Interannual variations of middle atmospheric temperature as measured by the JPL lidar at Mauna Loa Observatory, Hawaii (19.5°N, 155.6°W)

The Jet Propulsion Laboratory Rayleigh-Raman lidar at Mauna Loa Observatory (MLO), Hawaii (19.5 degrees N, 155.6 degrees W) has been measuring atmospheric temperature vertical profiles routinely since 1993. Linear regression analysis was applied to the 13.5-yearlong (January 1994 to June 2007) deseasonalized monthly mean lidar temperature time series for each 1-km altitude bin between 15 and 85 km. The regression analysis included components representing the Quasi-Biennial Oscillation (QBO), El Nino-Southern Oscillation (ENSO), and the 11-year solar cycle. Where overlapping was possible, the results were compared to those obtained from the twice-daily National Weather Service (NWS) radiosonde profiles at Hilo (5 -30 km) located 60 km east-north-east of the lidar site, and the four-times-daily temperature analysis of the European Centre for Medium Range Weather Forecast (ECMWF). The analysis revealed the dominance of the QBO (1 -3 K) in the stratosphere and mesosphere, and a strong winter signature of ENSO in the troposphere and lowermost stratosphere (similar to 1.5 K/MEI). Additionally, and for the first time, a statistically significant signature of ENSO was observed in the mesosphere, consistent with the findings of recent model simulations. The annual mean response to the solar cycle shows two statistically significant maxima of similar to 1.3 K/100 F10.7 units at 35 and 55 km. The temperature responses to QBO, ENSO, and solar cycle are all maximized in winter. Comparisons with the global ECMWF temperature analysis clearly showed that the middle atmosphere above MLO is under a subtropical/ extratropical regime, i. e., generally out-of-phase with that in the equatorial regions, and synchronized to the northern hemisphere winter/spring.