Dennis P. Lettenmaier and Fengge Su

1. Progress in hydrological modeling over high latitudes --under Arctic Climate System Study (ACSYS) Dennis P. Lettenmaier and Fengge Su

2. Arctic Climate System Study (ACSYS) Mission • What are the global consequences of natural or human-induced change in the Arctic climate system? • Is the Arctic climate system as sensitive to increased greenhouse gas concentrations as climate models suggest? ACSYS is a core project of the World Climate Research Programme (WCRP). It started from January 1994, and ended in December 2003.

3. Components of ACSYS • Arctic ocean circulation programme • Arctic sea-ice programme • Arctic atmosphere programme • Hydrological cycle in the Arctic region • ACSYS modelling programme • Data Management and Information

4. Objectives of ACSYS hydrological programme • Developing mathematical models of the hydrological cycle under specific Arctic climate conditions suitable for inclusion in coupled climate models; • Determining the elements of the fresh water cycle in the Arctic region and their time and space variability; • Quantifying the role of atmospheric, hydrological and land surface processes in the exchanges between different elements of the hydrological cycle; • Providing an observational basin for the assessment of possible long-term trends of the components of the fresh water balance in the Arctic region under changing climate.

5. Major components of the ACSYS hydrological programme • Development regional data bases for the main components of the fresh water balance of the Arctic region; • Development of hydrological models of selected Arctic river basins and their validation using appropriate observational data sets.

6. Projects contributing to ACSYS 1. The project for the Intercomparison ofLand-Surface Parameterization Schemes Phase 2(e) – PILPS 2(e) 2. GEWEX Continental Scale Experiments (CSEs) . MAGS . BALTEX . GAME-Siberia . GCIP/GAPP Hydrological modelling activities in ACSYS were performed in close collaboration with WCRP Global Water and Energy Experiment (GWEX) project.

7. The Project for the Intercomparison of Land-Surface Parameterization Schemes (PILPS) 2(e) A small working group was established by ACSYS in August 1998 for the purposes of planning an Arctic hydrology model intercomparison project. The resulting project, PILPS phase 2(e), was a joint experiment of ACSYS and GEWEX, and was designed to evaluate the performance of land surface models in high latitudes. Special Issue on PILPS 2(e): Global and Planetary, 38(1-2), 2003

8. List of participating models of PILPS Phase 2(e) Torne– Kalix River basin and the 218 computational ¼ ° latitude/longitude grid cells. Baltic Sea Bowling et al., 2003

9. Mean monthly observed (dots) and simulated (lines) discharge for the Kalix and Torne river basins. Observed (dots) and simulated (lines) snow water equivalentfor five locations Nijssen et al., 2003

10. Number of days with snow cover for models participating in PILPS 2(e). Lowest right panel shows a satellite derived estimate Mean annual latent heat flux for the model reruns. The last panel shows annual latent heat flux estimated from basin water balance. Bowling et al., 2003 after Nijssen et al, 2003

11. MAGS BALTEX GAME-Siberia

12. Mackenzie GEWEX Study (MAGS) Models • CLASS • WATFLOOD • WATCLASS • CRCM/CLASS WATFLOOD representation of Mackenzie River drainage basin. Each linear segment represents a 50 kilometre river reach. Snelgrove et al, 2005

13. Canadian Land Surface Scheme (CLASS)

14. Framework for hydrological modelling in MAGS Soulis et al., 2005

16. Snelgrove et al, 2005

17. WATFLOOD (Level 0) WATCLASS (Level 2) Snelgrove et al, 2005

18. Baltic Sea Experiment (BALTEX) Baltic Sea Drainage Basin Models: HBV- conceptual hydrological model SEWAB- land-surface scheme 49° N - 69 ° N

19. Monthly averages of freshwater flow into the major subbasins of the Baltic Sea, calculated with the HBV mode Baltic Sea drainage area: 1.6 ×106 km2 Raschke et al., 2001

20. Modeled seasonal river discharge to the Baltic Sea from HBV-Baltic for present-day conditions (shaded) and four climatechange scenarios. Baltic Sea Graham, 2004

