Snow analysis, parameterisation of deposition and melting

Ekaterina Machulskaya

Hydrometeorological Centre of Russian Federation, Moscow, Russia

Moscow State University, Russia

• Motivation

• Snow model description

• Results discussion

• Conclusions and outlook

Outline

Motivation

Snow water-equivalent depth, Valdai, 1972-75

0

20

40

60

80

100

120

140

160

1 61 121 181 241 301 361 421 481 541 601 661 721 781 841 901

observedsimulated

Snow models description

•Heat conduction•Melting when snow

surfacetemperature > 0°C orwhen soil surface temperature > 0°C

•Heat conduction•Liquid water transport•Gravitational compaction +metamorphosis •Solar radiation penetration

1 layer

Arbitrary number of layers;heat conduction: implicit

(combined with soil heat conduction),latent heat and solar radiation:

source terms

Numerical schemes

Implemented processesTERRA ctrl TERRA + new snow

Implemented processes (2)

- snow temperature, - snow liquid water content,- snow density, - snow specific heat content,

- snow heat conductivity,- latent heat for freezing/melting,

- melting rate, - refreezing rate, - infiltration rate due to gravity

Water percolation:

- snow hydravlic conductivity, - snow water holding capacity,

- snow porosity

Heat and water transport

Gravitational compaction and metamorphosis

describes the gravity effectWhere

term

term describes the snow metamorphosis, = 75 Pa

- the snow compaction viscosity

Solar radiation penetration

Implemented processes (3)

Results discussion: snow water-equivalent depth, Valdai, 1966-1972

0

20

40

60

80

100

120

140

160

180

200

1966

1966

1966

1966

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1967

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1968

1969

1969

1969

1969

1969

1969

1969

1969

TERRA ctrl

TERRA +new snowobserved

0

20

40

60

80

100

120

140

160

180

200

1969

1969

1969

1969

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1970

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1971

1972

1972

1972

1972

1972

1972

1972

1972

1972

Results discussion: snow mask, spring 2008

15.03.2008

15.03.2008

ctrl

new

Results discussion: snow water-equivalent depth, spring 2008

new – ctrl

15.03.2008

25.03.2008

Summary• A new, more physically based parameterization of snow is suggested

and implemented into TERRA-standalone. As the main component, this scheme includes description of the water phase transitions within snowpack.

• By means of the Valdai long-term data an comparison with the current snow model incorporated in COSMO is done. The new scheme represents the snow evolution more realistically, particularly during melting period.

Ongoing work

• Evaluation of the results obtained for the COSMO-EU domain during off-line experiments

Outlook

• Verification of the new model in operational mode

• Code consolidation + scientific and technical documentation

• Winter 2008/09: verification of the new scheme for the COSMO-RU domain

Thank you for your attention!