Tidal Response of the Mesosphere/Lower Thermosphere to the Madden-Julian Oscillation

Abstract:

Tides are key to understanding the connection between tropospheric weather/climate and space weather/climate. Tropospheric convection associated with the Madden-Julian Oscillation (MJO) has been known to modulate the intensity of upward-propagating gravity waves and Kelvin waves. An impact on tides was already proposed over two decades ago but only recent progress in data analysis now allows one to quantify the effect from observations. 18 years of daily atmospheric tidal diagnostics (observed by the SABER instrument onboard the TIMED satellite) at altitudes 60-105 km reveal a statistically significant intraseasonal tidal modulation as a response to the MJO. The preliminary results show that the magnitude of the response is on the order of ± 20% (~0.5-2 K) of the seasonal mean depending on the MJO phase. The tidal response to the MJO is present across all seasons. This paper statistically characterizes and investigates the physical mechanisms responsible for the MJO responses in the upper atmosphere region. Our results further point to an important role of background winds that partly cause a different response for equatorial and non-equatorial tidal modes in different seasons, which has implications for the MJO imprint on the ionospheric dynamo region and also the GOLD, ICON, COSMIC-2, and GDC mission objectives.