All models participating in PILPS Phase 2(e) capture the broad dynamics of annual evaporation, snow melt and runoff, but large differences in snow accumulation and ablation, turbulent heat fluxes, and streamflow exist.
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Figure 1. Location of the Torne and Kalix Rivers (red) within the BALTEX domain (white)
Mean monthly net radiation versus albedo and radiative surface temperature, and surface temperature versus albedo. The slope of the dashed lines in the first two columns shows how net radiation would change if either albedo or surface temperature were the only control on net radiation.
Predicted annual average latent heat flux (1989 – 1998) and estimate from basin water balance
Predicted average last day of snow cover (1989 – 1998) and estimate from visual satellite data
Top: surface temperature depression (land surface temperature minus air temperature). Bottom: Mean January sensible, latent and ground heat flux. Each bar and whisker shows the mean, one standard deviation on either side of the mean and the minimum and maximum value for all 218 model grid cells.
Calibration basins runoff statistics
Annual average melt for two sub-regions of the Torne-Kalix as a function of a) effective aerodynamic resistance and b) average snow albedo. The effective parameters were estimated by fitting equivalent bucket models to reproduce the complex LSS output.
Flow duration curves based on daily flows during the period 1989-1998.
Land-surface parameterizations in northern regions: Results from PILPS Phase 2(e) Laura C. Bowling and Dennis P. Lettenmaier, Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, USAB. Nijssen, Departments of Civil Engineering and Engineering Mechanics, Hydrology and Water Resources, University of Arizona
General Model Performance
A. SPONSOR, Russian Academy of Sciences
B. RCA, Swedish Meteorological and Hydrological Institute
C. IHAS, Frontier Research Center for Global Change, Japan
D. SEWAB, GKSS Research Center, Germany
E. ISBA, National Center for Atmospheric Research, CNRM, France
F. NSIPP, NASA Goddard Space Flight Center
G. CLASS, Meteorological Service of Canada
H. IBIS, Canadian Forest Service
I. CHASM, Macquarie University, Australia
J. VIC, University of Washington
K. MATSIRO, Frontier Research System for Global Change
L. HY-SSiB, NASA Goddard Space Flight Center
M. VISA, University of Arizona
N. SAST, University of Arizona
O. MECMWF, Royal Netherlands Meteorological Institute
P. NOAH, NCEP Environmental Modeling Center
Q. SWAP, Russian Academy of Sciences
R. SSiB, University of California, Los Angeles
S. ECMWF, European Centre for Medium-Range Weather Forecasts
T. MOSES-CEH, Centre for Ecology and Hydrology, U.K.
U. MOSES, Met Office, U.K.
The potential sensitivity of land-atmospheric interactions to climate warming at high latitudes has motivated improvements to parameterizations of cold region processes in land surface schemes used in numerical weather prediction and climate models. PILPS (Project for Intercomparison of Land-surface Parameterization Schemes) Phase 2(e) was designed to evaluate the performance of uncoupled land surface schemes for a high latitude watershed, the Torne/Kalix River system in northern Scandinavia. The Torne and Kalix Rivers drain 58,000 km2 along the border between Sweden and Finland, a domain that was represented by 218 grid boxes at ¼ degree spatial resolution for the ten-year period 1989-1998. Participants were asked to estimate parameters of their models using streamflow observations for two small subcatchments within th Torne/Kalix basin, prior to running models over the entire domain. Streamflow at the basin mouth(s) was not provided to participants, although observations were available for subsequent model evaluation. All twenty-one models participating in PILPS 2(e) were able to capture the broad dynamics of snowmelt and runoff, but large differences in snow accumulation, turbulent heat fluxes and streamflow were apparent. The results showed that limited net radiation in the high latitude environment (varying between 15 and 28 W/m2 on annual average) provides a lower bound on runoff generation. Net radiation during the snow accumulation season is primarily controlled by surface temperature, which in turn influences turbulent fluxes. Those models with the largest negative near surface temperature gradients tend to suppress turbulent fluxes through stability corrections. Although the timing of runoff was dominated primarily by snowmelt, annual runoff volume was controlled in large part by sublimation. Estimates of effective aerodynamic resistances for 13 of the models showed a clear trend toward reduced sublimation and increasing snow accumulation with increasing resistance.
