Amplified Water Vapor Feedback at High Altitude Regions in Winter
Abstract
During the last five decades, the Tibetan Plateau has experienced a warming trend of 0.4C/decade in winter, which is at least twice that of any other season. Some studies have suggested that this anomalous winter warming there is caused, in part, by the observed increases in lower atmospheric water vapor and its amplifying effect on the surface downwelling longwave radiation (DLR). This study uses observations of surface specific humidity (q) and temperature as input to a one-dimensional radiative transfer model to assess the influence of lower atmospheric increases in water vapor on surface DLR, and the sensitivity of this process to different elevations and seasons on the Tibetan Plateau. The results from these idealized experiments show that when an equal mass of water vapor is added into the atmospheric boundary layer during winter, a substantially greater increase (8x) in DLR is found at the high elevation site relative to the low elevation site. During summer, the DLR increases are much smaller as are the differences between the two sites. Experiments, where both q and temperature are increased, suggest that the influence of temperature changes on DLR are much greater than those caused by changes in q in all cases, except for the high-elevation-winter case when the opposite is true. These results provide further evidence for the possibility of a stronger modulation of surface DLR caused by increases in atmospheric water vapor in high altitude regions (>3000m) during the cold season.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.A31D0129R
- Keywords:
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- 1605 GLOBAL CHANGE / Abrupt/rapid climate change;
- 1637 GLOBAL CHANGE / Regional climate change;
- 3359 ATMOSPHERIC PROCESSES / Radiative processes;
- 3320 ATMOSPHERIC PROCESSES / Idealized model