Update on LMWG Proposed Hydrologic Improvements to CLM Overview of proposed hydrology schemes (3) CAM/CLM and offline CLM simulations – Follow the water Preliminary conclusions Validation against tower fluxes Project Objectives: Wetter soils, increased transpiration/photosynthesis, improved partitioning of evapotranspiration and representation of land- atmosphere feedbacks, particularly in the tropics (Amazon)

CLM Hydrology Project Simulations Hyd_con (released CAM3/CLM3) Hyd_sunsha (Two-leaf canopy model) P. Thornton, TSS/NCAR Hyd_plaw_plsc ( Surface Datasets (PFTs, LAI, Soil Albedo)) P. Lawrence, CU/CIRES Hyd_dlptmcs D. Lawrence, P. Thornton/NCAR Hyd_nli Z.L. Yang, G.Y. Niu/UTA Hyd_bd_nlai R. Dickinson/GIT

Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Ocean Soil Water Snow Drainage Summary of Hyd_dlptmcs (NCAR) Interception (decrease) – Reduce fraction of potential intercepted water by ¼. Transpiration (increase) –Soil moisture stress as in LSM (linear function between optimum and dry soil moisture). Soil Evaporation (decrease) – Reduce soil-canopy air space conductance. Surface Runoff (decrease) – Saturated fraction runoff unchanged. Runoff over non-saturated fraction controlled by enhancement factor based on root fraction in top 3 layers (macropores). Soil Water Dynamics (increase) – Remove exponential decrease in hydraulic conductivity. Depends only on sand content of each layer. Drainage (increase) – Eliminate saturated and non- saturated fraction drainage. Free drainage from layer 10 controlled by hydraulic conductivity. Note that Infiltration is a residual of surface water flux - evaporation - surface runoff.

Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Ocean Soil Water Snow Drainage Summary of Hyd_bd_nlai (GIT) Limit storage capacity and leaf wet fraction by fractional area of liquid precipitation (convective rain falls over 10% of gridcell). Interception (decrease) – Limit storage capacity and leaf wet fraction by fractional area of liquid precipitation (convective rain falls over 10% of gridcell). Surface Runoff (decrease) – Saturated fraction runoff is exponential function of existing water table scale height. No non-saturated fraction runoff. Soil Water Dynamics (increase) – Remove exponential decrease in hydraulic conductivity. Depends only on sand content of each layer. Drainage (increase) – Eliminate saturated and non- saturated fraction drainage. No flux boundary condition at bottom layer. Base flow consists of weighted contributions of freely draining soil and that impeded by coupling to water table and applied to bottom layer. Water table depth based on lowest saturated layer and soil matric potential.

Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Ocean Soil Water Snow Drainage Summary of Hyd_nli (convective precip falls over 10% of gridcell) Interception (decrease) – Reduce fraction of potential intercepted water by fractional area of precipitation (convective precip falls over 10% of gridcell). Leaf wet fraction unchanged. Applied to convective snow as well. Surface Runoff (decrease) – Saturated fraction runoff is exponential function of water table depth. Max saturated runoff provided by topographic index. Soil Water Dynamics (increase) – Exponential decrease in hydraulic conductivity but enhanced by factor of seven. Drainage (increase) – Eliminate saturated and non- saturated fraction drainage. No flux boundary condition at bottom layer. Excessive water above saturation added to above unsaturated layer. Base flow based on maximum baseflow parameter and exponential function of water table depth and applied to all layers.

CAM3/CLMx - Follow the water Ocean Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx - Follow the water Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

CAM3/CLMx Global Land Annual Average

CAM3/CLMx River Discharge to Ocean Offline CLM (“Examining the simulated hydrology under biased forcings makes no sense”) Atmospheric forcing courtesy of T.Qian/A. Dai - NCAR

CAM3/CLMx Discharge for World’s Top 10 Rivers Offline CLM

CAM/CLMx Climate Changes

CAM3/CLMx

CAM3/CLMx Volumetric Soil Moisture

Conclusions All schemes (in combination with sun/shade model and new surface datasets) offer substantial improvements in producing wetter soils, increasing transpiration and photosynthesis, and improving the partitioning of evapotranspiration. Hyd_dlptmcs and Hyd_bd_nlai are most similar in terms of partitioning of evapotranspiration and surface runoff ratio. Globally, Hyd_nli has less transpiration and canopy evaporation, more ground evaporation, lower surface runoff ratio than the other two schemes. All schemes produce reasonable river discharge to ocean compared to observations. In the Amazon, all schemes improve temperature and precipitation biases and hydrologic cycle. In general, the three schemes produce similar but small changes in climate. The most notable exceptions to this are: –All schemes produce cooling in Arabian Peninsula and India in DJF (undesirable) with Hyd_nli resulting in the largest cooling –Increase in wet season precipitation in the Amazon in all schemes (desirable) and an enhanced seasonal cycle in the Congo (undesirable). –In JJA, all schemes produce cooling in Europe and near Caspian/Black seas, most of U.S., and Amazon (desirable). All schemes increase positive bias in precipitation in Arabian Peninsula and southern India (undesirable).

