APPENDIX C 



"SEARCH" COMPUTER PROGRAM DESCRIPTION 



By R. Q. Robe 

 U.S. Coast Guard Research and Development Center 



"SEARCH" is a computerized data storage and 

 retrieval system adapted to International Ice 

 Patrol (IIP) dynamic height data requirements. 

 All historical dynamic height data are indexed 

 by 20 minute latitude and longitude intervals, 

 month, and year. "SEARCH" permits monthly 

 and yearly comparisons to be made between dy- 

 namic heights on file. The method used is to 

 calculate the sum of the squares of the differences 

 in dynamic height for corresponding locations 

 between the month and year of interest and all 

 other month and year data sets on file. Squaring 

 the difference eliminates negative values prior to 

 summing. The sum of the squares of the differ- 

 ence in dynamic heights between the reference 

 month and a historical month is calculated only 

 for the area of common geographical coverage. 

 When all sums of squares of differences in dy- 

 namic height have been calculated, they are 

 ranked from least sum upward. The sum of the 

 squares value should be treated as an ordering 

 index only and does not have any physical sig- 

 nificance. "SEARCH" also supplies the number 

 of dynamic height data points in each of the sets 

 (month and year) used in the comparison and 

 the number from each set that coincide with those 

 of the reference set. 



The "SEARCH" program output is designed 

 as an aid to IIP oceanographers in making better 

 use of the dynamic height data collected each 

 season by the IIP oceanographic vessel. It is 

 based on the assumption that history repeats it- 

 self to the extent that over a large number of 



years the current systems in the IIP area of 

 interest will show characteristics which are simi- 

 lar to other seasons. The months and years 

 picked for use from the ordered list by the 

 oceanographer should have a low sum of squares 

 and a high percentage of data locations in com- 

 mon with the reference month. 



An example will be instructive. Input 96 

 dynamic height data points from May 1975 as the 

 reference month. Comparisons are made with 

 data file and the following output is produced. 

 The oceanographer would then scan the output 

 and take a closer look at those months which have 

 a low sum of squares (the output ranks only the 

 top 25 possibilities) and also a high number of 

 data point locations in common with the reference 

 month. Probably the best months to look at 

 would be April 1959, May 1959, June 1959, May 

 1952, April 1939, and May 1958. The dynamic 

 height charts for these months can be examined 

 for the best qualitative fit with the reference 

 month. From this point, those months which 

 compare well can be used to qualitatively extend 

 the boundaries of the survey area and aid in 

 matching the contours of dynamic heights of the 

 reference data to those on the IIP normal charts 

 (which are included in the data file along with 

 the historical data). In this example, May 1975 

 compared well with April, May. and June 1959. 

 Thus it is likely that the current system in 1975 

 would be very similar to that in 1959. Given the 

 same availability of icebergs in both years, simi- 

 lar drift patterns can be expected. 



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