Chapter 18
Eddies in the Red Sea as seen
by Satellite SAR Imagery
Svetlana S. Karimova and Martin Gade
Abstract We present the results of our observations of mesoscale and sub-mesoscale
eddies in the Red Sea based on Synthetic Aperture Radar (SAR) imagery. The dataset
used includes about 500 Envisat Advanced SAR (ASAR) images obtained in 2006–
2011 over the Red Sea. We found more than 1,000 sub-mesoscale eddies, which
manifest in the SAR imagery both due to surfactant films (“black” eddies) and
wave/current interactions (“white” eddies), depending on the local wind speed. Submesoscale eddies in the Red Sea seem to be more innumerous than in other inner
seas, presumably due to a relatively deep upper mixed layer in this basin. Moreover,
more than 50 meso- and basin-scale eddies were found, whose rotation was mostly
anti-cyclonic and whose diameters ranged up to approximately 200 km. Most of the
basin-scale eddies were found between 21 and 24
◦ N, which is in agreement with
earlier observations and with numerical modeling.
18.1 Introduction
On a basin scale the water circulation in the Red Sea has been subject of several
studies (Barale and Gade 2014, and literature therein). Most of the efforts undertaken
focused either on analyses of large-scale gyres and were based on conductivitytemperature-depth (CTD) (Woelk and Quadfasel 1996; Manasrah et al. 2004) and
expendable bathythermograph (XBT) measurements (Quadfasel and Baudner 1993)
or on numerical models (Sofianos and Johns 2003). It was shown that the general
circulation in the Red Sea is of inverse estuarine type (Sofianos and Johns 2003),
with an additional wind-driven upper layer during summer (June–September). The
presence of some recurring or persistent large-scale gyres in the northern and central
parts of the basin was reported, though there were disagreements on the gyres’
S. S. Karimova ()
Space Research Institute, Russian Academy of Sciences, Moscow, Russia
e-mail: svetlana.karimova@hzg.de
Institut für Küstenforschung, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und
Küstenforschung GmbH, Geesthacht, Germany
M. Gade
Institut für Meereskunde, Universität Hamburg, Hamburg, Germany
e-mail: martin.gade@uni-hamburg.de
V. Barale, M. Gade (eds.), Remote Sensing of the African Seas,
357
DOI 10.1007/978-94-017-8008-7_18,
© Springer Science+Business Media Dordrecht 2014
Eddies in the Red Sea as seen
by Satellite SAR Imagery
Svetlana S. Karimova and Martin Gade
Abstract We present the results of our observations of mesoscale and sub-mesoscale
eddies in the Red Sea based on Synthetic Aperture Radar (SAR) imagery. The dataset
used includes about 500 Envisat Advanced SAR (ASAR) images obtained in 2006–
2011 over the Red Sea. We found more than 1,000 sub-mesoscale eddies, which
manifest in the SAR imagery both due to surfactant films (“black” eddies) and
wave/current interactions (“white” eddies), depending on the local wind speed. Submesoscale eddies in the Red Sea seem to be more innumerous than in other inner
seas, presumably due to a relatively deep upper mixed layer in this basin. Moreover,
more than 50 meso- and basin-scale eddies were found, whose rotation was mostly
anti-cyclonic and whose diameters ranged up to approximately 200 km. Most of the
basin-scale eddies were found between 21 and 24
◦ N, which is in agreement with
earlier observations and with numerical modeling.
18.1 Introduction
On a basin scale the water circulation in the Red Sea has been subject of several
studies (Barale and Gade 2014, and literature therein). Most of the efforts undertaken
focused either on analyses of large-scale gyres and were based on conductivitytemperature-depth (CTD) (Woelk and Quadfasel 1996; Manasrah et al. 2004) and
expendable bathythermograph (XBT) measurements (Quadfasel and Baudner 1993)
or on numerical models (Sofianos and Johns 2003). It was shown that the general
circulation in the Red Sea is of inverse estuarine type (Sofianos and Johns 2003),
with an additional wind-driven upper layer during summer (June–September). The
presence of some recurring or persistent large-scale gyres in the northern and central
parts of the basin was reported, though there were disagreements on the gyres’
S. S. Karimova ()
Space Research Institute, Russian Academy of Sciences, Moscow, Russia
e-mail: svetlana.karimova@hzg.de
Institut für Küstenforschung, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und
Küstenforschung GmbH, Geesthacht, Germany
M. Gade
Institut für Meereskunde, Universität Hamburg, Hamburg, Germany
e-mail: martin.gade@uni-hamburg.de
V. Barale, M. Gade (eds.), Remote Sensing of the African Seas,
357
DOI 10.1007/978-94-017-8008-7_18,
© Springer Science+Business Media Dordrecht 2014