Sea Surface Temperature 



Sea surface temperature is the 

 most important input to HP's 

 iceberg deterioration model. 

 Currently, the SST data used in 

 the model are from 

 FLENUlVlOCEANCEN's Expanded 

 Ocean Thermal Structure (EOTS) 

 analysis (NEPM, 1986). The 

 temperatures are for 1 m below 

 the sea surtace and are deter- 

 mined on a relatively coarse 320 

 km gird. As with the wind data, 

 the temperatures are interpolated 

 to a 140 km grid for use in the IIP 

 model. The temperature field is 

 valid for OOOOZ. Using the tem- 

 perature at the predicted OOOOZ 

 iceberg position, IIP models 

 iceberg deterioration over the 

 previous 24 hours. 



The major problem with the 

 coarsely-spaced EOTS tempera- 

 ture data was that it could not 

 represent the spatial variability in 

 the vicinity of the Grand Banks, 

 where the cold (3°C), narrow (50 

 km wide) iceberg-carrying Labra- 

 dor Current converges with the 

 warm (12°C) North Atlantic 

 Current. FLENUMOCEANCEN 

 worked with IIP to improve the 

 database and now provides a 

 composite SST field, which has a 

 35 km grid-spacing. FLE- 

 NUIVIOCEANCEN extracts data 

 from the global EOTS, a regional 

 Gulf Stream EOTS, and the 

 Labrador Sea EOTS products. 

 This FLENUMOCEANCEN effort 

 greatly improved the SST input to 

 the IIP deterioration model. The 

 new product, when "bogused", 

 agrees well with observations and 



82 



with the SST analyses produced 

 by Canadian Forces fvlETOC 

 Halifax. (Bogusing is the means 

 by which discontinuities, in this 

 case oceanid fronts, precludes 

 numerical models from blending 

 dissimilar data sets (Hawkins et al, 

 1986).) 



Wave Height and Period 



Wave height and period input is 

 produced by the FLE- 

 NUf^^OCEANCEN Global Spectral 

 Ocean Wave IVIodel (GSOWM) 

 (Clancy etal, 1986). The 

 GSOWI^ field is produced on a 

 geographically-referenced projec- 

 tion with a grid-spacing of approxi- 

 mately 235 km. FLE- 

 NUIVIOCEANCEN linearly-interpo- 

 lated it to approximately 140 km 

 grid-spacing. 



FLENUMOCEANCEN has pro- 

 vided twice daily now casts (valid 

 for OOOOZ and 1200Z) of wave 

 height, period and direction since 

 1983. The direction parameter is 

 not used by IIP since the deterio- 

 ration model assumes an omni- 

 directional wave field. Prior to 

 June 1988, significant wave height 

 and primary wave period were 

 provided. In June 1989 IIP began 

 receiving concurrently significant 

 wave height, primary wave period, 

 sea height, and sea period. Sea 

 height and period are derived from 

 a sea/swell separation algorithm 

 implemented in GSOWM (Clancy, 

 1987). 



In August 1988 IIP substituted sea 

 height and sea period for signifi- 

 cant wave height and primary 

 wave period respectively. 



DATA COLLECTION 



This year, all of the environmental 

 products have also been improved 

 by U. S. Navy support of new IIP 

 data collection efforts. This 

 provider/user cooperation signifi- 

 cantly improved Labrador Sea 

 temperature products and pro- 

 vided important barometric 

 pressure information in normally 

 data-sparse areas of the NW 

 Atlantic. Much of the IIP operating 

 area is often obscured by clouds 

 and fog, which limits the use of 

 satellite-derived temperature data. 

 The ice conditions, prevalent 

 through most of the year, also limit 

 shipping, thus synoptic weather 

 reports, in the northern part of the 

 IIP region. 



IIP, with technical and logistic 

 support from the Naval Oceano- 

 graphic Office, developed a 

 portable Air-droppable expend- 

 able BathyThermograph (AXBT) 

 system (Alfultis, 1988), which 

 accompanied nearly all HC-130 

 iceberg reconnaissance flights. 

 AXBTs were dropped near oce- 

 anic fronts and a Motorola AN/ 

 APS-135 side-looking airborne 

 radar mapped sea surface rough- 

 ness. Based on IIP procedures 

 derived from three years of 

 research (Thayer et al, 1988), the 

 radar imagery was used to infer 

 the presence of oceanic fronts. 

 JJXX messages were sent to both 

 FLENUMOCEANCEN and the U. 

 S. Navy Eastern Oceanography 

 Center (NAVEASTOCEANCEN), 

 located in Norfolk, Virginia; the 

 radar interpretation was telecopied 

 to NAVEASTOCEANCEN. 



