Aerosol layers in the free troposphere and their seasonal variations as observed in Wuhan, China

Shao, Jian‐Wei; Yi, Fan; Yin, Zhenping

doi:10.1016/j.atmosenv.2020.117323

Cited by 12 publications

(7 citation statements)

References 67 publications

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“…Dust frequently intruded into Wuhan over the years; however, very few sun photometer data sets can fulfill those constraints. This is caused by plenty of local aerosol emissions (especially within the boundary layer), which make the column-integrated aerosol properties observed here generally reflect a characteristic of mixed dust (dust particles mix with other urban aerosols) [Shao et al, 2020;Liu et al, 2021]. It is also worthy to note that the previous gravitational sedimentation and wet deposition of dust particles during transport may modify the dust optical and microphysical properties in Wuhan and thus result in the dust-related conversion factors different from those near-desert sites.…”

Section: Poliphon Conversion Factors Over Wuhanmentioning

confidence: 94%

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a central China megacity

Zhang

Liu

et al. 2021

Preprint

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Abstract. The POLIPHON (Polarization Lidar Photometer Networking) method is a powerful pathway to retrieve the height profiles of dust-related particle mass and ice-nucleating particles (INP) concentrations. The conversion factors fitted from the sun photometer observation data are the major part of the POLIPHON computations, which can convert the polarization-lidar-derived dust extinction coefficients into the dust-related particle mass and INP concentrations. For a central China megacity Wuhan (30.5° N, 114.4° E), located at the downstream area several thousands of kilometers far away from the source regions of Asian dust, dust particles always mix with other aerosols from local emission. Therefore, very few dust case data sets can be available when using the column-integrated Ångström exponent (for 440–870 nm) < 0.3 and aerosol optical depth (at 532 nm) > 0.1 recorded by sun photometer as the filtering criteria. Instead, we present another dust-case data-set screening scheme that applies the simultaneous polarization lidar observation to verify the occurrence of dust. Based on the 33 dust-intrusion days identified during 2011–2013, the extinction-to-volume (cv,d) and extinction-to-large particle (with radius > 250 nm) number concentration (c250,d) conversion factors are determined to be 0.52 × 10−12 Mm m3 m−3 and 0.11 Mm cm−3, respectively. They are both smaller than those observed at Lanzhou SACOL (36.0° N, 104.1° E), a site closer to the Gobi Desert, due to the partial dust sedimentation during transport. The conversion factors are applied in a dust event in Wuhan to reveal the typical dust-related INP concentration over East Asia city. The proposed dust-case data-set screening scheme may potentially be extended to the other polluted city sites more influenced by mixed dust.

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Section: Poliphon Conversion Factors Over Wuhanmentioning

confidence: 94%

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a central China megacity

Zhang

Liu

et al. 2021

Preprint

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“…The selection of suitable cloud scenarios for the underlying study was based on the availability of colocated data from the zenith‐pointed and the slant‐pointed polarization lidars. The zenith‐pointed polarization lidar system operated uninterruptedly, except for bad weather conditions (e.g., rain and snow) and equipment failure (Shao et al., 2020). In total, it operated for 172 days (>4 h/day) during the period from December 2012 to December 2013.…”

Section: Instrumentation and Methodologymentioning

confidence: 99%

“…A detailed description of the lidar system and a performance verification through a comparison with simultaneous and nearly collocated CALIPSO measurements were presented by Zhang et al (2014), Kong and Yi (2015), and Zhuang and Yi (2016). Over the years, this lidar system has been widely used in observational studies of clouds and aerosols, including the evolution of convective boundary layers (Kong & Yi, 2015), aerosol layers in the free troposphere (Shao et al, 2020), transported dust aerosols (He & Yi, 2015), volcanic aerosol event (Zhuang & Yi, 2016), ice cloud formation in the local atmosphere (Wu & Yi, 2017), and falling ice virga (Cheng & Yi, 2020). The emitted laser is a linearly polarized light at 532 nm with a pulse energy of ∼120 mJ, a pulse width of 6 ns, and a repetition rate of 20 Hz.…”

Section: Zenith-pointed Polarization Lidarmentioning

confidence: 99%

“…The gain ratio k between two channels is calibrated using the Δ90° method reported by Freudenthaler et al (2009). The volume (aerosol + molecular) depolarization ratio δ can be determined by the ratio of perpendicular-to parallel-oriented signals multiplied by the gain ratio k. Using this calibration method, the remaining relative error of δ is ≤5% (Shao et al, 2020). δ characterizes the nonspherical shape of backscattering targets, which can effectively distinguish dust aerosols and ice crystals from liquid water and other types of aerosols (Sassen, 2005).…”

Section: Zenith-pointed Polarization Lidarmentioning

confidence: 99%

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Heterogeneous Nucleation of Midlevel Cloud Layer Influenced by Transported Asian Dust Over Wuhan (30.5°N, 114.4°E), China

