Modeling of land hydrology with the use of topographical features V.N.Krupchatnikoff and A.I.Krylova Institute of Computational Mathematics and Mathematical Geophysics SB RAS, Novosibirsk, Russia

Introduction An anthropogenic changes in atmospheric composition are expected to cause climate changes: increasing surface temperature, intensification of the water cycle with a consequent increase of frequency of flood Output from 900-yr “control” (constant radiative forcing) experiment with coupled ocean- atmosphere-land model has been used to evaluate flood risk (P.C.D. Milly, R.T. Wetherald, K. A. Dunne, T.L. Delworth, 2002) An anthropogenic changes in atmospheric composition are expected to cause climate changes: increasing surface temperature, intensification of the water cycle with a consequent increase of frequency of flood Output from 900-yr “control” (constant radiative forcing) experiment with coupled ocean- atmosphere-land model has been used to evaluate flood risk (P.C.D. Milly, R.T. Wetherald, K. A. Dunne, T.L. Delworth, 2002) Focus of this work to prepare new version of the surface hydrology with topography-based runoff scheme to produce topography – related runoff and river discharge in coupled atmosphere-land model (INM/RAS – ICMMG/SB RAS) Focus of this work to prepare new version of the surface hydrology with topography-based runoff scheme to produce topography – related runoff and river discharge in coupled atmosphere-land model (INM/RAS – ICMMG/SB RAS)

Model Description AGCM/INM RAS 5x4 horizontal resolution and 21-level vertical resolution (Alexeev V., E.Volodin, V.Galin, V. Dymnikov, V. Lykosov, 1998) AGCM/INM RAS 5x4 horizontal resolution and 21-level vertical resolution (Alexeev V., E.Volodin, V.Galin, V. Dymnikov, V. Lykosov, 1998) LSM/ICMMG SB RAS - biophysical and biochemical surface model (V. Krupchatnikov, 1998 ) LSM/ICMMG SB RAS - biophysical and biochemical surface model (V. Krupchatnikov, 1998 )

Terrain-following vertical coordinate (21 σ-levels) Terrain-following vertical coordinate (21 σ-levels) Semi-implicit formulation of integration in time Semi-implicit formulation of integration in time Energy conservation finite-difference schemes (5x 4) (Arakawa-Lamb,1981) Energy conservation finite-difference schemes (5x 4) (Arakawa-Lamb,1981) Convection (deep, middle, shallow) Convection (deep, middle, shallow) Radiation (H2O, CO2, O3, CH4, N2O, O2; 18 spectral bands for SR and 10 spectral bands for LR) Radiation (H2O, CO2, O3, CH4, N2O, O2; 18 spectral bands for SR and 10 spectral bands for LR) PBL (5 σ-levels) PBL (5 σ-levels) Gravity wave drag over irregular terrain Gravity wave drag over irregular terrain 1. Atmospheric model (INM/RAS):

2. Land surface model(ICM&MG/SB RAS): Vegetation composition, structure Vegetation composition, structure Radiative fluxes Radiative fluxes Momentum and energy fluxes Momentum and energy fluxes Vegetation and ground temperature Vegetation and ground temperature Soil and lake temperature Soil and lake temperature Surface hydrology (snow, runoff, soil water, canopy water etc.) Surface hydrology (snow, runoff, soil water, canopy water etc.) CO2 emissions from terrestrial vegetation CO2 emissions from terrestrial vegetation CH4 emissions from natural wetlands CH4 emissions from natural wetlands

Структура ячейки сетки в модели поверхности

Плотность листового индекса в модели поверхности

Структура и состояние растительного покрова

Global Net CO2 fluxes(mmol CO2/m^2 c), (coupled simulation)

CH4 emissions from natural wetlands (coupled framework) West Siberia CH4 emissions from natural wetlands (coupled framework) West Siberia

Модель биосферы поверхности земли прогнозирует: Vegetation composition, structure (периодически сезонно меняющаяся) - нет Vegetation composition, structure (периодически сезонно меняющаяся) - нет Radiative fluxes - да Radiative fluxes - да Momentum and energy fluxes - да Momentum and energy fluxes - да Vegetation and ground temperature - да Vegetation and ground temperature - да Soil and lake temperature - да Soil and lake temperature - да Surface hydrology (snow, runoff, soil water, canopy water etc.) - да Surface hydrology (snow, runoff, soil water, canopy water etc.) - да CO2 emissions from terrestrial vegetation - да CO2 emissions from terrestrial vegetation - да CH4 emissions from natural wetlands - да CH4 emissions from natural wetlands - да

