Paper in Press
JOURNAL OF GEOPHYSICAL RESEARCH, doi:10.1029/2011JD016917
Using satellites to investigate the sensitivity of longwave downward radiation to water vapor at high elevations
- PWV vs. q universal for large q but elevation dependent for low q
- MODIS PWV and CERES LDR as accurate at high as low elevations
- Satellites observe high sensitivity of LDR to changes in q in dry locations
Many studies suggest that high-elevation regions may be among the most sensitive to future climate change. However, in-situ observations in these often remote locations are too sparse to determine the feedbacks responsible for enhanced warming rates. One of these feedbacks is associated with the sensitivity of longwave downward radiation (LDR) to changes in water vapor, with the sensitivity being particularly large in many high-elevation regions where the average water vapor is often low. We show that satellite retrievals from MODIS and CERES can be used to expand the current ground-based observational database and that the monthly-averaged clear-sky satellite estimates of humidity and LDR are in good agreement with the well-instrumented Center for Snow and Avalanche Studies ground-based site in the southwestern Colorado Rocky Mountains. The relationship between MODIS retrieved precipitable water vapor and surface specific humidity across the contiguous United States was found to be similar to that previously found for the Alps. More importantly, we show that satellites capture the non-linear relationship between LDR and water vapor and confirm that LDR is especially sensitive to changes in water vapor at high elevations in several mid-latitude mountain ranges. Because the global population depends on adequate freshwater, much of which has its source in high mountains, it is critically important to understand how climate will change there. We demonstrate that satellites can be used to investigate these feedbacks in high-elevation regions where the coverage of surface-based observations is insufficient to do so.
Received 22 September 2011; accepted 4 January 2012.
Citation: (2012), Using satellites to investigate the sensitivity of longwave downward radiation to water vapor at high elevations, J. Geophys. Res., doi:10.1029/2011JD016917, in press.