A Temporal Filtering Algorithm to Reconstruct Daily Albedo Series Based on GLASS Albedo product
Validation of outputs from the MAR regional climate...
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TEMPLATE DESIGN © 2008 www.PosterPresentations.com Figure 2: MAR profiles from June 27, 2010, the Small Pit (June 26) and the Big Pit (June 27). Measurements were linearly interpolated and averaged over MAR layers (bounded by horizontal lines) at the Summit. Table 1: MAR vs. Big Pit Bold = Significant at 95% CL De-trended MAR and Big Pit densities are well correlated: r 2 = 0.64 De-trended grain sizes are not well correlated: r 2 = 0.002 MAR Fresh Snow Density (ρ new ) formula: ρ new = max[ 30, 109 + 6(Air Temp) + 26(Wind Speed) ] Air temperature and wind speed biases only account for ~1/3 of density difference at the surface, if applied to above. Dry snow grain size: d = 0.4 – 0.1Sphericity No liquid water: grain size ranges between 0.3 and 0.4 mm. Bias in liquid water content could lead to underestimated grain size. Albedo depends on grain size; accurately representing albedo is important for capturing feedbacks. Satellite data suggest little albedo bias, but more analysis of potential MODIS bias is needed. Figure 3: June 2010 MAR results (every 30 min, dashed line) and GC-Net hourly weather station data (solid line) at Summit, for surface air temperature, wind speed, and albedo. Table 2: Temperature, windspeed are well correlated, with a slight bias. Albedo is not well correlated, but mean values are consistent. As part of a data assimilation framework to integrate results from a Regional Climate Model, the Modèle Atmosphérique Régional (MAR), in-situ observations, and remote sensing data over Greenland, we are validating model results against recently gathered field data and satellite measurements. Comparisons reveal model biases for density grain size, and albedo. Further validation will help facilitate model improvements for Surface Mass Balance (SMB) estimates over Greenland. •Snow pit data and GC-Net data 1 from GrIS Summit Camp (72.6096 N, 38.54980 W) compared to encompassing MAR grid box, June 2010. •For two snow pits within a 4 by 50 m trench (Figure 1) density was measured with a density cutter, grain size with a macroscope over a ruled card. The observed max and min were averaged for comparison. •Surface albedo product MCD43A from the Moderate Resolution Imaging Spectroradiometer (MODIS) was aggregated based on the MAR grid and compared to model results between 2001 and 2010. Forced at boundaries by reanalysis data from the European Center for Medium-Range Weather Forecasts (ECMWF) every 6 hours. • Crocus 1-D snowpack model: Includes fluxes, melt-water refreezing and grain metamorphism within 20 snow/ice layers. • Domain: 2500 by 3500 km; 25 km resolution; center at 70°N 40°W Validation of outputs from the MAR regional climate model through surface measurements and satellite data M. Tedesco (1,2), P. Alexander (2), N. Steiner (2), H.-P. Marshall (3), X. Fettweis (4) (1) CUNY, CCNY, EAS, NY USA (2) The Graduate Center, CUNY, NY,NY USA (3) Boise State University, Boise, ID USA (4) University of Liège, Liège, Belgium Abstract MAR Model Background Results: Comparison with Snow Pit Data Results: Comparison with Weather Station Data References and Acknowledgments Future Work 1. Steffen, K., J.E. Box, and W. Abdalati (1996), “Greenland Climate Network: GC-Net”, Colbeck C.S. Ed. CRREL (96-27) Special Report on Glaciers, Ice Sheets and Volcanoes, trib. To M. Meier, pp. 98-103. 2. Tedesco, M.., X. Fettweis, M.R. van den Broeke, R.S.W. van de Wal, C.J.P.P. Smeets, W.J. van de Berg, M.C. Serreze and J.E. Box (2011) The role of albedo and accumulation in the 2010 melting record in Greenland, Env. Res. Lett., 6. This work is supported by NSF Grant 0909388 Fieldwork is supported by the NASA Cryosphere Program Figure 1: Measurements at two snow pit sites: Summit, Greenland Small Pit, 1.6 m deep. Big Pit, 4.1 m deep. Methodology (1)Further comparisons with satellite data for albedo, grain size, and melt to identify large scale bias. (2)Model experiments to evaluate role of temperature, wind speed in fresh snow density. (3)Model improvements and assimilation of remote sensing data. MAR μ Big Pit μ Bias (μ) P-value (Diff μ) MAR σ (no trend) Big Pit σ (no trend) Bias (σ) P-value (Diff σ) Density (kg/m 3 ) 303.6 353.1 -49.5 0.005 25.5 14.0 11.5 0.108 Grain Size (mm) 0.543 0.919 -0.376 0.003 0.131 0.291 -0.16 0.044 Results: Preliminary Comparison with Satellite Data Figure 4: MODIS white sky albedo 16-day values aggregated to the nearest MAR grid box and averaged were subtracted from mean 16-day MAR values. The mean summer month (May 8 – Sep 5) albedo bias over 2001-2010 is shown. Two 16- day periods with many missing values were excluded. Mean positive MAR bias: 0.034 MAR μ GC-Net μ Bias (μ) P-value (Diff μ) Correlation (r 2 ) (Hourly Data) Temp. (°C) -13.72 -12.89 -0.83 0.000 0.658 Wind Speed (m/s) 3.03 4.09 -1.06 0.000 0.616 Albedo 0.815 0.812 0.003 0.075 0.154 Discussion and Conclusions
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Figure 2: MAR profiles from June 27, 2010, the Small Pit (June 26) and the Big Pit (June 27). Measurements were linearly interpolated and averaged over MAR layers (bounded by horizontal lines) at the Summit. Table 1: MAR vs. Big Pit
Bold = Significant at 95% CL
De-trended MAR and Big Pit densities are well correlated: r2 = 0.64 De-trended grain sizes are not well correlated: r2 = 0.002
MAR Fresh Snow Density (ρnew ) formula:
ρnew = max[ 30, 109 + 6(Air Temp) + 26(Wind Speed) ]
Air temperature and wind speed biases only account for ~1/3 of density difference at the surface, if applied to above. Dry snow grain size:
d = 0.4 – 0.1Sphericity
No liquid water: grain size ranges between 0.3 and 0.4 mm. Bias in liquid water content could lead to underestimated grain size. Albedo depends on grain size; accurately representing albedo is important for capturing feedbacks. Satellite data suggest little albedo bias, but more analysis of potential MODIS bias is needed.