21. Hydrological components of the land surface scheme SEWAB (Surface Energy and Water Balance) • VIC approach (Warrach et al., 1999) • TOPMODEL approach ( Stieglitz et al., 1997) • The concept of ponding at the surface (Mengelkamp et al., 2001) • The processes of soil freezing and thawing and the seasonal snow cover (Warrach et al., 2001) Various optional versions of SEWAB

22. Daily streamflow simulated with SEWAB and Lohmann et al. (1996) routing scheme The Odra drainage basin (119,000 km2 ) with 18 km mesh size 54° N 49° N Mengelkamp et al., 2001

23. GEWEX Asian Monsoon Experiment GAME-Siberia GAME-Siberia project concentrates on observation and modeling of land surface processes, and regional analysis of energy and water cycle in permafrost region of eastern Siberia. Lena River Basin

24. Six hydrological stations within the Lena River Basin. Simulated runoff at the six hydrological stations from October 1986 to September 1987, using a combined model which is composed of a SVAT model, runoff model, and river routing model. Ma et al., 2000

25. Precipitation, Oct 1986- Sep 1987 Simulated evapotranspiration (E), Oct 1986-Sep 1987 Annual effective rainfall (P-E), Oct 1986- Sep 1987 Ma et al., 2000

26. A number of changes have been made to improve the VIC model's representation of cold season processes, in conjunction with the GEWEX Continental-scale International Project (GCIP) activities in the upper Mississippi River basin, and the PILPS Phase 2(e) experiment in the Torne-Kalix River basin. The VIC model

27. Cold land processes Cold land processes in VIC A two-layer energy balance snow model (Storck et al, 1999; Cherkauer et al, 2003, JGR) A frozen soil/permafrost algorithm (Cherkauer et al, 1999; 2003, JGR) A lake and wetlands model (Bowling et al, 2003,WRR) A blowing snow model (Bowling et al, 2004, J. Hydromet)

28. A The VIC model was applied to the Mackenzie and Ob River basins at 2° spatial resolution and daily temporal resolution to examine the space-time structure of the predicted hydrologic variables (i.e., runoff, evaporation, soil moisture, and snow water equivalent) B Bowling et al., 2000 Routing networks for the Mackenzie (A) and the Ob (B)

29. Ob Mackenzie Bowling et al., 2000

30. The goal of ACSYS hydrological programme is to determine the space-time variability of the Arctic hydrological cycle and the fluxes of freshwater to the Arctic Ocean.

31. Arctic river network over 100km grid system

32. Estimates of Annual Continental Freshwater into the Arctic Ocean

33. Basin area-annual flow volume relationship for different estimations VIC2 VIC2 VIC1 VIC1

34. Simulated mean monthly streamflow discharge into the Arctic Ocean (1979-1999) Total =3354km3/yr Area = 1.5×106km2

35. What did the ACSYS achieve? • Several land surface models had been improved in representing snow accumulation and ablation, soil freeze/thaw and permafrost, and runoff generation motivated by the PILPS 2(e) experiment in Torne-Kalix River basin and other projects related to ACSYS. • Intensive field measurement under MAGS and GAME-Siberia promoted the development of process algorithms of snow accumulation, redistribution, and ablation, and water infiltration into frozen soil, and the development of one-dimensional land surface models for cold region. • The VIC model and the macroscale hydrological models developed under the MAGS, BELTEX, and GAME-Siberia have been used to simulate the surface water and energy balance of high-latitude river basins. • The Arctic river runoff in both gauged and ungauged basins and the freshwater river inflow to the Arctic Ocean were estimated and analyzed by using a macroscale hydrological model. • The water balance terms of the land surface water in the Arctic region and their time and space variability were determined and evaluated by using a land surface model and the ERA-40 reanalysis.

36. What remains to be done ? • The roles of frozen soil moisture and blowing snow parameterizations in the large-scale simulation of runoff, temperature, and evaporation are not completely clear. • Existing wetlands and lake models in land surface models need to be further improved and validated. • Many results from process investigations of snow and frost-related hydrological processes remain to be incorporated into large-scale hydrological models. • Continued development of hydrological models and linkages between atmospheric and hydrological models are needed in scientific studies of the interactions between climate, snow and frost hydrology. • Most of the key issues have also been addressed in the Science Plan of Climate and Cryosphere (CliC), which is the successor of ACSYS.

37. Thank You!