Geoscience Reference
In-Depth Information
products to end-users. Since 2006, the MarCoast service has been providing infor-
mation on oil spills and water quality including information on chl-
a
concentration,
SPM load, water transparency, and SST. The standard products of the WAQSS moni-
toring system are thematic maps of the North Sea and the Baltic Sea, including daily
animations. The end-users can also request specific, custom-made products.
Another web-based information system for water quality products, specifically
for the lakes Vänern, Vättern, and Mälaren, has been developed by Vattenfall
Power Consultant Sweden (
www.vattenkvalitet.se
). This service has recently
been extended to the coastal areas of the northwestern Baltic Sea, including
Himmerfjärden bay and the Stockholm Archipelago and is currently extended to
the Gulf of Bothnia. The water quality products include distribution of SPM, chl-
a
,
and CDOM, derived from MODIS and MERIS data. Interactive maps are provided
together with web-based user interface.
20.2.2 Autonomous Systems for Sea-Truthing of Satellite Data
20.2.2.1 The FerryBox System
The Baltic Sea is a productive ecosystem with strong nutrient input and frequent
algal bloom development. In coastal areas the water mass exchange rates are high.
For adequate monitoring of these highly dynamic areas it is necessary to develop
monitoring systems that provide both a good temporal and a good spatial resolu-
extend the two-dimensional coverage from satellite data through high frequency,
one-dimensional transects from ships of opportunity and vertical measurements
from oceanographic buoys at selected locations. The resulting operational system
has a well-resolved temporal and spatial resolution. Figure
20.7
shows an example
from the operational FerryBox website, where satellite products can be controlled
with FerryBox data near real time.
A typical FerryBox system consists of automated sensors for measuring tem-
perature, salinity, turbidity, and chlorophyll
-a
in vivo fluorescence. The data are
transmitted to a station on land in real time via Internet, GPRS, or GMS connec-
tion. The Norwegian Institute for Water Research (NIVA) make their water quality
products available on a web map server (
www.ferrybox.no
).
The FerryBox system is also equipped with an automatic, cooled water sampler
that is used to take discrete water samples for calibrating the automatic sensors
and also serves as sea-truthing data for satellite observations. The water samples
are taken into harbour and subsequently analysed in the laboratory. Chlorophyll
-a
in vivo fluorescence can be used as a proxy for chlorophyll
-a
concentration, but it
must be calibrated against measured chlorophyll
-a
. The turbidity sensor data can be
used as a proxy for TSM after calibration of turbidity against TSM concentration.
The measured water quality samples can also be used directly to validate satellite
data when the sample meets the satellite match-up criteria of water sampling within
half an hour of the satellite overpass.
