Abstract

Solar tides are thermally driven perturbations excited throughout the atmosphere that vary with local time and season; however not all sources of tidal variability are known. The Quasi-biennial Oscillation (QBO) is an oscillation in the stratospheric zonal winds near the equator with a 27.7-month... Show moreSolar tides are thermally driven perturbations excited throughout the atmosphere that vary with local time and season; however not all sources of tidal variability are known. The Quasi-biennial Oscillation (QBO) is an oscillation in the stratospheric zonal winds near the equator with a 27.7-month cycle that solar tides propagate through. This research examined the QBO effects on diurnal solar tides using a comprehensive model of the entire atmosphere called the Whole Atmosphere Community Climate Model (WACCM). Representative observational data of the QBO were inserted into WACCM to see if the QBO is a source of diurnal solar tidal variability. Hourly fields from three simulations for April were used to assess solar tidal variability with distinct stratospheric winds over the equator: control (no QBO), QBO winds from the east, and QBO winds from the west. These results were sorted and binned according to local time at each latitude and altitude. This produced monthly averaged meridional winds as a function of local time for April. A harmonic decomposition was performed on the meridional winds to determine the diurnal means, amplitudes, and phases of the three simulations. A comparison of the diurnal mean and amplitude revealed that the diurnal mean is not measurably affected by the QBO, but the QBO produces a 20 (m/s) difference in the diurnal amplitude. The latter result was highly significant, indicating that the QBO is a source of solar tidal variation in WACCM. In addition, this research further evaluates the performance of WACCM and provides insight into the underlying physical processes that govern tidal variability in the upper atmosphere. Show less