Summary
Chlorophyll-a can be detected by sensors mounted on satellites by virtue of peaks in the red and blue portions of the electromagnetic spectrum. After applying an area-specific atmospheric correction that accounts for turbidity in the Salish Sea and estimates of atmospheric aerosols, chlorophyll-a concentration can be estimated on a daily basis. The record of satellite imagery available extends from 1997 until the present, and a major goal of SPECTRAL satellite image processing is to apply these algorithms to this entire record.
Objectives
01. To extend an existing chlorophyll-a concentration time series of the Salish Sea from MODIS-Aqua to Suomi-NPP VIIRS
02. Validate satellite-derived chlorophyll-a concentrations with in situ data from a Sea-Keeper ferry box system (fluoreometer) and an autonomous hyperspectral radiomter system (SAS Solar Tracker).
03. Refine the time above time series by filling in spatial gaps in the records using temporal binning approach.
MODIS Sensor on the Aqua satellite. Image courtesy of NASA
VIIRS Sensor. Image courtesy of Raytheon Space and Airborne Systems.
Methods
Currently Andrea is working with MODIS-Aqua data, spanning 2002 until the present, with work beginning on inclusion of data from Suomi NPP's VIIRS sensor (with data available from 2012). Future work of the lab includes integration of pre-MODIS data into this time series, from SeaWiFS (1997 - 2010), as well as the latest ocean colour sensor Sentinel-3 (anticipated data delivery confirmation estimated to be 2016/2017).
Satellite imagery datasets often consist of condensed 'binned' images, mitigating some of the data lost by cloud cover. Andrea is currently applying DINEOF (data interpolating empirical orthogonal function) methods to investigate 'recovery' of surface chlorophyll estimates in areas where cloud cover or complex coastal features contribute to data loss.
Stay tuned for more updates!
VIIRS Image, Courtesy of NASA