Detection of dust aerosol by combining CALIPSO active lidar and passive IIR measurements

Chen, Bin; Huang, Jianping; Minnis, Patrick; Hu, Yongxiang; Yi, Yaling; Liu, Z.; Zhang, D.; Wang, X.

doi:10.5194/acp-10-4241-2010

Cited by 74 publications

(41 citation statements)

References 43 publications

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“…The CALIOP mask shows a complex situation with aerosols detected at different altitudes between the sea surface and 6 km that are potentially embedded with some optically thin cloudy structures. We observe some abrupt changes in the CALIOP results that we assume to be artificial for the most part since the CALIOP mask is sometimes subject to misclassification between aerosol and cloud layers, especially when dense dust layers are encountered (Chen et al, 2010). The CALIOP results obtained for the case study on mineral dust particles acquired on 4 August 2008 are reported in Fig.…”

Section: Mineral Dust Aerosolsmentioning

confidence: 91%

Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

et al. 2013

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Most of the current aerosol retrievals from passive sensors are restricted to cloud-free scenes, which strongly reduces our ability to monitor the aerosol properties at a global scale and to estimate their radiative forcing. The presence of aerosol above clouds (AAC) affects the polarized light reflected by the cloud layer, as shown by the spaceborne measurements provided by the POlarization and Directionality of Earth Reflectances (POLDER) instrument on the PARASOL satellite. In a previous work, a first retrieval method was developed for AAC scenes and evaluated for biomass-burning aerosols transported over stratocumulus clouds. The method was restricted to the use of observations acquired at forward scattering angles (90–120°) where polarized measurements are highly sensitive to fine-mode particle scattering. Non-spherical particles in the coarse mode, such as mineral dust particles, do not much polarize light and cannot be handled with this method. In this paper, we present new developments that allow retrieving also the properties of mineral dust particles above clouds. These particles do not much polarize light but strongly reduce the polarized cloud bow generated by the liquid cloud layer beneath and observed for scattering angles around 140°. The spectral attenuation can be used to qualitatively identify the nature of the particles (i.e. accumulation mode versus coarse mode, i.e. mineral dust particles versus biomass-burning aerosols), whereas the magnitude of the attenuation is related to the optical thickness of the aerosol layer. We also use the polarized measurements acquired in the cloud bow to improve the retrieval of both the biomass-burning aerosol properties and the cloud microphysical properties. We provide accurate polarized radiance calculations for AAC scenes and evaluate the contribution of the POLDER polarization measurements for the simultaneous retrieval of the aerosol and cloud properties. We investigate various scenes with mineral dust particles and biomass-burning aerosols above clouds. For clouds, our results confirm that the droplet size distribution is narrow in high-latitude ocean regions and that the droplet effective radii retrieved from both polarization measurements and from total radiance measurements are generally close for AAC scenes (departures smaller than 2 μm). We found that the magnitude of the primary cloud bow cannot be accurately estimated with a plane parallel transfer radiative code. The errors for the modeling of the polarized cloud bow are between 4 and 8% for homogenous cloudy scenes, as shown by a 3-D radiative transfer code. These effects only weakly impact the retrieval of the Aerosol Optical Thickness (AOT) performed with a mineral dust particle model for which the microphysical properties are entirely known (relative error smaller than 6%). We show that the POLDER polarization measurements allow retrieving the AOT, the fine-mode particle size, the Ångström exponent and the fraction of spherical particles. However, the complex refractive index and the coarse-...

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Section: Mineral Dust Aerosolsmentioning

confidence: 91%

Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

et al. 2013

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“…Guan et al (2015a) found that the enhanced warming in drylands was a result of radiativeforced temperature, which has a close relationship with aerosol column burden. The aerosol in drylands has an obvious warming effect (Huang et al, 2006aChen et al, 2010;Ye et al, 2012;Jin et al, 2015), and the aerosol has a wide distribution and tends to have a relatively large optical depth (H. Bi et al, 2011;Liu et al, 2011;, leading to a significant radiative effect in the drylands. According to the results of Tegen and Fung (1995), the existing atmospheric dust load is hard to explain by natural sources alone.…”

