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L.M. Mitnik and V.A. Dubina
SeaWiFS and Landsat ETM+, together with in-situ quasi-simultaneous measurements of ocean colour and SST, has opened a new era for observations of upper
ocean circulation, air-sea-ice interaction, biological productivity, and coastal environmental monitoring. In the following, the role and importance of integration
of SAR, visible, IR and passive microwave data is considered in the context of
detecting and interpretating oceanic processes.
The examples shown here were selected mostly from the archives of SAR images
and ancillary remote and/or in-situ observations of the northwestern Pacific Ocean
and the Indonesian Seas. They cover various oceanic processes, for which the
application of orbital SAR is well established. The high spatial resolution of the
SAR datasets (25–150 m) is significantly better than that provided by MODIS and
AVHRR (visible and IR images with resolution ranging from approximately 250
m to 1 km), AMSR-E (fields of the brightness temperatures T B s at frequencies
in the range of 6.9–89.0 GHz, with resolution of 5–20 km) and the scatterometer
QuikSCAT (fields of the sea surface wind with resolution of 12.5–25 km). Further,
in contrast to SAR observations, visible observations of the sea surface are limited
by the availability of sunlight, while both visible and IR observations are further
limited by the presence of clouds.
In the following, the mesoscale variability addressed will focus mostly on that
of eddies of various scales, including those in the marginal ice zone, frontal features, and internal waves (IWs) in the Japan Sea (Section 7.2), Okhotsk Sea and
Kuroshio-Oyashion frontal zone (Section 7.3) and Indonesian Seas (Section 7.4).
These phenomena are detected by SAR and thermal IR sensors, due to the high SST
gradients along the current/eddies boundaries, and visible sensors, due to the sea surface roughness anomalies induced by short-wave-current interaction (Johannessen
et al., 1996; Ufermann et al., 2002; Gagliardini and Clemente Colón, 2004). Finally,
Section 7.5 will provide a summary of the cases presented as well as a future
outlook.
7.2 Oceanic Phenomena in the Japan Sea
Test cases to study SAR oceanic signatures in the Japan Sea demonstrate the effectiveness of combining SAR images with information obtained by other satellite
sensors. The Japan Sea may be thought of as a miniature ocean, since it “possesses
a western boundary currents as the East Korean Warm Current, a mid-ocean jet as
one of two branches of the Tsushima Current, a polar front as the northern boundary
of the Tsushima Current” (Ichie, 1984). Figure 7.1 shows a map of the area and the
major circulation features of the Japan Sea.
This sea is characterized by great variability in the upper 200-m layer where
water properties are altered by lateral exchanges through the shallow straits and
vertical exchanges with the atmosphere. At the scales of 10–500 km, the upper column is known to be a combination of warm and cold currents, eddies and upwelling
zones. At still lesser scales, a significant contribution to the variability gives the
narrow streamers of the warmer and colder water, IWs, river plumes, etc.
L.M. Mitnik and V.A. Dubina
SeaWiFS and Landsat ETM+, together with in-situ quasi-simultaneous measurements of ocean colour and SST, has opened a new era for observations of upper
ocean circulation, air-sea-ice interaction, biological productivity, and coastal environmental monitoring. In the following, the role and importance of integration
of SAR, visible, IR and passive microwave data is considered in the context of
detecting and interpretating oceanic processes.
The examples shown here were selected mostly from the archives of SAR images
and ancillary remote and/or in-situ observations of the northwestern Pacific Ocean
and the Indonesian Seas. They cover various oceanic processes, for which the
application of orbital SAR is well established. The high spatial resolution of the
SAR datasets (25–150 m) is significantly better than that provided by MODIS and
AVHRR (visible and IR images with resolution ranging from approximately 250
m to 1 km), AMSR-E (fields of the brightness temperatures T B s at frequencies
in the range of 6.9–89.0 GHz, with resolution of 5–20 km) and the scatterometer
QuikSCAT (fields of the sea surface wind with resolution of 12.5–25 km). Further,
in contrast to SAR observations, visible observations of the sea surface are limited
by the availability of sunlight, while both visible and IR observations are further
limited by the presence of clouds.
In the following, the mesoscale variability addressed will focus mostly on that
of eddies of various scales, including those in the marginal ice zone, frontal features, and internal waves (IWs) in the Japan Sea (Section 7.2), Okhotsk Sea and
Kuroshio-Oyashion frontal zone (Section 7.3) and Indonesian Seas (Section 7.4).
These phenomena are detected by SAR and thermal IR sensors, due to the high SST
gradients along the current/eddies boundaries, and visible sensors, due to the sea surface roughness anomalies induced by short-wave-current interaction (Johannessen
et al., 1996; Ufermann et al., 2002; Gagliardini and Clemente Colón, 2004). Finally,
Section 7.5 will provide a summary of the cases presented as well as a future
outlook.
7.2 Oceanic Phenomena in the Japan Sea
Test cases to study SAR oceanic signatures in the Japan Sea demonstrate the effectiveness of combining SAR images with information obtained by other satellite
sensors. The Japan Sea may be thought of as a miniature ocean, since it “possesses
a western boundary currents as the East Korean Warm Current, a mid-ocean jet as
one of two branches of the Tsushima Current, a polar front as the northern boundary
of the Tsushima Current” (Ichie, 1984). Figure 7.1 shows a map of the area and the
major circulation features of the Japan Sea.
This sea is characterized by great variability in the upper 200-m layer where
water properties are altered by lateral exchanges through the shallow straits and
vertical exchanges with the atmosphere. At the scales of 10–500 km, the upper column is known to be a combination of warm and cold currents, eddies and upwelling
zones. At still lesser scales, a significant contribution to the variability gives the
narrow streamers of the warmer and colder water, IWs, river plumes, etc.