Dust and pollution transport on global scales: Aerosol measurements and model predictions

Abstract

Abstract. Vertical profiles of aerosol and gas phase species were measured on flights near Hawaii on April 9 and 10, 1999, during NASA' s Pacific Exploratory Mission (PEM) Tropics B program. These measurements characterized aerosol microphysics, inferred chemistry, optical properties, and gases in several extensive dust and pollution plumes, also detected by satellites, which hart 1 o,ooo-gan trajectories back to sources in Asia. Size-resolved measurements indicative of aerosol sulfate, black carbon, dust, light scattering, and absorption allowed determination of their concentrations and contributions to column aerosol optical depth. A new Chemical Transport Model (CTM) that includes aerosol, meteorological fields, dynamics, gas and particle source emissions, a chemistry component (MATCH), and assimilated satellite data was used to predict aerosol and gas concentrations and the aerosol optical effects along our flight path. Flight measurements confirmed the "river-like" plume structures predicted by the CTM and showed close agreement with the predicted contributions of dust and sulfate to aerosol concentrations and optical properties for this global-scale transport path. Consistency between satellite, model and in situ assessment of aerosol optical depth was found, with noted exceptions, within •25%. Both observations and model results confirmed that this aerosol was being entrained into the marine boundary layer between Hawaii and California where it can be expected to modify the type and concentration of cloud condensation nuclei in ways that may alter properties of low-level clouds. These observations document the significance and complexity of long-range aerosol transport and highlight the potential of emerging CTM models to extend observational data and address related issues on global scales.

Columnar aerosol single‐scattering albedo and phase function retrieved from sky radiance over the ocean: Measurements of Saharan dust

“…Alternatively, hematite, a naturally occurring iron oxide that absorbs strongly in the visible and near-infrared [Sokolik and Toon, 1999], could have been present in significantly greater quantities in the dust samples. Interestingly, in situ aircraft measurements of mineral dust aerosol of Asian origin also indicate a similar weak absorption [Clarke et al, 2001].…”

Particulate air pollution in Lanzhou China

“…This is caused by the transport of the TSP due to dust storms. Recent studies indicate that dust storms originated in the East Asia not only influence air pollution in the origins and their neighboring regions Murayama et al, 2001;Sun et al, 2001;Zhou et al, 2002), but also have a long-distance effect across Pacific by atmospheric circulation (Husar et al, 2001;Tratt et al, 2001;Sun et al, 2001;Laat et al, 2001;Clarke et al, 2001). The major sources of the dust storms are the Gobi desert in Mongolia and northern China and Taklimakan desert in western China (Sun et al, 2001).…”

Impact of Asian dust and continental pollutants on cloud chemistry observed in northern Taiwan during the experimental period of ABC/EAREX 2005

“…Asian mineral dust can be transported by the prevailing westerlies in the spring [e.g., Zhang et al, 1997], increasing particulate matter concentrations [e.g., Liu et al, 2006;Park et al, 2008] and pH values of rainwater [Wang et al, 2002] and cloud water in downwind areas. Aircraft observations through Asian outflow over the Asian continent [Dickerson et al, 2007] and the northwest Pacific Jordan et al, 2003;Maxwell-Meier et al, 2004], and in transpacific Asian plumes over the northeast Pacific [Andreae et al, 1988;Clarke et al, 2001;Price et al, 2003], have provided evidence of aerosol transport in the lower free troposphere. They reveal the spring months to be the time of maximum trans-Pacific transport of outflow and anthropogenic emissions associated with Asian dust, resulting in combined dust and pollution signatures in measurements of nominal air mass characteristics.…”