Forecast Sensitivity of Lake-Effect Snow to Choice of Boundary Layer Parameterization Scheme

Robert Conrick and Heather Reeves

What is already known:

• Relatively little work has been done to understand constraints and limitations of.high-resolution numerical weather prediction of lake-effect snow.
• Given that lake-effect snow cloud systems are completely contained within the boundary layer, it is reasonable to suspect some sensitivities to choice of PBL scheme may exist.

What this study adds:

• Six boundary layer schemes are tested on a case-study of lake-effect snow to assess forecast sensitivity to various boundary layer parameterization schemes
• The experiments reveal significant precipitation (as much as 20 mm over 6 h) and heat/moisture flux differences between the schemes.
• Forcing all schemes to use the same over-water heat and moisture fluxes causes the precipitation forecasts to be in closer agreement.
• The heat and moisture fluxes are found to be strongly dependent on a turbulence parameterization called the similarity-stability functions.
• When the similarity-stability functions are set constant, precipitation forecasts are similar in all schemes. Therefore these functions have a significant impact on lake-effect snow.
• Comparison of the forecast accumulated precipitation to observations shows that most schemes over predict the precipitation; however, closest agreement occurs with the Mellor-Yamada-Nakanishi-Niino scheme.