Blar i Geophysical Institute på forfatter "Johannessen, Johnny A."
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Annual cycles of sea level and sea surface temperature in the western Mediterranean Sea
Bouzinac, Catherine; Font, Jordi; Johannessen, Johnny A. (Peer reviewed; Journal article, 2003-03-01)In the western Mediterranean Sea, sea level variations are the result of seasonal steric effect, atmospheric forcing and mesoscale circulation activity, particularly in the Alboran and Algerian basins, as well as water ... -
Coastal ocean fronts and eddies imaged with ERS 1 synthetic aperture radar
Johannessen, Johnny A.; Shuchman, Robert A.; Digranes, G.; Lyzenga, D. R.; Wackerman, C.; Johannessen, Ola M.; Vachon, P. W. (Peer reviewed; Journal article, 1996-03-15)ERS 1 C band synthetic aperture radar (SAR) data were collected during the Norwegian Continental Shelf Experiment (NORCSEX) both in November 1991 during the ERS 1 commissioning phase and at different seasons in 1992 and ... -
COASTWATCH´95: ERS 1/2 SAR detection of natural film on the ocean surface
Espedal, Heidi A.; Johannessen, Ola M.; Johannessen, Johnny A.; Dano, E.; Lyzenga, D. R.; Knulst, Johan (Peer reviewed; Journal article, 1998-10-15)Ocean mesoscale phenomena such as eddies and current convergence zones can often be seen in synthetic aperture radar (SAR) images due to characteristic patterns caused by natural film induced damping of the waves. Such ... -
Direct ocean surface velocity measurements from space: Improved quantitative interpretation of Envisat ASAR observations
Johannessen, Johnny A.; Chapron, B.; Collard, F.; Kudryavtsev, Vladimir; Mouchet, A.; Akimov, D.; Dagestad, Knut-Frode (Peer reviewed; Journal article, 2008-11-29)Previous analysis of Advanced Synthetic Aperture Radar (ASAR) signals collected by ESA’s Envisat has demonstrated a very valuable source of high-resolution information, namely, the line-of-sight velocity of the moving ocean ... -
The European gravity field and steady-state ocean circulation explorer satellite mission: its impact on geophysics
Johannessen, Johnny A.; Balmino, G.; Le Provost, Christian; Rummel, R.; Sabadini, R.; Sünkel, H.; Tscherning, C. C.; Visser, P.; Woodworth, Philip; Hughes, C. W.; Le Grand, Pascal; Sneeuw, N.; Perosanz, F.; Aguirre-Martinez, M.; Rebhan, Helge; Drinkwater, M. R. (Journal article, 2003-07)Current knowledge of the Earth’s gravity field and its geoid, as derived from various observing techniques and sources, is incomplete. Within a reasonable time, substantial improvement will come by exploiting new approaches ... -
Evaluating two numerical advection schemes in HYCOM for eddy-resolving modelling of the Agulhas Current
Backeberg, Bjørn C.; Bertino, Laurent; Johannessen, Johnny A. (Ocean Science, Journal article, 2009-06-02)A 4th order advection scheme is applied in a nested eddy-resolving Hybrid Coordinate Ocean Model (HYCOM) of the greater Agulhas Current system for the purpose of testing advanced numerics as a means for improving the model ... -
The greater Agulhas Current system: an integrated study of its mesoscale variability
Backeberg, Bjørn C.; Johannessen, Johnny A.; Bertino, Laurent; Reason, Chris J.C. (Journal of Operational Oceanography, Journal article, 2008-02)For the purpose of developing an operational oceanography system for the greater Agulhas Current regime, a high resolution Hybrid Coordinate Ocean Model (HYCOM) has been set in a nested configuration. The intense and complex ... -
Mesoscale Eddies Are Oases for Higher Trophic Marine Life
Godø, Olav Rune; Samuelsen, Annette; Macaulay, Gavin J.; Patel, Ruben; Hjøllo, Solfrid Sætre; Horne, John; Kaartvedt, Stein; Johannessen, Johnny A. (Peer reviewed; Journal article, 2012-01-17)Mesoscale eddies stimulate biological production in the ocean, but knowledge of energy transfers to higher trophic levels within eddies remains fragmented and not quantified. Increasing the knowledge base is constrained ... -
North Sea circulation: Atlantic inflow and its destination
Winther, Nina Gjerde; Johannessen, Johnny A. (Peer reviewed; Journal article, 2006-12-22)This study investigates the Atlantic inflow to the North Sea; its variabil- ity, pathways and destination. Results from a numerical model show that the variability of Atlantic inflow is dependent on the inflow location. ... -
Observation and Simulation of Ice Tongues and Vortex Pairs in the Marginal Ice Zone
Johannessen, Ola M.; Sandven, Stein; Budgell, W. Paul; Johannessen, Johnny A.; Shuchman, Robert A. (Geophysical Monograph 85, Chapter, 1994)Recognizes the major advancements of the past decade in understanding the interactions among the polar oceans and global atmospheric and oceanic systems. This volume addresses the following topics: Polar Ocean Circulation ... -
On effect of wave breaking on short wind waves
Kudryavtsev, Vladimir; Johannessen, Johnny A. (Peer reviewed; Journal article, 2004-10)The paper presents an attempt to estimate short wave generation by wave breaking. A breaking wave crest disturbs the surface and generates sub-surface turbulence. The locally disturbed area further disperses and feeds short ... -
On radar imaging of current features: 1. Model and comparison with observations
Kudryavtsev, Vladimir; Akimov, D.; Johannessen, Johnny A.; Chapron, B. (Journal article, 2005-07-22)A new radar imaging model of ocean current features is proposed. The simulated normalized radar cross section (NRCS) takes into account scattering from ‘‘regular’’ surfaces (by means of resonant Bragg scattering and specular ... -
On radar imaging of current features: 2. Mesoscale eddy and current front detection
Johannessen, Johnny A.; Kudryavtsev, Vladimir; Akimov, D.; Eldevik, Tor; Winther, Nina Gjerde; Chapron, B. (Peer reviewed; Journal article, 2005-07-22)The surface signatures of meandering fronts and eddies have been regularly observed and documented in synthetic aperture radar (SAR) images. Wave-current interactions, the suppression of short wind waves by natural film, ... -
Sensitivity of remote sensing – derived phytoplankton productivity to mixed layer depth: Lessons from the carbon-based productivity model
Milutinović, Svetlana; Behrenfeld, Michael J.; Johannessen, Johnny A.; Johannessen, Truls (Peer reviewed; Journal article, 2009-10-01)Mixed layer depth (MLD) has long been recognized as having an important influence on underwater light budget and, thus, net primary productivity (NPP) of phytoplankton. The depth- and wavelength-integrated carbon-based ... -
Temporal and spatial variability of the sea surface salinity in the Nordic Seas
Furevik, Tore; Bentsen, Mats; Drange, Helge; Johannessen, Johnny A.; Korablev, Alexander (Peer reviewed; Journal article, 2002-11-02)In this paper, the temporal and spatial variability of the sea surface salinity (SSS) in the Nordic Seas is investigated. The data include a Russian hydrographical database for the Nordic Seas and daily to weekly observations ...