Vertical heat and constituent transport in the mesopause region by dissipating gravity waves at Maui, Hawaii (20.7°N), and Starfire Optical Range, New Mexico (35°N)

Abstract

Vertical heat flux profiles induced by dissipating gravity waves in the mesopause region (85–100 km altitude) are derived from Na lidar measurements of winds and temperatures at Maui (20.7°N, 156.3°W), Hawaii, and compared with earlier results from Starfire Optical Range (SOR, 35.0°N, 106.5°W), New Mexico. The heat flux profile at SOR has a single downward maximum of 2.25 ± 0.3 K m/s at 88 km, while the profile at Maui has two downward maxima of 1.25 ± 0.5 K m/s and 1.40 ± 0.5 K m/s at 87 and 95 km, respectively. The common maximum below 90 km can be attributed to high probability of convective instability. Comparison of the horizontal wind shear suggests that the second maximum at 95 km at Maui may be associated with dynamic instability. The measured Na flux and predicted Na flux based on measured heat flux at Maui agree well, further confirming earlier findings using SOR data. The dynamical flux of atomic oxygen estimated from the heat flux is smaller at Maui compared with that at SOR, but both are comparable to or larger than the eddy flux. The results also suggest that weaker gravity wave dissipation at Maui may cause two opposite effects on the energy balance in the mesopause region, a reduced cooling from heat transport and reduced chemical heating from atomic oxygen transport.