HR: 13:45h
AN: H23F-01 INVITED     [Abstracts]
TI: CO2-induced Changes in Extratropical Continental Hydrology
AU: * Delworth, T L
EM: tom.delworth@noaa.gov
AF: GFDL/NOAA, P.O. Box 308 Princeton University, Princeton, NJ 08542 United States
AU: Findell, K
EM: kirsten.findell@noaa.gov
AF: GFDL/NOAA, P.O. Box 308 Princeton University, Princeton, NJ 08542 United States
AB: In this work, we revisit the question of continental summer drying in a doubled-CO2 environment using the latest version of the Geophysical Fluid Dynamics Labs (GFDL) model of the atmosphere and land surface coupled to a mixed layer (slab) ocean. The model differs substantially from previous GFDL models, notably in terms of the inclusion of enhanced vertical resolution, the inclusion of an explicit boundary layer, and a diurnal cycle of insolation. In the earlier models, the simulated response to a doubling of atmospheric CO2 included an increase in wintertime rainfall over most mid-latitude continental regions, 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-latitudes in the doubled-CO2 experiment. 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 are playing an important role in driving regional hydrologic changes. We have conducted a set of additional experiments to isolate the relative roles of the land surface and the global ocean in generating the atmospheric circulation changes in the high CO2 simulation. We find that while tropical SST changes play the dominant role in driving the circulation changes, land surface feedbacks also play a crucial role. Such regional atmospheric circulation changes will play a critical role in projections of regional hydrologic changes in response to increasing greenhouse gases.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 1812 Drought
DE: 1866 Soil moisture
DE: 1620 Climate dynamics (3309)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting