Weather map motion. Two-dimensional streamlines based on wind speeds at various levels show areas of convergence and divergence in the wind field, which are helpful in determining the location of features within the wind pattern. A popular type of surface weather map is the surface weather analysis, which plots isobars to depict areas of high pressure and low pressure. Cloud codes are translated into symbols and plotted on these maps along with other meteorological data that are included in synoptic reports sent by professionally trained observers. The use of weather charts in a modern sense began in the middle portion of the
Closest pair of points problem left of the dividing line we have to compare the distances to the points that lie in the rectangle of dimensions bordering the dividing line on the right side, as shown in the figure. And what is more, this rectangle can contain at most six points with pairwise distances at least . Therefore, it is sufficient to compute at most left-right distances in step 4. The recurrence relation for the number of steps can be written as , which we can solve using the master theorem for divide-and-conquer recurrences to get . As the closest pair of points define an