1 Research on Integrated Earth System Modeling at Global and Regional Scales L. Ruby Leung Pacific Northwest National Laboratory, Richland, WA 2 nd RASM Workshop Monterey, CA, May 15 – 17, 2012

The needs for model coupling and new development Understand the role of biosphere-atmosphere feedbacks on droughts in the southwestern U.S. Asses the impacts of climate change in the southeastern U.S. (e.g., hurricanes) Impacts of land-atmosphere (Amazon) and atmosphere-ocean (Atlantic) interactions on the tropical Atlantic biases Develop an integrated model to represent human-earth system interactions for modeling and analysis of climate change mitigation and adaptation, with a focus on the nexus of energy, water, and land use 2

3 A regional earth system model is being developed using WRF, CLM, and ROMS, following the flux coupling approach used in CESM Regional Earth System Model (RESM) Atmosphere and ocean boundary conditions POP CLM Flux Coupler Atmospheric conditions Surface fluxes CESM CAM Global ROMS Flux Coupler Atmospheric conditions Surface fluxes RESM WRF CLM Regional Consistent representations of land processes at global and regional scales Flexibility to model land processes using resolution or grid different from the atmospheric model Integrate human systems in CLM Facilitate air-sea coupling at regional scale

Model development Developed global high resolution (0.05 o ) input data for CLM based on MODIS Implemented the VIC surface/subsurface runoff and groundwater parameterizations to CLM Tested grid based vs subbasin based approaches Developed a new river routing model for CLM for both grid based and subbasin based approaches (including global input data at 6 different resolutions) Developing a water management model for CLM Adding subgrid elevation classification in CLM Applied UQ to understand model sensitivity to hydrologic parameters Developing WRF-ROMS coupling through CPL7 4

5 A 0.05-degree input dataset for CLM

Comparison of new and old CLM input data 6 Bare soil Trees Shrubs Grass Crop

7 Introducing VIC soil hydrology to CLM Saturation excess runoff Infiltration excess runoff ARNO baseflow curve Surface- and groundwater interactions Hydraulic redistribution Interactions of water movement between the root system and soil porous media

8 Dynamic representation of surface and groundwater interactions Change of water table depth Change of total soil moisture in the unsaturated zone Net water recharge to the groundwater body  s porosity n e (t) effective porosity Change of soil moisture Diffusion term Drainage term Liang et al., JGR, 2003

9 Implementation of VICGROUND to CLM A runtime option activated through the namelist

10 Simulated water budget at Tonzi Ranch

11 Global testing of CLMVIC CLM4-SP Forcing: Qian et al Land cover: current (i.e., 2000) Simulation period: Resolution: standard one-degree (i.e., 0.9 x 1.25) CLM-CN Forcing: CRU-NCEP Land cover: potential vegetation (pre-industrial) Simulation period: (by randomizing ) Resolution: 0.5-degree grid

12 CLM4-SP: Summer LH, CLM4 CLM4VIC CLM4VIC – CLM4 CLM4VIC – CLM4, global mean

13 CLM4-CN: Summer LH CLM4CN CLM4VICCN CLM4VICCN – CLM4CN global mean, stabilized

14 Motivation for a new runoff routing model To provide more accurate freshwater flux to the ocean from subdaily to daily time scales To provide a linkage between the human (e.g., surface water withdrawal, reservoir operation) and natural systems For transport of nutrients and sediments Features Consistent process representation across various scales (global, regional, local) Easy to be coupled with water management model Easy to be coupled with other fluxes

15 River Transport Model (RTM) in CLM 4.0 Study area divided into cells Flow direction is determined by D8 algorithm Cell-to-cell routing with a linear advection model Limitations Over-simplification of river network Over-simplification of physical processes Global constant channel velocity (0.35m/s) No account for sub-grid heterogeneity

16 Grid-based approach This hierarchical dominant river tracing method preserves the baseline high resolution hydrography (flow direction, flow length, upstream drainage area) at any coarse resolution (Wu et al. 2011) Subbasin representation preserves the natural boundaries of runoff accumulation and river system organization Model for Scale-Adaptive River Transport (MOSART) Subbasin-based approach

17 Grid-based approach Model for Scale-Adaptive River Transport (MOSART) Subbasin-based approach Conceptualized network Hillslope routing Sub-network routing Main channel routing Hillslope routing to account for event dynamics and impacts of overland flow on soil erosion, nutrient loading, etc. Sub-network routing: scale adaptive across different resolutions to reduce scale dependence Main channel routing: explicit estimation of in-stream status (velocity, water depth, etc.)

18 Inputs and Parameters Daily runoff generation from UW VIC at 1/16 o resolution for the Columbia River Basin Spatial delineation and network based on HydroSHEDS DRT algorithm for grid-based representation 1/16, 1/8, ¼ and ½ degree resolutions (available globally) ArcSWAT package for subbasin-based representation (average size ~109km 2 ) Manning’s roughness for hillslope and channel routing set to 0.4 and 0.05, respectively Evaluate against monthly naturalized streamflow data at selected major stations

Improved streamflow simulations 19 Large drainage area Small drainage area

20 Water Resource Management Model: Conceptual Design For full coupling in an earth system model: Assume no knowledge of future inflow Use generic operating rules Two components: Regulation module: extraction of water at the reservoir Storage: stores water over extended period of time Regulation: Follows monthly operating rules for flood control, environmental flow, irrigation and hydropower Constrained extraction: Daily partitioning of reservoir releases for irrigation water supply, other consumptive uses and environmental constraints. It includes the distribution across demanding units. Local surface water extraction module: extracts water at the unit Hillslope surface runoff: represent irrigation retention ponds Unit main stem if unpounded by an upstream reservoir

21 CLM-MOSART-WRM coupling Loop over PFTs Irrigated fraction found Need irrigation Routing + reservoir model (T- Δt ) YES NO End of loop Updated ET, runoff, baseflow, irrigation demand YES CLM (t) PFTs: vegetation types Local surface water (t- Δt) contribution to irrigation demand (t). Remaining demand? Extraction from main stem if not impounded. Remaining demand? Extraction from reservoir release to complement the local supply NO Aggregated demand (t- Δt) Aggregated supply (t) YES NO CLMRouting model Natural flow in each units; irrigation demand WRM Generated runoff, Agg. irrigation demand Regulated flow; Irrigation supply at each unit Agg. irrigation supply

22 Data Preprocessing Create a “unit-reservoir dependency database”: - Local approach: independent tributaries, elevation constraint, constrained distance-based buffer - Global approach: elevation constraint and distance-based buffer Distribute the demand across the reservoir based on the dependency database and maximum storage capacity of each dependent dam

Downscaling CCSM Simulations 23 WRF-CLM is being used to downscale CMIP5 CCSM historical, RCP4.5, and RCP8.5 simulations from

24 Uncertainty quantification framework

25 Ranks of significance of input parameters over 10 Flux Tower Sites Larger sensitivity to parameters of subsurface processes

Effects of Barrier Layers on TC Intensification 26 Balaguru et al PNAS (in revision)

TC intensification rate is higher by 20% for TC that passes over BL than over non-BL 27