UMass Boston

The MCD43C4 Climate Modeling Grid (CMG) Nadir BRDF-Adjusted Reflectance (NBAR) Product (MODIS/Terra Nadir BRDF-Adjusted Reflectance Daily L3 Global 0.05 deg CMG) is computed for each of the MODIS spectral bands (1-7) at the local solar noon zenith angle of the day of interest. The data are provided in global files in a geographic (lat/long) projection. Since the view angle effects have been removed from the directional reflectances, the result is a stable and consistent reflectance product. These NBAR values are calculated from MCD43C1. Note that along coastlines, this means that the 30 arcsecond pixels that lie over shallow water will be averaged into the 0.05 degree CMG pixel. In addition to the spectral and broadband albedo quantities themselves, the MCD43C4 CMG NBAR Product also provides extensive quality information. The quality and inversion status of the majority of the underlying 30 arcsecond pixels is provided as well as the percentage of the underlying pixels that were present or were snow covered. The uncertainty layer gives the quality of the full inversion from the measure of the angular sampling of input surface reflectance for the BRDF retrieval.

Please note: We recommend that users use the MCD43D 30 arcsecond products (or the 30 arcsecond MCD43GF gapfilled products) instead of the MCD43C products as much as possible, since the MCD43C products merely represent averages of the direct BRDF retrievals obtained with the MCD43D processing. The averaged MCD43C products thus necessarily include various QA flags within each pixel, and are therefore less rigorously high quality than the MCD43D products.

Science Data Sets

While the full MCD43C4 specification (V006 and V006.1)

should be consulted for the most current description, the product includes Nadir_Reflectance (NBAR) at the local solar noon zenith angle of the day of interest for 7 spectral bands. They are provided in global files in a geographic (lat/long) projection (3600 rows X 7200 columns (X 7 bands)).

Note that the V006 and V006.1 MODIS MCD43 products are retrieved daily and represent the best BRDF possible based on 16 days’ worth of inputs with the day of interest emphasized. Unlike the earlier reprocessed versions (where the date of the product signifies the first day of the retrieval period), and the Direct Broadcast version (where the date signifies the last day of the retrieval period), the date associated with each daily V006 and V006.1 retrieval is the center of the moving 16 day input window. This change is in response to user requests.

Local Attributes

In addition to the actual SDS data values produced at each pixel in a tile, each SDS is associated with a number of standard Local Attributes that apply to the data.

Global Attributes (Metadata)

In addition to the albedo and quality information (SDSs and Local Attributes) that is provided at a per-cmg-pixel level, each Level 3 MCD43C4 CMG Albedo Product also Metadata which summarize the file. (See the full MCD43C4 specification (V006 and V006.1) for the complete listing.)