Californian forest fire plumes over Southwestern British Columbia: lidar, sunphotometry, and mountaintop chemistry observations

Abstract

Abstract. Forest fires in Northern California and Oregon were responsible for two significant regional scale aerosol transport events observed in southern British Columbia during summer 2008. A combination of ground based (CORALNet) and satellite (CALIPSO) lidar, sunphotometry and high altitude chemistry observations permitted unprecedented characterization of forest fire plume height and mixing as well as description of optical properties and physicochemistry of the aerosol. In southwestern BC, lidar observations show the smoke to be mixed through a layer extending to 5-6 km a.g.l. where the aerosol was confined by an elevated inversion in both cases. Depolarization ratios for a trans-Pacific dust event (providing a basis for comparison) and the two smoke events were consistent with observations of dust and smoke events elsewhere and permit discrimination of aerosol events in the region. Based on sunphotometry, the Aerosol Optical Thicknesses (AOT) reached maxima of ∼0.7 and ∼0.4 for the two events respectively. Dubovikretrieval values of r eff,f during both the June/July and August events varied between about 0.13 and 0.15 µm and confirm the dominance of accumulation mode size particles in the forest fire plumes. Both Whistler Peak and Mount Bachelor Observatory data show that smoke events are accompanied by elevated CO and O 3 concentrations as well as elevated K + /SO 4 ratios. In addition to documenting the meteorology and physic-chemical characteristics of two regional scaleCorrespondence to: I. McKendry (ian@geog.ubc.ca) biomass burning plumes, this study demonstrates the positive analytical synergies arising from the suite of measurements now in place in the Pacific Northwest, and complemented by satellite borne instruments.

Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo

“…Smoke clouds and other regions of aged smoke reside significantly higher than their plumes of origin (e.g., McKendry et al, 2011;Paris et al, 2009;Guan et al, 2010;Tosca et al, 2011). In Borneo smoke plumes, relative and absolute height initially decrease down-plume before increasing toward the plume end (Fig.…”

“…drought), the similarities in height distribution about the ABL suggest that processes governing the vertical distribution of plumes can be similar in geographically disparate regions. Aged plumes no longer associated with a clear fire source (hereinafter called smoke clouds, as per Tosca et al, 2011) can reach significantly greater heights, with Californian smoke several days old reaching 5 km (McKendry et al, 2011), while Siberian smoke events averaging 5.5 days old reached from 1.5 to 6 km (Paris et al, 2009). Additionally, smoke clouds are often located significantly higher than predicted by their aerosol indices (Guan et al, 2010), and higher than their plumes of origin (Tosca et al, 2011).…”

Developing a portable, autonomous aerosol backscatter lidar for network or remote operations

“…Heavily forested areas make up much of the northern and southern landscape around the CORALNet UBC site. As a result the area can frequently be impacted by forest fire plumes during the summer months (McKendry et al, 2011). The CORALNet UBC site is located just south of the major metropolitan area of Vancouver and shares the same Lower Fraser Valley that is surrounded by tall mountains to the north, east and south.…”

“…It provides a critical component into understanding whether the high-altitude observatory is sampling free tropospheric air or air from the village in the valley below or nearby biogenic sources. It also provides complementary data to the CORALNet UBC lidar when looking for similarities and differences of these long-range transport events (McKendry et al, 2011).…”

“…Particulate matter is tiny particles suspended in the air and depending on their size and the meteorological conditions can travel great distances around the globe (Uno et al, 2009;McKendry et al, 2007). Some occur naturally: biogenic substances ), volcanoes (O'Neill et al, 2012Schumann et al, 2011;Winker et al, 2012), dust storms (Ben-Ami et al, 2009;Fischer et al, 2011;Liu et al, 2008;McKendry et al, 2009;Yumimoto et al, 2010), forest and grassland fires (Dirksen et al, 2009;McKendry et al, 2011) and sea spray (Kunz et al, 2002), while others result from human activities (anthropogenic), such as burning fossil fuels (Komppula et al, 2012), industrial by-products (Strawbridge, 2006) and altering natural surface cover (Real et al, 2010). Obtaining vertical profiles of tropospheric aerosols provides critically important information towards understanding climate, air quality and visibility.…”