数据说明
Chlorophyll a (chlor_a) from Multi-Sensors
上传时间:2019-05-22 14:06:32 浏览次数:作者与来源:admin
Chlorophyll a refers to the amount of chlorophyll a in a unit volume of seawater.
Unit: mg/m3
Resolution:  4km pixel, daily, monthly
Duration: Sept. 1997 to Dec. 2016.
Source: Multi-sensors, Ocean Colour component of the European Space Agency Climate Change Initiative project
Version: 3.1
Processing: Original daily and monthly mean products are shown.
The chlorophyll-a values are calculated by blending algorithms based on the water-type as documented in the ATBD-OCAB document (Product User Guide.pdf). For this version, this involved the blending of the OCI algorithm (as implemented by NASA, itself a combination of CI and OC4), the OC5 algorithm (NASA 2010) and the OC3 algorithm. Each algorithm utilizes the same OC-CCI merged Rrs products described in Product User Guide.
These files are daily and monthly composites of merged sensor (MERIS, MODIS Aqua, SeaWiFS LAC & GAC, VIIRS) products. 
MODIS Aqua and MERIS were band-shifted and bias-corrected to SeaWiFS bands and values using a temporally and spatially varying scheme based on the overlap years of 2003-2007. 
VIIRS was band-shifted and bias-corrected in a second stage against the MODIS Rrs that had already been corrected to SeaWiFS levels, for the overlap period 2012-2013. 
VIIRS and SeaWiFS Rrs were derived from standard NASA L2 products; MERIS and MODIS from a combination of NASA's l2gen (for basic sensor geometry corrections, etc) and HYGEOS Polymer v3.5 (for atmospheric correction). 
The Rrs were binned to a sinusoidal 4km level-3 grid, and later to 4km geographic projection, by Brockmann Consult's BEAM. 
Derived products were generally computed with the standard SeaDAS algorithms. 
QAA IOPs were derived using the standard SeaDAS algorithm but with a modified backscattering table to match that used in the bandshifting. 
The final chlorophyll is a combination of OC4, Hu's CI and OC5, depending on the water class memberships. 
Uncertainty estimates were added using the fuzzy water classifier and uncertainty estimation algorithm of Tim Moore as documented in Jackson et al (2017).'
Known issues
root-mean-square (RMS)
1. Decay of MODIS calibration: It is to be reported that data after ~2013 will have reduced quality by NASA. Data in this period should be analyzed with caution.
2. Remaining bias: Users should be aware of the start and end times of the sensors used (SeaWiFS from September 1997 to December 2010, MERIS from April 2002 to April 2012, MODIS from July 2002 and on-going, and VIIRS from 2012 and on-going).
All the contents of this page are quoted fromOcean Colour Climate Change Initiative (OC_CCI), European Space Agency. All project documentation and related publications can be found at the website: http://www.esa-oceancolour-cci.org/