Figure 3: June 2010 MAR results (every 30 min, dashed line) and GC-Net hourly weather station data (solid line) at Summit, for surface air temperature, wind speed, and albedo. Table 2: Temperature, windspeed are well correlated, with a slight bias. Albedo is not well correlated, but mean values are consistent.
As part of a data assimilation framework to integrate results from a Regional Climate Model, the Modèle Atmosphérique Régional (MAR), in-situ observations, and remote sensing data over Greenland, we are validating model results against recently gathered field data and satellite measurements. Comparisons reveal model biases for density grain size, and albedo. Further validation will help facilitate model improvements for Surface Mass Balance (SMB) estimates over Greenland.
• Snow pit data and GC-Net data1 from GrIS Summit Camp (72.6096 N, 38.54980 W) compared to encompassing MAR grid box, June 2010.
• For two snow pits within a 4 by 50 m trench (Figure 1) density was measured with a density cutter, grain size with a macroscope over a ruled card. The observed max and min were averaged for comparison.
• Surface albedo product MCD43A from the Moderate Resolution Imaging Spectroradiometer (MODIS) was aggregated based on the MAR grid and compared to model results between 2001 and 2010.
Forced at boundaries by reanalysis data from the European Center for Medium-Range Weather Forecasts (ECMWF) every 6 hours.
• Crocus 1-D snowpack model: Includes fluxes, melt-water refreezing and grain metamorphism within 20 snow/ice layers.
• Domain: 2500 by 3500 km; 25 km resolution; center at 70°N 40°W
Validation of outputs from the MAR regional climate model "through surface measurements and satellite data
M. Tedesco (1,2), P. Alexander (2), N. Steiner (2), H.-P. Marshall (3), X. Fettweis (4)"(1) CUNY, CCNY, EAS, NY USA (2) The Graduate Center, CUNY, NY,NY USA (3) Boise State University, Boise, ID USA (4) University of Liège, Liège, Belgium
Abstract
MAR Model Background
Results: Comparison with Snow Pit Data
Results: Comparison with Weather Station Data
References and Acknowledgments
Future Work
1. Steffen, K., J.E. Box, and W. Abdalati (1996), “Greenland Climate��� Network: GC-Net”, Colbeck C.S. Ed. CRREL (96-27) Special Report��� on Glaciers, Ice Sheets and Volcanoes, trib. To M. Meier, pp. 98-103.
2. Tedesco, M.., X. Fettweis, M.R. van den Broeke, R.S.W. van de Wal, ��� C.J.P.P. Smeets, W.J. van de Berg, M.C. Serreze and J.E. Box��� (2011) The role of albedo and accumulation in the 2010 melting record��� in Greenland, Env. Res. Lett., 6.
This work is supported by NSF Grant 0909388 Fieldwork is supported by the NASA Cryosphere Program
Figure 1: Measurements at two snow pit sites: Summit, Greenland
Small Pit, 1.6 m deep. Big Pit, 4.1 m deep.
Methodology
(1) Further comparisons with satellite data for albedo, grain size, and melt to identify large scale bias.
(2) Model experiments to evaluate role of temperature, wind speed in fresh snow density.
(3) Model improvements and assimilation of remote sensing data.
MAR μ Big Pit μ Bias (μ) P-value (Diff μ)
MAR σ (no trend)
Big Pit σ (no trend)
Bias (σ) P-value (Diff σ)
Density (kg/m3) 303.6 353.1 -49.5 0.005 25.5 14.0 11.5 0.108
Grain Size (mm) 0.543 0.919 -0.376 0.003 0.131 0.291 -0.16 0.044
Results: Preliminary Comparison with Satellite Data
Figure 4: MODIS white sky albedo 16-day values aggregated to the nearest MAR grid box and averaged were subtracted from mean 16-day MAR values. The mean summer month (May 8 – Sep 5) albedo bias over 2001-2010 is shown. Two 16-day periods with many missing values were excluded.
Mean positive MAR bias: 0.034
MAR μ GC-Net μ Bias (μ) P-value (Diff μ) Correlation (r2) (Hourly Data)
Temp. (°C) -13.72 -12.89 -0.83 0.000 0.658
Wind Speed (m/s) 3.03 4.09 -1.06 0.000 0.616
Albedo 0.815 0.812 0.003 0.075 0.154
Discussion and Conclusions
