TY - JOUR
T1 - Full-wave modeling of small-scale gravity waves using Airborne Lidar and Observations of the Hawaiian Airglow (ALOHA-93) O(1S) images and coincident Na wind/temperature lidar measurements
AU - Hickey, Michael P.
AU - Taylor, Michael J.
AU - Gardner, Chester S.
AU - Gibbons, Christian R.
PY - 1998/3/27
Y1 - 1998/3/27
N2 - Measurements were made of mesospheric gravity waves in the OI (5577 A) nightglow observed from Maui, Hawaii, during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) campaign. Clear, monchromatic gravity waves were observed on several nights. By using a full-wave model that realistically includes the major physical processes in this region, we have simulated the propagation of four waves through the mesopause region and calculated the O(1S) nightglow response to the waves. Mean winds derived from Na wind/temperature lidar observations were employed in the computations. Wave amplitudes were calculated based on the requirement that the observed and simulated relative airglow fluctuation amplitudes be equal. Although the extrinsic (i.e., observed) characteristics of all four waves studied were quite similar (horizontal wavelengths 9a 20 to 30 km; periods 9a 9 min; horizontal phase speeds 9a 35 to 50 m s-1), the propagation characteristics of the waves are all quite different due to the different background mean winds through which the wave propagate. Three of the waves encounter critical levels in the mesopause region. For two of these waves the upward propagation beyond the 97 km level is severely impeded by their critical levels because the local value of the Richardson number exceeds unity there. The third wave is not severely attenuated at its critical level because the Richardson number there is about 0.25. The fourth wave does not encounter a critical level although it is strongly Doppler shifted to low frequencies over a limited height range by the mean winds. It appears to be able to propagate at least to the 110 km level essentially unimpeded. This study demonstrates that an accurate description of the mean winds is an essential requirement for a complete interpretation of observed wave-driven airglow fluctuations. The study also emphasizes that although the measured extrinsic properties of waves may be similar, their propagation to higher altitudes depends very sensitively on the mean winds through which the waves propagate.
AB - Measurements were made of mesospheric gravity waves in the OI (5577 A) nightglow observed from Maui, Hawaii, during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) campaign. Clear, monchromatic gravity waves were observed on several nights. By using a full-wave model that realistically includes the major physical processes in this region, we have simulated the propagation of four waves through the mesopause region and calculated the O(1S) nightglow response to the waves. Mean winds derived from Na wind/temperature lidar observations were employed in the computations. Wave amplitudes were calculated based on the requirement that the observed and simulated relative airglow fluctuation amplitudes be equal. Although the extrinsic (i.e., observed) characteristics of all four waves studied were quite similar (horizontal wavelengths 9a 20 to 30 km; periods 9a 9 min; horizontal phase speeds 9a 35 to 50 m s-1), the propagation characteristics of the waves are all quite different due to the different background mean winds through which the wave propagate. Three of the waves encounter critical levels in the mesopause region. For two of these waves the upward propagation beyond the 97 km level is severely impeded by their critical levels because the local value of the Richardson number exceeds unity there. The third wave is not severely attenuated at its critical level because the Richardson number there is about 0.25. The fourth wave does not encounter a critical level although it is strongly Doppler shifted to low frequencies over a limited height range by the mean winds. It appears to be able to propagate at least to the 110 km level essentially unimpeded. This study demonstrates that an accurate description of the mean winds is an essential requirement for a complete interpretation of observed wave-driven airglow fluctuations. The study also emphasizes that although the measured extrinsic properties of waves may be similar, their propagation to higher altitudes depends very sensitively on the mean winds through which the waves propagate.
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U2 - 10.1029/97JD03373
DO - 10.1029/97JD03373
M3 - Article
AN - SCOPUS:0032571202
SN - 0148-0227
VL - 103
SP - 6439
EP - 6453
JO - Journal of Geophysical Research Atmospheres
JF - Journal of Geophysical Research Atmospheres
IS - D6
ER -