An evaluation of CALIOP/CALIPSO's aerosol‐above‐cloud detection and retrieval capability over North America

Kacenelenbogen, M. S.; Redemann, Jens; Vaughan, Mark; Omar, Ali; Russell, Philip B.; Burton, S. P.; Rogers, Raymond R.; Ferrare, R. A.; Hostetler, C. A.

doi:10.1002/2013jd020178

Cited by 63 publications

(71 citation statements)

References 82 publications

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“…This could indicate a bias in CALIPSO retrieval. The detection threshold in the feature detection algorithm varies depending on the background lighting conditions and thus on the presence of clouds as well as the surface albedo during the daytime (see Hunt et al, 2009;Vaughan et al, 2009;5790 C. E. Chung et al: Relationship between low-cloud presence and the amount of overlying aerosols Chepfer et al, 2013;Kacenelenbogen et al, 2014). This means that the daytime AOD ct above low bright clouds reported here might be underestimated compared to the AOD ct in clear sky in the same grid cell.…”

Section: Discussionmentioning

confidence: 89%

“…This may, in turn, lead to an underestimation of the total daytime AOD compared to that derived from nighttime data . Moreover, during daytime, reflection of solar radiation from clouds can contribute to the background noise in the lidar profiles, and could, in a similar manner, lead to undetected faint aerosol layers above clouds (Kacenelenbogen et al, 2014).…”

Section: Datamentioning

confidence: 99%

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Relationship between low-cloud presence and the amount of overlying aerosols

2016

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Abstract. Aerosols are often advected above cloud decks, and the amount of aerosols over cloud has been assumed to be similar to that at the same heights in nearby clear sky. In this assumption, cloud and aerosol above cloud-top height are considered randomly located with respect to each other. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are analyzed here to investigate this assumption on global scales.The CALIPSO data reveal that the aerosol optical depth (AOD) above low cloud tends to be smaller than in nearby clear sky during the daytime, and the opposite is true during the nighttime. In particular, over oceanic regions with widespread low cloud, such as the tropical southeastern Atlantic Ocean and northeastern Pacific Ocean, the daytime AOD above low cloud is often 40 % smaller than in surrounding clear skies.

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Section: Discussionmentioning

confidence: 89%

Section: Datamentioning

confidence: 99%

Relationship between low-cloud presence and the amount of overlying aerosols

2016

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“…Spatial mismatch between the CALIOP footprints and the AERONET sites also contributes to these differences. Lastly, Kacenelenbogen et al (2014) used the NASA High Spectral Resolution Lidar (HSRL) data to study CALIOP AOD only over clouds. This study, on the other hand, assesses both the CALIOP layer AOD and the total column AOD, and also includes nighttime measurements.…”

Section: Introductionmentioning

confidence: 99%

Looking through the haze: evaluating the CALIPSO level 2 aerosol optical depth using airborne high spectral resolution lidar data

et al. 2014

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Abstract. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument onboard the Cloud-Aerosol Lidar and Pathfinder Satellite Observations (CALIPSO) spacecraft has provided over 8 yr of nearly continuous vertical profiling of Earth's atmosphere. In this paper we investigate the V3.01 and V3.02 CALIOP 532 nm aerosol layer optical depth (AOD) product (i.e the AOD of individual layers) and the column AOD product (i.e., the sum AOD of the complete column) using an extensive database of coincident measurements. The CALIOP AOD measurements and AOD uncertainty estimates are compared with collocated AOD measurements collected with the NASA High Spectral Resolution Lidar (HSRL) in the North American and Caribbean regions. In addition, the CALIOP aerosol lidar ratios are investigated using the HSRL measurements.In general, compared with the HSRL values, the CALIOP layer AOD are biased high by less than 50 % for AOD < 0.3 with higher errors for higher AOD. Less than 60 % of the HSRL AOD measurements are encompassed within the CALIOP layer 1 SD uncertainty range (around the CALIOP layer AOD), so an error estimate is created to encompass 68 % of the HSRL data. Using this new metric, the CALIOP layer AOD error is estimated using the HSRL layer AOD as ±0.035 ± 0.05 · (HSRL layer AOD) at night and ±0.05 ± 0.05 · (HSRL layer AOD) during the daytime. Furthermore, the CALIOP layer AOD error is found to correlate with aerosol loading as well as aerosol subtype, with the AODs in marine and dust layers agreeing most closely with the HSRL values. The lidar ratios used by CALIOP for polluted dust, polluted continental, and biomass burning layers are larger than the values measured by the HSRL in the CALIOP layers, and therefore the AODs for these types retrieved by CALIOP were generally too large.We estimated the CALIOP column AOD error can be expressed as ±0.05 ± 0.07 · (HSRL column AOD) at night and ±0.08 ± 0.1 · (HSRL column AOD) during the daytime. Multiple sources of error contribute to both positive and negative errors in the CALIOP column AOD, including multiple layers in the column of different aerosol types, lidar ratio errors, cloud misclassification, and undetected aerosol layers. The undetected layers were further investigated and we found that the layer detection algorithm works well at night, although undetected aerosols in the free troposphere introduce a mean underestimate of 0.02 in the column AOD in the data set examined. The decreased signal-to-noise ratio (SNR) during the daytime led to poorer performance of the layer detection. This caused the daytime CALIOP column AOD to be less accurate than during the nighttime, because CALIOP frequently does not detect optically thin aerosol layers with AOD < 0.1. Given that the median vertical extent of aerosol detected within any column was 1.6 km during the nighttime and 1.5 km during the daytime, we can estimate the minimum extinction detection threshold to be 0.012 km −1 at night and 0.067 km −1 during the daytime in a layer median sense.This extensive valida...

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“…Over the years, researchers have used various quality screening methods for level 2 aerosol products, sometimes in collaboration with CALIPSO algorithm developers (Kittaka et al, 2011;Campbell et al, 2012a;Koffi et al, 2012;Redemann et al, 2012;Toth et al, 2013;Kacenelenbogen et al, 2014). These quality screening methods were similar to 10 those used to generate the level 3 aerosol product.…”

mentioning

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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An evaluation of CALIOP/CALIPSO's aerosol‐above‐cloud detection and retrieval capability over North America

Cited by 63 publications

References 82 publications

Relationship between low-cloud presence and the amount of overlying aerosols

Relationship between low-cloud presence and the amount of overlying aerosols

Looking through the haze: evaluating the CALIPSO level 2 aerosol optical depth using airborne high spectral resolution lidar data

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

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