MODIS Radiance counts (MOD01)
This Level 1A data set contains counts for 36 MODIS channels, along with raw instrument engineering and spacecraft ancillary data. The Level-1A data are used as input for geolocation, calibration, and processing. Quality indicators are added to the data to indicate missing or bad pixels and instrument modes. Visible, SWIR, and NIR measurements are made during daytime only, while radiances for TIR are measured during both the day and the night portions of the orbit.
The Level 1B data set contains calibrated and geolocated at-aperture radiances for 36 bands generated from MODIS Level 1A sensor counts (MOD 01). The radiances are in W/ (m2-μm-sr). In addition, reflectance may be determined for the solar reflective bands (bands 1-19, 26) through knowledge of the solar irradiance (e.g., determined from MODIS solar-diffuser data, and from the target-illumination geometry). Additional data are provided, including quality flags, error estimates, and calibration data.
MODIS Geolocation data set (MOD03)
This product contains geodetic coordinates, ground elevation, and solar and satellite zenith, and azimuth angle for each MODIS 1 km sample. These data are provided as a companion data set to the Level 1B calibrated radiances and the Level 2 data sets to enable further processing. These geolocation fields are determined using the spacecraft attitude and orbit, instrument telemetry, and a digital elevation model.
MODIS Aerosol product (MOD04)
This product monitors the ambient aerosol optical thickness over the oceans globally and over the continents. Furthermore, the aerosol size distribution is derived over the oceans, and the aerosol type is derived over the continents. “Fine” aerosols (anthropogenic/pollution) and “coarse” aerosols (natural particles; e.g., dust) are also derived. Daily Level 2 (MOD 04) data are produced at the spatial resolution of a 10 × 10 1 km (at nadir) pixel array. The aerosol product includes the “deep-blue” algorithm for retrieving aerosol optical thickness over bright land surfaces.
MODIS Total precipitable water (MOD05)
This product consists of column water-vapor amounts. During the daytime, a near-infrared algorithm is applied over clear land areas of the globe and above clouds over both land and ocean. Over clear ocean areas, water vapor estimates are provided over the extended glint area. An infrared algorithm for deriving atmospheric profiles is also applied both day and night for Level 2. The Level 2 data are generated at the 1-km spatial resolution of the MODIS instrument using the near-infrared algorithm during the day, and at 1-km pixel resolution both day and night using the infrared algorithm.
MODIS Cloud product (MOD06)
This product combines infrared and visible techniques to determine physical and radiative cloud properties. Cloud particle phase, effective radius, cloud optical thickness, and cloud integrated water path are derived at 1-km pixel resolution using the MODIS visible, near-infrared, and shortwave infrared bands. Cloud optical parameters are derived following cloud top temperature, cloud top pressure, effective emissivity, and cloud particle phase parameters that are produced by infrared retrieval methods (both day and night using 5 × 5 1 km pixels). Finally, it includes cirrus reflectance in the visible at 1 km pixel resolution, useful for removing cirrus scattering effects from the land surface reflectance product.
MODIS Atmospheric profiles (MOD07)
This product consists of several parameters: they are total-ozone burden, atmospheric stability, temperature and moisture profiles, and atmospheric water vapor. The MODIS atmospheric profile algorithm is a statistical regression that accounts for surface emissivity. The retrievals are performed using clear sky radiances measured by MODIS within a 5 x 5 field of view (approximately 5 km resolution) over land and ocean for both day and night.
MODIS Atmosphere gridded product (MOD08)
There are three MODIS Level 3 Atmosphere Products, each covering a different temporal scale: Daily, 8-Day, and Monthly. Each of these Level 3 products contains statistics derived from over 100 science parameters from the Level 2 Atmosphere products: Aerosol, Precipitable Water, Cloud, and Atmospheric Profiles. A range of statistical summaries (scalar statistics and 1- and 2-dimensional histograms) are computed, depending on the Level 2 science parameter. Statistics are aggregated to a 1° × 1° equal-angle global grid. The daily product contains ~700 statistical summary parameters. The 8-day and monthly products contain ~900 statistical summary parameters
MODIS Atmosphere joint product (MODATML2)
The MODIS Atmosphere Level 2 Joint Product contains 27 key data sets gleaned from the complete set of standard Level 2 products: Aerosol, Water Vapor, Cloud, Atmospheric Profiles, and Cloud Mask. The Joint Atmosphere product was designed to be small enough to minimize data transfer and storage requirements, yet robust enough to be useful to a significant number of MODIS data users. Scientific data sets (SDSs) contained within the Joint Atmosphere product cover a full set of high-interest parameters produced by the MODIS Atmosphere group, and are stored at 5 km and 10 km (at nadir) spatial resolutions.
