Analysis of ALOHA-93 Campaign Data in Terms of Gravity and Tidal Wave Modes: Considerations on the Jet Stream as a Gravity-Wave Source.

摘要

We report on two particular phenomena observed in the ALOHA-93 Campaign. On 20 Oct 1993, the data showed a sudden sharp rise in temperature over an exceedingly narrow height range, with an initially modest temperature peak at 93 km rising to a peak value two hours later at a height of 88 km, then subsiding to a much smaller value near 87 km some 4-1/2 hours later. The second phenomenon is the simultaneous observation of OH airglow wave structure propagating along an azimuth of 340 deg with a phase speed of 35 m/s, a horizontal wavelength of 80 km remaining for the duration of temperature- inversion layer observation. Our analysis shows that a critical layer exists at about 87 km between the beginning of observation at 0830 UYT until after 1200 UT. By plotting The vertical gradient of horizontal wind we show that it has a maximum in the 340-160 deg direction. By plotting the Richardson number vs height, we show that the shear grows and becomes sufficiently large to initiate the KH instability only over a height range of 2 to 3 km centered at 87-88 km between 1000 and 1230 UT. We conclude that the source 0 energy and momentum for the temperature inversion layer and associated large wind shear observed near 88 km is a downward-propagating gravity wave interacting with the total background wind field, including the diurnal tide.