The purpose of the MODIS (Moderate-resolution Imaging Spectroradiometer) system is to collect data for calibrated global interactive Earth models as a single system. These models predict global changes with sufficient accuracy to inform decisions concerning environmental protection. Both Terra- and Aqua-MODIS instruments view the entire surface of the Earth every 1 to 2 days, acquiring data across 36 spectral MODIS bands from 0.4s to 14.4 μm. The MODIS satellite survey materials have a wide range of applications for the study of the atmosphere, land, and ocean.
The main atmospheric research areas that benefit from MODIS are cloud cover, aerosols, and water vapor; all important climate-forming factors. Central to MODIS research is the study of the ozone layer. Channel 30 (9.580-9.880 μm) operates in the area of ozone absorption and is specifically designed for studying the total thickness of the ozone layer in the troposphere and stratosphere. Both day and night survey data are used in the calculation of this value. The resulting images have a resolution of 5 km and are used not only to study the dynamics of the ozone layer, but also for atmospheric correction of other MODIS images, and the study of jet streams in the atmosphere.
Water vapor, one of the main greenhouse gases, is easily detected by the MODIS system, which measures gas concentrations in the air column under the satellite by the transparency of the atmosphere in the absorption zone of water vapor. The water vapor content is obtained from daytime imaging data in the near infrared range with a resolution of 1 km, as well as data from day and night photography in the zones of the thermal range with a resolution of 5 km. These measurements are used to study the global water cycle, the interaction between aerosols and clouds, the energy balance and the Earth’s climate.
MCD43A4 provides the 500 meter reflectance data of the MODIS “land” bands 1-7 adjusted using the bidirectional reflectance distribution function to model the values as if they were collected from a nadir view.