Horizontal and vertical heat fluxes between 85 and 100 km were computed using temperature and wind profiles observed on 21 October 1993 by the Na Wind/Temperature lidar operated at Haleakala during the ALOHA‐93 Campaign. On this night a warm layer developed between 85 and 90 km. The temperature increased by almost 40 K near 88 km, reaching a maximum of approximately 235 K at 1030 UT before decreasing throughout the remainder of the 5 h observation period. This substantial temperature increase was associated with a large amplitude wave, possibly the diurnal tide, and with a sporadic Na layer. The meridional wind field exhibited a strong vertical shear zone within the warm layer and sporadic Na layer which briefly exceeded the shear instability limit of ≈ 42 m/s/km at the time the temperature reached maximum. The vertical heat flux was directed upward within the warm layer reaching maximum at 88 km and downward above resulting in strong flux convergence. The average heat fluxes between 85 and 100 km were 2.5±2.4 K m/s (vertical), 77±25 K m/s (zonal), and −19±20 K m/s (meridional). The maximum heating rate associated with the convergence of vertical heat flux was 11±4.1 K/h at 91 km. The average heating rate between 85 and 100 km was 1.9±0.8 K/h.
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)