Amanda Tan, CEE 599L, Snow Hydrology, Spring 2007
Research Proposal: Evaluation and improvement of albedo in a land surface
hydrology model for the Siberian Arctic
I. Introduction
Pronounced changes have occurred in the Arctic and sub-Arctic within the last few
decades. These changes are most significant in land surface processes. In recent years,
temperatures have risen while precipitation levels have remained largely the same, with
some shifts in snow melt duration. Satellite data have confirmed that average snow cover
has decreased, especially in the spring and summer. An implication of the disappearance
of snow cover in early spring is that the amount of energy used to melt snow is now
absorbed by the ground, thereby lowering the albedo and thus leading to more snowmelt.
This is termed as the snow-albedo positive feedback. Increased snowmelt is linked to an
increase in river discharge which in turn entails damaging effects on the thermohaline
circulation (Peterson et al. 2002) and is postulated to interfere with the formation of the
North Atlantic Deep Water and the northward-flowing Gulf Stream.
II. Objectives
This project seeks to 1) Identify changes in albedo fields over the Siberian Arctic 2)
Validate the ability of current land surface models to infer historical changes in albedo
and allow for segregation of catchments to forested vs. open areas since albedo effects
are much different where canopy dominates.
III. Rationale and Scope
The Arctic is particularly sensitive to the large release and uptake of latent heat causing
the water cycle to be strongly coupled to the energy budget. Significant hydrological
changes can occur with even small changes key physical processes. Energy and water
balance algorithms in models are still far from perfect. Arctic hydrology can therefore be
further understood if albedo and fractional coverage of snow is adequately represented in
existing hydrological and climate models (Slater et al. 2006).
IV. Research Management Plan
a. Methods
1. Use a land surface model (VIC) to infer historical changes in snow cover, albedo
and temperature through the surface energy balance scheme.
2. Retrieve historical albedo fields from the NSIDC database of AVHRR Polar
Pathfinder Twice-Daily 1.25km EASE-Grid Composites.
3. Validate the ability of the model to capture albedo by comparing simulated and
observed data and evaluate the plausibility of segregating catchments by forested
versus open areas, as well as testing the sensitivity of the model to snow
parameterization.
b. Facilities
The project is to be conducted on a Linux interface with the Variable Infiltration Capacity
(VIC) land surface model (Liang et al., 1994). AVHRR data is available through NSIDC.
c. Progress to date
Hydrologic simulations for the Aldan basin in Eastern Siberia have been conducted for
the period of 1930 - 2000. The simulated dataset contains outputs of soil temperature, and
surface albedo. Thus far, the simulations have revealed a significant difference between
observed (satellite) and simulated data with respect to soil temperature and albedo. This
indicates that the surface energy balance iteration does not seem to be capturing longwave radiation well.
d. Project schedule
April 9 – 15: Extract land cover data from AVHRR database.
April 16 – 29: Segregating forested versus open areas using a land cover algorithm.
April 30 – May 6: Rerun the modified algorithm and determine differences in the
sensitivity of the LSM with respect to albedo and temperature.
May 7 – May 13: Compare modeled albedo with the observed.
May 14 – May 20: Compilation of results and generate corresponding inference based on
results.
May 22: Presentation of results in class.
e. Immediate results
This project will produce an improved algorithm that generates albedo simulation based
on forested versus open areas to account for changes in the energy balance equation used
in a land surface hydrology model.
f. Anticipated future research
It is anticipated that prolonged sensitivity tests will have to be made in order to attain
satisfactory results in modeling albedo fields and snow cover to match the observed. The
results of this research will lead to a better understanding of the physical processes
occurring in the Arctic.
References
A. G. Slater, C. A. Schlosser, C. E. Desborough , A. J. Pitman, A. Henderson- Sellers , A. Robock , K. Ya.
Vinnikov , N. A. Speranskaya, K. Mitchell, A. Boone, H. Braden, F. Chen, P. Cox, P. de Rosnay, R.E.
Dickinson, Y-J. Dai, Q. Duan, J. Entin, P. Etchevers, N. Gedney, Ye. M. Gusev, F. Habets, J.Kim, V.
Koren, E.Kowalczyk, O.N.Nasonova, J.Noilhan, J. Shaake, A.B. Shmakin,T. Smirnova, D. Verseghy, P.
Wetzel , Y. Xue, Z-L. Yang (2001), The Representation of Snow in Land-surface Schemes; Results from
PILPS 2(d). J. Hydrometeorology, 2, pp. 7-25
Liang, X., D.P. Lettenmaier, E.F. Wood, and S.J. Burges, “A simple hydrologically based model of land
surface water and energy fluxes for general circulation models,” J. Geophys. Res., 99(D7), 14,415-14,428,
July 1994.
Peterson, B. J., R. M. Holmes, J. W. McClelland, C. J. Vörösmarty, R. B. Lammers, A.I. Shiklomanov, I.
A. S. Shiklomanov, and S. Rahmstorf. 2002, Increasing river discharge to the Arctic Ocean: Science. 298
2171-2173.