The OMEGA-2 Western Mediterranean Cruise (D244) took place during December 1996, in the Alboran Sea (34.8 - 37.2°N, 3°W - 1°E).

Satellite and aircraft data are being used to establish a temporal and spatial context for the in situ measurements and to explore the extent to which surface signatures are representative of the underlying water column. During the cruise remotely sensed data were also used in near real-time to aid cruise planning. The principal sources were infra red images of sea surface temperature (SST) obtained by the AVHRR sensor on NOAA satellites, sea surface height measured by radar altimeters on ERS-2 and TOPEX/POSEIDON, and SSTs given by an infra red radiometer flown on the UK Met. Office's Hercules.

Sea Surface Height

TOPEX altimeter data were processed by NOAA, Washington to give sea surface heights every 0.1° latitude relative to a pass earlier in the year along the same ground track . The data were sent by email to the ship. Similar data were available from ERS-2 but with the difference that the referencing to an earlier pass was carried out on the ship. Although this information is limited by the infrequency of the passes and the narrowness of the swath it does provide data on subsurface flow and is not constrained by cloud conditions. Because of the higher variability observed on one particular track it was decided to include this transect as one of the legs in the fine scale.

Sea Surface Temperature

The AVHRR data were acquired by NERC's Dundee Satellite Receiving Station and processed by NERC's Remote Sensing Data Analysis Service . The Research Vessel Services then compressed and forwarded data to the ship in Near Real Time.

During the first part of the OMEGA-2 cruise several cloud free images were obtained e.g.

These showed the location of the Almeria-Oran Front, the east Alboran gyre and warm water intrusions to the east of the Front. There was a strong correspondence with SST gradients measured from the ship during the initial large scale surveys. In particular the surface signatures were shown to extend well below the surface and so could be used with confidence in mapping dynamically significant structures. This information was an important input into designing the orientation and size of the fine scale surveys.

Along Track Scanning Radiometer (ATSR) data is being collected for the OMEGA-2 cruise period: Browse these images.

NERC's Atmospheric Research Airborne Support Facility and the UK Met. Office's Research Flight (MRF) used a Hercules aircraft to over-fly the observational area on two consecutive days, 14 and 15 December 1996, spending approximately 8 hours in the air after taking off from Valencia in Spain.

On both days the aircraft carried out vertical profiles from 27,000 ft to 50 ft (for radiation and aerosol studies), large scale SST mapping close to a height of 300 ft and some low level inter-comparisons with the ship in which the aircraft passed within 50 ft laterally at an altitude of 100 ft. On approaching the ships position significant aspects of the temperature, humidity and wind profiles were obtained from the most recent radiosonde ascent and relayed to the aircraft.

Maps for the combined aircraft surveys:

Altitude (m)	Air Temperature (°C)
Sea Surface Temperature (°C)	Interpolated sea surface temperature (°C)