The Source, Size and Chemical Composition of the Winter Arctic Tropospheric Aerosol Layer Observed by Lidar at Eureka, Canada.

Ishii, Shoken; Shibata, Takashi; Sakai, Tetsu; Kido, Masaru; Hara, Keiichiro; Osada, Kazuo; Iwasaka, Yasunobu; Nagai, Tomohiro; Fujimoto, Toshifumi; Itabe, Toshikazu; Mizutani, K.; Uchino, Osamu

doi:10.2151/jmsj.79.61

Cited by 6 publications

(7 citation statements)

References 36 publications

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“…To discriminate aerosols from other atmospheric scatterers, we apply a linear depolarization threshold of 10 %. This value is con- sistent with previous measurements of aerosol depolarization ratio at Eureka (Ishii et al, 2001). While aerosol extinctions are also retrieved by the Eureka HSRL, the values are very noisy because of the very small field of view of the receiver.…”

Section: High Spectral Resolution Lidar At Eureka Canadasupporting

confidence: 91%

Spatial and seasonal distribution of Arctic aerosols observed by the CALIOP satellite instrument (2006–2012)

et al. 2013

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We use retrievals of aerosol extinction from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite to examine the vertical, horizontal and temporal variability of tropospheric Arctic aerosols during the period 2006–2012. We develop an empirical method that takes into account the difference in sensitivity between daytime and nighttime retrievals over the Arctic. Comparisons of the retrieved aerosol extinction to in situ measurements at Barrow (Alaska) and Alert (Canada) show that CALIOP reproduces the observed seasonal cycle and magnitude of surface aerosols to within 25 %. In the free troposphere, we find that daytime CALIOP retrievals will only detect the strongest aerosol haze events, as demonstrated by a comparison to aircraft measurements obtained during NASA's ARCTAS mission during April 2008. This leads to a systematic underestimate of the column aerosol optical depth by a factor of 2–10. However, when the CALIOP sensitivity threshold is applied to aircraft observations, we find that CALIOP reproduces in situ observations to within 20% and captures the vertical profile of extinction over the Alaskan Arctic. Comparisons with the ground-based high spectral resolution lidar (HSRL) at Eureka, Canada, show that CALIOP and HSRL capture the evolution of the aerosol backscatter vertical distribution from winter to spring, but a quantitative comparison is inconclusive as the retrieved HSRL backscatter appears to overestimate in situ observations by a factor of 2 at all altitudes. In the High Arctic (>70° N) near the surface (<2 km), CALIOP aerosol extinctions reach a maximum in December–March (10–20 Mm⁻¹), followed by a sharp decline and a minimum in May–September (1–4 Mm⁻¹), thus providing the first pan-Arctic view of Arctic haze seasonality. The European and Asian Arctic sectors display the highest wintertime extinctions, while the Atlantic sector is the cleanest. Over the Low Arctic (60–70° N) near the surface, CALIOP extinctions reach a maximum over land in summer due to boreal forest fires. During summer, we find that smoke aerosols reach higher altitudes (up to 4 km) over eastern Siberia and North America than over northern Eurasia, where they remain mostly confined below 2 km. In the free troposphere, the extinction maximum over the Arctic occurs in March–April at 2–5 km altitude and April–May at 5–8 km. This is consistent with transport from the midlatitudes associated with the annual maximum in cyclonic activity and blocking patterns in the Northern Hemisphere. A strong gradient in aerosol extinction is observed between 60° N and 70° N in the summer. This is likely due to efficient stratocumulus wet scavenging at high latitudes combined with the poleward retreat of the polar front. Interannual variability in the middle and upper troposphere is associated with biomass burning events (high extinctions observed by CALIOP in spring 2008 and summer 2010) and volcanic eruptions (Kasatochi in August 2008 and Sarychev in June 2009). CALIOP displays below-a...

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Section: High Spectral Resolution Lidar At Eureka Canadasupporting

confidence: 91%

Spatial and seasonal distribution of Arctic aerosols observed by the CALIOP satellite instrument (2006–2012)

et al. 2013

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“…To discriminate aerosols from other atmospheric scatterers we apply a linear depolarization threshold of 10 %. This value is consistent with previous measurements of aerosol depolarization ratio at Eureka (Ishii et al, 2001 Figure 8 shows CALIOP and HSRL vertical profiles of aerosol 180 • backscatter for January-February (JF) and March-April (MA). In JF, HSRL measurements show a maximum of 0.8 Mm −1 sr −1 below 1 km, with 55 % of the column-integrated backscatter found below 2 km (dashed red line, left panel).…”

Section: High Spectral Resolution Lidar At Eureka Canadasupporting

confidence: 91%

Spatial and seasonal distribution of Arctic aerosols observed by CALIOP (2006–2012)

