Direct comparison of extinction coefficients derived from Mie-scattering lidar and number concentrations of particles, subjective weather report in Japan

https://doi.org/10.1016/j.jqsrt.201412005 Get rights and content

Highlights

  • Two components of extinction coefficient (dust and sphere) below 500 m are continuously retrieved by several lidars in Japan.
  • Number concentration of particles measured at the surface by OPC corresponded with dust/sphere extinction coefficients.
  • Kosa (Asian dust) reported at meteorological observatories sometimes do not suite with dust extinction coefficient by lidar.
  • Report of En׳mu (haze) and period of higher spherical extinction coefficient were well corresponded.

Abstract

Two components of the lidar extinction coefficient, the dust extinction and the spherical particles extinction, were obtained from observations made by the National Institute for Environmental Studies lidar network in Japan. These two extinctions were compared with the number concentration of particles measured by an optical particle counter, and with subjective weather reports recorded at the nearest meteorological observatories. The dust extinction corresponded well with the number concentration of large particles with diameters as great as 5μm and during dry conditions with the number concentration of particles larger than 2μm. The relationship between the spherical particle extinction and the number of small particles was nearly constant under all conditions. Asian dust was sometimes reported by meteorological observatories in the period of lower dust extinction. This indicates contradicting relationship between human-eye based reports and optical characteristics observed by lidars in some cases. The most consistent results between lidar observation and meteorological reports were obtained in dry mist conditions, in which lidars exhibited higher spherical extinction as expected by the definition of the atmospheric phenomenon of dry mist or haze.

Introduction

Light detection and ranging (lidar) with polarization is a powerful technique for distinguishing non-spherical Asian dust and spherical (liquid droplet) particles in the troposphere [1], [2]. Sugimoto et al. [3] and Shimizu et al. [4] have proposed a method that separates aerosol extinction coefficients into two categories: dust extinction and spherical extinction. Dust extinction (extD), in particular, has been used in variety of applications related to Asian dust, including, inter alia, data assimilation and epidemiology [5], [6], [7]. Spherical extinction (extS) has also been used to evaluate seasonal and long-term variations of the abundance of anthropogenic particles in East Asia [8], [9]. However, there has been no thorough comparison of these two extinction coefficients with other metrics of particle characteristics obtained by independent measurements. For example, Sugimoto et al. [3] and Shimizu et al. [10] have reported a relationship between extD and the total mass of suspended particulates (TSP) based on filter sampling data during dense Asian dust events at Beijing and several stations in Japan, respectively. Kaneyasu et al. [11] showed that there was a relationship between extD and the mass of iron (Fe) on sample filters. They also reported a relationship between extD and the difference between the concentrations of suspended particulate matter (SPM) and particulate matter smaller than 2.5μm (PM2.5) during Asian dust periods in Japan. This difference is considered to be a measure of the mass of coarse particles. Spherical extinction (extS) has not been compared with other metrics directly, although Hara et al. [9] have reported temporal variations of extS similar to those of satellite-based aerosol optical depth (AOD). Sakai et al. [12] compared mass concentrations and backscatter coefficients in Tsukuba for two cases: dust and sea salt.
Furthermore, the relationship between official records of haze, mist, Asian dust, etc. reported by meteorological observatories (weather reports) and extinction coefficients determined from lidar data are important, because citizens are sensitive to announcements from observatories and expect extinction coefficients estimated by lidar to agree with such official announcements. Although official records are qualitative because judgments are subjective, official records have a long history and wide coverage in East Asia. For future applications, it will be important to have quantitative understanding of the characteristics of the official record.
In this paper, extD and extS values are compared with measurements of number concentrations made with an optical particle counter (OPC) and with atmospheric phenomena recorded in the official weather reports of local observatories of Japan Meteorological Agency (JMA). Measurement methods and comparisons are described in Section 2, and Section 3 includes comparisons of extD and extS results with OPC data and weather reports. Concluding remarks follow.

