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Published July 1941 | Published
Journal Article Open

Atmospheric-pressure waves near Pasadena

Abstract

In a previous paper [see 1 of "References" at end of paper] the authors have described results obtained from records of electromagnetic microbarographs. These experiments have been continued, and special interest has been given to the rather regular waves with periods of usually 2 to 5 seconds, which have been called "microbaroms" in the earlier paper. In January, 1940, a barograph with a larger loudspeaker-element was installed at point 2a, Figure 1, and connected with a galvanometer, constructed by F. Lehner, at the Seismological Laboratory, having a free period of about ½ second. This instrument has recorded regularly on a drum with a speed of one mm per second. The older two instruments were connected with Lehner galvanometers and remained at points 1 and 2a, respectively. Records were taken at irregular intervals with various speeds of recording, up to five cm per second. In December, 1940, a third instrument of this type was added. Figure 2a was taken with the three instruments side by side and shows that their characteristics were alike within small limits. From December 26, 1940, to March 31, 1941, the three instruments were located at the points 1, 2b, and 3 of Figure 1, respectively, and recorded usually twice every day for about one hour with a speed of three mm per second. Figures 2b, 2c, and 2d show examples of the records. The distances are as follows: 1 to 2a, 130 meters (426 feet); 1 to 2b, 320 meters (1,050 feet); 2b to 3 , 290 meters (950 feet); 3 to 1, 264 meters (865 feet). Instruments 1 and 3 are in dense shrubs under high trees; instrument 2b is under small shrubs without trees. In general, the records of instrument 2b were much more frequently disturbed by wind than those of the other two. Besides, during the day and sometimes at night there appear to be more or less regular air-currents up or down the slope near 2b.

Additional Information

© 1941 American Geophysical Union. Contribution 312, Balch Graduate School of the Geological Sciences, California Institute of Technology.

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August 19, 2023
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October 23, 2023