Estimates of 100-yr flood discharges based on model and observations ( P.C.D. Milly, R.T. Wetherald, K. A. Dunne, T.L. Delworth, 2002 )

ECHAM4 and HadCM3 climate models Effect on river discharge of increasing surface temperature

Results. INM/RAS-ICMMG/SB RAS coupled model response

1. The topography-based hydrological model (TOPMODEL ) By using the a priori computed topography index of a catchment and average water storage deficit calculated in the drainage, TOPMODEL directly estimate spatial distributions of the groundwater table and local water storage deficit in the unsaturated zone, and predict the portion of area in the catchment where saturation excess runoff will occur:.... In TOPMODEL total streamflow is the sum of saturation overland flow and subsurface flow. Saturation overland flow is the sum of direct precipitation on saturated areas and return flow.

Direct runoff flow is generated when precipitation falls on a saturated area: A sat is calculated by computing s at any point. If s is less than or equal to zero, the soil is completely saturated and any rain on the surface will become direct overland flow. This occurs most easily for points within the catchment where the topographic index is large. Return flow occurs where s is less than zero. The return flow is given by:... To compute the mean subsurface discharge, q subsurface is integrated along the length of all stream channels and divided by the catchment area: or.

2. Topography-related runoff model 2. Topography-related runoff model 2.1. Saturated hydraulic conductivity In the ICM&MG land-surface model, the soil moisture is calculated at the interface level of the model layers,. For the i- th layer,. Hydraulic conductivity at saturation k sat vary with percent of sand according to, where  and  can be determined through optimization procedures.

2.2. Bottom drainage The gravitational loss of soil water from the bottom of the model soil column is given by the following: for bottom layer i=6, 2.3. Saturation excess The soil water may exceed the physical constraints. Any soil in excess of saturation is added to the soil, starting at the top of the soil layer. If a column becomes oversaturated, the subsurface runoff due to a saturation excess is

The water table depth z wt is used to determine a saturated function, a surface runoff and a baseflow. The water table depth z wt is computed by the iterative solution of the equality.. /;;;;;;; …… …………………… Subsurface runoff The subsurface runoff is parameterized in the form where is a subsurface runoff due to the topographical control (calculated by the TOPMODEL), is the bottom drainage, and is a saturation excess.

2.5. Topographical control The subsurface runoff due to the topographical control is given by, where  is a factor with allowance for a difference in the saturated hydraulic conductivity in the lateral and the vertical directions. 3. The river discharge model Using linear advection scheme at 10 0 resolution river rout water model from one cell to its downstream neighboring cell by considering balance of horizontal water inflows and outflows:, where is divergence source of river water,, is the effective water flow velocity ; W riv is storage of stream water within the cell (m 3 ).

Figure 2. Upscaling function for obtaining 10' equivalent of a topographic index from its values for 30-arc-second DEM

Figure 1. ln(a/tan b) distribution function computed from GTOPO30 DEMs for the Tom river basin

Figure 3. Seasonal water discharge of the Tom river. The solid line – the model result (off-line simulation). Clauster of lines – observations of discharge for period of years.

Conclusion Total runoff (surface and sub-surface drainage) is routed downstream to oceans using a river routing model. River routing model is based on TOPMODEL ideas A river routing model is coupled to the Land Surface Model (ICMMG SB RAS) for hydrological applications and for improved land-ocean-sea ice-atmosphere coupling in the Climate System Model (CSM). A river routing model is coupled to the Land Surface Model (ICMMG SB RAS) for hydrological applications and for improved land-ocean-sea ice-atmosphere coupling in the Climate System Model (CSM). We have implemented this model (off-line) on a 1-degree grid. Land model interpolates the total runoff from the column hydrology (2.8 by 2.8 degree) to the river routing 1-degree grid. We have implemented this model (off-line) on a 1-degree grid. Land model interpolates the total runoff from the column hydrology (2.8 by 2.8 degree) to the river routing 1-degree grid. Pictures we shown here are results from a regional 1° by 1° simulation (River Tom basin) using global ICMMG LSM. The model is driven with AMIP data from 1979 to Pictures we shown here are results from a regional 1° by 1° simulation (River Tom basin) using global ICMMG LSM. The model is driven with AMIP data from 1979 to Thank you