Section snippets

Lidar equipment and data analysis

Each lidar constructed by the National Institute for Environmental Studies (NIES) for the lidar network automatically measures the vertical profile of backscatter intensity at wavelengths of 532 and 1064 nm every 15 min with a vertical resolution of 6 m, up to 18 km regardless of weather condition. The depolarization ratio, which is an indicator of the non-spherical nature of particles in the measurement volume, is also measured at 532 nm. Vertical profiles of extinction coefficients with a vertical

OPC

Scatter diagrams of the simultaneously measured NC(0.5), NC(2.0), and NC(5.0) and the two extinctions are shown in Fig. 4 using all data from 2011 and 2012. If all data are included, no correlation between NC and extD or extS is apparent. The most apparent correlation is between NC(0.5) and extS. The implication is that the spherical extinction determined by lidar is related to the number concentration of small particles. The relationship for other pairs was strongly dependent on the ambient

Summary and conclusions

Extinction estimated from lidar data was compared with independent measurements to assess the characteristics of two metrics obtained from lidar measurements: the dust extinction coefficient and the spherical particle extinction coefficient.
It is apparent that the correlation between the extinctions and number concentrations of particles of various diameter depended on the ambient humidity. During dry conditions, both NC(5.0) and NC(2.0) were in fairly good agreement with the extD. The

Acknowledgments

This study was partly supported by a grant from the Environmental Research and Technology Development Fund S-7-1. The authors appreciate the assistance with lidar operations by Nagasaki Prefecture, Shimane Prefecture, Toyama Prefecture, Kin׳ki University, the Ministry of Environment and the Sibata corporation. SPM data were obtained from the Environmental Numerical Database at NIES website, and the meteorological data were downloaded from Japan Meteorological Agency website. Authors express

References (15)

  • T. Sakai et al.

    Aerosol optical and microphysical properties as derived from collocated measurements using polarization lidar and direct sampling

    Atmos Environ

    (2012)
  • Y. Iwasaka et al.

    The transport and spatial scale of Asian dust-storm cloudsa case study of the dust-storm event of April 1979

    Tellus

    (1983)
  • T. Murayama et al.

    Ground-based network observation of Asian dust events of April 1998 in east Asia

    J Geophys Res

    (2001)
  • N. Sugimoto et al.

    Record heavy Asian dust in Beijing in 2002observations and model analysis of recent events

    Geophys Res Lett

    (2002)
  • A. Shimizu et al.

    Continuous observations of Asian dust and other aerosols by polarization lidars in China and Japan during ACE-Asia

    J Geophys Res

    (2003)
  • K. Yumimoto et al.

    Adjoint inversion modeling of Asian dust emission using lidar observations

    Atmos Chem Phys

    (2008)
  • T.T. Sekiyama et al.

    Data assimilation of CALIPSO aerosol observations

    Atmos Chem Phys

    (2010)
There are more references available in the full text version of this article.

Cited by (12)

  • Investigate the relationship between multiwavelength lidar ratios and aerosol size distributions using aerodynamic particle sizer spectrometer

    2017, Journal of Quantitative Spectroscopy and Radiative Transfer
    Citation Excerpt :

    Therefore, it is important to find out the relationship between the lidar ratio and the aerosol size distribution and the wavelength of the incident light. Several studies have been conducted to determine the relationship between the aerosol optical properties and the microphysical properties of the aerosols [17–20]. However the relationship between the multiwavelength lidar ratio and the aerosol size distribution and the wavelength dependency of the lidar ratio has not been discussed in the above papers.

  • Understanding interannual variations of biomass burning from Peninsular Southeast Asia, part I: Model evaluation and analysis of systematic bias

    2015, Atmospheric Environment
    Citation Excerpt :

    For Beijing and Banyu on the other hand, larger underestimation should be attributed to the impacts of dust storm. Spring time dust storm from Taklimakan and Gobi desert in EA have been demonstrated by many studies to have dominant impact on the elevated PM10 levels over north part of China and the influence can reach oversea to Japan (Onishi et al., 2012; Shimizu et al., 2014; Watanabe et al., 2014). Table 2 suggested that 2006 and 2010 had the largest underestimated PM10 for EA, which were also the two years with most frequent dust storms during this period (Yang et al., 2013).

View all citing articles on Scopus
View full text
Copyright © 2014 Elsevier Ltd. All rights reserved.