For further details, please see the appropriate Algorithm Theoretical Basis
Document (ATBD). A more descriptive summary can also be found at the MODIS Ocean Discipline
Group web page or by downloading the EOS
Data Products Handbook (PDF format). A list of the MODIS ocean products can be
found in Table 1 : MODIS Standard Ocean Products.
The MODIS ocean parameters within these products are listed in Table 11 : MODIS Ocean Parameters.
Final Atmosphere Products
Atmospheric Correction | Clouds | Aerosols and Clear Water Epsilons
Final Ocean Products
Coccolith and Calcite Concentration | Phycoerythrin
Pigment Concentration | Case I and II Chlorophyll Concentration |
Downwelling Irradiance | PAR | ARP
| CFE | Primary Production | SST
Data Analysis
Matchup Database and Sensor Calibration
ATMOSPHERIC CORRECTION
Gordon, ATBD 17
| goal | atmospheric correction for MODIS to retrieve normalized water-leaving radiance |
| method | calculate atmospheric effects at 750 and 865 nm, where water-leaving radiance is minimal, and extrapolate to visible wavelengths |
| input | 415, 443, 490, 531, 551, 667, 681, 750, 865 and 1375 nm wavebands, extraterrestrial irradiance, ozone concentration, surface pressure, wind speed, relative humidity, water temperature and air-sea temperature difference |
| output | daily, 1 km resolution, normalized water leaving radiances at the 415-681 nm ocean wavebands (MODIS product 18), aerosol optical thickness (MODIS product 37), algorithm index and flags |
CLOUDS
Ackerman et al., ATBD 06
| goal | to distinguish clear sky from cloudy sky or shadowed land, with confidence estimates. |
| method | perform a series of threshold tests at the various wavebands and combinations of them, based on the surface illumination and type. From the results, estimate the confidence that the sky is clear. |
| input | 470, 555, 659, 865 (15 nm), 865 (35 nm), 936, 1375, 1640, 3959, 6715, 8550, 11030, 12020 and 13935 wavebands, sun/viewing angles, land/water map, snow/ice masks, surface temperature, windspeed and clear-sky radiance maps. |
| output | a number of cloud and shadow flags at different confidence levels, and associated algorithm flags (MODIS product 35). |
IRON-RICH AEROSOLS, CLEAR-WATER EPSILONS
Carder et al., ATBD 21
| goal | to estimate iron-rich aerosol concentrations, and remove their effects from retrievals of water-leaving radiance. |
| method | calculate the ratio of aerosol reflectances derived from measured total reflectance (at wavelengths where water reflectance is zero), and extrapolate to shorter wavelengths using an exponential function, to obtain the water leaving radiance at 443 nm and the aerosol contribution. |
| input | total, Rayleigh and whitecap reflectances, and diffuse transmittance of the atmosphere (from the atmospheric correction routine) at 531, 551 and 667 nm wavebands. |
| output | light absorption, aerosol iron content over clear waters and flags (MODIS product 39). |
DETACHED COCCOLITH AND SUSPENDED CALCITE CONCENTRATION
Gordon and Balch, ATBD 23
goal |
to determine the concentration of detached coccoliths and perhaps the suspended calcite concentration directly. Also yields an estimate for chlorophyll concentration when coccoliths are present. |
method |
use lookup tables, based on the scattering properties of coccoliths, to estimate coccolith and chlorophyll concentrations from [Lw(443)]N and [Lw(551)]N, the normalized water-leaving radiances. |
input |
443 and 551 nm water-leaving radiances. |
output |
detached coccolith concentration, calcite concentration, pigment concentration and flags (MODIS product 25). |
PHYCOERYTHRIN PIGMENT CONCENTRATION
Hoge, ATBD 27
goal |
retrieval of phycoerythrin pigment concentration, including phycourobilin-rich phycoerythrin (PUB) and phycoerythrobilin-rich phycoerythrin (PEB). Used with the chlorophyll concentration (C), can provide global distributions of different phytoplankton species. |
method |
using the reflectance equation as a function of absorption and scattering, derives an equation with 5 unknowns which can be solved using 5 wavebands. Uses Gaussian expressions for the absorption of the different constituents. |
input |
412, 443, 490, 551 and 667 nm wavebands of water-leaving radiances, and chlorophyll concentration. |
output |
PUB and PEB concentrations and flags (MODIS product 31). |
CASE I AND II CHLOROPHYLL CONCENTRATION (2 METHODS)
Method A
Clark, ATBD 18
goal |
to estimate total pigment concentration (C), chlorophyll-a concentration and downwelling diffuse attenuation at 490 nm in Case 1 and 2 waters. |
method |
Formed new empirical relationship of the form : log(C) = a(log(X))3 +b(log(X))2+c(log(X))+d, where X=[eLw(443) + fLw(490) + gLw(531)]/Lw(551), where a, b, c, d, e, f, and g are coefficients. A similar relationship was derived for the downwelling diffuse attenuation coefficient at 490 nm. |
input |
443, 490, 531 and 551 nm wavebands of water-leaving radiances. |
output |