Yang

et al. 2021

JGR Atmospheres

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Mixed-phase clouds, which contain both supercooled liquid water droplets and ice crystals, cover >34% of the Earth's surface (Zhang et al., 2018) and significantly impact the atmospheric radiation budget: they cool the Earth by reflecting incoming solar radiation and warm the Earth by prohibiting the escape of outgoing longwave radiation (IPCC, 2013; Rosenfeld et al., 2014; Zhao et al., 2018). Mixed-phase clouds are also essential to cloud electrification and the production of precipitation (Liu et al., 2019; Rosenfeld et al., 2008). Ice formation in the atmosphere is primarily the result of competition between the activation energy and interface energy for water molecules (DeMott, 2002; Seifert, 2011). To generate ice particles, the energy barrier needs to be broken by increasing the interface energy, which depends on temperature and the logarithm of supersaturation. This breakage can be realized either by homogeneous nucleation occurring at temperatures below −38°C (Pruppacher, 1995) or by heterogeneous nucleation at warmer temperatures ranging from −38°C to 0°C with some insoluble aerosols acting as ice-nucleating particles (INPs). For mixed-phase clouds, ice crystals are produced by heterogeneous nucleation process via four basic ice nucleation modes, e.g., deposition nucleation, immersion nucleation, contact nucleation, and condensation nucleation (Pruppacher & Klett, 1997). However, the heterogeneous nucleation process is still poorly understood due to the complexity of the INP nucleation efficiency corresponding to its chemical and microphysical properties (Cantrell & Heymsfield, 2005; Kanji et al., 2017). Moreover, current assessments suggest that the net radiation forcing related to the interaction between aerosols and mixed-phase clouds shows a large uncertainty and even exhibits a contradictory variation from −0.67 to +0.70 W m −2 (Fan et al., 2016; IPCC, 2013). Dust, soot, and biological particles are considered the three most effective INPs in the atmosphere. The yearly averaged emission of dust aerosols is estimated to be 1,000-3,000 Tg, which is far more than that of either soot (∼50 Tg) or organic material (∼60 Tg) (Seifert, 2011), and thus provides a promising opportunity to study heterogeneous nucleation in an actual atmospheric environment. Numerous studies concerning dust-related heterogeneous ice formation have involved laboratory experiments (

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“…δ p values that range between δ nd and δ d are a mix of non-dust and pure dust components. The dust backscatter coefficient β d can be expressed as follows (Tesche et al, 2009):…”

Section: Retrieval Scheme Of Dust Mass Concentration and Dust-related Inpcmentioning

confidence: 99%

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a megacity in central China

Zhang

Liu

et al. 2021

Atmos. Meas. Tech.

Self Cite

View full text Add to dashboard Cite

Abstract. The POLIPHON (polarization lidar photometer networking) method is a powerful pathway to retrieve the height profiles of dust-related particle mass and ice-nucleating particle (INP) concentrations. The conversion factors fitted from the sun photometer observation data are the major part of the POLIPHON computations, which can convert the polarization-lidar-derived dust extinction coefficients into dust-related particle mass and INP concentrations. For the central Chinese megacity of Wuhan (30.5∘ N, 114.4∘ E), located at the downstream area several thousands of kilometers far away from the source regions of Asian dust, dust particles always mix with other aerosols from local emissions. Therefore, very few dust case data sets can be available when using the column-integrated Ångström exponent (for 440–870 nm) <0.3 and aerosol optical depth (at 532 nm) >0.1 recorded by a sun photometer as the filtering criteria. Instead, we present another dust case data set screening scheme that applies the simultaneous polarization lidar observation to verify the occurrence of dust. Based on the 33 dust-intrusion days identified during 2011–2013, the extinction-to-volume (cv,d) and extinction-to-large particle (with radius >250 nm) number concentration (c250,d) conversion factors are determined to be (0.52±0.12)×10-12Mmm3m-3 and 0.19±0.05 Mm cm−3, respectively. The c250,d for Wuhan is 27 % larger than that observed at Lanzhou SACOL (36.0∘ N, 104.1∘ E), a site closer to the Gobi Desert, and tends to be closer to those observed in North Africa and the Middle East, indicating dust aerosols from these two sources are also possibly involved in the dust events observed over Wuhan. As a comparison, the conversion factor c290,c of 0.11±0.02Mmcm-3 for continental aerosol is much smaller than c250,d, indicating that there is no significant influence of urban aerosols on the retrievals of dust-related conversion factor over Wuhan. The conversion factors are applied in a dust event in Wuhan to reveal the typical dust-related immersion-mode INP concentration over East Asian cities. The proposed dust case data set screening scheme may potentially be extended to the other polluted city sites that are more influenced by mixed dust.

show abstract

Aerosol layers in the free troposphere and their seasonal variations as observed in Wuhan, China

Cited by 12 publications

References 67 publications

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a central China megacity

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a central China megacity

Heterogeneous Nucleation of Midlevel Cloud Layer Influenced by Transported Asian Dust Over Wuhan (30.5°N, 114.4°E), China

Retrievals of dust-related particle mass and ice-nucleating particle concentration profiles with ground-based polarization lidar and sun photometer over a megacity in central China

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