In: Wagner W., Szekely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
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A COMPARISON OF TOTAL SHORTWAVE SURFACE ALBEDO RETRIEVALS FROM 
MODIS AND TM DATA 
M. Pape a , M. Vohland b ’ * 
a formerly Faculty of Geography/Geosciences, University of Trier, D-54286 Trier, Germany 
b Remote Sensing Department, Faculty of Geography/Geosciences, University of Trier, D-54286 Trier, Germany - 
vohland@uni-trier.de 
KEY WORDS: MODIS, Landsat TM, broadband albedo, sensor simulation 
ABSTRACT: 
Total shortwave albedo is one key variable controlling the radiation energy budget of the land surface. Thus, the monitoring of its 
spatial and temporal variations is one important issue e.g. for the application of climate models. Routine albedo products are 
available from the Moderate Resolution Imaging Spectroradiometer (MODIS), e.g. MODIS MCD43A3 as 16-day 500m combined 
product generated from data of Terra and Aqua MODIS. Furthermore, surface spectral reflectances from monotemporal multispectral 
sensor data may be used to estimate broadband albedos; for this purpose, conversion formulae have been developed for a number of 
sensors. Mismatches between different albedo products may arise e.g. from the atmospheric correction process, different scan view 
geometries, BRDF adjustments, the range of wavelengths used or the particular narrowband to broadband conversion formulae. In 
this study, albedo retrievals from Thematic Mapper (TM) data and MODIS data/products were analysed for their consistency. In 
detail, the following MODIS products were considered: MOD09 - daily bidirectional surface reflectance, and 16 days albedo-product 
MCD43A3. To allow a comprehensible comparison between TM and MODIS, TM data have been aggregated to 500m MODIS 
resolution using the Point Spread Function (PSF) of MODIS. The analysis was performed for different acquisition periods, which 
resulted in different levels of consistency and thus uncertainties associated with the particular products. 
1. INTRODUCTION 
Currently a number of satellite sensors are used to receive 
information about the reflectance of the earth's surface. As a 
key parameter controlling the radiation budget and thus the 
energy budget of the surface, the hemispherical reflectance 
called albedo is required by climate models as input parameter. 
With the appearance of routine albedo products derived from 
data of satellite sensors like MODIS (Gao et al., 2005; Lucht et 
al., 2000; Schaaf et al., 2002) and the Multi-angle Imaging 
SpectroRadiometer (MISR) (Martonchik et al. 1998), albedo 
data sets with different spatial and temporal resolutions have 
become available. In addition to automatically generated albedo 
composites, a derivation of daily albedo from provided surface 
reflectances is also possible. Effects by scan view geometry, 
atmospheric correction or spectral interpolation remain to 
distort the signal and cause uncertainties and variabilities 
between the data derived from different sensor types. 
Therefore the main issue of this paper was the use of MODIS 
(500m) and TM (30m) data to derive and compare data fields of 
shortwave broadband albedo. As method for converting 
reflectance values to albedo, the conversion formulae of Liang 
(2000) were applied to atmospherically corrected MODIS and 
TM data. A validation of the calculated albedo was achieved by 
the MODIS albedo product MCD43A3 (“black-sky” albedo 
under clear-sky conditions, 0.25-5pm). This product is derived 
by means of a semi-empirical BRDF model using 16-day 
observations (Liu et al., 2009). 
The bidirectional spectral reflectance received bandwise from 
satellite observations equals surface spectral albedo under the 
assumption of Lambertian surfaces. To retrieve the broadband 
albedo from narrowband sensors, Liang (2000) developed 
formulae based on radiative transfer simulations that 
incorporated many different atmospheric conditions and surface 
* Corresponding author. 
reflectance spectra (taken from spectral libraries and AVIRIS- 
Airbome Visible/Infrared Imaging Spectrometer data). In our 
study, the formulae for MODIS and TM broadband albedo were 
verified using ideal (simulated) data prior their application to 
real sensor data. 
2. SATELLITE DATA AND STUDY SITE 
MODIS is an instrument onboard the Earth Observing System 
(EOS)-AMl (Terra) and EOS-PM1 (Aqua). Designed as an 
opto-mechanical cross-track scanner, MODIS is observing 
nearly the entire earth every two days. The scanner receives ra 
diances in 36 spectral bands with 250m, 500m and 1km geo 
metric instantaneous-fields-of-view (GIFOV's) at nadir. The 
bands numbered 1-2 with 250m GIFOV and the bands 3-7 with 
500m GIFOV are responsible for observing land cover features 
as well as cloud and aerosol properties (Barnes et al., 1998). 
The spectral coverage of the bands is very similar to Landsat 
TM bands (Figure 5), only for MODIS band 5 there is no 
correspondent. 
In this study, the MODIS products MOD09GA and MCD43A3 
were used. The bidirectional reflectance product MOD09GA 
contains an estimate of the surface spectral reflectance without 
atmospheric influences like scattering or absorption. The used 
bands cover the spectral range from 0.459 to 2.155pm . The 
albedo product MCD43A3 covers 16 days of observation and 
provides both directional hemispherical reflectance (black-sky 
albedo) and bihemispherical reflectance (white-sky albedo). 
Both data products (surface reflectance and albedo) are 
available as a gridded data set in sinusoidal projection with a 
geometric resolution of 500m and were received for this study 
through the NASA “Warehouse Inventory Search Tool” 
(WIST).