Simultaneously inferring above‐cloud absorbing aerosol optical thickness and underlying liquid phase cloud optical and microphysical properties using MODIS

Meyer, Kerry; Platnick, Steven; Zhang, Zhibo

doi:10.1002/2015jd023128

Cited by 92 publications

(157 citation statements)

References 78 publications

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“…We are aware that MODIS effective radius may be affected by the presence of aerosols above clouds. For example, Haywood et al (2004) found biases of ±2 µm for r eff in case of strong dust events above clouds and Meyer et al (2015) found an increase in the r eff monthly mean of 2 % in case of above-cloud absorbing aerosols. We expect that large biases on r eff could be possible in case of high aerosol loading for detached cases.…”

Section: Aot Vs R Effmentioning

confidence: 99%

“…Another method that can retrieve the ACAOT and, simultaneously, the aerosol-corrected cloud optical thickness (COT) is the "colour ratio" method proposed by Jethva et al (2013) that employs measurements in visible and shortwave infrared channels from the Moderate Resolution Imaging Spectroradiometer (MODIS). Also, Meyer et al (2015) developed an algorithm that employs reflectance measurements from six MODIS channels (from the visible to the shortwave infrared) to retrieve the ACAOT, as well as the COT and droplet effective radius (r eff ) of the underlying cloud.…”

Section: Introductionmentioning

confidence: 99%

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Consistency of aerosols above clouds characterization from A-Train active and passive measurements

et al. 2017

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Abstract. This study presents a comparison between the retrieval of optical properties of aerosol above clouds (AAC) from different techniques developed for the A-Train sensors CALIOP/CALIPSO and POLDER/PARASOL. The main objective is to analyse the consistency between the results derived from the active and the passive measurements. We compare the aerosol optical thickness (AOT) above optically thick clouds (cloud optical thickness (COT) larger than 3) and their Ångström exponent (AE). These parameters are retrieved with the CALIOP operational method, the POLDER operational polarization method and the CALIOP-based depolarization ratio method (DRM) -for which we also propose a calibrated version (denominated DRM SODA , where SODA is the Synergized Optical Depth of Aerosols). We analyse 6 months of data over three distinctive regions characterized by different types of aerosols and clouds. Additionally, for these regions, we select three case studies: a biomass-burning event over the South Atlantic Ocean, a Saharan dust case over the North Atlantic Ocean and a Siberian biomass-burning event over the North Pacific Ocean. Four and a half years of data are studied over the entire globe for distinct situations where aerosol and cloud layers are in contact or vertically separated. Overall, the regional analysis shows a good correlation between the POLDER and the DRM SODA AOTs when the microphysics of aerosols is dominated by fine-mode particles of biomass-burning aerosols from southern Africa (correlation coefficient (R 2 ) of 0.83) or coarse-mode aerosols of Saharan dust (R 2 of 0.82). A good correlation between these methods (R 2 of 0.68) is also observed in the global treatment, when the aerosol and cloud layers are separated well. The analysis of detached layers also shows a mean difference in AOT of 0.07 at 532 nm between POLDER and DRM SODA at a global scale. The correlation between the retrievals decreases when a complex mixture of aerosols is expected (R 2 of 0.37) -as in the East Asia region -and when the aerosol-cloud layers are in contact (R 2 of 0.36). The correlation coefficient between the CALIOP operational method and POLDER is found to be low, as the CALIOP method largely underestimates the aerosol loading above clouds by a factor that ranges from 2 to 4.Potential biases on the retrieved AOT as a function of cloud properties are also investigated. For different types of scenes, the retrieval of above-cloud AOT from POLDER and from DRM are compared for different underlying cloud properties (droplet effective radius (r eff ) and COT retrieved with MODIS). The results reveal that DRM AOT vary with r eff . When accounting for r eff in the DRM algorithm, the consistency between the methods increases. The sensitivity study shows that an additional polarized signal coming from aerosols located within the cloud could affect the polarization method, which leads to an overestimation of the AOT retrieved with POLDER algorithm. In addition, the aerosols attached to or within the cloud can potentially impact the DRM...