Pierro¹,

Jaeglé²,

Eloranta³

et al. 2013

Preprint

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We use retrievals of aerosol extinction from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the CALIPSO satellite to examine the vertical, horizontal and temporal variability of tropospheric Arctic aerosols during 2006–2012. We develop an empirical method that takes into account the difference in sensitivity between daytime and nighttime retrievals over the Arctic. Comparisons of the retrieved aerosol extinction to in situ measurements at Barrow (Alaska) and Alert (Canada) show that CALIOP reproduces the observed seasonal cycle and magnitude of surface aerosols to within 25%. In the free troposphere, we find that daytime CALIOP retrievals will only detect the strongest aerosol haze events as demonstrated by a comparison to aircraft measurements obtained during NASA's ARCTAS mission during April 2008. This leads to a systematic underestimate of the column aerosol optical depth by a factor of 2–10. However, when the CALIOP sensitivity threshold is applied to aircraft observations, we find that CALIOP reproduces in situ observations to within 20% and captures the vertical profile of extinction over the Alaskan Arctic. Comparisons with the ground-based HSRL Lidar at Eureka, Canada, show that CALIOP and HSRL capture the evolution of the aerosol backscatter vertical distribution from winter to spring, but a quantitative comparison is inconclusive as the retrieved HSRL backscatter appears to overestimate in situ observations factor of 2 at all altitudes. In the High Arctic (> 70° N) near the surface (< 2 km), CALIOP aerosol extinctions reach a maximum in December-March (10–20 Mm<sup>−1</sup>), followed by a sharp decline and a minimum in May–September (1–4 Mm<sup>−1</sup>), thus providing the first Pan-Arctic view of Arctic Haze seasonality. The European and Asian Arctic sectors display the highest wintertime extinctions, while the Atlantic sector is the cleanest. Over the Low Arctic (60–70° N) near the surface, CALIOP extinctions reach a maximum over land in summer due to boreal forest fires. During summer, we find that smoke aerosols reach higher altitudes (up to 4 km) over Eastern Siberia and North America than over Northern Eurasia, where it remains mostly confined below 2 km. In the free troposphere, the extinction maximum over the Arctic occurs in March–April at 2–5 km altitude and April–May at 5–8 km. This is consistent with transport from the mid-latitudes associated with the annual maximum in cyclonic activity and blocking patterns in the Northern Hemisphere. A strong gradient in aerosol extinction is observed between 60° N and 70° N in the summer. This is likely due to efficient stratocumulus wet scavenging at high latitudes combined with the poleward retreat of the polar front. Interannual variability in the middle and upper troposphere is associated with biomass burning events (high extinctions observed by CALIOP in spring 2008 and summer 2010) and volcanic eruptions (Kasatochi in...

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“…However, a few sea‐salt particles (a few%) were observed in middle free troposphere (3–6 km asl) on 26 March, 12 April, and 17 April. The presence of sea‐salt particles in the Arctic free troposphere was also suggested by Ishii et al [2001]. Sea‐salt particles are dominantly emitted from the open‐sea‐surface, so that they might be transported over relatively long range in the middle‐upper troposphere.…”

Section: Resultsmentioning

confidence: 77%

“…As suggested by Shapiro et al [1987], Raatz [1993], and Zahn [2001], mixing or exchange of air mass between the midlatitudes and the polar region might occur in the upper troposphere around the latitudes of 65-75°N. As mineral/dust particles can be transported from the arid regions and industrial regions in the midlatitudes to Arctic regions through the cyclonic systems and blocking conditions [Raatz, 1993;Ishii et al, 2001], the obtained mineral/dust particles around the jet stream on 17 and 19 April might be derived from not only the industrial regions in the Arctic circle (e.g., Russian) but also the arid and industrial regions in midlatitudes.…”

Section: Mixing States and Distributions Of Other Particulate Speciesmentioning

confidence: 99%

Mixing states of individual aerosol particles in spring Arctic troposphere during ASTAR 2000 campaign

Hara¹

2003

J. Geophys. Res.

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The present study mainly focuses on the mixing states of aerosol constituents and their vertical distribution in spring Arctic troposphere during the ASTAR 2000 campaign (T. Yamanouchi et al., Arctic Study of Tropospheric Aerosol and Radiation (ASTAR) campaign: An overview and first results, submitted to Bulletin of the American Meteorological Society, 2002) (hereinafter referred to as Yamanouchi et al., submitted manuscript, 2002). Sulfate and soot were identified as major aerosol under both Arctic haze and background conditions, and sea‐salts are major only in lower troposphere (<3 km above sea level). Mineral/dusts and unknown species were obtained as minor constituents during the ASTAR 2000 campaign. Airborne aerosol measurements were carried out under the Arctic haze (23 March), and aerosol‐enriched (20 March and 12 April) conditions. The highest relative abundance of soot (∼94.7%) was observed in free troposphere on 23 March, when the heaviest Arctic haze condition during the ASTAR 2000 campaign (Yamanouchi et al., submitted manuscript, 2002) was transported directly from Russian industrial regions to the measuring area for several days. Moreover, whereas the external mixing of soot and sulfate dominated under the Arctic haze and aerosol enriched conditions, in the background conditions the internal mixing is dominant. On the other hand, most of aerosol particles containing sulfate had the external mixing states with soot and other aerosol constituents in the free troposphere under both the Arctic haze and background conditions. Sea‐salts are dominant only in the lower troposphere (<3 km asl), although a few sea‐salt particles were observed in the middle‐upper troposphere (3–7 km). Some sea‐salt particles were modified (Cl− depleted) in the lower troposphere (<3 km) during the ASTAR 2000 campaign.

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The Source, Size and Chemical Composition of the Winter Arctic Tropospheric Aerosol Layer Observed by Lidar at Eureka, Canada.

Cited by 6 publications

References 36 publications

Spatial and seasonal distribution of Arctic aerosols observed by the CALIOP satellite instrument (2006–2012)

Spatial and seasonal distribution of Arctic aerosols observed by the CALIOP satellite instrument (2006–2012)

Spatial and seasonal distribution of Arctic aerosols observed by CALIOP (2006–2012)

Mixing states of individual aerosol particles in spring Arctic troposphere during ASTAR 2000 campaign

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