Analysis of the Internal Gravity Wave Occurrence of 19 April 1970 in the Midwest

Abstract

An analysis is made of high frequency, fluctuations of surface pressure and wind with a period of 3–4 h observed in the midwestern United States in the early morning hours of 19 April 1470. The phenomenon is shown to be of subsynoptic scale and clear interrelationships are established between the surface pressure, wind, and cloudiness variations. Solutions from a simple model of atmospheric dynamics for a compressible and hydrostatic flow are compared with the observations. It is shown that the fluctuations in the atmosphere correspond well to simple gravity wave concepts and in particular to internal gravity waves propagating to the northeast with an approximate speed of 50 m/s and an average wavelength of 500 km.