MODIS Cloud mask (MOD35)
The MODIS cloud mask product indicates whether a pixel is unobstructed between the surface and satellite.The product provides 48 bits of output per 1 km pixel that includes information on sets of multispectral test results (from 19 MODIS spectral bands), the decision tree used to arrive at the product, and limited ancillary information such as a land/ocean and snow/no snow flags. The first eight bits provide a summary sufficient for most applications. Additionally, the first two bits simply offer information in four categories: confident clear, probably clear, uncertain/probably cloudy, and cloudy.
MODIS Surface reflectance (MOD09)
The MODIS Surface Reflectance products provide an estimate of the surface spectral reflectance as it would be measured at ground level in the absence of atmospheric scattering or absorption. Low-level data are corrected for atmospheric gases and aerosols, yielding a Level 2 basis for several higher-order gridded products. In the 8-day product, each surface reflectance pixel contains the best possible observation during an 8-day period as selected on the basis of high observation coverage, low view angle, the absence of clouds or cloud shadow, and aerosol loading.
The Land Surface Temperature (LST) and Emissivity daily data are retrieved at 1 km pixels by the generalized split-window algorithm and at 6 km grids by the day/night algorithm. In the split-window algorithm, emissivities in bands 31 and 32 are estimated from land cover types, atmospheric column water vapor and lower boundary air surface temperature are separated into tractable sub-ranges for optimal retrieval. In the day/night algorithm, daytime and nighttime LSTs and surface emissivities are retrieved from pairs of day and night MODIS observations in seven TIR bands. The product is comprised of LSTs, quality assessment, observation time, view angles, and emissivities.
MODIS Land cover and dynamics (MOD12)
The MODIS Combined Terra and Aqua Land Cover
product incorporates five different land cover classification schemes, derived through a supervised decision-tree classification method. The primary land cover scheme identifies 17 classes defined by the IGBP, including 11 natural vegetation classes, three human-altered classes, and three non-vegetated classes. The Land Cover Dynamics product includes layers on the timing of vegetation growth, maturity, and senescence that mark the seasonal cycles. Estimates of vegetation phenology are provided twice annually from the two 12-month focus periods, July-June, and January-December, allowing for hemispheric differences in the growing seasons, and enabling the product to capture two growth cycles if necessary.
MODIS Vegetation Indices (NDVI and EVI) (MOD/MYD 13)
MODIS vegetation indices, produced on 16-day intervals and at multiple spatial resolutions, provide consistent spatial and temporal comparisons of vegetation canopy greenness, a composite property of leaf area, chlorophyll and canopy structure. Two vegetation index products are derived from atmospherically corrected in the red, near-infrared, and blue wavebands; the MODIS normalized difference vegetation index (NDVI) which provides continuity with NOAA’s AVHRR NDVI time series record for historical and climate applications, and the enhanced vegetation index (EVI) which minimizes canopy-soil variations and improves sensitivity over dense vegetation conditions. The two products more effectively characterize the global range of vegetation states and processes.
MODIS Fire and thermal anomalies (MOD14)
MODIS Thermal Anomalies/Fire products are primarily derived from MODIS 4 and 11 µm radiances. The fire detection strategy is based on absolute detection of a fire (when the fire strength is sufficient to detect), and on detection relative to its background (to account for variability of the surface temperature and reflection by sunlight). The product includes a fire-mask, detection confidence, fire radiative power, and numerous other layers describing fire pixel attributes. MODIS data on Terra (and Aqua) are acquired twice daily at mid-latitudes allowing for up to four daily MODIS fire observations. These observations serve operational fire management needs and advance global monitoring of the fire process and its effects on ecosystems,
the atmosphere, and climate.
LAI is defined as the one-sided green leaf area per unit ground area in broadleaf canopies and as half the total needle surface area per unit ground area in coniferous canopies. FPAR is the fraction of photosynthetically active radiation (400-700 nm) absorbed by green vegetation. Both variables
are used for calculating surface photosynthesis, evapotranspiration, and net primary production, which in turn are used to calculate terrestrial energy, carbon, water cycle processes, and biogeochemistry of vegetation. Algorithm refinements have improved quality of retrievals and consistency with field measurements over all biomes, with a focus on woody vegetation.
MODIS Evapotranspiration (MOD16)
Terrestrial evapotranspiration (ET) is the summation of plant transpiration and soil evaporation. The MOD16 ET algorithm is based on the Penman-Monteith equation. Net solar radiation is partitioned into components of vegetation and soil by vegetation cover fraction estimated with MOD13 Enhance Vegetation Index (EVI). Air vapor pressure deficit (VPD) and minimum air temperature are used to constraint leaf conductance, which is up-scaled to canopy conductance with MOD15 Leaf Area Index (LAI). Potential soil evaporation is reduced by air humidity and VPD to estimate soil evaporation. MOD16 ET estimates at AmeriFlux towers agree well with measured ET seasonally and inter-annually.
