A reexamination of the QBO period modulation by the solar cycle

Abstract

[1] Using the updated Singapore wind from 1953 to 2007 for the lower stratosphere 70-10 hPa, courtesy of Barbara Naujokat of Free University of Berlin, we examine the variation of the period of the Quasi-Biennial Oscillation (QBO) as a function of height and its modulation in time by the 11-year solar cycle. The analysis is supplemented by the ERA-40 reanalysis up to 1 hPa. Previously, it was reported that the descent of the easterly shear zone tends to stall near 30 hPa during solar minimum, leading to a lengthened QBO westerly duration near 44-50 hPa and the reported anticorrelation of the westerly duration and the solar cycle. Using an objective method, continuous wavelet transform (CWT), for the determination of local QBO period, we find that the whole QBO period is almost invariant with respect to height, so that the stalling mechanism affects only the partition of the whole period between easterly and westerly durations. Using this longest data set available for equatorial stratospheric wind, which spans five and half solar cycles (six solar minima), we find that in three solar minima, the QBO period is lengthened, while in the remaining almost three solar cycles, the QBO period is lengthened instead at solar maxima. We suggest that the decadal variation of the QBO period originates in the upper stratosphere, where the solar-ozone radiative influence is strong. The solar modulation of the QBO period is found to be nonstationary; the averaged effect cannot be determined unless the data record is much longer. In shorter records, the correlation can change sign, as we have found in segments of the longest record available, with or without lag.

Examining the stratospheric response to the solar cycle in a coupled WACCM simulation with an internally generated QBO

“…This correlation changes sign over ∼ 40 year periods, indicating the change in the QBO period is not directly forced by the solar cycle. This result is in agreement with Fischer and Tung (2008), who analyzed an equatorial zonal wind data set and found that while the QBO period was anticorrelated with the solar cycle during the first three solar cycles, it became positively correlated in the latter three cycles. There is one caveat regarding our internally generated QBO: since the internally generated QBO in the WACCM4 simulations is forced primarily by a parameterization of inertial gravity waves (Xue et al, 2012), the source of the waves is largely deterministic.…”

“…This change in the period was shorter than the observed 3-6 month variation found in Salby and Callaghan (2000), but larger than the ∼ 1 month variation found in an earlier model study by McCormack (2003). Fischer and Tung (2008), however, provide results from an equatorial zonal wind data set showing that the QBO period was anticorrelated with the solar cycle during the first three solar cycles during this period and positively correlated in the latter three cycles. The modulation of the QBO by the solar cycle remains an open question.…”

Global and long-term comparison of SCIAMACHY limb ozone profiles with correlative satellite data (2002–2008)

“…In the case of monthly mean ozone data the trend model should, in addition to the constant term and the linear trend, include harmonic terms representing seasonal variations and QBO (quasi-biennial oscillation) frequencies and phases. For instance Fischer and Tung (2008) revealed dominant QBO frequencies during the first decade in this century with periods of 26, 27, 28 and 29 months. Fitting all four nearby frequencies simultaneously may result in undesirable beat frequencies.…”

Diagnosis of Annual Synchronization of the Quasi-Biennial Oscillation: Results from JRA-25/JCDAS Reanalysis and MRI Chemistry-Climate Model Data

“…Note that the modulation by the solar cycle is nonstationary in time and induces some uncertainty (Hamilton 2002;Fischer and Tung 2008). It is also shown in GCM and chemistry climate model (CCM) studies that simulated QBO-like oscillations change with global warming (Kawatani et al 2011;Shibata and Deushi 2012).…”