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Water Vapor and Cloud Feedbacks
Contact: Hui Su


Summary

Water vapor plays an important role in global climate change through its influence in hydrological and energy cycles, and for its radiative effect as the strongest greenhouse gas. The ability of the atmosphere to hold more water vapor with increasing temperature leads to an important positive feedback for the estimate of global warming in response to the increase in CO2. This feedback is highly sensitive to upper tropospheric water vapor (UTWV). Meanwhile, clouds provide significant radiative forcing to the climate system in their own right.

The Microwave Limb Sounder on Aura satellite provides unprecedented simultaneous measurements of UTWV and cloud ice profiles. Analysis of these datasets has contributed and will continue contributing to our understanding of the dynamics controlling water vapor and cloud variations, and to help quantifying their feedbacks to climate change. In particular, MLS observations contradict the so-called 'Iris hypothesis' which holds that changes in upper tropospheric clouds will give a negative feedback on climate change.


MLS-related publications related to water vapor and cloud feedbacks on climate

2007

  1. Kahn, B.H., "Towards the characterization of upper tropospheric clouds using AIRS and MLS observations", vol doi:10.1029/2006JD007336, num 112, 2007. Reprint Preprint

2006

  1. Su, H., "Enhanced positive water vapor feedback associated with tropical deep convection: New evidence from Aura MLS", vol doi:10.1029/2005GL025505, num 33, 2006. Preprint
  2. Su, H., "Relationships of upper tropospheric water vapor, clouds and SST: MLS observations, ECMWF analyses and GCM simulations", vol doi:10.1029/2006GL027582, num 33, 2006. Preprint

1998

  1. Chandra, S., "Effects of 1997-1998 El Nino on tropospheric ozone and water vapor", num 25, 1998. Preprint
  2. Clark, H.L., "Variability of water vapor in the tropical upper troposphere as measured by the Microwave Limb Sounder on UARS", num 103, pgs. D24, 1998. Reprint Preprint
  3. Hu, H., "The impact of upper tropospheric humidity from Microwave Limb Sounder on the midlatitude greenhouse effect", num 25, 1998. Preprint

1997

  1. Newell, R.E., "Relationship between tropical upper tropospheric moisture and eastern tropical Pacific sea surface temperature on seasonal and interannual time scales", num 24, 1997. Preprint


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