## 2 Materials and Methods
### MISR Data and Processing  
The MSMD satellite data used in this study were acquired by the MISR instrument, which features nine cameras. One camera is pointing towards nadir (designated An at 0.1\({}^{0}\) zenith angle), while the eight off-nadir cameras are pointing in the forward (f) and aft or backward (a) direction (designated Df: 70.3\({}^{0}\), Cf: 60.2\({}^{0}\), Bf: 45.7\({}^{0}\), Af: 26.2\({}^{0}\), Aa: 26.2\({}^{0}\), Ba: 45.7\({}^{0}\), Ca: 60.2\({}^{0}\) and Da: 70.6\({}^{0}\)) [53]. Each MISR camera uses a push-broon sensor, with separate detectors for the four spectral bands: blue (446.4 nm), green (557.5 nm), red (671.7 nm) and near infrared (864.4 nm). The swath width is about 380 km wide. As part of the pre-processing to Level 1B2, the four spectral bands of each camera are radiometrically calibrated, geo-rectified and spatially co-registered [41; 82]. A detailed description of the instrument and processing can be found in [PERSON] et al. [82]. As hinted earlier, to keep the data rate within the downlink allocation, only 12 of the 36 MSMD data channels are transmitted at full spatial resolution in the Global Mode of operation, and hence, all standard products generated by NASA Langley Atmospheric Research Center are delivered at a spatial resolution of 1.1 km or coarser. Recently, a MISR-High Resolution (HR) processing system [53; 83] was designed to reconstruct observations at the original spatial resolution of 275 m in all spectral bands and for all cameras. This system also produced a full range of higher level products at 275 m spatial resolution, including RPV model parameters, spectral and broadband albedos, as well as key vegetation products such as LAI and FAPAR [53; 83]. The BRF and RPV products used in this study were generated with the MISR-HR processing system, version 1.04-5, hosted at the Global Change Institute of the University of the Witwatersrand in Johannesburg, South Africa [83]. The following data are used as inputs to generate the MISR-HR products [53]:  
1. The MISR L1B2 Terrain-projected Global Mode data, which contains top of atmosphere (TOA) radiance measurements, resampled at surface level and topographically corrected. 2. The MISR L2 Terrain-projected bottom of atmosphere (BOA) bidirectional reflectance factors (BRFs), generated by NASA's standard processing system at 1.1 km spatial resolution. 3. Geometric Parameters Product (GPP). 4. Ancillary Geographic Product (AGP), which are the reference datasets containing the full latitude/longitude information. The first step in the MISR-HR processing routine consists of reconstructing radiance data at the nominal \"Top of the Atmosphere (ToA)\" (the L1B3 product) at the full spatial resolution in all 36 data channels. Those data are then converted to surface reflectance (BRF product) by isolating the surface from the atmospheric contribution to the measurements. This process also screens out cloud-covered areas. The MISR-HR 12 RPV model parameters (\(\rho_{0}\), \(k\), \(\Theta\) for each spectral band) are the result of the third step in the MISR-HR processing system ([[http://www.misrhr.org/rpv](http://www.misrhr.org/rpv)]([http://www.misrhr.org/rpv](http://www.misrhr.org/rpv))) [53]. These parameters are retrieved by inverting the RPV model against the nine surface bidirectional reflectance values, separately in each of the four spectral bands. The bidirectional reflectance factor \(\rho\) can be represented by the RPV model as follows [45; 46]:  
\[\rho(\theta_{s},\ \theta,\ \phi,\ \rho_{0},\ k,\ \Theta)=\rho_{0}M(\theta_{s}, \ \theta,\ k)\ F_{HG}\ (g;\ \Theta_{HG}) \tag{1}\]where \(\theta_{S}\), \(\theta\) and \(\phi\) are the solar zenith angle, the observation zenith angle and the relative azimuth between the directions of illumination and observation, respectively, \(\rho_{0}\) is the amplitude parameter of the RPV model and \(M\) is the modified Minnaert function.