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Diagnostics and Enhancements to the Noah LSM Snow Model . By: Ben Livneh With contributions from: Youlong Xia, Kenneth E. Mitchell, Michael B. Ek, and Dennis P. Lettenmaier. Presentation Overview. Motivation for the project. Model background Problem description Nature of model extensions
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By: Ben Livneh
With contributions from:
Youlong Xia, Kenneth E. Mitchell, Michael B. Ek, and Dennis P. Lettenmaier
Noah SWE (mm)
Observed SWE (mm)
Mitchell et al, 2004
Snow cover frac.
T1, WMAXαMAX, ρ, CH
1. Evaluation of a snow albedo decay scheme that captures the varying characteristics of the snowpack, currently not addressed in the control model;
2. Implementation of an algorithm that accounts for liquid water storage and refreeze within the pore space of the snowpack; a process that is not represented in the control.
DMSP Satellite image, 1979
Control Noah αMAX-satelliteconverted from DMSP satellite imagery (1979)
Defense Meteorological Satellite Program (DMSP)
Snow albedo decay phenomenon confirmed by numerous studies (e.g Warren et al., 1980). Rate is determined by character of snow surface (metamorphism, recrystalization, debris, etc…).
One method to quantify decay, via age of snow surface (equation).
Seasonal decay rate (lower left) is faster during melt season:
Shift between seasonal curves determined by snow surface temperature.
αMAX ≈ 0.85;
t: days since last snowfall;
Albedo decay scheme; based on Corps of Engineers, 1956; CA
Warren, S. G. and W. J. Wiscombe, 1980: A model for the spectral albedo of snow, II, Snow containing atmosphenc aerosols, J. Atmos. Sci., 37, 2734-2745.
U.S. Army Corps Of Engineers, 1956: Summary report of the snow investigations, "Snow Hydrology", U. S. Army Engineer Division, North Pacific, 210 Custom House, Portland, Oregon 97209.
A: Accumulation season curve (αMAX = 0.85)
B: Melt season curve (αMAX = 0.85)
C: Accumulation season curve (C = 0.5)
D: Melt season curve (C = 0.5)
E: αMAX-satellite = constant (e.g. 52%)
*Key difference in new energy balance
Qm = Energy available for melt;
Qn = Net radiation flux
Qh = Sensible heat flux
Qe = Latent heat flux
Qg = Ground flux
Qa = Advected heat flux
ΔCC = Change in internal energy of the snow pack (cold content) → *New Term: Allows for monitoring of thermal inertia between successive time steps; necessary for controlling melt and refreeze processes; involves new variable: Tpack
Where: SWE = snow water equivalent; dsnow = snow depth, φ = porosity, ρ = density
* Based on observations, Denoth et al., 2003
0.04 m, 0.02 m (forest, non-forest)
0.20 m, 0.01 m (forest, non-forest)
* Wang Z, Zeng X (2009) Evaluation of snow albedo in land models for weather and climate studies. Journal of Applied Meteorology and Climatology: In Press
Adjust areal depletion threshold for SWE; forest vs. non-forest.
*Related to recent collaborative work at the University of Arizona.
RiB: dimensionless form of bulk richardson number
CH,CM: exchange coefficients for heat and momentum transfer, respectively.
αMAX = 0.85
αMAX → C=0.5
Comparison between albedo decay scheme (C=0.5) and control model
Depiction of Noah forest vegetation classes
W.C. = 4% p.v.
W.C. = 3.5% SWE
Comparison between melt/refreeze model and control model
Comparison between stability corrected model and uncorrected model
Comparison between suggested model extensions and control model
Youlong Xia, Kenneth E. Mitchell, Michael B. Ek (NCEP)
John Schaake (NWS)
Ming Pan (Princeton)
Livneh, B., Y. Xia, K.E. Mitchell, M.B. Ek, and D.P. Lettenmaier, 2010: Noah LSM Snow Model Diagnostics and Enhancements, J. of Hydrometeorology, in press
Qm = Qn + Qh + Qe + Qg + Qa- ΔCC
* Snowpack temperature is a new variable