A pervasive and persistent Asian dust event over North America during spring 2010: lidar and sunphotometer observations

Abstract

Among the many well-documented cases of springtime trans-Pacific transport of crustal dust from Asia to North America (significant events include those of 1998, 2001, and 2005), the events of March and April 2010 were extraordinary both in the extent of the dust distribution and in the unique meteorological conditions that caused the dust layers in the free troposphere to linger and be detectable across Canada and the northern United States for over a month. This study focuses on extending previous research by combining data from CORALNet (Canadian Operational Research Aerosol Lidar Network) lidars in Vancouver, BC, and Egbert, ON, with AERONET (AErosol RObotic NETwork) sunphotometer retrievals and model results from HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) and NAAPS (Navy Aerosol Analysis and Prediction System) to monitor the arrival and distribution of dust layers across North America. This is the first documented instance of lidar detection of Asian dust from the Egbert CORALNet installation, where layers identified as dust using depolarization ratios corresponded with retrievals of coarse-mode optical depth at the co-located AEROCAN/AERONET site. In Vancouver dust layer depolarization ratios varied from 0.27 for dust above 6 km to less than 0.10 for the first 1.5–2 km above the surface. Similar layers of elevated dust exhibited much lower volume depolarization ratios for all altitudes in Egbert, ON, where maximum depolarization ratios stayed below 0.15 for all layers from 2–8 km with no clear variation with altitude, or over time. The relative lack of variation is an indication that as the layers of dust were transported across North America the rates of change in their optical properties slowed. HYSPLIT back trajectories performed throughout the free troposphere above these sites showed a majority of air parcels originating from central Asia on the days in question. Using these techniques, it was shown that elevated layers of aerosol reaching the west coast of North America as early as 17 March also included dust from the same central Asian sources, extending the known duration of the 2010 event by almost a full month

East Asian dust storm in May 2017: observations, modelling, and its influence on the Asia-Pacific region

“…Fine particulates reaching high altitudes may be transported by tropospheric winds (Shao, 2000;Eguchi et al, 2009). Trans-Pacific transport of mineral dust from East Asia to North America has been frequently detected during springtime (Merrill et al, 1989;Mahowald et al, 1999;Zhao et al, 2003;McKendry et al, 2008;Cottle et al, 2013a). Longrange transport of dust aerosol has been substantiated by ice core samples taken at the North Pole (Jaffe et al, 1999;Mahowald et al, 2017).…”

“…Unfortunately, lidar observations in Beijing were not possible on 6 May due to routine maintenance. In the lidar measurement for this study, the well-mixed boundary layers in East Asia, prior to the obvious intermingling of subsiding layers from above, show depolarization ratios 150-250 % higher than boundary layers in North America (Cottle et al, 2013a). This indicates that dust clouds moved across the North China Plain at altitudes < 1500 m. Our lidar observations of dust being uplifted to altitudes of 3.5 km above the Korea Peninsula and Japan agree closely with those of Murayama et al (2001) who observed dust being uplifted to altitudes of 3 km over Japan and 4-5 km over the Korean Peninsula as a result of a wind erosion event in northwestern China and Mongolia in 1998.…”

“…The ground-based lidars were developed by the Japanese National Institute for Environmental Studies (NIES) and operated as part of the Japanese NIES lidar network and AD-Net (Murayama et al, 2001;. Dust particles tend to be highly non-spherical and show a high degree of depolarization (Cottle et al, 2013a); therefore we used non-spherical data observed by the lidar network. Depolarization at dual-wavelength channels of 1064 and 532 nm was used to identify aerosol types from the lidar measurements .…”

“…Mineral aerosols can influence air quality by reducing visibility and bolstering concentrations of inhalable particulate matter (Sharratt and Lauer, 2006;Huneeus et al, 2011;Goudie, 2014). In dust source regions, atmospheric dust concentrations can approach 1-10 mg m −3 , while dust particles can be uplifted to altitudes of 2-10 km under strong wind shear stress (McTainsh and Strong, 2007;Cottle et al, 2013a;Shao et al, 2013;Goudie, 2014). Fine particulates reaching high altitudes may be transported by tropospheric winds (Shao, 2000;Eguchi et al, 2009).…”

Integrated Analysis of Dust Transport and Budget in a Severe Asian Dust Event

“…Some studies have reported that Asian dust aerosols can be transported to vast downwind areas, including the coastal seas of China, Korea, Japan, and even North America (Fang et al, 1999;Mori et al, 2002;Zhao et al, 2011;Cottle et al, 2013;Li et al, 2015). These transported aerosols are often mixed with high concentrations of regional pollution aerosols that largely reduce visibility and worsen air quality in downwind areas of East Asia (Guo et al, 2013).…”