Abstract
Abstract. Despite Australian dust's critical role in the regional climate and surrounding marine ecosystems, the controlling factors of the spatiotemporal variations of Australian dust are not fully understood. Here we assess the connections between observed spatiotemporal variations of Australian dust with key modes of large-scale climate variability, namely the El Niño–Southern Oscillation (ENSO) and Madden–Julian Oscillation (MJO). Multiple dust observations from the Aerosol Robotic Network (AERONET), weather stations, and satellite instruments, namely the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR), are examined. The assessed multiple dust observations consistently identify the natural and agricultural dust hotspots in Australia, including the Lake Eyre basin, Lake Torrens basin, Lake Frome basin, Simpson Desert, Barwon–Darling basin, Riverina, Barkly Tableland, and the lee side of the Great Dividing Range, as well as a country-wide, austral spring-to-summer peak in dust activity. Our regression analysis of observed dust optical depth (DOD) upon an ocean Niño index confirms previous model-based findings on the enhanced dust activity in southern and eastern Australia during the subsequent austral spring and summer dust season following the strengthening of austral wintertime El Niño. Our analysis further indicates the modulation of the ENSO–dust relationship with the MJO phases. During sequential MJO phases, the dust-active center moves from west to east, associated with the eastward propagation of MJO, with the maximum enhancement in dust activity at about 120, 130, and 140∘ E, corresponding to MJO phases 1–2, 3–4, and 5–6, respectively. MJO phases 3–6 are favorable for enhanced ENSO modulation of dust activity, especially the occurrence of extreme dust events, in southeastern Australia, currently hypothesized to be attributed to the interaction between MJO-induced anomalies in convection and wind and ENSO-induced anomalies in soil moisture and vegetation.
Highlights
Australia represents a major contributor of dust to the Southern Hemisphere (Tanaka and Chiba, 2006), influencing regional climate and the marine ecosystems of the surrounding ocean basins
Multi-angle Imaging SpectroRadiometer (MISR) coarse-mode AOD (cmAOD) and nonspherical AOD (nsAOD) are generally lower than Moderate Resolution Imaging Spectroradiometer (MODIS) dust optical depth (DOD) in magnitude and exhibit minimal spatial variation
The failure of MISR in capturing the agricultural dust hotspots in Australia is likely attributed to a lack of dust–smoke mixture in the look-up table involved in the operational MISR retrieving algorithm (Kahn et al, 2010)
Summary
Australia represents a major contributor of dust to the Southern Hemisphere (Tanaka and Chiba, 2006), influencing regional climate and the marine ecosystems of the surrounding ocean basins. On longer timescales, Lamb et al (2009) revealed a pronounced and consistent dust maximum during 1959 to 1973 and a much more dust-free period after 1977 across central eastern Australia, based on the frequency of dust events reported at weather stations This regime shift in Australian dustiness was attributed to wind field changes associated with oscillations in the Pacific climate system, including the latitudinal displacement of the South Pacific Convergence Zone, and SST changes of the Pacific Decadal Oscillation and North Pacific Oscillation (Lamb et al, 2009).
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