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gfdl on-line bibliography > 2007 citations
Decadal to Centennial scale changes in Summer continental hydrology
| Delworth, T. L., and K. L. Findell, 2007: Decadal to Centennial scale changes in Summer continental hydrology. In, Climate Variability and Change: Past, Present, and Future, John E. Kutzbach Symposium, Madison, WI: Center for Climatic Research, University of Wisconsin-Madison; 49-56. |
| Abstract: Past studies have suggested that increasing atmospheric CO2 will lead to a substantial reduction of soil moisture during summer in the extratropics. We revisit this topic using a new climate model developed at NOAA's Geophysical Fluid Dynamics Laboratory. The new model has a horizontal resolution of 2.5° longitude by 2.0° latitude, with 24 vertical levels, and has both a diurnal and seasonal cycle of insolation. The model incorporates substantially updated physics relative to previous versions. |
| Results from earlier studies showed, among other things, an increase in wintertime rainfall over most mid-latitude continental regions when CO2 is doubled, an earlier snowmelt season and onset of springtime evaporation, and a higher ratio of evaporation to precipitation in summer. These factors led to large-scale increases in soil moisture in winter and decreases in summer in mid-latitude in doubled-CO2 experiments. The new model shows similar results, and the processes discussed above are important in this model as well. In addition, we find that changes in atmospheric circulation play an important role in regional hydrologic changes. Additional experiments have been run to probe the causes of the circulation changes. These simulations show that global scale sea surface temperature increases caused by the CO2 doubling explain the majority of the atmospheric circulation changes, while positive feedbacks from the land surface have a secondary impact. These results highlight the importance of global scale sea surface temperature changes for future regional hydrology changes. |