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Concentrations and distributions of stratospheric aerosol, hydrogen fluoride and ozone from the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) are used to investigate features associated with transport by the secondary meridional circulation induced by the quasi-biennial oscillation (QBO). The points of maxima in the divergence and convergence of the QBOinduced meridional velocity at the equator are identified from the meridional gradients of the tracers. Such points can be identified from the tracer fields in the westerly shear zones but not in the easterly shear zones. The temporal variation of tracer concentration at the equator is determined mainly by vertical advection, which is significantly larger during the westerly shear phase of the QBO than during the easterly shear phase, since the QBO-induced equatorial sinking motion amplifies the vertical gradient. Thus, the vertical advection associated with the secondary circulation has a stronger influence on the equatorial tracer variation during the westerly shear phase than during the easterly shear phase.

Asian dust aerosols are composed of quartz, plagioclase, K-feldspar, calcite, and phyllosilicates. The optical constants for mixtures of these minerals are important not only to understand the effects of Asian dust on climate but also to retrieve the properties of Asian dust. In this work, the optical constants for labradorite and orthoclase, representative minerals of plagioclase and K-feldspar, respectively, are determined for the spectral range of 500-2000 cm À1 using bidirectional reflectance data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer. Assuming an internal mixture of component minerals, the effective refractive indices for Asian dust are calculated using Bruggeman's rule. The results are proposed as optical constants for Asian dust and differ from those for other dust aerosols, such as the refractive indices for "Saharan dust" derived from aerosol samples collected at Barbados. The imaginary refractive index for Asian dust is larger, indicating more absorptive, than the index for Saharan dust in the range of 1000-1300 cm À1. Using the optical constants derived in this study, the brightness temperatures of satellite measurements are simulated for typical loading scenarios of Asian dust aerosols. The simulated brightness temperatures exhibit a notable decrease with wave number in the region of 800-1000 cm , can also be simulated using the derived optical constants for Asian dust.

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Asian dust aerosols consist of various minerals, such as quartz, clay minerals, feldspars, and calcite. Complex refractive index of Asian dust is determined for a spectral range from 0.2 to 1.0 μm, assuming that the particles are an internal mixture of the component minerals in dust samples reported in previous literature. The derived optical constants for Asian dust are quite different from the refractive indices for other desert dusts. The imaginary refractive index for Asian dust is much smaller than that of the “mineral” model in Optical Properties of Aerosols and Clouds (OPAC) across the whole range. At wavelengths shorter than 650 nm, the present imaginary index is smaller than the index for Saharan dust, determined from mineralogical compositions of dust samples at Tinfou, Morocco, during the Saharan Mineral Dust Experiment (SAMUM). The simulated spectrum for an Asian dust event on 15 March 2009 in north‐east China using the present optical constants agree well with the spectrum measured by the Ozone Monitoring Instrument (OMI) on board the Aura spacecraft.