Fluxes over snow surfaces

Larry Mahrt

Oregon State University

mahrt@coas.oregonstate.edu

Main Participants

1. L. Mahrt, Dean Vickers, Young-Hee Lee, Richard Cuenca, Yutaka Hagimoto, Oregon State University

2. Robert Kelly, U. of Wyoming3. Glen Liston, John Strak, Chris Heimstra,

C.S.U.4. Bill Massman, U.S.F.S.5. Jielun Sun, Sean Burns, NCAR6. Steve Oncley, Tony Delany and staff. NCAR

ATD

Wyoming King Air

Regional map

Main Tower Site

Dependence of roughness length on snow cover over native grass

Dependence of evaporative fraction on snow cover

Surface energy budget over snow covered grass

Low winter sun angles over the sage

Some preliminary conclusions

• During the experiment period, snow patchiness was less important than sage patchiness

• Sage has low albedo with respect to low winter sun angles, even if it is sparse

• Heating of the air by the sage apparently increases snow melt in windy conditions,

• but reduces snow melt during weak wind conditions due to formation of an inversion over the snow.

• Advection of heat and turbulence, partly due to Peterson Ridge, sometimes exerts a strong influence on local conditions.

• The bulk aerodynamic approach grossly overestimates the sublimation/evaporation (model or observational error?).