CZCS pigments, MODIS pigments (MODIS product 19), diffuse attenuation coefficient at 490 nm (MODIS product 26) and suspended solids concentration (MODIS product 23). |
Method B
Carder et al., ATBD 19
goal |
to estimate C in Case 2 waters. Also yields spectral phytoplankton absorption and colored dissolved organic matter absorption at 400 nm. |
method |
For low-chlorophyll waters, uses a semianalytic algorithm derived from two reflectance ratio equations. For high chlorophyll waters, uses an empirical algorithm as a function of reflectance ratios. |
input |
the remotely-sensed reflectances at the sea surface Rrs(412), Rrs(443), Rrs(490), and Rrs(551). |
output |
chlorophyll-a concentration (MODIS product 21), spectral phytoplankton absorption and total absorption at the visible MODIS wavebands (MODIS product 36), and colored dissolved organic matter absorption at 400 nm (MODIS product 24). |
DOWNWELLING IRRADIANCE ABOVE THE SEA SURFACE
Carder et al., ATBD 20
goal |
to determine the downwelling spectral irradiance just above the sea surface. |
method |
either use solar irradiance model, or calculate using measurements and atmospheric correction. |
input |
extraterrestrial irradiance, solar zenith angle, day of year, pressure, ozone scale height, water vapor concentration, clear water epsilons, aerosol optical thickness, airmass, relative humidity and absorption coefficients of ozone, oxygen and water. |
output |
downwelling irradiance just above the sea surface at 415, 443, 490, 531, 551 and 667 nm wavebands. |
PAR BELOW THE SEA SURFACE
Carder et al., ATBD 20
goal |
to determine instantaneous PAR (IPAR) just below the sea surface. |
method |
calculate weighted sum of downwelling irradiance from 6 visible channels. |
input |
downwelling irradiance at the 415, 443, 490, 531, 551 and 667 nm wavebands, solar zenith angle and windspeed. |
output |
IPAR (MODIS product 22) |
ABSORBED RADIATION BY PHYTOPLANKTON (ARP)
Carder et al., ATBD 20
goal |
to determine the absorbed radiation by phytoplankton. |
method |
calculate the integrated product of absorption by phytoplankton and scalar irradiance. |
input |
downwelling irradiance, total absorption coefficient, phytoplankton absorption coefficient, remote-sensing reflectance, solar zenith angle and satellite viewing angle. |
output |
ARP (MODIS product 22) |
CHLOROPHYLL FLUORESCENCE EFFICIENCY
Abbott and Letelier, ATBD 22
goal |
to estimate the fluorescence line height (FLH), chlorophyll fluorescence efficiency (CFE) and perhaps primary production. |
method |
calculate fluorescence line height, then divide by ARP (the number of photons absorbed) to yield the chlorophyll fluorescence efficiency. |
input |
667, 678 and 748 nm water-leaving radiances, C and ARP. |
output |
FLH, fluorescence baseline, CFE and flags (MODIS product 20). |
ANNUAL CARBON, NEW NITROGEN AND EXPORT CARBON PRODUCTION
Esaias, ATBD 24 (see also the ocean primary productivity web site)
goal |
to estimate annual carbon production, annual new nitrogen production and annual export carbon production to advance the understanding of primary production variability. |
method |
using empirical relationships between each of the desired quantities and C : Pt=51.9C+125.6 (total), Pn=8.58C+4.24 (new), and Px=0.63C-32.2 (export) |
input |
8-day averaged C or annual averaged C, SST, mixed-layer depth and PAR. |
output |
gridded level-3 fields at 9 km resolution of total carbon, new nitrogen and export production, and annual C, along with sample sizes and variances (MODIS product 27). |
SEA-SURFACE TEMPERATURE
Brown and Minnett, ATBD 25
goal |
to estimate sea-surface temperature (SST) to within 0.2oC accuracy for 2o x 2o squares. |
method |
(1) use a linear equation involving temperature differences of two nearby channels to
calculate SST from brightness temperature: SST = a0+a1T1+a2(T1-T2)Tb+a3(sec(q) -1), where the ai's are coefficients, T1 and T2 are the brightness temperatures of the nearby channels at 11030 and 12020 nm, Tb is an estimate for SST and q is the solar zenith angle. (2) use a linear function of two nearby channels (Feb 1999): SST = a0 + a1T1+a2T2 + day_term, where day_term = b0 + b1cos[(yearday-d0)2pi/365], d0 is the yearday for the summer solstice (northern hemisphere) or winter solstice (southern hemisphere), the ai's and bi's are latitudinally dependent coefficients, and T1 and T2 are the brightness temperatures of the channels at 3959 and 4050 nm (or 3750 nm). |
input |
3750, 3959, 4050, 11030 and 12020 nm brightness temperatures and cloud mask. |
output |
SST and flags (MODIS product 28). |
MATCHUP DATABASE AND SENSOR CALIBRATION
Evans, ATBD 26
| goal | create a matchup database for calibration of MODIS bands and to combine the ocean product algorithms into one group. |
| method | matches satellite data with in situ data, applies calibration corrections, calculates water-leaving radiances and brightness temperatures. |
| input | level 1 satellite data, in-situ data. |
| output | calibration data and flags (MODIS product 32). |
Related Links
Documented by Jasmine S. Bartlett, COAS, Oregon State University.