Abstract
AbstractThe quasi‐quadrennial oscillation (QQO) and its ∼4 year period in Jupiter's atmosphere were first discovered in 7.8 μm infrared observations spanning the 1980s and 1990s from detecting semiregular variations in equatorial brightness temperatures near 10 hPa. New observations that probe between 0.1 and 30 hPa in Jupiter's atmosphere using the Texas Echelon Cross Echelle Spectrograph (TEXES), mounted on the NASA Infrared Telescope Facility, have characterized the vertical structure of the QQO during a complete cycle between January 2012 and April 2016. These new observations show the thermal oscillation previously detected at 10 hPa and that it extends over a pressure range of 2–17 hPa. We have incorporated a spectrum of wave drag parameterizations into the Explicit Planetary Isentropic Code general circulation model to simulate the observed Jovian QQO temperature signatures inferred from the TEXES observations as a function of latitude. A new stochastic wave drag parameterization explores vertical wind structure and offers insight into the spectra of waves that likely exist in Jupiter's atmosphere to force the QQO. High‐frequency gravity waves produced from convection likely contribute significantly to the QQO momentum budget. The model temperature outputs show strong correlations to equatorial and surrounding latitude temperature fields retrieved from the TEXES data sets at different epochs. Our results reproduce the QQO phenomenon as a zonal jet that descends over time in response to Jovian atmospheric forcing (e.g., gravity waves from convection).
Highlights
The quasi-biennial oscillation (QBO) in Earth’s equatorial stratosphere is an alternating pattern in the zonal wind
We have incorporated a spectrum of wave drag parameterizations into the Explicit Planetary Isentropic Code general circulation model to simulate the observed Jovian quasi-quadrennial oscillation (QQO) temperature signatures inferred from the Texas Echelon Cross Echelle Spectrograph (TEXES) observations as a function of latitude
We find that the 4 Earth year QQO period established from prior observations in the pressure range of 10–20 hPa is consistent with the thermal behavior seen in the TEXES data at a pressure of 13.5 hPa
Summary
The quasi-biennial oscillation (QBO) in Earth’s equatorial stratosphere is an alternating pattern in the zonal wind. Theories proposed by Lindzen and Holton (1968) and Holton and Lindzen (1972) assumed a steady source of equatorially trapped gravity or planetary waves that provided the momentum to drive the QBO’s wind reversals, which in turn affect the temperatures in this region of the atmosphere; see Figure 1. Most QBO theories invoke critical level absorption of vertically propagating waves such that in eastward shear zones, eastward traveling waves that encounter a zonal wind near a wave’s phase speed will cause the wave to break and deposit its momentum. The zonal wind below the critical layer is “dragged” toward the phase speed of the wave. The convention of eastward and westward is applied to winds and waves traveling to the east and to the west, respectively
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