Abstract:
This data set consists of satellite measurements of global ocean color data obtained by the Moderate Resolution Imaging Spectroradiometer (MODIS), in orbit on the Aqua (formerly EOS PM) platform. MODIS ocean color products are processed and distributed by the Ocean Biology Processing Group (OBPG). Processing details can be found at http://oceancolor.gsfc.nasa.gov/DOCS/MODISA_processing.html
Each ... Level-2 Local Area Coverage (LAC) product is generated from a corresponding Level-1B product. The main data contents of the product are the geophysical values for each pixel, derived from the Level-1B radiances by applying the atmospheric corrections and bio-optical algorithms. Each Level-2 product corresponds exactly in geographical coverage (scan-line and pixel extent) to that of its parent Level-1B product and is stored in one physical HDF file. The resolution is the same as the corresponding level 1B file (1 km).
The standard Ocean Color product contains the following geophysical values derived for each pixel: -Normalized water-leaving radiances at 412, 443, 488, 531, 551 & 667 nm -Chlorophyll a concentration -Diffuse attenuation coefficient at 490 nm (measure of optical clarity) -Epsilon of aerosol correction at 748 and 869 nm -Angstrom coefficient, 531 to 869 nm (for atmospheric correction) -Aerosol optical thickness at 869 nm (for atmospheric correction)
In addition, 32 flags are associated with each pixel indicating if any algorithm failures or warning conditions occurred for that pixel.
Level-2 processing is performed using the Multi-Sensor Level-1 to Level-2 (MSl12) code, which is developed and maintained by the OBPG. MSL12 is used for the standard processing of all ocean products distributed through the web browsers and FTP sites. This software is capable of retrieving oceanic optical properties and various derived products from the observed top-of-atmosphere (TOA) radiances collected by a variety of ocean remote sensing radiometers, including MODIS. Full documentation, updated code source, sensor files, and output product descriptions can be found at http://oceancolor.gsfc.nasa.gov/DOCS/MSL12/. For MODIS, the Level-1B file and the GEO file for each 5-minute granule are input to MSl12.
The Level-2 processing also makes use of meteorological and ozone information from ancillary sources. In the near real-time (NRT) stream, climatological meteorological and ozone data are used. The NRT Quick Look products are then immediately available on the web browser and in the rolling FTP archive within 6-10 hours of observation. When the definitive attitude and orbit and coincident meteorological and ozone data are received several days later, they are used in the Refined processing stream, and the Level-2 products are regenerated.
Description:
MODIS/Aqua Level-2 Ocean Color data for the most-recent days. The files are organized by YYYYDDD in the following subdirectories: /Quicklook - best-available ancillary data used for GEO and L2. /Refined - optimal ancillary data used for GEO and L2 -or- 10-day wait period for optimal data expired.
Quality
ATTRIBUTE ACCURACY REPORT: Limits of Detection Method Detection Limits (MDL), the lowest concentration of a parameter that an analytical procedure can reliably detect, have been established by the VIMS Nutrient Analytical Laboratory. The MDL is determined as 3 times the standard deviation of a minimum of 7 replicates of a single low concentration sample. Table 1 presents the current MDL’s; these ... values are reviewed and revised periodically. Table 1. Method Detection Limits (MDL) for measured water quality parameters. Parameter Variable MDL Dates in use Ammonium NH4F 0.0015 mg/l as N 2002 Nitrite NO2F 0.0008 mg/l as N 2002 Nitrate + Nitrite NO23F 0.0008 mg/l as N 2002 Orthophosphate PO4F 0.0006 mg/l as P 2002 Chlorophyll CHLA 0.5 µg/l 2002 Pheophytin PHEA 0.5 µg/l 2002 Reporting of Missing Data and Data with Concentrations Lower than Method Detection Limits Nutrient/Chla comment codes and definitions are provided in the following table. Missing data are denoted by a blank cell “ ” and commented coded with an “M”. Laboratories in the NERRS System submit data that are censored at a lower detection rate limit, called the Method Detection Limit or MDL. MDL’s for specific parameters are listed in the Laboratory Methods and Detection Limits Section (Section I, Part 12) of this document. Concentrations that are less than this limit are denoted by a –9999 and comment coded with a “B” in the variable code comment column. For example, the measured concentration of NO23F was 0.0005 mg/L as N (MDL=0.0008), the reported value would be -9999 with a “B” placed in the NO23F comment code column. Calculated parameters are comment coded with a “C” and if any of the components used in the calculation are below the MDL, the calculated variable is denoted by –9999 and also comment coded with a “B”. If a calculated value is negative, the value is reported as a -9999. Table 2: Comment Coded Definitions Comment Code Definition A Value above upper limit of method detection B Value below method detection limit C Calculated value D Data deleted or calculated value could not be determined due to deleted data, see metadata for details H