The Gross Primary Productivity (GPP) product is a cumulative composite of GPP values based on the radiation use efficiency concept that may be used as inputs to data models for calculating terrestrial energy, carbon, water cycle processes, and biogeochemistry of vegetation. Modifications of parameters in Biome Property Look-Up Table (BPLUT) have been made to agree with GPP derived from measurements at eddy flux towers and synthesized NPP. Have included a spatially non-linear interpolation of coarse-resolution meteorological data at 1 km MODIS pixel level, instead of nearest neighbor sampling, to increase the accuracy of meteorological data input at pixel level.
The Bidirectional Reflectance Distribution Function (BRDF) and Albedo Model Parameters product contains three-dimensional data sets providing users with weighting parameters for the models used to derive the Albedo and BRDF products. The models support the spatial relationship and parameter characterization best describing the differences in radiation due to the scattering (anisotropy) of each pixel, relying on multi-date, atmospherically corrected, cloud-cleared input data measured over 16-day periods. Both Terra and Aqua data are used in the generation of this product, providing the highest probability for quality input data.
Proportional estimates of cover are developed from global training data derived using high-resolution imagery. The training data and phenological metrics are used with a regression tree to derive percent cover globally. The model is then used to estimate areal proportions of life form, leaf type, and leaf longevity. The current Version 4 collection of the yearly MODIS Vegetation Continuous Fields (VCF) product contains only percent tree cover, with the other layers to follow in later releases. The data layers in the VCF product are generated on an annual basis from monthly composites of 500 m Surface Reflectance data. Compositing is based on the second darkest albedo to remove clouds and cloud shadow.
MODIS Burned area product (MCD45)
The Burned Area product contains burning and quality information on a per-pixel basis. Produced from both the Terra and Aqua MODIS-derived daily surface reflectance inputs, the algorithm analyzes the daily surface reflectance dynamics to locate rapid changes, and uses that information to detect the approximate date of burning, mapping the spatial extent of recent fires only. It provides varied quality assessment information and a single summary quality assessment score for each pixel. The algorithm improves on previous methods by using a BRDF model-based change detection approach to handle angular variations in the data and uses a statistical measure to identify change probability from a previously observed state.
MODIS Snow cover (MOD10)
MODIS snow cover data are based on a snow mapping algorithm that employs a Normalized Difference Snow Index (NDSI) and other criteria tests. The MODIS snow product suite is composed of products covering a range of spatial and temporal resolutions, from 500 m to 0.05°, and from swath to daily, to 8-day to monthly. All products provide fractional snow cover, and snow albedo is provided in the 500 m resolution products. The overall absolute accuracy of the 500 m resolution products is ~93%, varying by land cover and snow condition. The snow products are used by climatologists, and by modelers both as input to hydrological models, e.g., to develop snow-cover depletion curves, and to compare with GCM output.
The MODIS sea ice product is the sea ice extent and
ice-surface temperature (IST) measured during daylight and darkness. The sea ice algorithm uses a Normalized Difference Snow Index (NDSI) modified for sea ice to distinguish sea ice from open ocean based on reflective and thermal characteristics. The sea ice product suite is composed of both swath and gridded products at a range of spatial and temporal resolutions, from 1 km to 0.05° (or ~4 km), and temporal resolutions ranging from swath to daily with gridded data in a polar grid (EASE-grid). IST under frozen conditions is accurate to ±1.6 K.
Sea surface temperatures (SST) are generated from the mid-range infrared channels of MODIS for both the daytime and nighttime global oceans. A second estimate of sea surface temperatures (SST4) is generated from the shortwave infrared channels for the nighttime portion of the orbit only. In addition, a quality assessment parameter is included for each pixel, as well as a standard deviation and bias estimate, for both the SST and SST4 products.
The principal measurement in ocean color is the spectral distribution of normalized water-leaving radiance, NLw(l), which is defined as the upwelling radiances just above the ocean surface, normalized to represent the case of no atmosphere with the Sun directly overhead. For application in bio-optical algorithms, this quantity is converted to remote sensing reflectance, Rrs, which is simply nLw divided by mean extraterrestrial solar irradiance. From these reflectances, information on a host of ocean optical properties (dissolved substance and particle absorption and scattering coefficients) and constituent concentrations (e.g., chlorophyll-a) are derived. Rrs products are generated for each of the nine MODIS visible wavelengths (400-700 nm).
Chlorophyll-a is the main plant pigment involved in photosynthesis and is a good indicator of phytoplankton biomass. It is required for estimation of primary production and ocean biological sequestration of carbon. It is a core mission product. Records started in September 1997 with SeaWiFS and they are now also derived from the MODIS sensors on Terra and Aqua. Chlorophyll a algorithms have reached maturity and are very reliable over ~90% of the World Ocean. The chlorophyll-a data is available to the community through the NASA Ocean Biology Processing Group Ocean Color Web server.
