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PhD Defense - Antonia Gambacorta

Drs Antonia Gambacorta & Lynn SparlingAntonia successfully defended her dissertation on November 20, 2008.

TITLE:
Temperature Change And Water Vapor Feedback In The Atmosphere. A Comprehensive Assessment Using The Atmospheric Infrared Sounder Instrument On NASA Aqua Satellite

ABSTRACT:
Global surface temperature has increased ~0.2 degree Celsius per decade in the past 30 years. Observational data recorded from 1850 to 2007 indicate that the warmest 11 years have occurred between 1995 and 2006. The 2007 report of the Intergovernmental Panel on Climate Change concluded that there is a "very high confidence - 95% confidence - that the global average net effect of human activities since 1750 has been one of warming" and that "most of the observed increase in global average temperatures since the mid-20th century is very likely - 90% confidence - due to the observed increase in anthropogenic greenhouse gas concentrations".

Processes in the climate system that can either amplify or dampen the climate response to an external forcing such as an increase in anthropogenic greenhouse gas concentrations, and directly or indirectly affect the Earth's radiation budget at the top of the atmosphere are normally referred to as "climate feedbacks". Among all trace gases, water vapor is the most sensitive to temperature variations. In fact, water vapor absorbs strongly in the vibration-rotation and pure rotation bands at wavelengths in which a large portion of infrared emission occurs at temperature characteristic of the Earth's surface and atmosphere.

In the present study, we exploit the uniform spatial coverage and high vertical resolution of the Atmospheric InfraRed Sounder database of temperature and water vapor profiles to perform a detailed investigation of the covariance between temperature and water vapor. Differently from the previous studies, who only analyzed the overall tropically averaged water vapor and temperature relationship, we make a more comprehensive analysis by investigating this relationship on a local basis. By doing so, we explore the horizontal gradient of this relationship in the tropics, in order to better confine its range of variability and the interplay of the physical processes underneath it. An overall conclusion on the sign and magnitude of the tropical sensitivity to surface temperature variations by mean of water vapor feedback will be assessed.

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