HydroThermodynamicSoilVegetationScheme

In HTSVS (Kramm 1987, Kramm et al. 1994, 1996, Mölders and Kramm 1999), the treatment of the (vertical) heat- and water-transfer processes is based on the Philips-and-de-Vries-type soil physics, i.e., it is based on the principles of the linear thermodynamics of irreversible processes (including the Richards-equation) allowing long-term integration. The exchange of energy and matter between vegetation and atmosphere is parameterized analogous to the resistance networks shown in Figure 1. Vegetation is represented by a single layer. The heterogeneity of the system 'soil-vegetation' on microscale is described by a Deardorff-type mixture-approach, i.e., the effects of bare and plant-covered soil are linearly weighted by the shielding factor associated with the degree to which foliage prevents shortwave radiation from reaching the ground (Fig. 1). Transpiration of water by plants is described by using a Jarvis-type bulk-stomatal resistance approach. Additions are made to HTSVS to accommodate the effects of water extraction by roots and soil wetness on soil albedo (Mölders et al. 1999). Soil albedo now depends on volumetric water content. Moreover, the simple parameterization of infiltration is replaced by an explicit formulation of the Green-and-Ampt-approach (Mölders 1999).

HTSVS was developed at University of Frankfurt by Dr. G. Kramm (see, e.g., Kramm and Herbert 1984, Kramm 1987) and further developed for 3D-purposes by Dr. habil. N. Mölders (see, e.g., Mölders 1999) at University of Leipzig. Moreover, HTSVS was enlarged by the inclusion of parameterizations of infiltration and root effects by Dr. habil. N. Mölders (see, e.g., Mölders 1999, Mölders et al. 1999, 2000). In 2000, HTSVS was implemented into MM5 at NCAR by Dr. habil. N. Mölders.

  • Evaluation

HTSVS is evaluated using GREIV74-, Great PlainsExperiment- (see, e.g., Kramm 1987, 1995, Kramm et al. 1994, 1996), lysimeter- and tensiometer data (see, e.g., Mölders et al. 1999, 2000, 2003) as well as CASES97-data

  • Options already tested/coupled in MM5

FRAD=1,2,3,4

ICLOUD=1

ICUPA=2,3

IMPHYS=6,7

IBLTYP=5

ISHALLO=0,1

  • Preliminary results

Within the framework of MM5, HTSVS was run for IOP5 of CASES97

  • How to run HTSVS

Like OSULSM, but set ISOIL=4. The parameter IGIVLAI allows to chose how the vegetation fraction and leaf area index are dealt with. IGIVLAI=0 shielding factor is pregiven, =1 LAI is pregiven, =2 LAI and shielding factor are taken from DATA statement, =3 2D-field of vegetation fraction is read in and LAI is taken from DATA statement. The parameter ZSLMAX (negative values required) gives the depth of first soil layer (m). ZSLMIN (negative values required) gives the deepest soil layer (m) and TKR=0.5 is a coefficient in the implicit scheme of HTSVS. TKR should be changed for sensitivity studies purposes only.

  • Comparison with OSULSM
 

OSULSM

HTSVS

canopy layer

one

one

prognostic variables

Interception, snow stored on ground, soil temperature, volumetric water content

ponded water, volumetric water content, soil temperature

soil layers

free to choose

free to choose, but logarithmically increasing thickness

roots

in upper 1 m of soil, function of vegetation type

depth limited to depth of model, unequal vertical-distribution depending on vegetation type, root depth, distribution and length

lower boundary condition

reservoir with gravity drainage at the bottom

constant values of volumetric water content, soil temperature

exchange of heat and matter

single linearized energy balance equation, representing the combined ground/vegetation surface

coupled energy and water budgets for the temperatures and humidity of foliage and ground, respectively

determination of soil heat and moisture fluxes

decoupled equations soil heat and moisture fluxes

coupled equations for soil heat and moisture fluxes

Infiltration

Schaake et al. (1996)

explicit Green-Ampt (Schmid 1990)

Interception

Jacquemin and Noilham (1990)

Rutter-type, not yet implemented

Canopy evapotranspiration

resistance approach, Jarvis-type correction functions

resistance network, Jarvis-type correction functions

Snow model

Ek and Mahrt (1990); one layer snow model

Fröhlich and Mölders (2002), Mölders and Walsh (2004); multi-layer snow model based on snow metamorphism

Frozen ground

only in further-developed NOAH version

Mölders et al. (2003), Mölders and Walsh (2004)

