Downscaling of forcing data Temperature, Shortwave (Solar) & Longwave (Thermal) CHARIS meeting, Dehra Dun, India, October 2014 Presented by: Karl Ritt
Jan 04, 2016
Downscaling of forcing dataTemperature, Shortwave (Solar) & Longwave (Thermal)
CHARIS meeting, Dehra Dun, India, October 2014
Presented by: Karl Rittger
Spatial variability in forcing variables
Temperature and precip. gradients
North and south facing slopes
Kanjin, Langtang Himal, November 2013
Along valley gradients
2 CHARIS meeting, Dehra Dun, India, October 2014
Snow heterogeneity
Wind redistribution (D. Marks)
Differential ablation (E. Bair)
3 CHARIS meeting, Dehra Dun, India, October 2014
Meteorological stations
• Sparse coverage• Few high elevation
stations• Possibly short series• How representative
are they• Need to be
“upscaled”/extrapolated
• Needs knowledge of lapse rates for P and T.
4 CHARIS meeting, Dehra Dun, India, October 2014
Snow cover from Landsat 5 & in-situ data
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July 02
Fractional snow cover
July 18
Fractional snow cover
Automated SWE observations
Streamflow observations
CHARIS meeting, Dehra Dun, India, October 2014
Climate reanalysis
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•Numerical description of the recent climate
•Combines models of physical processes in the atmosphere and oceans with observations
•Observations
•Air temperature, pressure, wind
•Rainfall, soil moisture, sea-surface temp• Simplified
topography
• May be biased
• Needs to be downscaled
•Globally complete
•Long time series
•consistent
CHARIS meeting, Dehra Dun, India, October 2014
Atmospheric reanalysis used in NASA’s Land Data Assimilation System (LDAS)
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http://ldas.gsfc.nasa.gov/index.php
GLDAS-1: CurrentHigher
resolution
GLDAS-2: Long time scale
Consistent
CHARIS meeting, Dehra Dun, India, October 2014
Atmospheric reanalysis used in NASA’s Land Data Assimilation System (LDAS)
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http://ldas.gsfc.nasa.gov/index.php
Drives multiple land surface models from simple to complex
CHARIS meeting, Dehra Dun, India, October 2014
Downscaling of forcing data
• Temperature Based on lapse rates and elevation differences between
coarse and fine DEMs
• Shortwave and Longwave Scale (time and space) Elevation Topography Forest
9 CHARIS meeting, Dehra Dun, India, October 2014
Downscaling of forcing data
• Temperature Based on lapse rates and elevation differences between
coarse and fine DEMs
• Shortwave and Longwave Scale (time and space) Elevation Topography Forest
10 CHARIS meeting, Dehra Dun, India, October 2014
GLDAS-1-NOAH: air temperature
11 CHARIS meeting, Dehra Dun, India, October 2014
Sierra Nevada, California (Elevation)
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500m(1/8° or about 14km)
CHARIS meeting, Dehra Dun, India, October 2014
Sierra Nevada, California (Elevation)
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500m scale
(1/8° or about 14km)
CHARIS meeting, Dehra Dun, India, October 2014
Downscaling temperature using a lapse rate and change in elevation
14 CHARIS meeting, Dehra Dun, India, October 2014
Air Temperature, 1999-01-01 0100
Air Temperature (Ta), 1999-01-01 0100 (Video)
15 CHARIS meeting, Dehra Dun, India, October 2014
• But environmental lapse rates change through time and from place to place.
• Reanalysis data has air temperatures for many levels in the atmosphere
• Atmospheric profile can be used to estimate lapse rate.
A more rigorous approach to the lapse rate, γ
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• Simplest approach is to use a standard lapse rate to disaggregate model temperature to finer grid.
CHARIS meeting, Dehra Dun, India, October 2014
Downscaling of forcing data
• Temperature Based on lapse rates and elevation differences between
coarse and fine DEMs
• Shortwave and Longwave Scale (time and space) Elevation Topography Forest
17 CHARIS meeting, Dehra Dun, India, October 2014
GLDAS: incoming solar
18 CHARIS meeting, Dehra Dun, India, October 2014
Net Shortwave Radiation:Tuolumne-Merced River basinsMarch 1, 2006 12:00
Painter et al., 2009;Dozier et al., 2008
Link and Marks, 1999; Garren and Marks, 2005
Dozier and Frew, 1990Erbs et al., 1982;Olyphant et al., 1984
Dubayah and Loechel., 1997
Cosgrove et al., 2003;Pinker et al., 2003;Mitchell et al., 2004
19 CHARIS meeting, Dehra Dun, India, October 2014
GLDAS: incoming thermal
20 CHARIS meeting, Dehra Dun, India, October 2014
Net Longwave Radiation:Tuolumne-Merced River basinsMarch 1, 2006 12:00
Dozier and Frew, 1990
Link and Marks, 1999; Garren and Marks, 2005
Dubayah and Loechel, 1997
21 CHARIS meeting, Dehra Dun, India, October 2014
Summary
• Need to capture processes at small scale in modeling snow accumulation and melt
• Global re-analysis data available from several sources
• Coupled with land surface models to provide surface fluxes
• Downscaling based on Elevation, slope, aspect, solar angles, vegetation,
shading, dynamic lapse rates
22 CHARIS meeting, Dehra Dun, India, October 2014