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Development of a Simple Groundwater Model for Use in Climate Models and Evaluation with Gravity and Climate Experiment Data. Guo-Yue Niu, Zong-Liang Yang, Robert E. Dickinson, Lindsey E. Gulden, and Hua Su, Journal of Geophysical Research , Vol. 112, D07103, doi:10.1029/2006JD007522, 2007.
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Development of a Simple Groundwater Model for Use in Climate Models and Evaluation with Gravity and Climate Experiment Data Guo-Yue Niu, Zong-Liang Yang, Robert E. Dickinson, Lindsey E. Gulden, and Hua Su, Journal of Geophysical Research, Vol. 112, D07103, doi:10.1029/2006JD007522, 2007
Motivations • Develop a simple groundwater model (SIMGM) to represent groundwater dynamics in GCMs • Evaluate SIMGM against observations to see whether this model is realistic • Compare the updated model to the previous model to investigate the impact of this modification on the simulation of soil moisture and evapotranspiration
Background • Recent study shows that surface runoff is an exponential function of water table depth. • TOPMODEL-based runoff scheme formulates the base flow as an exponential function of water table depth. • Deficiencies of current land surface models • Several methods to improve the model
Add an unconfined aquifer to an LSM’s soil column Apply a simple TOPMODEL-based runoff scheme: Model Descriptions
Represent groundwater recharge and discharge processes Update the gravitational drainage with the groundwater recharge as the lower-boundary condition The water table depth is converted from the aquifer water storage scaled by the specific yield (0.2) Model Descriptions
Conclusions • SIMGM was developed to represent groundwater dynamics in GCMs. • Global runoff produced by SIMGM agrees well with the GRDC runoff. • Both modeled total water storage and water table depth anomalies are in good agreement with those from GRACE, • Discharge, recharge, soil water and water table depth are controlled by P-E. • SIMGM produced much more soil moisture and 4% - 16% more annual ET than FD.
Discussions • Integration elements • Is aquifer connected to the bottom layer of the soil column? • Specific yield? • Initialization of the model