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Water Vapor Feedback and Links to Mechanisms of Recent Tropical Climate VariationsRecent variations of tropical climate on interannual to near-decadal scales have provided a useful target for studying feedback processes. A strong warm/cold ENSO couplet (e.g. 1997-2000) along with several subsequent weaker events are prominent interannual signals that are part of an apparent longer term strengthening of the Walker circulation during the mid to late1990 s with some weakening thereafter. Decadal scale changes in tropical SST structure during the 1990s are accompanied by focusing of precipitation over the Indo-Pacific warm pool and an increase in tropical ocean evaporation of order 1.0 %/decade. Here we use a number of diverse satellite measurements to explore connections between upper-tropospheric humidity (UTH) variations on these time scales and changes in other water and energy fluxes. Precipitation (GPCP, TRMM), turbulent fluxes (OAFlux), and radiative fluxes (ERBE / CERES, SRB) are use to analyze vertically-integrated divergence of moist static energy, divMSE, and its dry and moist components. Strong signatures of MSE flux transport linking ascending and descending regions of tropical circulations are found. Relative strengths of these transports compared to radiative flux changes are interpreted as a measure of efficiency in the overall process of heat rejection during episodes of warm or cold SST forcing. In conjunction with the diagnosed energy transports we explore frequency distributions of upper-tropospheric humidity as inferred from SSM/T-2 and AMSU-B passive microwave measurements. Relating these variations to SST changes suggests positive water vapor feedback, but at a level reduced from constant relative humidity.
Document ID
20090014193
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Robertson, F. R.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Miller, Tim L.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 24, 2013
Publication Date
October 20, 2008
Subject Category
Meteorology And Climatology
Report/Patent Number
MSFC-2139
Meeting Information
Meeting: Chapman Conference on Atmospheric Water Vapor and Its Role in climate
Location: Kailua-Kona, HI
Country: United States
Start Date: October 20, 2008
End Date: October 24, 2008
Sponsors: American Geophysical Union
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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