Parameters needed

a , zo, s f, rst,min, rgl, hs, h s, y s, Ks, cSr S, h fc, h pwp

e f, e g, a f, zo, rst,min, rr, h, h s, Ks, y s, h fc, h pwp, cSr S, zd, bst, m, a, Tmin, Topt, Tmax, zroot, y c, r r, s f

other dependencies

 

a g(h ), h(zo)

 

  • Documentation
  1. Mölders, N., and J.E. Walsh, 2004. Atmospheric response to soil-frost and snow in Alaska in March. Theor. Appl. Climat., 77, 77-105.
  2. Mölders, N., Haferkorn, U., Döring, J., Kramm, G., 2003. Long-term numerical investigations on the water budget quantities predicted by the hydro-thermodynamic soil vegetation scheme (HTSVS) - Part I: Description of the model and impact of long-wave radiation, roots, snow, and soil frost. Meteor. Atmos. Phys., 84, 115-135.
  3. Mölders, N., Haferkorn, U., Döring, J., Kramm, G., 2003. Long-term numerical investigations on the water budget quantities predicted by the hydro-thermodynamic soil vegetation scheme (HTSVS) - Part II: Evaluation, sensitivity, and uncertainty. Meteor. Atmos. Phys., 84, 137-156
  4. Fröhlich, K., and Mölders, N., 2002. Investigations on the impact of explicitly predicted snow metamorphism on the microclimate simulated by a meso-beta/gamma-scale non-hydrostatic model. Atmos. Res., 62, 71-109 (Abstract)
  5. Mölders, N., and Rühaak,W., 2002. On the impact of explicitly predicted runoff on the simulated atmospheric response to small-scale land-use changes - An integrated modeling approach. Atmos. Res. 63, 3-38 (Abstract)
  6. Mölders, N., 2000. Application of lysimeter- and tensiometer data for evaluation of a module to couple hydrological and atmospheric models. In: Gerold, G. (Ed.),Heterogenität landschaftshaushaltlicher Wasser- und Stoffumsätze in Einzugsgebieten, Eco Regio, 8, 97-105.
  7. Mölders, N., Haferkorn, U., Knappe, S., Döring, J., Kramm, G., 1999. Evaluation of simulated water budegts by means of measurements at Brandis lysimeter station. In: Tetzlaff, G., Gruenewald, U. (Eds): Tagung des Fachausschusses Hydrometeorologie 15. / 16. November 1999 in Leipzig, Meteorol. Mitt. Leipzig 16: 67-83.
  8. Mölders, N., Kramm, G., 1999. On the influence of the parameterization of soil and vegetation processes upon the simulated evapotranspiration. In: Döll, P., N. Fohrer, Modellierung des Wasser- und Stofftransports in großen Einzugsgebieten, Kassel University Press, 163-172.
  9. Kramm, G., Foken, T., Mölders, N., Müller, H., Paw U, K.T., 1996. On the determination of the sublayer Stanton numbers of heat and matter for different types of surfaces. Contrib. Atmos. Phys. 69: 417-430.
  10. Kramm, G., Dlugi, R., Dollard, G.J., Mölders, N., Müller, H., Seiler, W., Sievering, H., 1995. On the dry deposition of ozone and reactive nitrogen compounds. Atmos. Environ., 29: 3209-3231.
  11. Kramm, G., Dlugi, R., Mölders, N., Müller, H., 1994. Numerical investigations of the dry deposition of reactive trace gases. In: Baldasano, J.M., Brebbia, C.A., Power, H., Zannetti, P. (Edn.), Air Pollution II Vol. 1: Computer Simulation. Computational Mechanics Publications, Southampton, Boston, 285-307.
  • Acknowledgements

This work was funded by DFG under contract Mo770/2-1. Investigations on the uncertainty of parameters and parameterizations as well as evaluation studies are now partly funded by BMBF (grant 07 ATF30) and GIPAS. Development of a frozen ground/permafrost module is funded by NSF under contract OPP-0327664.

  • Recent work and future plans

HTSVS is further-developed for application in Artic and Subarctic regions. In doing so, a soil-frost-module is developed within the framework of DEKLIM funded by BMBF. It is now under evaluation as a stand-alone version as well as coupled to MM5.

The one-layer-snow-module will be substituted by a multi-layer snow model which is currently developed and evaluated in the stand-alone mode as well as when coupled to MM5.

Within the framework of CAMP (IARC) funded by NSF the soil frost part of HTSVS will be incorporated into the NCAR Climate Community System Model (CCSM) to examine the impact of snow and permafrost on regional climate. Below you find a schematic view of the snow and soil frost modules.

   Schematic view of snow and frozen ground part of HTSVS

 

For further information mail to: molders@gi.alaska.edu