Section: Introductionmentioning

confidence: 99%

The relationship between anthropogenic dust and population over global semi-arid regions

et al. 2016

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Abstract. Although anthropogenic dust has received more attention from the climate research community, its dominant role in the production process is still not identified. In this study, we analysed the relationship between anthropogenic dust and population density/change over global semi-arid regions and found that semi-arid regions are major source regions in producing anthropogenic dust. The results showed that the relationship between anthropogenic dust and population is more obvious in cropland than in other land cover types (crop mosaics, grassland, and urbanized regions) and that the production of anthropogenic dust increases as the population density grows to more than 90 persons km −2 . Four selected semi-arid regions, namely East China, India, North America, and North Africa, were used to explore the relationship between anthropogenic dust production and regional population. The most significant relationship between anthropogenic dust and population occurred in an Indian semi-arid region that had a greater portion of cropland, and the high peak of anthropogenic dust probability appeared with 220 persons km −2 of population density and 60 persons km −2 of population change. These results suggest that the influence of population on production of anthropogenic dust in semi-arid regions is obvious in cropland regions. However, the impact does not always have a positive contribution to the production of anthropogenic dust, and overly excessive population will suppress the increase of anthropogenic dust. Moreover, radiative and climate effects of increasing anthropogenic dust need more investigation.

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“…The corrected data mask also agrees with the BTD values of MODIS. For comparison of LDF applicability, results from LDF developed by Chen et al (2010) (hereafter referred to as LDF') are shown in Fig. 9c.…”

Section: Reclassification Of the Cloud Layers In The Caliop Cloud Maskmentioning

confidence: 99%

“…The corresponding data mask is rarely different from the data mask before the LDF correction, which indicates that LDF' is less effective than LDF in this study. The reason for false detection by LDF' is that Chen et al (2010) did not collect training data during the nighttime, resulting in uncertainties in the true PDF, which is needed for creating an accurate discrimination model. These two demonstrations of the discriminant analysis result in the successful reclassification of dust over land and sea during the daytime and nighttime.…”

Section: Reclassification Of the Cloud Layers In The Caliop Cloud Maskmentioning

confidence: 99%

“…In general, higher dimensional data allow for better classification, but the VFM mask has a limitation in regard to the classification of dust and clouds. Chen et al (2010) developed a new method which combined the CALIPSO active lidar and passive Infrared Imaging Radiometer (IIR) measurements. They incorporated both CALIOP and IIR measurements into their discriminant model.…”

Section: Discriminant Analysis For Detecting Misclassified Clouds In mentioning

confidence: 99%

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Improvement of CALIOP Cloud Masking Algorithms for Better Estimation of Dust Extinction Profiles

Jin

Kai

Okamoto

et al. 2014

Journal of the Meteorological Society of Japan

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Mineral dust suspended in the atmosphere affects the Earth's radiation budget. To accurately predict the effect of dust on the climate system, information regarding its extinction profiles is needed. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite has enabled the global observation of the vertical distributions of aerosols and clouds since June 2006. To correctly retrieve extinction coefficients from CALIOP signals, the lidar-observed layers must be classified into aerosols or clouds. The cloud masking algorithms of CALIOP should be improved since the cloud mask products occasionally misclassify dense dust as clouds. This study attempts to discriminate misclassified clouds from the CALIOP cloud mask with a discriminant analysis. The training data are collected by tests with the CloudSat cloud mask, the Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask, and relative humidity. Discrimination of dust from clouds is successful in cases over land and water surfaces during the daytime and nighttime. In contrast, the discrimination model of previous studies was inadequate during the nighttime since training data were not collected during the nighttime. The accuracy rate of the linear discriminant function classification is 91.7 % for misclassified clouds. The cloud mask is most frequently misclassified in the Taklimakan Desert. The proportion of misclassified clouds to the observed dust is ~34.6 % (below 2 km) in the desert. Comparison of our results with CALIOP level 3 products indicates that the extinction profile using the improved cloud mask is at most twice larger than that of CALIOP level 3 products. This study suggests that the smaller extinction coefficients of CALIOP level 3 products are mainly caused by misclassification of dust as clouds in the vertical feature mask.

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Detection of dust aerosol by combining CALIPSO active lidar and passive IIR measurements

Cited by 74 publications

References 43 publications

Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

Retrieval of aerosol microphysical and optical properties above liquid clouds from POLDER/PARASOL polarization measurements

The relationship between anthropogenic dust and population over global semi-arid regions

Improvement of CALIOP Cloud Masking Algorithms for Better Estimation of Dust Extinction Profiles

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