KLIWAS 
Seite 19 
MODIS SST: 
KLIWAS 
Climatology 
of North Sea 
Fronts 
The Level-2 product is built from a corresponding Level-1A product. The main data 
contents of the product are the geophysical values for each pixel, derived from the 
Level-1A raw radiance counts by applying the sensor calibration, atmospheric 
corrections, and bio-optical algorithms. Each Level-2 product corresponds exactly in 
geographical coverage (scan-line and pixel extent) considering its parent Level-1A 
product and is stored in one physical HDF-file (Ocean Color 2009). The software 
SEADAS (SeaWiFS Data Analysis System) developed and provided by NASA can 
be used for processing individually defined Level-2 products. So the required MODIS 
Level-2 product for the front analysis contains 6 geophysical values derived for each 
pixel: the TOA reflectance of band 2135 nm, the brightness temperature of band 
8.8Mm and 11pm, the SST, the chlorophyll-a concentration and the KD490. In 
addition, 32 flags are associated with each pixel indicating if any of the applied 
algorithms failed or warning conditions occurred for that pixel. 
For the SST retrieval the standard MODIS 11pm SST algorithm is chosen, which 
uses the 11 and 12 micron channels. 
AVHRR SST BSH: 
Since 1990 the BSH has been receiving and processing AVHRR-data from the polar 
orbiter NOAA-satellites and since September 2009 in addition data from the 
European weather satellite MetOp by EUMETCast. BSH generates daily marine 
products including North Sea SST. The BSH data products available include the SST- 
values with a no-data value for invalid pixels on a pre-defined grid. 
MERIS OC: 
The MERIS Level-2 product is built from a corresponding Level-lb product. The 
main data contents of the product are the geophysical values for each pixel, derived 
from the Level-IB radiances by applying the radiometric correction, atmospheric 
corrections, and bio-optical algorithms. The OC retrieval algorithm used for the front 
detection is the Case 2 Regional algorithm (C2R). It performs an atmospheric 
correction above water and derives the ocean bio-optical parameters from the 
resulting water leaving reflectance. This algorithm is valid for all water types, 
including yellow substance dominated and waters with excessive back-scattering 
(Doerffer and Schiller 2008). In addition, flags are also associated with each pixel 
indicating if any algorithm failures or warning conditions occurred for that pixel such 
as high glint, aerosol as well as indicating the type of water.