An advanced snow parameterization for the models of atmospheric circulation
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An advanced snow parameterization for the models of atmospheric circulation. Ekaterina E. Machul’skaya ¹ , Vasily N. Lykosov ¹ Hydrometeorological Centre of Russian Federation, Moscow, Russia ² Moscow State University, Russia

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An advanced snow parameterization for the models of atmospheric circulation

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An advanced snow parameterization for the models of atmospheric circulation

An advanced snow parameterization for the models of atmospheric circulation

Ekaterina E. Machul’skaya¹, Vasily N. Lykosov

¹Hydrometeorological Centre of Russian Federation, Moscow, Russia

²Moscow State University, Russia

³Institute for Numerical Mathematics, Russian Academy of Sciences, Moscow, Russia


Introduction

Introduction

  • Numerous observational studies and model simulations have shown that snow cover affects atmospheric circulation, air temperature, and the hydrologic cycle, due to its especial properties (high albedo, reduced roughness etc.)

  • Snow is related to a number of feedbacks, the most obvious being the snow albedo feedback:

larger snow melt,

faster snow cover depletion

decrease

of surface albedo

a positive temperature bias

more absorption of solar radiation


Snow models description 1

Snow models description (1)

INM

COSMO

Implemented processes

  • Heat conduction

  • Liquid water transport

  • Gravitational compaction +

  • metamorphosis

  • Solar radiation penetration

  • Heat conduction

  • Melting when snow

  • temperature > 0°C or

  • when soil surface

  • temperature > 0°C

Numerical schemes

Arbitrary number of layers,

in this study 5

1 layer


Implemented processes 2

Implemented processes (2)

Heat and water transport

- snow temperature,

- snow liquid water content,

- snow heat conductivity,

- latent heat for freezing/melting,

- snow density,

- snow specific heat content,

- melting rate,

- refreezing rate,

- infiltration rate due to gravity

Water percolation:

- snow hydravlic conductivity,

- snow water holding capacity,

- snow porosity


Gravitational compaction and metamorphosis

Gravitational compaction and metamorphosis

Implemented processes (3)

Where

member

describes the gravity effect

member

describes the snow metamorphosis, = 75 Pa

- the snow compaction viscosity

Solar radiation penetration


Data 1

Data (1)

Valdai

Russia, European part

58 N, 33 E

boreal mixed forest zone

grassland site

Yakutsk

Russia, East Siberia

62 N, 130 E

boreal coniferous forest zone

grassland site


Data 2

Data (2)

Atmospheric forcing

Evaluation data

Valdai: 1966 – 1983

Yakutsk: 1937 – 1984

snow water-equivalent

depth

Valdai: 1966 – 1983

Yakutsk: 1971 – 1973

In winter: every 10 days

In spring: more often

Every 3 hours:

air temperature

air pressure

air humidity

wind speed at 10 m

precipitation rate

Estimated:

shortwave radiation

longwave radiation

at 2 m


An advanced snow parameterization for the models of atmospheric circulation

Results discussion (1)


An advanced snow parameterization for the models of atmospheric circulation

observations

COSMO

INM

Results discussion (2): SWE in Yakutsk


An advanced snow parameterization for the models of atmospheric circulation

observations

COSMO

INM

Results discussion (3): SWE in Valdai

1967/68

1966/67

1968/69

1977/78

1978/79

1979/80

Days from Jan. 1st, 1966


An advanced snow parameterization for the models of atmospheric circulation

Results discussion (3): Impact on the surface temperature (TS)

COSMO TS

INM TS

COSMO SWE

INM SWE


Summary

Summary

  • A new advanced snow parameterization is suggested, implemented and tested by means of long-term data.

  • This multilayered scheme takes into account the latent heat of the phase transfer of water and the interaction with radiative fluxes in the snowpack.

  • In comparison with the more simple model incorporated in COSMO at present, the new more physical scheme represents the snow evolution more realistically, particularly during melting period.

  • The implementation of the new scheme in COSMO is recommended since it can improve the quality of the surface air temperature prediction, particularly in spring.

  • Results of the long-term continues integration with a real forcing data can be used as initial approximation fields for reanalysis of the surface temperature, snow mask and albedo for the adjustment of initial conditions of weather forecast model.


Futher possible directions of the study

Futher possible directions of the study

  • The Valdai observational data set includes data related to the snow density and albedo, as well as to the snow cover fraction.

  • It is known that fractional snow cover, snow albedo, and their interplay have a considerable effect on the energy available for ablation (Slater et al., 2001; Luce et al., 1998). In alpine environment, elevation, aspect, and slope exert a major control on snow distribution affecting snow accumulation and snowmelt energetics (Pomeroy et al. (2003)).

  • Different data sets that are obtained at present from different field experiments and regular observations (in mountain regions as well), allow to further evaluate the COSMO snow model and to understand to what extent the adequate simulation of different variables is important, in order to improve the prediction of snow evolution and surface air temperature.


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