National Geographic : 1900 Feb
KITE WORK OF THE WEATHER BUREAU cally the same, the differences being confined to a deflection toward the right at the kite. This deflection frequently increased with the altitude, but rarely exceeded 90 degrees. In some few instances the kite was deflected toward the left, but not to any great extent. When the deflection was toward the left, the wind velocity decreased with increase of altitude, as shown by the diminished pull on the kite wire. As a matter of interesting coincidence, and without intention of en deavoring to establish a direct relation of cause and effect between the two, it may also be stated that these deflections toward the left were quite frequently followed by thunderstorms within a few hours. At Duluth, Minn., there were occasionally wide divergencies of the kite toward the left, due to the northeast wind from Lake Superior. This northeast wind was very often purely local, attributable entirely to the influence of the lake, and corresponding in a minor way to the sea breezes of the ocean shores. It developed upon investigation that these local currents were sometimes not more than 700 or 800 feet in depth, and rarely more than 2,000 feet. Hammon * and McAdie recorded a somewhat similar experience with the westerly surface winds at San Francisco during their kite experiments in 1896, and in his paper on the subject Mr Hammon concluded that the strong westerly surface wind which prevails on the Pacific Coast nearly every afternoon has a depth of only 800 to 2,500 feet. An extension of the aerial observations to other seacoasts would doubtless prove conclusively that the diurnal sea breezes are extremely shallow. After November, 1898, all kite stations were closed except that at Pierre, S. Dak., where ascensions were made whenever possible dur ing the year 1899, and still continue. No extended study of the ob servations made during this time has as yet been made, but a cursory examination of the winter temperature records discloses a condition of affairs radically different from that which prevails during the re maining seasons of the year. The inversions are very frequent and decidedly marked. Indeed they are so persistent during the colder weather as to lead to the inevitable conclusion that during a cold wave the belt of cold air is not much over one mile in height, and often but little over half a mile. On several days it was also noticed that there were at least three * Experiments with Kites at San Francisco, Cal., by W. H . Hammon, forecast official. Monthly Weather Review, August, 1896.