AUTHOR(S): Charlie Zender and Xianwei Wang
Name: Charlie Zender
Department of Earth System Science
3323 Croul Hall
University of California
Irvine, CA 92697-3100
FUNDING SOURCE AND GRANT NUMBER:
DATA SET OVERVIEW:
The MODIS snow albedo retrieval algorithm for low quality retrievals is susceptible to biases at large Solar Zenith Angle (SZA). Wang and Zender (RSE, 2010a) documented this effect on Greenland by comparison to theory and to in situ measurements from Greenland Climate Network (GC-Net). Wang and Zender (JGR, 2010b) show how to compensate for this SZA bias in the low quality MODIS retrievals by employing and adjustment based on the the high quality MODIS retrievals, GC-Net data, and theory. The adjusted MODIS albedo is more physically plausible, presumably more accurate, and covers nearly the entirety of Greenland in all sunlit months. The datasets stored here are the original (unadjusted) and adjusted MODIS albedo datasets for Greenland.
The data are monthly averages through 2000-2010, and as The "daily" (i.e., 8-day) datasets in netCDF format on the 0.05 degree climate modeling grid.
DATA COLLECTION AND PROCESSING:
MODIS instruments on Terra and Aqua satellites, adjusted by factors derived from GC-Net.
The data are archived in four different filetypes that are a matrix of original (i.e., unadjusted) MODIS data and adjusted MODIS data at monthly and 8-day time-resolutions. "rgn" is the mnemonic for "original", "adj" for "adjusted".
Full description of data processing is in Wang and Zender (2010b).
As described in Wang and Zender (2010b), none of the high quality MODIS retrievals are altered in any way. The adjustments are performed solely on low quality retrievals.
The MODIS field name for albedo products obtained from the combined Terra and Aqua satellites is "mod43c". MODIS 8-day files are named mod43c_TYP_YYYYDDD.nc where DDD is the Day-of-Year and "TYP" is the type, "rgn" or "adj". MODIS monthly files are averages of four eight-day files, and are named mod43c_TYP_YYYYMM.nc
All data are stored in netCDF, a self-describing data format. Spatial coverage is 60.0 < latitude < 85.0, 290.0 < longitude < 340.0. Grid is 500 latitude by 1000 longitude cells. Grid resolution is a uniform 0.05 degrees.
wsa_sw = White-Sky Albedo (WSA) [fraction]
bsa_sw = Black-Sky Albedo (BSA) [fraction]
sza = Solar Zenith Angle (SZA) [degrees]
scf = Snow Cover Fraction (SCF) [percent]
Original names of MODIS fields are stored in long_name attribute. Missing values are indicated by the missing_value and _FillValue metadata attributes.
These data are as published in Wang and Zender (2010b).
Read Wang and Zender (2010b) to understand the data limitations.
Wang, X., and C. S. Zender (2010a), MODIS snow albedo bias at high
solar zenith angle relative to theory and to in situ observations in
Greenland, Rem. Sens. Environ., 114(3), 563-575,
Wang, X., and C. S. Zender (2010b), Constraining MODIS snow albedo at large solar zenith angles: Implications for the surface energy budget in Greenland, J. Geophys. Res. Earth Surf., 115, F04015, doi:10.1029/2009JF001436.