Model Controls on Energy Fluxes
Annual average sensible heat versus average latent heat for the 21 PILPS 2(e) LSS. Dashed boxes indicate the basis for division into four groups for interpretation purposes.
The land surface characteristics provided to participants included spatially distributed (cell-specific) soil textures, elevations, vegetation type and LAI. Hourly meteorological forcings (solar and terrestrial radiation, precipitation, humidity, air temperature and wind speed) were compiled from station data provided by the Swedish Meteorological and Hydrological Institute (SMHI) for the ten year period 1989-1998.
The effect of calibration on model performance was explored for two sub-basins, the 566 km2 Ovre Abiskojokk and the 1,341 km2 Ovre Lansjarv. Daily observed streamflow was provided for 1989 through 1998 and modelers were instructed to calibrate their models to the extent possible.
Mean monthly precipitation from three stations: a) Haparanda, b) Katterjakk and c) Naimakka, versus the corrected precipitation used for PILPS 2(e) and using the correction method derived from the WMO solid precipitation intercomparison project
Mean annual snowfall and the proportion lost to melt and sublimation
For more information, see the PILPS 2(e) home page, at: http://www.hydro.washington.edu/Lettenmaier/CurrentResearch/PILPS-2e/index.htm.
A full description of the PILPS 2(e) experiment design and summary analyses will be available in the following publications:
Bowling, L.C., D.P. Lettenmaier, B. Nijssen, L.P. Graham, D.B. Clark, M. El Maayar, R. Essery, S. Goers, Y.M. Gusev, F. Habets, B. van den Hurk, J. Jin, D. Kahan, D. Lohmann, X. Ma, S. Mahanama, D. Mocko, O. Nasonova, G.Y. Niu, P. Samuelsson, A.B. Shmakin, K. Takata, D. Verseghy, P. Viterbo, Y. Xia, Y. Xue, and Z.L. Yang, 2002, Simulation of high latitude hydrological processes in the Torne-Kalix basin: PILPS Phase 2(e) 1: Experiment description and summary intercomparisons, Journal of Global and Planetary Change, accepted.
Nijssen, B., L.C. Bowling, D.P. Lettenmaier, D.B. Clark, M. El Maayar, R. Essery, S. Goers, Y.M. Gusev, F. Habets, B. van den Hurk, J. Jin, D. Kahan, D. Lohmann, X. Ma, S. Mahanama, D. Mocko, O. Nasonova, G.Y. Niu, P. Samuelsson, A.B. Shmakin, K. Takata, D. Verseghy, P. Viterbo, Y. Xia, Y. Xue, and Z.L. Yang, 2002, Simulation of high latitude hydrological processes in the Torne-Kalix basin: PILPS Phase 2(e) 2: Comparison of model results with observations, Journal of Global and Planetary Change, accepted.
Bowling, L.C., D.P. Lettenmaier, B. Nijssen, J. Polcher, R.D. Koster and D. Lohmann, 2002, Simulation of high latitude hydrological processes in the Torne-Kalix basin: PILPS Phase 2(e) 3: Equivalent model representation and sensitivity experiment, Journal of Global and Planetary Change, in review.
Mean annual runoff and the proportion derived from surface and subsurface runoff. The dashed horizontal line indicates observed mean annual runoff.
Observed daily average solar insolation at Kiruna: a) versus the PILPS base-run forcing data, b) versus the PILPS rerun forcing data and c) versus the mean annual cycle of rerun forcing data.
Simulated and observed mean monthly discharge (1989 – 1998) at the basins mouths