Conclusions All schemes require minimal software engineering for implementation and only small changes to documentation (tech note) All schemes have free parameters that could be “tuned”. Final optimal scheme will likely consist of some combination of desirable aspects of each scheme. How to determine this requires more testing against observations and a deeper understanding of why each scheme performs as it does.

EXTRA SLIDES

Hydrology Canopy Water Evaporation Interception Melt Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Ocean Soil Water Snow Drainage Summary of Hyd_con (CAM3/CLM3) Interception – Fraction of potential intercepted water is an exponential function of leaf and stem area. Transpiration – Soil moisture stress is a non-linear function of root distribution and soil water potential. Soil Evaporation – Soil-canopy air space conductance is a weighted function of bare soil and dense canopy conductances where weights depend on leaf and stem area. Surface Runoff – Sum of runoff from saturated and unsaturated fractions which are determined from a water table scale height (conceptual TOPMODEL). Soil Water Dynamics – Exponential decrease in hydraulic conductivity. Drainage (increase) – Sum of drainage from saturated and non-saturated fractions plus drainage from layer 10 controlled by hydraulic conductivity. Note that Infiltration is a residual of surface water flux - evaporation - surface runoff.

ABRACOS CLMx (solid line), Observed (dashed line) Latent Heat Flux (Aug 8-Oct 4, 1992) Broadleaf evergreen tropical forest Hyd_con Hyd_dlptmcs Hyd_nli Hyd_bd_nlai

ABRACOS CLMx

Atmospheric forcing –Magnitude of wind (m s -1 ) –Specific humidity (kg kg -1 ) (or relative humidity or dewpoint temperature) –Pressure (Pa) –Air temperature (K) –Incident longwave radiation (W m -2 ) (or derived from vapor pressure and temp) –Precipitation (mm s -1 ) –Incident direct and diffuse visible and near-infrared solar radiation (W m -2 ) (or total solar radiation) –Netcdf format, ½ hour resolution preferred Surface characteristics –Plant functional types and abundance –Soil color –Soil texture (vertical profile of %sand/%clay) –Monthly LAI and SAI –Monthly canopy top and bottom heights CLM Forcing and Validation Requirements – Tower Flux Sites

Validation –Radiative fluxes (m s -1 ) –Turbulent fluxes (including CO 2 ) –Soil temperature and soil moisture –Runoff CLM Forcing and Validation Requirements – Tower Flux Sites

FIFE (grassland prairie in Kansas) BOREAS (old aspen, old black spruce in Canadian boreal forest) Cabauw (grassland in the Netherlands) Valdai (grassland in Russia) ABRACOS (rainforest in Brazil) Tucson (semi-arid desert) Other possibilities –LBA (primary rainforest, pasture) –FLUXNET (various ecosystems) –Hapex-Mobilhy (soybean field in France) Tower Flux Site Forcing and Validation Data In-house

Interception Hyd_con Hyd_dlptmcs Hyd_nli Hyd_bd_nlai

Transpiration (Soil Moisture Stress) Hyd_con Hyd_dlptmcs

Soil Evaporation Hyd_con Hyd_dlptmcs

Surface Runoff Hyd_con Hyd_dlptmcs Hyd_nli Hyd_bd_nlai

Soil Water Dynamics (hydraulic conductivity) Hyd_con Hyd_dlptmcs Hyd_nli Hyd_bd_nlai

Drainage Hyd_con Hyd_dlptmcs Hyd_nli Hyd_bd_nlai

Drainage

CAM/CLMx Climate Changes

CCSM Hyd_dlptmcs Climate Changes

CAM3/CLMx Hydrology Canopy Water Evaporation Interception Sublimation Throughfall Stemflow Infiltration Surface Runoff Evaporation Transpiration Precipitation Redistribution Soil Water Snow Drainage

Mean Annual Cycle of River Flow for Amazon and Congo CAM3/CLMx Offline CLM