Appendix C 



Upgrade of Environmental Inputs to Iceberg 



Forecasting Models 



LCDR Walter E. Hanson, Jr. 



INTRODUCTION 



The International Ice Patrol (IIP) 

 uses two numerical models in its 

 operations: an iceberg drift model 

 and a model to estimate deteriora- 

 tion. The currently-used drift 

 model (Mountain, 1980) balances 

 iceberg acceleration, air and water 

 drag, the coriolis acceleration and 

 a sea-surface slope term. The 

 iceberg deterioration model 

 (White, et al 1980 and Anderson, 

 1983) sums the effects of calving 

 from wave erosion, heat convec- 

 tion from the relative movement of 

 the iceberg through the water, 

 buoyant heat convection, and 

 solar radiation. 



Both of HP's models require 

 substantial input data. The drift 

 model requires marine surface 

 wind and oceanic current data for 

 its twice-daily drift predictions. 

 The deterioration model, which is 

 run once each day, requires sea 

 surface temperature (SST), wave 

 height, and wave period data. 

 Most of these data requirements 

 (all except oceanic current data) 

 are filled by the U. S. Navy's Fleet 

 Numerical Oceanography Center 

 (FLENUMOCEANCEN), located in 

 Monterey, California. All of the 

 data are transferred to IIP over 

 telephone lines using the Navy/ 

 NOAA Ocean Data Distribution 

 System (NNODDS). 



Recently, close cooperation 

 between FLENUMOCEANCEN 

 and IIP oceanographers has 

 resulted in significant improve- 

 ments in the inputs to HP's mod- 

 els. The efforts are occurring in 

 two areas. First, with USN help. 



IIP is making use of the latest in 

 the rapidly-improving suite of 

 I^lENUMOCEANCEN data 

 products. Second, IIP has been 

 working to increase its oceano- 

 graphic data collection in its 

 operating area (40°N - 52°N, 

 39°W - 57'='W), recognizing that if 

 FLENUMOCEANCEN receives 

 more and better data, then prod- 

 ucts will improve. The following 

 two sections briefly describe some 

 of the recent activities in each 

 area. 



ENVIRONMENTAL PRODUCTS 



Wind 



HP's iceberg drift model requires a 

 96-hour wind history for its air drag 

 calculations. To satisfy this 

 requirement FLENUMOCEANCEN 

 produces a 12-hour averaged 

 wind field for IIP from its Navy 

 Operational Global Atmospheric 

 Prediction System (NOGAPS) 

 (NEPM, 1986) marine surface 

 wind. It is a thermally-stable wind 

 at 19.5 m above the sea surface. 



NOGAPS calculates wind vectors 

 on a geographically referenced 

 projection with a grid spacing of 

 approximately 250 km. FLE- 

 NUNOCEANCEN lineraly-interpo- 

 lates the wind to approximately 

 140 km grid-spacing for use in the 

 IIP model. The data are provided 

 twice a day (OOOOZ and 1200Z), 

 with forecasts for each 12 hours 

 out to 36 hours. 



Beginning in mid-March 1989, 

 FLENUMOCEANCEN will provide 

 IIP with marine surface winds 

 interpolated for 10 m above the 

 sea surface (NOGAPS 3.1). Since 

 marine wind speeds vary logarith- 

 mically with height above the sea 

 surface, and because wind forcing 

 plays an important role in estimat- 

 ing the drift of small icebergs, 

 particularly growlers, this 10 m 

 wind should improve IIP iceberg 

 drift predictions. 



The linear interpolation used by 

 FLENUMOCEANCEN to produce 

 ICEWINDS at 140 km grid-spacing 

 does not adequately represent 

 mesoscale features, such as 

 meteorological waves. By sum- 

 mer 1989, FLENUMOCEANCEN 

 plans to spectrally interpolate the 

 winds (NOGAPS 3.2). This will 

 better describe wind curvature 

 along mesoscale features and 

 should improve the direction of the 

 wind forcing component. The grid- 

 spacing of this product will be 155 

 km, thus no further interpretation 

 will be required to use the data in 

 the IIP drift model. 



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