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Section: Aot Vs R Effmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Consistency of aerosols above clouds characterization from A-Train active and passive measurements

et al. 2017

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“…On the one hand, the evaporation of cloud droplets caused by locally absorbing aerosol makes clouds thinner, which is a radiative effect. On the other hand, the presence of absorbing aerosol may influence the satellite-retrieved COT because it can absorb radiation and thus reduce the cloud reflectance measured by the sensors on the satellite (Meyer et al, 2013(Meyer et al, , 2015Ten Hoeve et al, 2011). Meyer et al (2013) reported that adjusting for above-cloud aerosol attenuation can increase the retrieved regional mean COT by roughly 18 % for polluted marine boundary layer clouds.…”

Section: Difference Between Separated and Mixed Conditionsmentioning

confidence: 99%

Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

et al. 2017

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Abstract. Aerosol effects on low warm clouds over the Yangtze River Delta (YRD, eastern China) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA-Interim reanalysis data. This study shows that the relation between cloud properties and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD < 0.35 and AOD > 0.35). This applies to cloud droplet effective radius (CDR) and cloud fraction (CF), but not to cloud optical thickness (COT) and cloud top pressure (CTP). COT is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, CTP tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. It also shows that the COT-CDR and CWP (cloud liquid water path)-CDR relationships are not unique, but affected by atmospheric aerosol loading. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that aerosol-cloud interaction (ACI) is stronger for clouds mixed with smoke aerosol than for clouds mixed with dust, which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for various relative humidity and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity favours larger cloud droplet particles and increases cloud formation, irrespective of vertical or horizontal level. Stable atmospheric conditions enhance cloud cover horizontally. However, unstable atmospheric conditions favour thicker and higher clouds. Dynamically, upward motion of air parcels can also facilitate the formation of thicker and higher clouds. Overall, the present study provides an understanding of the impact of aerosols on cloud properties over the YRD. In addition to the amount of aerosol particles (or AOD), evidence is provided that aerosol types and ambient environmental conditions need to be considered to understand the observed relationships between cloud properties and AOD.

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“…Nonetheless, cloud cover continues to hinder our ability to monitor the trans-Pacific transport of aerosols when using observations from passive (low-earth orbiting, LEO) satellites alone. There has been recent progress in retrieving AOD for absorbing aerosols above clouds from MODIS (Jethva et al, 2013;Meyer et al, 2015) and the Ozone Monitoring Instrument (OMI) (Torres et al, 2012), which could prove very beneficial for tracking the trans-Pacific transport of aerosols. These retrieval techniques take advantage of the highly reflective nature of clouds along with the absorption characteristics of aerosols in the near-UV to visible wavelengths to retrieve AOD when aerosols are lofted above clouds.…”

Section: Introductionmentioning

confidence: 99%

Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth composites

et al. 2016

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Abstract. The primary goal of this study was to generate a near-real time (NRT) aerosol optical depth (AOD) product capable of providing a comprehensive understanding of the aerosol spatial distribution over the Pacific Ocean, in order to better monitor and track the trans-Pacific transport of aerosols. Therefore, we developed a NRT product that takes advantage of observations from both low-earth orbiting and geostationary satellites. In particular, we utilize AOD products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Suomi National Polar-orbiting Partnership (NPP) Visible Infrared Imaging Radiometer Suite (VI-IRS) satellites. Then, we combine these AOD products with our own retrieval algorithms developed for the NOAA Geostationary Operational Environmental Satellite (GOES-15) and Japan Meteorological Agency (JMA) Multi-functional Transport Satellite (MTSAT-2) to generate a NRT daily AOD composite product. We present examples of the daily AOD composite product for a case study of trans-Pacific transport of Asian pollution and dust aerosols in mid-March 2014. Overall, the new product successfully tracks this aerosol plume during its trans-Pacific transport to the west coast of North America as the frequent geostationary observations lead to a greater coverage of cloud-free AOD retrievals equatorward of about 35 • N, while the polar-orbiting satellites provide a greater coverage of AOD poleward of 35 • N. However, we note several areas across the domain of interest from Asia to North America where the GOES-15 and MTSAT-2 retrieval algorithms can introduce significant uncertainties into the new product.

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Simultaneously inferring above‐cloud absorbing aerosol optical thickness and underlying liquid phase cloud optical and microphysical properties using MODIS

Cited by 92 publications

References 78 publications

Consistency of aerosols above clouds characterization from A-Train active and passive measurements

Consistency of aerosols above clouds characterization from A-Train active and passive measurements

Analysis of aerosol effects on warm clouds over the Yangtze River Delta from multi-sensor satellite observations

Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth composites

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