What would this time series look like if the very short term variability was also largely removed? To explore that, here are the 15-day moving averages of ADA (“adjusted daily averages”):
This smoothed anomaly data has the appearance of oscillatory behavior. Typically, about every 25 to 40 days, the troposphere (as represented by the channel 5 data) warms and then cools by 0.1 to 0.2 K.
Is this oscillatory appearance confined to 2005-2006? No. A similar plot covering eight years (2003-2010) is here . The 2005-2006 data is representative of the full period.
Regarding the oscillation period, a plot of the period (days between peaks) for 2003-2010 is here . Most of the days-between-peaks are between 20 and 45 days, a bit shorter than the 30 to 60 day oscillation period generally associated with the Madden-Julian Oscillation (MJO).
If the oscillation is associated with a real tropospheric oscillation or pattern, which one?
Among the candidates (thanks to WUWT for a list ) are the Madden Julian Oscillation (MJO), Arctic Oscillation, Antarctic Oscillation, North Atlanic Oscillation, Southern Oscillation, Pacific North American Index, East Pacific North Pacific Pattern, West Pacific Pattern, Pacific Transition Pattern, Tropical Northern Hemisphere Pattern, Polar Eurasian Pattern, Scandanavian Pattern, 27-Day UV Oscillation and Stratospheric Antarctic Intraseasonal Oscillation.
The physical nature of such an apparent temperature oscillation, whatever its name or association and assuming that it’s real, is intriguing.
* Does the oscillation represent changes in heat input, such as changes in tropical thunderstorms moving energy from the surface layer into the mid troposphere?
* Does it involve changes in the rate of energy loss to outer space, perhaps from changes in water vapor/cloud coverage?
* Is it associated with changes in atmospheric angular momentum? Does it involve a negative feedback mechanism?
* Is it a stratospheric phenomenom, not tropospheric, the result of contamination of channel 5 data by its stratospheric component?
* If it is tropospheric, does the oscillation affect tropospheric water vapor content?
* Is the oscillation a local intense event or is it diffused across the globe?
* Does its amplitude have any relationship to the timing or severity of extreme events (an interest of mine)?
The conventional candidate is MJO but I’ve found little relationship between ADA and the traditional MJO indicators like tropical OLR and zonal wind variability.