CRYOWRF
Since 2021 CRYOS group has started working on a model called CRYOWRF (Sharma et.al. 2023). At its core lies the Weather Research and Forecasting (WRF) model, a state of the art mesoscale numerical weather prediction system designed for both atmospheric research and operational forecasting applications. Lower boundary conditions for snowy terrain are computed with SNOWPACK (Lehning et.al.), a high-complexity snowpack and ground surface model capable to simulate the development of the snowpack during the winter based on weather data coming from WRF. Additionally, two-moment prognostic equations for mass and number mixing ratio of blowing snow particles are introduced in the model to investigate the effect of transported snow in the cryosphere.
Figure 1 shows a result of a simulation in Antarctica where surface mass balance is computed and analyzed.
Redistribution of snow in alpine regions is also important to correctly estimate.
Figure 2 shows results of a simulation at Jungfraujoch where blowing snow particles are transported by strong winds, here represented by arrows, where the vertical velocities w are scaled for clarity.
Research on CRYOWRF is ongoing focusing in implementing radiation effects of blowing snow, and the interaction between blowing snow particles and cloud microphysics.
CRYOWRF can be downloaded from the gitlab page.
REFERENCES :
- Sharma, F. Gerber, and M. Lehning. “Introducing CRYOWRF v1.0: multiscale atmospheric flow simulations with advanced snow cover modelling”. In: Geoscientific Model Development 16.2 (2023), pp. 719–749.
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Lehning, M., Bartelt, P., Brown, B., Russi, T., Stockli, U., and Zimmerli, M.: SNOWPACK model calculations for avalanche warning based upon a new network of weather and snow stations, Cold Reg. Sci. Technol., 30, 145–157, https://doi.org/10.1016/S0165-232X(99)00022-1, 1999.
HICAR
The High-resolution Intermediate Complexity Atmospheric Research (HICAR) model uses many of the same equations as WRF to parameterize physical processes such as cloud formation and evapotranspiration at the surface. Where HICAR differs from traditional atmospheric models like WRF is in its dynamics — the equations of motion, which determine how winds blow. Winds exist due to differences in pressure in the atmosphere; when there is a pressure difference, you experience the atmosphere equalizing this difference as a gust of wind. Pressure affects wind, and thus wind affects pressure. This feedback requires careful numerical calculation to keep the solution stable and often employs solutions of the infamously challenging Navier-Stokes equations.
HICAR instead uses the simple constraint of a divergence-free wind field and relies on forcing data from models like WRF to resolve large-scale atmospheric structures. This shortcut makes the model 100’s of times faster than WRF, enabling high-resolution atmospheric modeling at time scales of entire winter seasons. Ultimately, process-level understandings gained from WRF runs can be implemented into HICAR to study how cryospheric processes shape the snowpack over whole seasons.
REFERENCES :
- Reynolds, D., Gutmann, E., Kruyt, B., Haugeneder, M., Jonas, T., Gerber, F., Lehning, M., and Mott, R.: The High-resolution Intermediate Complexity Atmospheric Research (HICAR v1.1) model enables fast dynamic downscaling to the hectometer scale, Geosci. Model Dev., 16, 5049–5068, https://doi.org/10.5194/gmd-16-5049-2023, 2023.