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Abstract
Abstract. Unusual aerosol enhancement is often observed at Syowa Station, Antarctica, during winter and spring. Simultaneous aerosol measurements near the surface and in the upper atmosphere were conducted twice using a ground-based optical particle counter, a balloon-borne optical particle counter, and micropulse lidar (MPL) in August and September 2012. During 13–15 August, aerosol enhancement occurred immediately after a storm condition. A high backscatter ratio and high aerosol concentrations were observed from the surface to ca. 2.5 km over Syowa Station. Clouds appeared occasionally at the top of the aerosol-enhanced layer during the episode. Aerosol enhancement was terminated on 15 August by strong winds from a cyclone's approach. In the second case, on 5–7 September, aerosol number concentrations in Dp > 0.3 μm near the surface reached > 104 L−1 at about 15:00 UT (Universal Time) on 5 September despite calm wind conditions, whereas MPL measurement exhibited aerosols were enhanced at about 04:00 UT at 1000–1500 m above Syowa Station. The aerosol enhancement occurred near the surface to ca. 4 km. In both cases, air masses with high aerosol enhancement below 2.5–3 km were transported mostly from the boundary layer over the sea-ice area. In addition, air masses at 3–4 km in the second case came from the boundary layer over the open-sea area. This air mass history strongly suggests that dispersion of sea-salt particles from the sea-ice surface contributes considerably to aerosol enhancement in the lower free troposphere (about 3 km) and that the release of sea-salt particles from the ocean surface engenders high aerosol concentrations in the free troposphere (3–4 km). Continuous MPL measurements indicate that high aerosol enhancement occurred mostly in surface–lower free troposphere (3 km) during the period July–September.
Highlights
The Antarctic region, which is isolated from human activity on other continents of low latitudes and midlatitudes, is regarded as the cleanest on the Earth
Tethered balloon-borne aerosol measurements over Syowa Station in 2005 revealed that aerosols were enhanced in the boundary layer and lower free troposphere, and that sea-salt particles were dominant under the aerosol-enhanced conditions (Hara et al, 2011b, 2013)
This study focused on occurrence of Antarctic haze over Syowa Station in 2012, the occurrence of Antarctic haze and its vertical and seasonal features over longer periods will be discussed elsewhere
Summary
The Antarctic region, which is isolated from human activity on other continents of low latitudes and midlatitudes, is regarded as the cleanest on the Earth. Tethered balloon-borne aerosol measurements over Syowa Station in 2005 revealed that aerosols were enhanced in the boundary layer and lower free troposphere, and that sea-salt particles were dominant under the aerosol-enhanced conditions (Hara et al, 2011b, 2013). These measurements provided important knowledge, especially knowledge related to the thickness of the aerosol-enhanced layer and aerosol constituents, but the time series of vertical distributions of aerosol properties under the Antarctic haze (aerosol enhancement) conditions have never been reported. This investigation aimed to understand vertical structures and seasonal features of Antarctic haze (aerosol enhancement) based on the simultaneous aerosol measurements conducted over Syowa Station, Antarctica
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