Diffuse attenuation is related to the exponential decrease in light intensity with water depth, i.e., it is the wavelength dependent coefficient of depth in the exponent. Therefore, it is an indicator of water clarity and is used to estimate light penetration and absorption, both of which are important for calculations of primary production and mixed layer heating. The diffuse attenuation at 490 nm (Kd490) is a core product for SeaWiFS and MODIS/Aqua and Terra, so the global time series starts with the SeaWiFS data in 1997.
MODIS Aerosol optical thickness (for ocean color atmospheric correction)
Aerosol optical thickness at band 869 nm, a ta(869) (dimensionless), over ocean is derived from the ocean color data processing for every pixel with a clear atmosphere using the MODIS near-infrared (NIR) measurements at 748 and 869 nm. Aerosol NIR spectral reflectance is used to retrieve aerosol models and derive ta(869) value. For productive waters, the NIR ocean contributions are estimated using the biooptical models. The ta(869) is defined as the integrated extinction coefficient at 869 nm over a vertical column of unit cross section. The ta(869) value is proportional to the aerosol particle concentration and can be related to atmosphere turbidity (visibility).
Aerosol Angstrom exponent α(443) (dimensionless) over ocean is the estimated slope at 443 nm of the curve plotting the log of the optical depth versus the log of the wavelength. It is derived from the MODIS bands at 531 nm, 748 nm, and 869 nm for every pixel with a clear atmosphere. The α(443) is a measure of the spectral variation of the aerosol
optical thickness and is a function of the aerosol particle size (the larger the exponent, the smaller the particle size).
Particulate Organic Carbon (POC) is the carbon stored in organic particles (soft tissues) suspended in the water column. Because passive radiometers like MODIS only sense the light that scattered out of the water column very near the surface, the MODIS POC is essentially the surface concentration in gC/m3. POC is an important component of the ocean carbon cycle.
Particulate Inorganic Carbon (PIC) is a form of particulate calcium carbonate and constitutes the skeletons of microscopic marine plankton (plants and animals). Coccolithophores are a well-known source of calcite particles because they shed calcite platelets during a phase of their lifecycle. The Cliffs of Dover are composed of calcite from such plankton species. Like POC, PIC is another important component of the marine carbon cycle and carbon is in concentrations of gC/m3.
FLH (mW/cm2-µm-sr) is a measure of the chlorophyll fluorescence that peaks at around 685 nm. The MODIS fluorescence band at 678 nm is offset from the peak to avoid an atmospheric water vapor absorption band. MODIS FLH is derived by subtracting a baseline radiance computed from the 667 and 748 nm bands which lie outside the fluorescence band. Recent research on FLH has shown that it can be used to study phytoplankton physiology, or health (see below). The maturity of the FLH product is provisional.
Instantaneous Photosynthetically Available Radiation (iPAR) is total downwelling flux of photons just below the sea surface at the instant MODIS views the pixel, integrated over the wavelength range of 400-to-700 nm. It is derived for all cloud free pixels using the retrieved atmospheric properties to attenuate the extraterrestrial solar irradiance at each MODIS visible wavelength, and then integrating over wavelength space. The iPAR can be used in combination with the FLH to estimate chlorophyll fluorescence quantum yield. Variations in fluorescence quantum yield have been interpreted as indicators of phytoplankton physiology (e.g., iron stress).
Like iPAR, Daily Mean Photosynthetically Available Radiation (PAR) is total downwelling photon flux integrated over the wavelength range of 400-to-700 nm. However, PAR is derived for all ocean pixels (both clear and cloudy), and uses a model of 24-hour solar illumination to integrate over a full daily cycle. Thus, PAR represents the average energy available for photosynthesis over each day, at each MODIS pixel. PAR is a critical input to models of net primary productivity, and SeaWiFS PAR has been in widespread use for a decade. PAR has previously been produced only for SeaWiFS, as the MODIS ocean channels saturate over cloudy pixels. It is now being produced for MODIS using the land channels at 469, 555, and 645 nm.
The polar wind product provides tropospheric wind
speed, direction, and height over the Arctic and Antarctic, poleward of approximately 70 degrees latitude. It has been generated in real-time since 2002 using MODIS data from the Terra and Aqua satellites, and is now a NOAA/NESDIS operational product. The polar wind data are used by 10 numerical weather prediction centers in six countries.
The Disturbance Index is a new algorithm aimed at
quantifying annual landcover changes that result from major disturbances at global scales. The DI is computed once per year from the MODIS Enhanced Vegetation Index and Land Surface Temperature products as a maximum composite ratio LST/EVI. The DI is a dimensionless index computed globally at 1 km and detects for each pixel a departure
from the historical landcover. The purpose if this
data product is a globally consistent and repeatable analysis of rates of landcover change and ecosystem recovery.