CALIPSO‐inferred aerosol direct radiative effects: Bias estimates using ground‐based Raman lidars

Thorsen, Tyler J.; Fu, Qiang

doi:10.1002/2015jd024095

Cited by 38 publications

(46 citation statements)

References 86 publications

(95 reference statements)

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“…Figure 1b displays that the aerosol mostly occurs under 5 km m.s.l., and its extinction coefficient is exponentially weakened with the increase in altitude in South Asia. This result is consistent with previous work [42,43]. Moreover, the vertical aerosol extinction coefficient increases distinctly during the monsoon season in South Asia from 2006 to 2015, especially below 2 km.…”

Section: Of 17supporting

confidence: 93%

Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season

et al. 2018

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South Asia is experiencing a levelling-off trend in solar radiation and even a transition from dimming to brightening. Any change in incident solar radiation, which is the only significant energy source of the global ecosystem, profoundly affects our habitats. Here, we use multiple observations of the A-Train constellation to evaluate the impacts of three-dimensional (3D) aerosol, cloud, and water vapor variations on the changes in surface solar radiation during the monsoon season (June-September) in South Asia from 2006 to 2015. Results show that surface shortwave radiation (SSR) has possibly increased by 16.2 W m −2 during this period. However, an increase in aerosol loading is inconsistent with the SSR variations. Instead, clouds are generally reduced and thinned by approximately 8.8% and 280 m, respectively, with a decrease in both cloud water path (by 34.7 g m −2 ) and particle number concentration under cloudy conditions. Consequently, the shortwave cloud radiative effect decreases by approximately 45.5 W m −2 at the surface. Moreover, precipitable water in clear-sky conditions decreases by 2.8 mm (mainly below 2 km), and related solar brightening increases by 2.5 W m −2 . Overall, the decreases in 3D water vapor and clouds distinctly result in increased absorption of SSR and subsequent surface brightening.

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Section: Of 17supporting

confidence: 93%

Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season

et al. 2018

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“…Level 2 atmospheric samples classified as "clear-air" (i.e., no feature is detected) are assumed in the level 3 algorithm to have aerosol extinction equal to 0 km Several researchers have recently sought to characterize the optical depths of the aerosol layers undetected by CALIOP using collocated observations (Kacenelenbogen et al, 2011;Sheridan et al, 2012;Rogers et al, 2014;Thorsen and Fu, 2015;Toth et al, 2018) or independent retrievals Kim et al, 2017). Exactly how these undetected layers affect the level 3 mean extinction is difficult to estimate given that the resulting underestimate depends on the 20 magnitude of missing extinction and the frequency of non-detection.…”

Section: Aerosol In "Clear-air" Regionsmentioning

confidence: 99%

CALIPSO lidar level 3 aerosol profile product: version 3 algorithm design

Tackett¹,

Winker²,

Getzewich³

et al. 2018

Preprint

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Abstract. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) level 3 aerosol profile product reports globally-gridded, quality-screened monthly mean aerosol extinction profiles retrieved by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). This paper describes the quality screening and averaging methods used to 10 generate the version 3 product. The fundamental input data are CALIOP level 2 aerosol extinction profiles and layer classification information (aerosol, cloud, and clear-air). Prior to aggregation, the extinction profiles are quality-screened by a series of filters to reduce the impact of layer detection errors, layer classification errors, extinction retrieval errors, and biases due to an intermittent signal anomaly at the surface. The relative influence of these filters are compared in terms of sample rejection frequency, mean extinction, and mean AOD. The "extinction QC flag" filter is the most influential in 15 preventing high-biases in level 3 mean extinction, while the "misclassified cirrus fringe" filter is most aggressive at rejecting cirrus misclassified as aerosol. The impact of quality screening on monthly mean aerosol extinction is investigated globally and regionally. After applying quality filters, monthly mean AOD is reduced by −24 and −31 % for global ocean and global land, respectively, thus indicating the importance of quality screening.

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“…[] found that the marine boundary aerosols below the elevated smoke layers are frequently undetected by the CALIOP layer detection algorithm due to attenuation, which leads to underestimation of CALIOP AOD for smoke aerosols. Thorsen and Fu [] also showed that CALIOP detects significantly less aerosol layers for the middle and lower atmosphere compared to ground‐based Raman lidars at two Atmospheric Radiation Measurement sites. Moreover, they noted that the undetected aerosols lead to underestimation of the CALIOP‐inferred aerosol direct radiative effect by 30–50%.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the low bias of CALIPSO's column aerosol optical depth due to undetected aerosol layers

et al. 2017

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The Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) data processing scheme only retrieves extinction profiles in those portions of the return signal where cloud or aerosol layers have been identified by the CALIOP layer detection scheme. In this study we use 2 years of CALIOP and Moderate Resolution Imaging Spectroradiometer (MODIS) data to quantify the aerosol optical depth of undetected weakly backscattering layers. Aerosol extinction and column‐averaged lidar ratio is retrieved from CALIOP level 1B (version 4) profile using MODIS aerosol optical depth (AOD) as a constraint over oceans from March 2013 to February 2015. To quantify the undetected layer AOD (ULA), an unconstrained retrieval is applied globally using a lidar ratio of 28.75 sr estimated from constrained retrievals during the daytime over the ocean. We find a global mean ULA of 0.031 ± 0.052. There is no significant difference in ULA between land and ocean. However, the fraction of undetected aerosol layers rises considerably during daytime, when the large amount of solar background noise lowers the signal‐to‐noise ratio. For this reason, there is a difference in ULA between day (0.036 ± 0.066) and night (0.025 ± 0.021). ULA is larger in the northern hemisphere and relatively larger at high latitudes. Large ULA for the polar regions is strongly related to the cases where the CALIOP level 2 product reports zero AOD. This study provides an estimate of the complement of AOD that is not detected by lidar and bounds the CALIOP AOD uncertainty to provide corrections for science studies that employ the CALIOP level 2 AOD.

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CALIPSO‐inferred aerosol direct radiative effects: Bias estimates using ground‐based Raman lidars

Cited by 38 publications

References 86 publications

Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season

Impacts of 3D Aerosol, Cloud, and Water Vapor Variations on the Recent Brightening during the South Asian Monsoon Season

CALIPSO lidar level 3 aerosol profile product: version 3 algorithm design

Quantifying the low bias of CALIPSO's column aerosol optical depth due to undetected aerosol layers

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