Halogen Occultation Experiment observations of the quasi‐biennial oscillation and the effects of Pinatubo aerosols in the tropical stratosphere

The time series of Halogen Occultation Experiment (HALOE) observed mixing ratios of chemical tracers in the tropical stratosphere (O3, HCl, HF, CH4, NO2, NO, and H2O) exhibit obvious quasi‐biennial oscillatory (QBO) characteristics. The pressure‐time cross sections for the QBO signals in the mixing ratios of HCl, HF, CH4, NO, and H2O are presented for the first time. The QBO in O3 and NO2 exibits similar amplitudes and patterns as observed and analyzed previously. An apparent in‐phase relationship between O3 and NO2 above 4 mbar is noted, which implies that ozone QBO may not be caused by NO2 chemical destruction in the upper stratosphere. During the early time period of the UARS mission (late 1991 to early 1992), the QBOs in most HALOE species are seen to be strongly affected by Pinatubo aerosols. In order to quantitatively define the different aerosol effects (heating versus chemical) from HALOE data, we calculate the vertical displacements of constant volume mixing ratio surfaces of HALOE‐measured species in the tropical lower stratosphere. The time evolutions of the vertical displacements of HCl and NOx (HALOE NO2 + NO) isopleths are seen to approximately follow that of HF. This indicates that the enhanced vertical velocity that acts to uplift the tracer profiles due to aerosol radiative heating is a significant effect. However, because of the uncertainty in the vertical displacement analyses of these tracers from HALOE data, it can only be concluded that changes in HCl and NOx from chemical effects are less than 30% and 80%, respectively.