Sample held beyond specified holding time K Check metadata for further details M Data missing, sample never collected or calculated value could not be determined due to missing data P Significant precipitation (reserve defined, see metadata for further details) U Lab analysis from unpreserved sample S Data suspect, see metadata for further details QA/QC Programs a) Precision i) Field Variability – NOCNERR collects two successive grab samples for the monthly grab sample program. ii) Laboratory Variability – The VIMS Analytical Service Center for Nutrients analyzes a laboratory duplicate once for every ten samples. b) Accuracy i) Sample Spikes – The VIMS Analytical Service Center for Nutrients analyzed a matrix spike once for every ten samples. ii) Standard Reference Material Analysis – none iii) Cross Calibration Exercises – none LOGICAL CONSISTENCY REPORT: NACOMPLETENESS REPORT: Data collection period Diel Sampling: Site Start Date Start Time End Date End Time RC 04/22/02 10:00 04/23/00 10:00 RC 05/22/02 10:00 05/23/00 10:01 RC 06/26/02 03:00 06/27/02 03:01 RC 07/22/02 12:19 07/23/02 12:20 RC 08/21/02 12:49 08/22/02 12:50 RC 09/24/02 09:15 09/25/02 09:16 RC 10/21/02 09:45 10/22/02 09:46 RC 11/18/02 12:00 11/19/02 12:01 RC 12/16/02 11:45 12/17/02 11:46 Grab Sampling: Site Start Date Start Time End Date End Time LC 04/23/02 10:40 04/23/02 10:40 EC 04/23/02 15:05 04/23/02 15:05 ZB 04/23/02 15:35 04/23/02 15:35 LC 05/23/02 10:00 05/23/02 10:00 EC 05/24/02 08:50 05/24/02 08:50 ZB 05/24/02 09:20 05/24/02 09:20 LC 06/27/02 09:00 06/27/02 09:00 EC 06/24/02 10:14 06/24/02 10:14 ZB 06/24/02 10:35 06/24/02 10:35 LC 07/22/02 10:10 07/22/02 10:10 EC 07/24/02 09:15 07/24/02 09:15 ZB 07/24/02 09:40 07/24/02 09:40 LC 08/22/02 15:03 08/22/02 15:03 EC 08/26/02 10:34 08/26/02 10:34 ZB 08/26/02 11:31 08/26/02 11:31 LC 09/24/02 09:00 09/24/02 09:00 EC 09/24/02 10:25 09/24/02 10:25 ZB 09/24/02 10:40 09/24/02 10:40 LC 10/21/02 09:47 10/21/02 09:47 EC 10/23/02 11:50 10/23/02 11:50 ZB 10/23/02 12:06 10/23/02 12:06 LC 11/18/02 10:30 11/18/02 10:30 EC 11/21/02 11:19 11/21/02 11:19 ZB 11/21/02 11:41 11/21/02 11:41 LC 12/16/02 09:45 12/16/02 09:45 EC 12/17/02 09:25 12/17/02 09:25 ZB 12/17/02 09:40 12/17/02 09:40 Note: Time is coded based on a 2400 hour clock and is referenced to Eastern Standard Time (EST). LINEAGE/PROCESS STEP: PROCESS DESCRIPTION: Additional Description: Entry verification Monthly nutrient and Chla data files, in excel format, were sent to NOCNERR by the VIMS Analytical Service Center for Nutrients. Files consist of sampling station ID, date and parameter values expressed in unit concentrations. The research associate verified all parameter values in the excel file through cross comparison with laboratory data files. Missing data were verified through inspection of field logs, inserted into the data files and denoted by a blank cell by Paula May, NOCNERR research associate. PROCESS DATE: 20060224
Access Constraints
Data collected in conjunction with the National Estuarine Research Reserve System's (NERRS) System-wide Monitoring Program (SWMP) is considered public information. Please see site for further information: http://cdmo.baruch.sc.edu/aboutdata.htm
DISTRIBUTION LIABILITY: Distribution National Oceanic and Atmospheric Administration (NOAA)/Estuarine Reserves Division (ERD) retains the ... right to analyze, synthesize and publish summaries of the NERRS SWMP data. The PI retains the right to be fully credited for having collected and processed the data. Following academic courtesy standards, the PI and NERR site where the data were collected will be contacted and fully acknowledged in any subsequent publications in which any part of the data are used. Manuscripts resulting from the NOAA/OCRM supported research that are produced for publication in open literature, including refereed scientific journals, will acknowledge that the research was conducted under an award from the ERD, OCRM, National Ocean Service (NOS), NOAA. The data set enclosed within the package/transmission is only as good as the quality assurance/quality control procedures outlined by the enclosed metadata reporting statement. The user bears all responsibility for its subsequent use/misuse in any further analyses or comparisons. The Federal government does not assume liability to the Recipient of third persons, nor will the Federal government reimburse or indemnify the Recipient for it liability due to any losses resulting in any way from the use of this data. NERR water quality data and metadata can be obtained from the Research Coordinator at the individual NERR site (see section I. 1. Principal investigators and contact persons), from the Data Manager at the Centralized Data Management Office (see personnel directory under the general information link on the CDMO home page) and online at the CDMO home page http://cdmo.baruch.sc.edu/. Data are available in text tab-delimited format, Microsoft Excel spreadsheet format and comma-delimited format.
Use Constraints
The principal investigator (PI) listed in the enclosed metadata retains the right to be fully credited for having collected and processed the data. Please see the site for further information: http://cdmo.baruch.sc.edu/aboutdata.htm
