I04 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. JO 



more important for the surface temperatures, the direction of the 

 wind or its strength. Furthermore the influence on the surface 

 temperature is certainly not simply proportional to the strength of 

 the wind and still less is it proportional to the sine of the angle, 

 positive or negative, which the wind makes with the direction of 

 the normal wind.^ But in spite of this inaccuracy the process gives 

 the means of determining the influence of the wind on the variations 

 of the surface temperature qualitatively and to a certain degree 

 quantitatively at least in the colder part of the year, with which we 

 have here to do. 



ANGLE BETWEEN THE DIRECTIONS OF THE ISOBARS AND 

 THE ISOTHERMS 



The average isobar directions for January, February, and March 

 for the eleven-year period 1898 to 1908 are given in tables 12D and 

 1 3D, and for January and February they are also given on the 

 chart, figure 7 (see also pi. i, and for March, pi. 7). The relation 

 between these isobar directions and the directions of the isotherms 

 is of interest. In most of our 10° longitude fields the isotherms 

 cut the average direction of the isobars in a pretty constant angle 

 (see chart fig. 7). An exception appears in the four eastern fields 

 near the Spanish Peninsula, as well as in the most westerly field 

 near the American coast. The same holds for the two fields south 

 of Newfoundland Bank where the current direction is strongly 

 influenced by the ocean bottom. Also in the four fields for the 

 Danish observations north of 50° north latitude, the isotherms do 



^ Several considerations may be mentioned which have an influence but which 

 the method takes no notice of. For example, if the isobars in a field during a 

 month have a normal direction, then the deviation angle is equal to 0° and the 

 product of the sine with reciprocal value of the air pressure gradient will 

 also be equal to o, however great the latter value may be. Now it is possible 

 that the increased strength of a wind of a favorable direction tends to raise 

 the surface temperature in a field with warm ocean currents on the surface. 

 Thus the increase of the strength of the wind even if it blows in the normal 

 direction may produce an increase of the surface temperature because it in- 

 creases the velocity of a warm current. Indeed it is possible that a wind which 

 is uncommonly strong may raise the temperature even if it comes from a 

 direction which would have a negative sine value to the normal direction. 

 We can make no consideration of these conditions in our process. On the 

 other hand, it is not certain that an increase in the strength of the warm wind, 

 that is to say, one whose direction is on the positive side of the normal direc- 

 tion, would always have the tendency to raise the surface temperature of the 

 ocean. 



