BOBA

Soil frost and snow metamorphism simulations for the BALTEX-region with a complex hydro-thermodynamic soil-vegetation scheme


Principal investigator: Nicole Mölders
Research assistants: Balachandrudu Narapusetty, Ipshita Majhi
Undergraduate students: Anne Cherry, Pam Spier

- Brief summary of the project goals and achievements

An adequate initialization of soil moisture and soil temperatures as well as of the treatment of snow metamorphism and soil frost are required to determine the energy and water fluxes of BALTEX-region (without prior-calibration) in long-term studies like, for instance, climate modeling. Therefore, the hydro-thermodynamic soil-vegetation model HTSVS (Hydro-Thermodynamic Soil-Vegetation Scheme; Kramm et al., 1996) was enlarged by processes of soil frost and snow metamorphism (Mölders et al., 2003). To achieve a step forward in (regional) process studies and climate modeling a reliable determination of the volume-representative areas of several square kilometers times soil depth) distributions of soil moisture and soil temperature is required for initialization of climate or numerical weather prediction models. Furthermore, in numerical modeling, the soil has to be divided into several layers. Therefore, uncertainties in the water and energy fluxes simulated at the surface and within soil result as a consequence of the rare initial data and the vertical resolution of soil. The degree of these uncertainties was elucidated systematically. However, the traditional method, wherein the various parameters are varied to optimize the results, is inefficient because of the non-linear characteristics and interactions of the processes. Therefore, so-called tangent-linear and adjoint components of the model (4D-variational data assimilation) were developed for HTSVS concurrently to the development of the soil frost and snow metamorphism modules. In doing so, distributions of soil temperature and soil moisture were determined by objective analysis. Furthermore, the application of these tools allowed to calculate the sensitivity and uncertainty of the simulated energy and water fluxes and to evaluate their influence on the simulated energy and water fluxes of the BALTEX-region. HTSVS enlarged by frost and snow metamorphism modules was evaluated by use of data that were not applied in the data assimilation (Narapusetty and Mölders, 2005) . Furthermore, the role of soil frost and snow metamorphism for the energy and water fluxes of Alaska (Mölders and Walsh, 2004) and the BALTEX-region was examined.


- Relevance

The project joint state-of-the-art land-surface-, tropospheric and hydrologic modeling, data assimilation, parameter optimization andscientific computing. The work contributed to important objectives of BALTEX, namely, the progress of regional process studies on water and energy fluxes of heterogeneous terrain and the determination of the water budget of the Baltic watershed. Furthermore, there were important relations to DEKLIM-BALTEX-groups (e.g., EVA_GRIPS, BALTIMOS). The activities allowed to examine the annual variability of the energy and water fluxes by developing tools to adequately simulate snow metamorphism, freezing and thawing in soils (Mölders et al., 2003; Mölders and Walsh, 2004; Narapusetty and Mölders , 2005) . Thus, the project contributed to improve land-surface modeling that is an essential need in understanding the climate system (GEWEX). Operational data, data of recent field campaigns (e.g., NOPEX, LITFASS, ATLAS), ENVISAT-data were used for either data assimilation or evaluation. The activities led to improved data assimilation techniques (Mölders et al., 2004). The further-development of HTSVS by inclusion of soil frost and snow metamorphism processes was an important step forward for the calculation of ground water recharge and subsurface runoff because it is based on a physically closed concept.


- Scientific and/or technical goals of the project

HTSVS was enlarged by parameterizations to consider the processes of soil frost and snow metamorphism (Mölders et al., 2003). Furthermore, data assimilation procedures were developed for HTSVS to allow an optimized choice of the vertical resolution of the soil and to initialize soil moisture and soil temperatures. The aim of the activities was to improve the calculation of the energy and water fluxes of BALTEX-region and to guarantee a transferability of the developed model package for use in other regions of the earth.

Fig. 1. Schematic view of the desgin of the snow and soil frost module of HTSVS.


- Results

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HTSVS with soil frost and snow module integrated in MM5

The soil frost module and snow module have been implemented in MM5. The following five figures show the model domain and the surface temperatures as provided by a simulation with MM5 plus HTSVS without soil frost and snow processes and with MM5 under inclusion of HTSVS with soil frost and snow processes after 240 hours of simulation. The fourth figure illustrates the 48 hour accumulated precipitation at the end of the simulation with HTSVS without soil frost and snow processes (192-240 hour). The fifth figure shows the differences in 48 hour accumulated (192-240 hour) precipitation without - with inclusion of the processes.

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Interim report 2002

Interim report 2003

Progress report Cherry and Mölders 2003

Progress report Spier and Mölders 2003

Interim report: Mölders, Elbern, Majhi, Klyuchnikova 2003

Interim report: Mölders, Cherry, Majhi, Spier, Klyuchnikova, Elbern 2003

Majhi, I. M.S. Project Thesis, 2004

Final report: Mölders, Narapusetty, Majhi, Cherry, Spier, Elbern, Klyuchnikova, 2005

Narapusetty, B., M.S. Thesis, 2005


- Peer reviewed publications resulting from this project

Narapusetty, B., and Mölders, N., 2005, Evaluation of snow depth and soil temperatures predicted by the Hydro Thermodynamic Soil Vegetation Scheme (HTSVS) coupled with the PennState/NCAR Mesoscale Meteorological Model (MM5), J. Appl. Meteorol. 44: 1827-1843 .

Mölders, N., and Walsh, J.E., 2004, Atmospheric response to soil-frost and snow in Alaska in March, Theor. Appl. Climatol., 77, 77-115 (pdf-file copyright Springer).

Mölders, N., Haferkorn, U., Döring, J., and Kramm, G., 2003a, 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, Meteorol. Atmos. Phys., 84 , 115-135 (pdf-file copyright Springer).

Mölders, N., Haferkorn, U., Döring, J., and Kramm, G., 2003b, Long-term numerical investigations on the water budget quantities predicted by the hydro-thermodynamic soil vegetation scheme (HTSVS) – Part II: Evaluation, sensitivity, and uncertainty, Meteorol. Atmos. Phys., 84, 137-156 (pdf-file copyright Springer).


- Acknowledgements

This research was performed in cooperation with University of Cologne, EURAD (PI Hendrik Elbern, post-doc Anna Klioutchnikova). It was financially supported by BMBF under contract 01LD0036.


For further information or cooperation contact molders@gi.alaska.edu

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