhanced over 80°E. Hydration of the stratosphere mainly occurs over the summertime subtropical-extratropical continents. The Asian monsoon provides the strongest stratospheric hydration during Northern Hemispheric summer. The hydration rates associated with the Asian monsoon is modulated by the MJO, becoming larger when the tropical convection is enhanced over the Indo/Pacific region (120°-160°E), when the Asian monsoon deep convective activity is also enhanced.